tag:theconversation.com,2011:/global/topics/eyesight-1868/articlesEyesight – The Conversation2023-11-10T16:34:37Ztag:theconversation.com,2011:article/2173322023-11-10T16:34:37Z2023-11-10T16:34:37ZAll the Light We Cannot See: how progressive congenital cataracts can lead to blindness<p>In the new Netflix series <a href="https://www.imdb.com/title/tt15320362/">All the Light We Cannot See</a>, a blind French girl called Marie-Laure LeBlanc makes illicit radio broadcasts from her uncle’s house in Nazi-occupied France. We are told that Marie-Laure has congenital cataracts in both eyes. But what is this condition?</p>
<p>The word “cataract” comes from the Latin word for waterfall and describes a condition where the usually transparent lens of the eye is cloudy or opaque. This prevents a clear image being projected onto the back of the eye and causes poor vision. </p>
<p>Many people will have heard of cataracts in the context of older adults because the lens becomes cloudier throughout life, slowly causing blurry vision. Surgery to remove the cloudy lens and replace it with a clear plastic one is commonplace and quite routine nowadays. In fact, cataract surgery in adults is one of the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7812090/">most common operations</a> performed in healthcare systems across the world.</p>
<p>However, around three in 10,000 children are <a href="https://www.moorfields.nhs.uk/content/childrens-cataracts#:%7E:text=In%20the%20UK%203%20in,Cataracts%20may%20not%20require%20treatment.">born with cataracts</a> (congenital cataracts) and this poses a much more urgent problem. During very early childhood, the brain learns to see and so anything causing poor vision must be dealt with rapidly to allow the brain time to adjust. </p>
<p>In modern healthcare systems, most babies with cataracts have surgery before the age of ten weeks to avoid very poor lifelong vision. Some children are born with milder cataracts and then they progress (become cloudier), as we can assume was the case for the fictional character Marie-Laure. Nowadays, these children are watched closely because their cataracts can <a href="https://www.rnib.org.uk/your-eyes/eye-conditions-az/congenital-cataracts/">progress slowly, or very quickly</a>, depending on their cause.</p>
<p>Surgery is offered when the potential benefits outweigh the risks. Marie-Laure’s story is quite different. In the 1940s, surgery was far riskier and a far cry from modern micro-surgery under general anaesthetic. Most children had no treatment at all.</p>
<figure class="align-center ">
<img alt="An intraocular lens." src="https://images.theconversation.com/files/558675/original/file-20231109-29-pvi0kl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/558675/original/file-20231109-29-pvi0kl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558675/original/file-20231109-29-pvi0kl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558675/original/file-20231109-29-pvi0kl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558675/original/file-20231109-29-pvi0kl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558675/original/file-20231109-29-pvi0kl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558675/original/file-20231109-29-pvi0kl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In cataract surgery, the cloudy lens is replaced.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/iol-intraocular-lens-cataract-ophthalmology-2057263202">Simpotich Photography/Shutterstock</a></span>
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<h2>Treatment is very different today</h2>
<p>In most developed healthcare systems in 2023, newborns are examined routinely after birth and one part of this is to look for eye problems, including cataract. This was not the case in the 1940s, and so how Marie-Laure’s cataracts developed and at what age, is probably unclear. This is important, because there are many different underlying causes of congenital cataract, including conditions affecting just the eyes, conditions affecting other parts of the body such as <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6975004/#:%7E:text=Nance%E2%80%93Horan%20syndrome%20(NHS),%2C%20congenital%20cataract%2C%20and%20strabismus.">Nance-Horan syndrome</a>, and even life-limiting metabolic diseases. </p>
<p>Nowadays, when a cataract is found in newborns or children, doctors seek these conditions using genetic testing and other blood tests.</p>
<p>Importantly, congenital cataracts which do get worse in childhood (as is the story for Marie-Laure) are more likely to be due to conditions that affect other parts of the body, and so it is possible that Marie-Laure also had other medical problems related to an underlying condition.</p>
<p>One critic <a href="https://www.stylist.co.uk/entertainment/tv/all-the-light-we-cannot-see-netflix/568157">praised</a> All the Light We Cannot See for being “a significant leap forward for disability inclusion, rights and representation on screen and beyond”. Marie-Laure’s teenage character is played by <a href="https://www.imdb.com/name/nm13200978/">Aria Mia Loberti</a>, an American actor who has a congenital eye condition called <a href="https://www.moorfields.nhs.uk/condition/achromatopsia">achromatopsia</a>. And the young Marie-Laure is played by <a href="https://www.imdb.com/name/nm15346843/">Nell Sutton</a>, who has another rare condition called <a href="https://www.moorfields.nhs.uk/content/childrens-glaucoma">congenital glaucoma</a>. </p>
<p>Achromatopsia causes low vision, moving eyes and no colour vision at all, and congenital glaucoma causes the pressure inside the eye to be very high and when untreated, causes loss of vision and the eyeball to enlarge way beyond its normal size. In the 1940s little would have been known about any of these conditions or indeed, how to treat them.</p>
<p>Medical treatment, surgery and support have changed vastly since the 1940s, but the challenges faced by young people living with low vision, despite the cause, are still very real.</p><img src="https://counter.theconversation.com/content/217332/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jay E. Self does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Cataracts aren’t just something people develop in older age. Some people are born with them.Jay E. Self, Associate Professor and Consultant Ophthalmologist, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2131452023-09-25T01:41:27Z2023-09-25T01:41:27ZDo blue-light glasses really work? Can they reduce eye strain or help me sleep?<figure><img src="https://images.theconversation.com/files/549203/original/file-20230919-25-ucj5dq.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1000%2C666&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/asian-womans-eyes-stress-blue-blocking-1391138681">Shutterstock</a></span></figcaption></figure><p>Blue-light glasses are said to <a href="https://www.baxterblue.com.au/collections/blue-light-glasses">reduce eye strain</a> when using <a href="https://www.blockbluelight.com.au/collections/computer-glasses">computers</a>, improve your <a href="https://www.ocushield.com/products/anti-blue-light-glasses">sleep</a> and protect your eye health. You can buy them yourself or your optometrist can prescribe them.</p>
<p>But <a href="https://mivision.com.au/2019/03/debate-continues-over-blue-blocking-lenses/">do they work</a>? Or could they do you harm?</p>
<p>We <a href="https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD013244.pub2/full">reviewed</a> the evidence. Here’s what we found.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-will-i-damage-my-eyes-if-i-dont-wear-sunglasses-68582">Health Check: will I damage my eyes if I don't wear sunglasses?</a>
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<h2>What are they?</h2>
<p>Blue-light glasses, blue light-filtering lenses or blue-blocking lenses are different terms used to describe lenses that reduce the amount of short-wavelength visible (blue) light reaching the eyes. </p>
<p>Most of these lenses prescribed by an optometrist decrease blue light transmission by <a href="https://onlinelibrary.wiley.com/doi/10.1111/opo.12615">10-25%</a>. Standard (clear) lenses do not filter blue light.</p>
<p>A wide variety of lens products are available. A filter can be added to prescription or non-prescription lenses. They are widely marketed and are becoming <a href="https://onlinelibrary.wiley.com/doi/10.1111/opo.12615">increasingly popular</a>.</p>
<p>There’s often an added cost, which depends on the specific product. So, is the extra expense worth it?</p>
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<p>
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<strong>
Read more:
<a href="https://theconversation.com/how-eye-disorders-may-have-influenced-the-work-of-famous-painters-92830">How eye disorders may have influenced the work of famous painters</a>
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<h2>Blue light is all around us</h2>
<p>Outdoors, sunlight is the main source of blue light. Indoors, light sources – such as light-emitting diodes (LEDs) and the screens of digital devices – emit varying degrees of blue light. </p>
<p>The amount of blue light emitted from artificial light sources is much lower than from the Sun. Nevertheless, artificial light sources are all around us, at home and at work, and we can spend a lot of our time inside.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Blue light-filtering lenses block some blue light from screens from reaching the eye" src="https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/549210/original/file-20230920-16-tsb23b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Screens emit blue light. The lenses are designed to reduce the amount of blue light that reaches the eye.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/blue-light-blocking-ray-filter-lens-2286229107">Shutterstock</a></span>
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</figure>
<p>Our research team at the University of Melbourne, along with collaborators from Monash University and City, University London, sought to see if the best available evidence supports using blue light-filtering glasses, or if they could do you any harm. So we conducted a <a href="https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD013244.pub2/full">systematic review</a> to bring together and evaluate all the relevant studies. </p>
<p>We included all randomised controlled trials (clinical studies designed to test the effects of interventions) that evaluated blue light-filtering lenses in adults. We identified 17 eligible trials from six countries, involving a total of 619 adults.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/does-my-treatment-work-how-major-medical-reviews-can-be-gold-standard-evidence-yet-flawed-205014">Does my treatment work? How major medical reviews can be 'gold standard' evidence, yet flawed</a>
</strong>
</em>
</p>
<hr>
<h2>Do they reduce eye strain?</h2>
<p>We found no benefit of using blue light-filtering lenses, over standard (clear) lenses, to reduce eye strain with computer use. </p>
<p>This conclusion was based on consistent findings from three studies that evaluated effects on eye strain over time periods ranging from two hours to five days.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/screentime-can-make-you-feel-sick-here-are-ways-to-manage-cybersickness-163851">Screentime can make you feel sick – here are ways to manage cybersickness</a>
</strong>
</em>
</p>
<hr>
<h2>Do they help you sleep?</h2>
<p>Possible effects on sleep were uncertain. Six studies evaluated whether wearing blue-light filtering lenses before bedtime could improve sleep quality, and the findings were mixed. </p>
<p>These studies involved people with a diverse range of medical conditions, including insomnia and bipolar disorder. Healthy adults were not included in the studies. So we do not yet know whether these lenses affect sleep quality in the general population.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/booting-up-or-powering-down-how-e-readers-affect-your-sleep-36145">Booting up or powering down: how e-readers affect your sleep</a>
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</em>
</p>
<hr>
<h2>Do they boost your eye health?</h2>
<p>We did not find any clinical evidence to support using blue-light filtering lenses to protect the macula (the region of the retina that controls high-detailed, central vision). </p>
<p>None of the studies evaluated this.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/macular-diseases-cause-blindness-and-treatment-costs-millions-here-is-how-to-look-after-yours-196796">Macular diseases cause blindness and treatment costs millions. Here is how to look after yours</a>
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</em>
</p>
<hr>
<h2>Could they do harm? How about causing headaches?</h2>
<p>We could not draw clear conclusions on whether there might be harms from wearing blue light-filtering lenses, compared with standard (non blue-light filtering) lenses. </p>
<p>Some studies described how study participants had headaches, lowered mood and discomfort from wearing the glasses. However, people using glasses with standard lenses reported similar effects.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-what-causes-headaches-42254">Health Check: what causes headaches?</a>
</strong>
</em>
</p>
<hr>
<h2>What about other benefits or harms?</h2>
<p>There are some important general considerations when interpreting our findings. </p>
<p>First, most of the studies were for a relatively short period of time, which limited our ability to consider longer-term effects on vision, sleep quality and eye health. </p>
<p>Second, the review evaluated effects in adults. We don’t yet know if the effects are different for children.</p>
<p>Finally, we could not draw conclusions about the possible effects of blue light-filtering lenses on many vision and eye health measures, including colour vision, as the studies did not evaluate these.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-people-colour-blind-107599">Curious Kids: why are people colour blind?</a>
</strong>
</em>
</p>
<hr>
<h2>In a nutshell</h2>
<p>Overall, based on relatively limited published clinical data, our review does not support using blue-light filtering lenses to reduce eye strain with digital device use. It is unclear whether these lenses affect vision quality or sleep, and no conclusions can be drawn about any potential effects on the health of the retina. </p>
<p>High-quality research is needed to answer these questions, as well as whether the effectiveness and safety of these lenses varies in people of different ages and health status.</p>
<p>If you have eye strain, or other eye or vision concerns, discuss this with your optometrist. They can perform a thorough examination of your eye health and vision, and discuss any relevant treatment options.</p><img src="https://counter.theconversation.com/content/213145/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>In the past three years, Laura Downie's research laboratory at the University of Melbourne has received funding from Alcon Laboratories, Azura Ophthalmics, CooperVision and Novartis for clinical research studies unrelated to this article. She is affiliated with the Tear Film and Ocular Surface Society, as a global ambassador.</span></em></p>They’re heavily promoted. Your optometrist may even prescribe them. But when we looked at the evidence, this is what we found.Laura Downie, Associate Professor in Optometry and Vision Sciences, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2124202023-09-04T17:37:53Z2023-09-04T17:37:53ZDogs don’t see life through rose-coloured glasses, nor in black and white<p>For a few months now, I’ve been treating six-year-old Samuel, who has the beginnings of myopia. He’s very quick for his age and often asks me questions about tests I give him, and about what I see inside his eyes. </p>
<p>But the last question surprised me. </p>
<p>Samuel knows that some people, like his father, don’t see colours well. But what about his little poodle, Scotch, he asked?</p>
<p>I’m not a veterinarian and don’t want to intrude on their domain of expertise. However, as an optometrist, I can offer some insights that might help answer Samuel’s question. </p>
<h2>Cones and rods</h2>
<p>Ambient light is composed of <a href="https://www.britannica.com/science/photon">particles (photons)</a>, which line up in rays. Light rays travel and strike objects. Some rays are absorbed, while others are reflected, depending on the characteristics of their surfaces and the composition of their materials. The wavelengths of the reflected rays determine the colour of the object as it is perceived by the eye. </p>
<p>Like everything about human vision, colour perception is complex. The retina, the sensitive part that lines the back of the eye, has two types of photon receptors: cones and rods. The cones, in the centre of the retina (fovea), perceive bright light and are <a href="https://askabiologist.asu.edu/rods-and-cones">responsible for colour perception</a>.</p>
<p>There are three types of cones. Each type contains a specific photo-pigment called opsin, which defines its nature. The opsin is produced under the influence of specific genes. The shortest opsin (“Cone S” for <em>short</em>) reacts mainly to blue light (420 nm). The longer one (“Cone L”) is more sensitive to orange-red light (560 nm) and the one in between (“Cone M” for <em>middle</em>) <a href="https://opentextbc.ca/biology/chapter/17-5-vision/">is activated in the presence of green (530 nm)</a>.</p>
<p>However, each cone reacts to each of the rays entering the eye. For example, a red ball will produce a weak response from the S cone (3/10), a slightly stronger response from the M cone (5/10) and a <a href="https://opentextbc.ca/biology/chapter/17-5-vision/">strong response from the L cone</a> (8/10). </p>
<p>The brain combines the signals emitted by each of these cones to form the colour it perceives. So, in the previous example, the perceived colour would be coded 3-5-8, corresponding to what we know as red. A pink colour might have the code 4-6-6, and blue, 8-6-3. Each combination of the 3-cone signals is unique, which allows us to appreciate different hues in all their variations. </p>
<p>That is, as long as the genetic code is intact. </p>
<p>The genes associated with colour vision can be mutated or defective, in which case the person will be partially or completely impaired. The best known of these anomalies is colour blindness (red-green deficiency or daltonism).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="perception of a plant according to a colour-blind person" src="https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=331&fit=crop&dpr=1 600w, https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=331&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=331&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=415&fit=crop&dpr=1 754w, https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=415&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/544341/original/file-20230823-249-j6j8jf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=415&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Colour blindness is associated with difficulty in perceiving red and green.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<h2>And what about animals?</h2>
<p>Colour vision, in humans as in animals, <a href="https://www.discoverwildlife.com/animal-facts/animal-vision-how-do-animals-see/">has developed throughout evolution</a> and results from the needs of each species according to their environment, the prey they hunt and the threats they need to avoid.</p>
<p>For example, birds have a fourth opsin that allows them to see ultraviolet (UV) light. Humans cannot perceive this light because our crystalline (internal) lens <a href="https://www.nwf.org/Magazines/National-Wildlife/2012/AugSept/Animals/Bird-Vision">filters UV rays</a>. UV rays influence birds’ behavioural decisions, including foraging and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0065345408601059#:%7E:text=Publisher%20%20Summary,light%2C%20depending%20on%20the%20species.">their choice of a mate</a>.</p>
<p>So the colour vision of birds is more complex, with the result that the pigeon, which can perceive a myriad of colours, wins the <a href="https://nuscimagazine.com/the-world-through-the-eyes-of-a-pigeon/#:%7E:text=Though%20this%20range%20of%20vision,is%20one%20of%20these%20animal">award for best color vision among all species</a>.</p>
<p>Insects also perceive UV light. This function is essential for them to spot pollen, although their colour vision is very poor. Their eyes are made up of multiple lenses (ommatidia) that perceive <a href="https://www.mpg.de/14337047/how-flies-see-the-world">more movement than colour</a>. That’s much more practical while in fast flight.</p>
<p>Most forest-dwelling mammals have only two opsins. That’s because they lost the one associated with orange-red over the course of evolution. This explains why, unlike humans, these animals don’t perceive the orange bibs of hunters. </p>
<p>Snakes, on the other hand, are more sensitive to red and infrared light, thanks to their infrared receptors. This is an advantage when it comes to spotting prey, as <a href="https://phys.org/news/2006-08-snakes-vision-enables-accurate-prey.html">they can distinguish their heat even at night</a>. </p>
<p>Unsurprisingly, it’s the monkey that’s closest to the human, with its three opsins. It is said to be trichromatic. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="close-up of a black dog's eyes" src="https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/544344/original/file-20230823-19-pd8rjz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Dogs only perceive yellow-green and violet-blue. Colours are perceived as paler, like pastels.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<h2>Back to Scotch</h2>
<p>The vision of dogs — such as our friend Scotch — is <a href="https://ophtalmoveterinaire.com/maladies_oculaires/vision-comment-voit-mon-chien/#:%7E:text=For%20r%C3%A9sumer%2C%20the%20vision%20of,for%20his%20life%20of%20dog.">quite different</a>. </p>
<p>Unlike humans, dogs’ eyes are located on the side of the skull. As a result, dogs have a wider field of vision (250 to 280 degrees), but less simultaneous vision. </p>
<p>So Scotch’s vision of movement is well developed throughout his visual field. But his central vision is actually six times weaker than ours. This is equivalent to the vision of a very myopic person not wearing glasses. Why? Because the dog’s retina contains no fovea, and therefore fewer cones. </p>
<p>But while dogs eyes have fewer cones, they have more rods. And as an added bonus, they have an extra layer of the retina, called the tapetum lucidum — or carpet. When combined, these ingredients mean dogs see better in dim light and at night. This layer receives light and reflects it back onto the retina for a second exposure. This explains why your dog’s eyes seem to glow at night.</p>
<p>When it comes to colours, dogs are dichromats. They perceive only yellow-green and violet-blue. Colours are perceived paler, like pastels. And some colours don’t contrast: that’s why a red ball on green grass will appear to them as pale yellow on a grey background, with little contrast.</p>
<p>So it’s possible, depending on the colour of the ball, that Scotch will not see it, and as a result, will gaze up at Samuel with a lost look. As for the infrared, he perceives heat through his nose, not through his eyes.</p>
<p>Cats are also dichromats. Their vision is therefore similar to that of dogs, but their colour palette is different — more oriented towards violet and green. Having no perception of red-green, they are essentially colour-blind. They are also very short-sighted. Their clear vision is limited to a few meters in front of them.</p>
<p>Throughout cats’ evolution, other senses came to compensate for this. Among other things, although they only perceive certain contrasts, they are <a href="https://www.wired.com/2013/10/cats-eye-view/">formidable at perceiving movement</a>. Mice move quickly! </p>
<p>Every species adapts to its environment, and humans are no exception. Who knows what our colour vision will be like 500 years from now, after we’ve been exposed to more and more electronic devices and artificial colours? </p>
<p>But that’s a question for Samuel to answer when he’s older.</p><img src="https://counter.theconversation.com/content/212420/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Langis Michaud ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>Your faithful companion sees the world differently than you do, but it’s a mistake to assume dogs only see black, white and shades of grey.Langis Michaud, Professeur Titulaire. École d'optométrie. Expertise en santé oculaire et usage des lentilles cornéennes spécialisées, Université de MontréalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2029522023-04-24T12:24:51Z2023-04-24T12:24:51ZCan rainbows form in a circle? Fun facts on the physics of rainbows<figure><img src="https://images.theconversation.com/files/521644/original/file-20230418-20-88ojk7.jpg?ixlib=rb-1.1.0&rect=0%2C13%2C8959%2C5547&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The higher your vantage point, the more likely you’ll see more of the rainbow’s circle. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/double-rainbow-hangs-in-the-sky-above-buildings-and-the-news-photo/1405823752">Chen Hui/VCG via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>Can rainbows form in a circle? – Henry D., age 7, Cambridge, Massachusetts</strong></p>
</blockquote>
<hr>
<p>The legend goes that there is a pot of gold hidden at the end of every rainbow. But is there really an “end” to a rainbow, and can we ever get to it?</p>
<p>Most us go through life seeing rainbows only as arches of color in the sky, but that’s only half of what is really a circle of color.</p>
<p>Normally, when you look at a rainbow, the Earth’s horizon in front of you hides the bottom half of the circle. But if you are standing on a mountain where you can see both above and below you, and the sun is behind you and it is misty or has just rained, chances are good that you will see more of the rainbow’s circle.</p>
<figure class="align-center ">
<img alt="A rainbow in the mist below a waterfall in Iceland." src="https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&rect=0%2C52%2C5000%2C3270&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521643/original/file-20230418-23-n2b6wd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">How full this rainbow looks depends in part on how high up you’re standing while watching sunlight hit the waterfall’s mist.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/iceland-south-coast-skogarfoss-waterfall-rainbow-news-photo/452271798">Wolfgang Kaehler/LightRocket via Getty Images</a></span>
</figcaption>
</figure>
<p>To see the full circle, however, you will have to be in an airplane, literally above the clouds. Or you could create your own rainbow. I am <a href="https://www.uml.edu/Honors/People/chowdhury-partha.aspx">a physicist</a>, and I’ll explain how to do that in a minute.</p>
<h2>How a rainbow forms</h2>
<p><a href="https://scijinks.gov/rainbow/">Rainbows form</a> when sunlight from behind you hits millions of tiny round water droplets in front of you and bounces back to your eyes.</p>
<p>As a sunbeam hits a droplet at an angle, it bends into the water and separates out into a spectrum of colors. Scientists <a href="https://global.canon/en/technology/s_labo/light/001/02.html">call the bending of light “refracting</a>.” The colors separate because each “color” of light <a href="https://www.metoffice.gov.uk/weather/learn-about/weather/optical-effects/rainbows/colours-of-the-rainbow">travels with a different speed</a> in water, or, for that matter, any transparent material that light can travel through, like glass in a prism.</p>
<p>When the colors hit the back wall of the water droplet, the angle is now too shallow for them to bend out into the air, so they reflect back into the water droplet and return to its entrance wall. From there, the colors can bend out again into air and reach your eye.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/q73VNpFA-0Q?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The United Kingdom’s Meteorology Office explains how light refracts, or bends, in a water droplet or a prism.</span></figcaption>
</figure>
<p>As you look at these droplets, the different colors happen to bunch up at a slightly different angle, and each color forms the <a href="https://atoptics.co.uk/rainbows/primcone.htm">circular rim of a cone</a> with your eye at the tip of the cone. And, voila, you have your own personal rainbow.</p>
<p>The droplets that send the colors to your eye cannot send them to anyone else, so even though everyone near you sees the same rainbow at a distance, each person really sees their own slightly different rainbow. It’s all in the eye of the beholder.</p>
<p>For rainbows to form, the shape of the water droplets has to be very close to a sphere for all of them to bend and reflect the colors in harmony. This happens for very small droplets, such as a fine mist, or just after a rain shower when the air is just moist. As the droplets get larger, gravity distorts their shape and the rainbow vanishes.</p>
<figure class="align-center ">
<img alt="An elephant in water closes its eyes while the photographer captures a rainbow across its trunk and forehead." src="https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521647/original/file-20230418-764-w4nbr5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Even though it looks like this elephant is bathing in a rainbow, the elephant wouldn’t see it in the same way.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/an-elephant-is-pictured-under-a-rainbow-of-water-sprayed-to-news-photo/1242012110">Mads Claus Rasmussen / Ritzau Scanpix / AFP</a></span>
</figcaption>
</figure>
<p>A rainbow is not physically present where it appears to be, similar to your image in a mirror. So, I’m sorry to say that you can never actually reach your rainbow. And, alas, nobody can ever find that pot of gold.</p>
<p>But you can <a href="https://www.youtube.com/watch?v=dIdE-pqYqbs">create your own rainbow</a>. </p>
<h2>How to create and see a circular rainbow</h2>
<p>One experiment you can try in summer is to turn on a sprinkler hose using the “mist” setting. Remember to have the sun behind you. If you create a fine mist screen in front of you and look at your shadow, you might see a rainbow. </p>
<figure class="align-center ">
<img alt="A young boy plays in a fountain, with a rainbow overhead." src="https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=497&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=497&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521649/original/file-20230418-20-u1rnce.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=497&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">It might take some work, but you can see your own full-circle rainbows in the mist.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/young-boy-cools-off-under-a-rainbow-in-a-fountain-on-a-warm-news-photo/1266045824">Gary Hershorn/Getty Images</a></span>
</figcaption>
</figure>
<p>It is not difficult to see colors, but to see a full circle, you will need some patience and practice, just like scientists.</p>
<p>So next time you are on an airplane, grab the window seat. If you are flying a little above the cloud cover, keep a lookout for the small shadow of your plane on the clouds. That means the sun is behind you. </p>
<p>The clouds are tiny water droplets, so chances are you may see a small circle of color around the shadow of the airplane. This phenomenon is <a href="https://science.howstuffworks.com/nature/climate-weather/atmospheric/pilots-glory-rainbow-airplane-shadow.htm">nicknamed “pilot’s glory</a>,” because pilots who fly all the time and have a good view from the cockpit have a better chance of seeing it.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An airplane's shadow has a circular rainbow around it as it flies over mountains." src="https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521423/original/file-20230417-28-hkye8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The circular rainbow you see around an airplane’s shadow is called ‘pilot’s glory.’</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/imatty35/6708114761/">Matthew Straubmuller/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>And if you really can’t wait to see what it looks like, there’s <a href="https://education.nationalgeographic.org/resource/rainbow/">always the internet</a>.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/202952/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Partha Chowdhury does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Each rainbow is personal – the rainbow you see isn’t exactly the same rainbow the next person sees. It’s all in the eye of the beholder.Partha Chowdhury, Professor of Physics, UMass LowellLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1969202022-12-21T13:42:42Z2022-12-21T13:42:42ZReindeer eyes change color, putting Rudolph’s red nose in the shade – new research podcast<figure><img src="https://images.theconversation.com/files/502245/original/file-20221220-22-ecence.jpg?ixlib=rb-1.1.0&rect=562%2C1059%2C2994%2C1934&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Reindeer have adapted to the dim, blue light of the Arctic winter.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Reindeer_in_Winter_-_geograph.org.uk_-_3371243.jpg#/media/File:Reindeer_in_Winter_-_geograph.org.uk_-_3371243.jpg">Alice/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Reindeer noses may not glow red, but these creatures of cold climes have evolved the ability to change the color of their eyes to help them thrive in dark, northern winters. In this Discovery episode, we speak with <a href="https://scholar.google.com/citations?user=UYlObKkAAAAJ&hl=en&oi=ao">Glen Jeffery</a>, a professor of neuroscience at the Institute of Opthamology at UCL (University College London) in the U.K. about what makes reindeer eyes truly unique in the animal kingdom. </p>
<iframe src="https://embed.acast.com/60087127b9687759d637bade/63a1af7253df78001130274d" frameborder="0" width="100%" height="190px"></iframe>
<p><iframe id="tc-infographic-561" class="tc-infographic" height="100" src="https://cdn.theconversation.com/infographics/561/4fbbd099d631750693d02bac632430b71b37cd5f/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Most people have seen the gold, glowing eyes of a cat, a raccoon or some other nocturnal animal staring back at them during a nighttime drive. The part of the eye that produces that golden reflection, as Jeffery explains, “is a mirror that lots of animals have called the tapetum lucidum.” A taptetum helps animals see better in the dark by bouncing light from the back of the eye through the retina a second time. In most mammals, the tapetum is a “standard golden,” as Jeffery describes the color, and that color doesn’t change.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/502246/original/file-20221220-12-k4w2js.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of a raccoon with glowing, gold eyes." src="https://images.theconversation.com/files/502246/original/file-20221220-12-k4w2js.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/502246/original/file-20221220-12-k4w2js.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=514&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502246/original/file-20221220-12-k4w2js.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=514&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502246/original/file-20221220-12-k4w2js.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=514&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502246/original/file-20221220-12-k4w2js.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=645&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502246/original/file-20221220-12-k4w2js.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=645&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502246/original/file-20221220-12-k4w2js.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=645&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many animals’ eyes shine in the darkness because of a reflective layer called the tapetum lucidum that is usually gold.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Raccoon_red_eye.JPG#/media/File:Raccoon_red_eye.JPG">Bowlhover/Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>One day, Jeffery received a box in the mail out of the blue. It contained two jars filled with reindeer eyes from a slaughterhouse in Norway. One jar was labeled summer and one was labeled winter.</p>
<p>“I opened up the summer ones first and I thought, ‘I’m wasting my time here,’” says Jeffery. He saw golden eyes, just what he expected.</p>
<p>“But then we opened up the other eyes, and that was when there was a shock, because the winter eyes were blue,” he said. “I’d never seen anything like that in my life.”</p>
<p>Jeffery and his colleagues spent years studying the biology of reindeer eyes and the environment they are made for – the dim, blue-hued months of the Arctic winter. What they discovered is a marvelous bit of evolution that has given reindeer some of the most interesting eyes on Earth. Listen to this Discovery episode of the Conversation to hear about how Jeffery and his colleagues study reindeer eyes, why winter eyes are such a unique color and how light pollution can alter this finely tuned adaptation.</p>
<hr>
<p>This episode was written and produced by Katie Flood with Gemma Ware and hosted by Dan Merino. Eloise Stevens does our sound design, and our theme music is by Neeta Sarl.</p>
<p>You can find us on Twitter <a href="https://twitter.com/TC_Audio">@TC_Audio</a>, on Instagram at <a href="https://www.instagram.com/theconversationdotcom/">theconversationdotcom</a> or <a href="mailto:podcast@theconversation.com">via email</a>. You can also sign up to The Conversation’s <a href="https://theconversation.com/newsletter">free daily email here</a>. A transcript of this episode is <a href="https://cdn.theconversation.com/static_files/files/2795/Discovery_Ep3_Reindeer_Eyes_Transcript.pdf?1694453126">now available</a>.</p>
<p>Listen to “The Conversation Weekly” via any of the apps listed above, download it directly via our <a href="https://feeds.acast.com/public/shows/60087127b9687759d637bade">RSS feed</a> or find out <a href="https://theconversation.com/how-to-listen-to-the-conversations-podcasts-154131">how else to listen here</a>.</p><img src="https://counter.theconversation.com/content/196920/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Glen Jeffery receives funding from the Biotechnology and Biological Sciences Research Council of the UK.</span></em></p>In winter, light in the northern latitudes is dim and very blue compared to summer light. Reindeer eyes have evolved to be better suited at seeing in this unique environment.Daniel Merino, Associate Science Editor & Co-Host of The Conversation Weekly Podcast, The ConversationLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1931922022-10-25T20:22:51Z2022-10-25T20:22:51ZDevelopment of vision in early childhood: No screens before age two<figure><img src="https://images.theconversation.com/files/491691/original/file-20221025-22-wx4aqi.jpg?ixlib=rb-1.1.0&rect=14%2C7%2C979%2C655&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Electronic devices are not, in and of themselves, a source of visual problems. Using these devices inappropriately can interfere with the natural development of the eye, as well as reading and learning skills. </span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Things are busy on a rainy Saturday afternoon when I make a trip to the mall to finalize some back-to-school shopping. I pass by a lot of people, including several parents with young children under two years old, in strollers, and am struck by the fact that all of the children have a tablet or phone in their hands. Has technology become the ultimate tool for keeping children calm?</p>
<p>As an optometrist and eye health expert, this observation saddens me every time I see it, since I know all the harmful effects such exposure to electronic tools can have on children.</p>
<p>These effects are all the more critical during the first years of life, both on the <a href="https://pubmed.ncbi.nlm.nih.gov/34625399/">visual level</a> and on the <a href="https://pubmed.ncbi.nlm.nih.gov/36190219/">cognitive and social development of children</a>.</p>
<h2>Visual development of children</h2>
<p>The human eye develops <a href="https://www.nationwidechildrens.org/family-resources-education/health-wellness-and-safety-resources/helping-hands/infant-vision-birth-to-one-year">through stimulation</a>. The quality of the optical stimulus influences the growth of the eyeball via a complex and balanced mechanism. At birth, the eye is hyperopic, that is to say, its power is not perfectly adjusted to its size. A child sees at short distances and is barely able to distinguish a shadow when grandpa comes to the bedroom door.</p>
<p>In the first few weeks, the eye grows, the retina matures and a balance is established between the growth of the eyeball and the power of the inner lens. At six months of age, each of the toddler’s two eyes has the vision of an adult eye. From this moment on, the eyes will develop their coordination, in order to generate vision in three dimensions. It’s also starting at the age of six months that the communication between the eyes develops in the visual brain as well.</p>
<p>Billions of neurological connections will have to be made during the <a href="https://opto.umontreal.ca/clinique/pdf/EFFETS%20DES%20ECRANS%20SUR%20LE%20D%C3%89VELOPPEMENT%20VISUEL%20DES%20ENFANTS.pdf">first eight years of life</a>. This maturation time is long, but necessary, considering that <a href="https://www.sciencedirect.com/science/article/pii/S0149763413001917">more than a third of the brain’s neurons are dedicated to vision</a>.</p>
<h2>A question of distance</h2>
<p>Electronic devices are not, in themselves, a source of visual problems. Rather, the inappropriate use of these devices can interfere with the natural development of the eye, as well as reading and learning skills.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/489407/original/file-20221012-17-g43eu3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two small children with glasses sitting on white chairs : a boy with a tablet computer, a girl with a cell phone" src="https://images.theconversation.com/files/489407/original/file-20221012-17-g43eu3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/489407/original/file-20221012-17-g43eu3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/489407/original/file-20221012-17-g43eu3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/489407/original/file-20221012-17-g43eu3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/489407/original/file-20221012-17-g43eu3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/489407/original/file-20221012-17-g43eu3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/489407/original/file-20221012-17-g43eu3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">For normal visual development, it is recommended that exposure to electronic devices be avoided between the ages of zero and two years.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>The first thing to consider is viewing distance. The eye is designed to look at a near distance that is about equal to the length of the forearm (distance from the elbow to the fingertips of the hand). That means about <a href="https://www.sciencedirect.com/science/article/pii/S0042698913000795">30 cm for a young child, and 40 cm for an adult</a>. However, tablets and phones are held on average 20-30 cm from the eye, and this distance <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/cxo.12453">becomes shorter with prolonged exposure</a>. The visual effort required to maintain a clear image at this distance is therefore doubled.</p>
<p>A distance that is too short influences the quality of the retinal image (and therefore visual development) and causes <a href="https://books.google.ca/books?hl=fr&lr=&id=jGGROHBFYt8C">excessive eye fatigue</a>. It is also important to understand that when eyes must accommodate short distances, they automatically converge towards the nose in order to focus at the normal reading distance. Too much effort spent accommodating the short distance is therefore accompanied by a greater than normal convergence. As the eye cannot maintain this prolonged effort over a long period of time, it will relax its effort and the perceived image will become blurred for a while, a sensory penalty that we want to avoid. After a period of rest, the eye will resume its effort, and this alternation between the clearness and the blur will continue as long as attention to the close image is required. So, ideally, the tablet or phone should always be kept at the distance of the forearm.</p>
<h2>Constant stimulation is not recommended</h2>
<p>The use of electronic tools, with games or videos, requires a constant attention span, without breaks. This is the second factor to consider. When a child draws in a notebook or reads a paper book, he or she will instinctively stop at some point, look elsewhere, far away, and become interested in something else around them. These pauses and breaks are beneficial <a href="https://www.aoa.org/healthy-eyes/eye-and-vision-conditions/computer-vision-syndrome?sso=y">for the visual system to recover from its effort</a>. Focusing on targets at a distance is also beneficial to the child’s visual development. With electronic tablets, it is not uncommon to see children doing sessions of more than two to three hours continuously, without looking up from the screen.</p>
<p>The visual apparatus of children from zero to two years old is simply not sufficiently developed and robust to undergo such stress from constant stimulation in front of the screen. In particular, the structural elements of the sclera (the deep layer of the eye), which give the eye rigidity and determine its size, develop between zero and two years of age and then stabilize. The visual stimulus at these ages can interfere and therefore <a href="https://www.researchgate.net/publication/335108098_Scleral_structure_and_biomechanics">influence the development of visual defects and pathology in later life</a>.</p>
<p>It is also important to note that the screen can emit blue light. Children’s eyes do not filter these rays like those of an adult. This means that children are exposed to more blue light, which may stimulate nearsightedness and disrupt the secretion of melatonin, <a href="https://www.myopiainstitute.com/eye-care/how-blue-light-affects-your-vision-and-overall-health/">which regulates our biological clock</a>. This can disrupt the naps necessary for children of this age, as well as sleep during the night. Sleep loss can also lead to myopia.</p>
<h2>Let’s learn about electronics</h2>
<p>For normal visual development, it is therefore recommended to <a href="https://publications.aap.org/pediatrics/article/128/5/1040/30928/Media-Use-by-Children-Younger-Than-2-Years?_ga=2.208746386.1459529850.1665228699-655911314.1665228699?autologincheck=redirected?nfToken=00000000-0000-0000-0000-000000000000">avoid all exposure to electronic devices between the ages of zero and two</a>. The exception would be occasional video conversations, under the supervision of a parent, to say hello to a grandparent who lives far away, for a few minutes.</p>
<p>From the age of two years on, an hour of exposure per day can be considered, especially to consult educational sites, always accompanied by a parent or an educator.</p>
<p>When the visual system is mature, around the age of six to eight, exposure can be increased gradually, without exceeding two to three hours per day, with 10-minute breaks every hour. Electronic device use should be avoided during meals, family activities, and at least one hour before sleep.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/489410/original/file-20221012-24-ip7l62.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Young mother holding her cute, crying baby daughter, looking at a tablet during a virtual video call business or family meeting at a distance" src="https://images.theconversation.com/files/489410/original/file-20221012-24-ip7l62.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/489410/original/file-20221012-24-ip7l62.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/489410/original/file-20221012-24-ip7l62.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/489410/original/file-20221012-24-ip7l62.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/489410/original/file-20221012-24-ip7l62.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/489410/original/file-20221012-24-ip7l62.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/489410/original/file-20221012-24-ip7l62.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Rare video conversations, with parental supervision, to wave to a grandparent from a distance, for a few minutes, can be considered.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<h2>Let’s play outside!</h2>
<p>The best advice for successful visual development is to encourage exposure to outdoor light for <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6678505/#:%7E:text=Each%20additional%20hour%20of%20daily,by%2013%25%20%5B23%5D.">at least one hour per day, ideally two hours</a>. We are talking about playing, walking, and activities that are done outside. The amount of light is then much greater than indoors, which would stimulate the production of dopamine, a chemical mediator essential to regulating the growth of the eye. This is the most effective way to prevent the onset of myopia in children.</p>
<p>It is also important to make sure that a child’s visual system is normal and developing naturally. Therefore, the first examination by an optometrist should be done at six months of age (to validate that the eye has normal optics and that there are no congenital defects), and then at three years of age to evaluate eye coordination. If everything is normal, the next examination will take place at five years of age, and annually thereafter, <a href="http://nada.ca/wp-content/uploads/2018/09/BK-ChildrenAndTheirVision-2018-EN.pdf">considering that vision can change rapidly</a>.</p>
<p>In the case of an abnormality, the earlier we intervene in the process, the easier it is to restore normal oculo-visual function, either by exercise or by optical means.</p>
<p>By following these recommendations for visual hygiene, we will protect children’s visual system and ensure their normal development.</p>
<p>And let’s not forget that the most beautiful screen in the world is nature! We should offer it to our children more often.</p><img src="https://counter.theconversation.com/content/193192/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Langis Michaud ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>The impact of using electronic devices is critical during the first years of life, both visually and on the cognitive and social development of the child.Langis Michaud, Professeur Titulaire. École d'optométrie. Expertise en santé oculaire et usage des lentilles cornéennes spécialisées, Université de MontréalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1843722022-07-25T12:08:38Z2022-07-25T12:08:38ZWhy do hammerhead sharks have hammer-shaped heads?<figure><img src="https://images.theconversation.com/files/472633/original/file-20220705-26-hsvjms.jpg?ixlib=rb-1.1.0&rect=8%2C0%2C5882%2C3895&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A great hammerhead shark's two eyes can be 3 feet apart on opposite sides of its skull.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/underwater-portrait-of-hammerhead-shark-royalty-free-image/723496437">Ken Kiefer 2/Image Source via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>Why do hammerhead sharks have hammer-shaped heads? – Landon, age 10</strong></p>
</blockquote>
<hr>
<p>Hammerhead sharks are the strange-looking ones. They look like someone grabbed their skull by the eye sockets and stretched their heads out sideways, while the rest of their bodies look like those of a normal shark. </p>
<p>You might wonder – what are the advantages of having a hammer-shaped head? And how did hammerhead sharks get that way in the first place? </p>
<p>I’m a <a href="https://scholar.google.com/citations?hl=en&user=FKrC4FYAAAAJ">scientist who has been studying sharks</a> for almost 30 years. The answers to some of these questions have surprised even me.</p>
<h2>Benefits of the hammer</h2>
<p>Scientists think sharks with hammer-shaped heads have three main advantages.</p>
<p>The first has to do with eyesight. If your eyes were pointing in two opposite directions, say, by your ears, it would give you <a href="https://www.nationalgeographic.com/science/article/widely-set-eyes-give-hammerhead-sharks-exceptional-binocular-vision">a much wider field of vision</a>. Each eye would see a different part of the world, so you’d have a better sense of what was around you. But it would be hard to tell how far away things are. </p>
<p>To make up for that trade-off, hammerhead sharks have special sense organs, <a href="https://www.world-of-sharks.com/shark-senses.html">called ampullae of Lorenzini</a>, scattered on the underside of their hammer. These porelike organs can detect electricity. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/472628/original/file-20220705-24-xkf1t2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Closeup of the underside of a great hammerhead shark. Its multiple sensory pores look like black dots." src="https://images.theconversation.com/files/472628/original/file-20220705-24-xkf1t2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472628/original/file-20220705-24-xkf1t2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472628/original/file-20220705-24-xkf1t2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472628/original/file-20220705-24-xkf1t2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472628/original/file-20220705-24-xkf1t2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472628/original/file-20220705-24-xkf1t2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472628/original/file-20220705-24-xkf1t2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">If you look closely at this great hammerhead shark (<em>S. mokarran</em>) you can see the sensory pores on the underside of its hammer.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/close-up-of-great-hammerhead-shark-swimming-close-to-the-news-photo/1297372757">Alexis Rosenfeld/Getty Images News via Getty Images</a></span>
</figcaption>
</figure>
<p>The pores basically act like a metal detector, sensing and locating prey buried under sand on the ocean floor. Regular sharks have these sensory organs too, but hammerheads have more. The farther apart these sensory organs are on a hammerhead’s stretched-out head, the more accurate they are at pinpointing the location of food. </p>
<p>And finally, scientists think hammers help sharks make <a href="https://www.nytimes.com/2020/09/20/science/hammerhead-sharks-cephalofoil.html">quicker turns while swimming.</a> If you’ve ever walked in gusty wind with an umbrella or flown on an airplane, you know how powerful large surfaces can be in motion. If you’re a hammerhead shark, and your intended dinner swims by quickly, you can turn more rapidly to catch it than other fish can. </p>
<h2>The hammerhead family tree</h2>
<p>It would be nice if scientists like me could look at fossils and trace the development of hammerhead sharks over time. Unfortunately, <a href="https://www.floridamuseum.ufl.edu/discover-fish/sharks/fossil/shark-teeth/">fossils of hammerhead sharks are almost entirely of their teeth</a>. That’s because the bodies of sharks do not have bones. Instead <a href="https://theconversation.com/why-do-humans-have-bones-instead-of-cartilage-like-sharks-170526">they’re made of cartilage</a>, which is what your ears and nose are made of. Cartilage breaks down much more quickly than teeth or bones do, so it rarely gets fossilized. And tooth fossils don’t tell us anything about the evolution of hammerhead skulls. </p>
<p>Nine different kinds of hammerhead sharks swim in the oceans today. They vary both in size and in the shapes of their heads. Some have very wide heads relative to their bodies. These include the winghead shark (<em>E. blochii</em>), the great hammerhead (<em>S. mokarran</em>), the smooth hammerhead (<em>S. zygaena</em>), the scalloped hammerhead (<em>S. lewini</em>) and the Carolina hammerhead (<em>S. gilberti</em>). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/472643/original/file-20220705-4524-x5u50p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Hammerhead shark with a rounded, smaller hammerhead." src="https://images.theconversation.com/files/472643/original/file-20220705-4524-x5u50p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472643/original/file-20220705-4524-x5u50p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=306&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472643/original/file-20220705-4524-x5u50p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=306&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472643/original/file-20220705-4524-x5u50p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=306&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472643/original/file-20220705-4524-x5u50p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=384&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472643/original/file-20220705-4524-x5u50p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=384&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472643/original/file-20220705-4524-x5u50p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=384&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The narrowest hammer belongs to the bonnethead shark (<em>S. tiburo</em>).</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Bonnethead#/media/File:Sphyrna_tiburo_SI.jpg">D. Ross Robertson/Smithsonian Tropical Research Institute</a></span>
</figcaption>
</figure>
<p>Others have smaller hammers relative to their bodies, including the bonnethead (<em>S. tiburo</em>), scoophead shark (<em>S. media</em>), small-eye hammerhead (<em>S. tudes</em>) and scalloped bonnethead (<em>S. corona</em>). </p>
<p>Scientists long assumed the first hammerhead sharks did not have much of a hammer but, over time, some slowly evolved bigger hammers. We thought the different hammerhead sharks living today were snapshots from different periods in the <a href="https://theconversation.com/curious-kids-how-do-scientists-know-evolution-is-real-122039">evolutionary process</a> – with the small hammerheads being the oldest species on the family tree and the huge hammerheads being the newest ones on the scene.</p>
<p>Since we don’t have fossils to look at, scientists like me have explored this idea using DNA. <a href="https://kids.britannica.com/kids/article/DNA/390730">DNA is the genetic material found in cells</a> that carries information about how a living thing will look and function. It can also be used to see how living things are related.</p>
<p>We took DNA from eight of the nine hammerhead species and used it to look at the relationships among them. The results were not what we expected at all. The <a href="https://doi.org/10.1016/j.ympev.2010.01.037">older species had the proportionally bigger hammers</a> and the younger species had the smaller hammers.</p>
<h2>Deformities as assets</h2>
<p>When scientists think about evolution, we usually assume that living things change a little bit at a time, slowly fine-tuning themselves to take better advantage of their environment. This <a href="https://education.nationalgeographic.org/resource/natural-selection">process is called natural selection</a>. But that’s not always the way it works, as hammerhead evolution shows.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/472620/original/file-20220705-24-xl7400.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Left diagram shows outlines of hammerhead shapes progressing from small to large. Right diagram starts with a small hammerhead, then jumps to a huge hammer. The hammers get progressivly smaller after that." src="https://images.theconversation.com/files/472620/original/file-20220705-24-xl7400.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472620/original/file-20220705-24-xl7400.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472620/original/file-20220705-24-xl7400.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472620/original/file-20220705-24-xl7400.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472620/original/file-20220705-24-xl7400.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472620/original/file-20220705-24-xl7400.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472620/original/file-20220705-24-xl7400.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">On the left is the expected evolution of hammerheads, assuming a gradual change of head shape. On the right is the observed pattern of evolutionary change based on DNA sequence data.</span>
<span class="attribution"><span class="source">Gavin Naylor</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Sometimes an animal can be born with a genetic defect that turns out to be really useful for its survival. So long as the abnormality is survivable and the animal is able to mate, that trait can be passed down. We think that’s exactly <a href="https://doi.org/10.1016/j.ympev.2010.01.037">what happened with hammerhead sharks</a>. </p>
<p>The hammerhead species that branched off the earliest is the winghead shark (<em>E. blochii</em>), which has one of the widest heads. Over time natural selection has actually shrunk the size of the hammer. It turns out the most recent hammerhead species is the bonnethead shark (<em>S. tiburo</em>), which has the smallest hammer of all.</p>
<hr>
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<p class="fine-print"><em><span>Gavin Naylor works for University of Florida . He receives funding from National Science Foundation</span></em></p>The first hammerhead shark was likely the result of a genetic deformity. A biologist explains how shark DNA reveals hammerheads’ history.Gavin Naylor, Director of Florida Program for Shark Research, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1807622022-05-05T12:43:20Z2022-05-05T12:43:20ZNew eye drops can help aging people see better – an optometrist explains how Vuity treats presbyopia<figure><img src="https://images.theconversation.com/files/461367/original/file-20220504-14-mcdrca.jpg?ixlib=rb-1.1.0&rect=55%2C132%2C7293%2C4759&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Nearly all people start to develop blurry vision once they hit their 40s and 50s.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/senior-woman-having-vision-problems-royalty-free-image/1319027194?adppopup=true">demaerre/iStock via Getty Images</a></span></figcaption></figure><p>When people get into their 40s and beyond, their close-up vision starts to worsen. For many people, cranking up the font size on a phone or maxing out the brightness on a computer is the only way to be able to read some text. </p>
<p>This condition is known as <a href="https://doi.org/10.3390/jcm11051385">presbyopia</a>, and it affects around <a href="https://dx.doi.org/10.2147%2FOPTH.S318065">128 million people</a> in the U.S. and more than a <a href="https://dx.doi.org/10.1097%2FAPO.0000000000000297">billion people worldwide</a>. </p>
<p>In late 2021, the U.S. Food and Drug Administration approved a new eye drop medication to treat presbyopia. As an <a href="https://ophthalmology.pitt.edu/people/robert-bittner-od-faao">optometrist</a>, I was initially skeptical. Prior to the release of these eye drops – <a href="https://news.abbvie.com/news/press-releases/us-food-and-drug-administration-approves-vuity-pilocarpine-hci-ophthalmic-solution-125-first-and-only-eye-drop-to-treat-presbyopia-age-related-blurry-near-vision.htm">called Vuity</a> – people would either need glasses, contacts or eye surgery to alleviate presbyopia. But after learning how these eye drops work, I recognized that for many people, they could offer an easier and safer way to see clearly again. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461319/original/file-20220504-25-sehqkq.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram labelling the human eye." src="https://images.theconversation.com/files/461319/original/file-20220504-25-sehqkq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461319/original/file-20220504-25-sehqkq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=439&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461319/original/file-20220504-25-sehqkq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=439&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461319/original/file-20220504-25-sehqkq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=439&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461319/original/file-20220504-25-sehqkq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=552&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461319/original/file-20220504-25-sehqkq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=552&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461319/original/file-20220504-25-sehqkq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=552&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The pupil and lens are two of the most important parts of the eye involved in focusing on objects.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/eye-human-anatomy-royalty-free-illustration/478855654?adppopup=true">ttsz/iStock via Getty Images</a></span>
</figcaption>
</figure>
<h2>How eyes focus</h2>
<p>Many parts of the human eye interact with incoming light to produce a clear image.</p>
<p>The first thing light hits is the cornea, the clear outer layer that initially bends the light. Then light passes through the iris and pupil, which can shrink or grow to let more or less light into the inside of the eye. It then travels through the lens, which further bends the light and precisely focuses it onto the center of the retina. Finally, the light signal is transferred to the optic nerve at the back of the eye, for the brain to interpret as an image.</p>
<p>To produce a clear image, your eyes need to adjust to how far away an object is. Your eyes take three major steps <a href="https://www.ncbi.nlm.nih.gov/books/NBK542189/">to focus on objects</a> close to your face: your eyes point toward the object you want to look at, your lenses change shape and your pupils constrict. </p>
<p>Once you point your gaze at what you’re interested in, a small muscle in the eye contracts, which changes the shape of the lens to make it thicker. The thicker the lens is, the more the light bends as it passes through. At the same time, your pupils constrict to block some of the incoming light from other objects in the distance. When light bounces off an object and enters your eye, the rays of light at the center are what provide a clear image. Blocking the scattering light by constricting the pupil helps to sharpen the image of close objects.</p>
<p>You can simulate this process using a camera on your cellphone. First, point the camera at something in the distance. Then, move your thumb into the image, holding it about 6 inches away. Your thumb will start off blurry, but as the camera’s lens changes shape, your thumb will come into focus.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461370/original/file-20220504-25-lthi7q.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing how the point of focus moves when a person has presbyopia." src="https://images.theconversation.com/files/461370/original/file-20220504-25-lthi7q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461370/original/file-20220504-25-lthi7q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461370/original/file-20220504-25-lthi7q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461370/original/file-20220504-25-lthi7q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461370/original/file-20220504-25-lthi7q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461370/original/file-20220504-25-lthi7q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461370/original/file-20220504-25-lthi7q.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Presbyopia stiffens the lens in the eye, and when a person can’t bend their lens as easily, they are unable to focus incoming light on the correct part of the retina and images appear blurry.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Presbyopia.png#/media/File:Presbyopia.png">BruceBlaus via WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>What is presbyopia?</h2>
<p>Presbyopia is the inability of the eyes to focus on close objects, which results in blurry images. It <a href="https://doi.org/10.1016/S0042-6989(97)00102-8">begins when people are in their 40s</a> and progresses until it plateaus around the age of 60.</p>
<p>Researchers know that <a href="https://doi.org/10.1016/S0042-6989(97)00102-8">age is the main driver of presbyopia</a>, but there is an ongoing debate over the <a href="https://doi.org/10.1016/j.preteyeres.2004.11.001">mechanical causes at its root</a>.</p>
<p>One theory suggests that as lenses age, they <a href="https://doi.org/10.3928/1081597X-20170621-05">get heavier</a> and can’t change shape as easily. Another theory suggests that the <a href="https://doi.org/10.3928/1081597X-20170621-05">muscle that pull on the lens become weaker</a> with age. I suspect presbyopia likely occurs due to a combination of both. Regardless of the cause, the result is that when looking at close objects, people’s eyes are no longer able to bend incoming light enough to direct it at the center of the retina. Instead, the light is focused at a place behind the retina, resulting in blurry vision. </p>
<h2>How the eye drops work</h2>
<p>Remember, there are two major things an eye does to focus on close objects: the lens changes shape and the pupil gets smaller. Since presbyopia limits the ability of the lens to change shape, these eye drops <a href="https://doi.org/10.1007/s40123-022-00482-2">compensate by causing the pupil to get smaller</a>. Constricting the pupil reduces the amount of light scatter. This makes it so that the light entering the eye is better concentrated onto the retina, thus creating a wider range of distances where objects are in focus and allowing people to see both close and far objects clearly.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/461320/original/file-20220504-12-pummws.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing different depths of field." src="https://images.theconversation.com/files/461320/original/file-20220504-12-pummws.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461320/original/file-20220504-12-pummws.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=547&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461320/original/file-20220504-12-pummws.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=547&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461320/original/file-20220504-12-pummws.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=547&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461320/original/file-20220504-12-pummws.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=687&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461320/original/file-20220504-12-pummws.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=687&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461320/original/file-20220504-12-pummws.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=687&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Making the pupil smaller and allowing less light into the eye increases depth of field, making closer objects appear in focus – as seen in diagram a above – compared to a larger pupil and narrower depth of field as seen in diagram b.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Depth-of-field.svg#/media/File:Depth-of-field.svg">MikeRun via WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Once you put the drops in your eyes, it takes about 15 minutes for the active ingredient, pilocarpine, to begin working. Pilocarpine is a medication that was first discovered in the late 1800s, and can <a href="https://www.drugs.com/mtm/pilocarpine-ophthalmic.html">treat conditions such as glaucoma and ocular hypertension</a>. The effect on pupils lasts for about six hours.</p>
<p>Smaller pupils mean that less light gets into the eye. While this isn’t a problem during the day when there is a lot of sun, it can cause difficulty seeing in low-lighting conditions. Aside from these downsides, the most common side effects of the drops are headache and red eyes.</p>
<h2>Presbyopia in the future</h2>
<p>Vuity is currently approved for <a href="https://www.rxabbvie.com/pdf/vuity_pi.pdf">once-daily use</a> in each eye. A bottle will cost around $80, requires a prescription and will last for nearly a month if used daily. For some people, it could be a great alternative or adjunct to glasses or surgery. </p>
<p>While Vuity may be the first FDA-approved eye drops to treat presbyopia, researchers are studying a <a href="https://dx.doi.org/10.1016%2Fj.jcrs.2012.07.028">number of other approaches</a>. Some are developing eye drops that include <a href="https://dx.doi.org/10.1097%2FAPO.0000000000000297">non-steroidal anti-inflammatory drugs</a> to help constrict the pupil – similarly to Vuity. Other teams are studying drops that <a href="https://dx.doi.org/10.1097%2FAPO.0000000000000297">soften and reduce the weight of the lens</a> to promote easier focusing. Finally, some early research has shown that pulsed electrostimulation of eye muscles can help strengthen them and improve people’s ability to bend their lenses.</p>
<p>The future of presbyopia treatment is exciting as researchers work on many potential ways to overcome this universal condition of old age. For now, Vuity – while not a magic cure for everyone with presbyopia – is an innovative option and may be worth asking your eye doctor about.</p>
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<p class="fine-print"><em><span>Robert Bittner does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>As people age, their eyes lose the ability to focus on close objects. A new eye drop treatment called Vuity can improve vision without the need for glasses, contacts or surgery.Robert Bittner, Assistant Professor of Ophthalmology, University of PittsburghLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1805862022-04-19T01:24:06Z2022-04-19T01:24:06ZLonger-acting eye treatment could reduce vision loss for Indigenous Australians<figure><img src="https://images.theconversation.com/files/457284/original/file-20220411-23-z8jc37.jpg?ixlib=rb-1.1.0&rect=36%2C18%2C5907%2C3926&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://image.shutterstock.com/image-photo/woman-looking-refractometer-eye-test-600w-764143345.jpg">Shutterstock</a></span></figcaption></figure><p>Indigenous people in Australia experience <a href="https://healthinfonet.ecu.edu.au/key-resources/publications/?id=35922&title=Review+of+eye+health+among+Aboriginal+and+Torres+Strait+Islander+people">three times more vision loss than non-Indigenous people</a>, creating a concerning <a href="https://mspgh.unimelb.edu.au/__data/assets/pdf_file/0006/1984173/roadmap-summary-september-2015.pdf">gap for vision</a>.</p>
<p>Much of this is due to diabetic macular oedema (DMO). Here, blood vessels in the back of the eye (the retina) are damaged by high blood sugar levels. Over time, this <a href="https://www.mdfoundation.com.au/about-macular-disease/diabetic-eye-disease/about-diabetic-retinopathy/">causes swelling (oedema) of the central part of the retina (the macula)</a>. </p>
<p>Macular oedema blurs the central vision, diminishing the ability to recognise people’s faces, to drive and work, and perform other essential tasks. DMO affects around <a href="https://www.sciencedirect.com/science/article/pii/S0161642016322564">23,000 Indigenous people in Australia</a>, with most of them of working age. Similar trends are reported in other developed states with Indigenous populations, including <a href="https://pubmed.ncbi.nlm.nih.gov/24157988/">New Zealand</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/16043760/">Canada</a> and the <a href="https://pubmed.ncbi.nlm.nih.gov/29924846/">United States</a>.</p>
<p>The good news is DMO is treatable, with medications known as <a href="https://www.mdfoundation.com.au/about-macular-disease/diabetic-eye-disease/treatment-for-diabetic-retinopathy/">anti-VEGF agents</a>. We undertook a world-first <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/ceo.14079">clinical trial</a> to test longer-acting DMO treatment for Indigenous Australians. In doing so, we also learned about undertaking culturally sensitive research on Country. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/how-can-the-new-closing-the-gap-dashboard-highlight-what-indicators-and-targets-are-on-track-163809">How can the new Closing the Gap dashboard highlight what indicators and targets are on track?</a>
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<h2>A longer-lasting treatment</h2>
<p>When injected into the eye by an ophthalmologist (an eye surgeon), anti-VEGF drugs are safe and effective for treating DMO. The injections don’t hurt, since the eye is anaesthetised. The catch is that anti-VEGF agents are relatively short-acting, requiring them to be re-administered as often as every month. </p>
<p>Many Indigenous patients find it impractical, for complex and varied reasons, to attend <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7042588/">ten to 12 eye appointments a year</a>. There is, therefore, a need for an alternative. </p>
<p>Longer-acting medications do exist. One example is a dexamethasone implant (commercially known as <a href="https://www.ozurdex.com/Content/pdf/DME_Patient_Brochure.pdf">Ozurdex(R)</a>), a steroid injected into the eye. The dexamethasone implant only needs to be dosed every three months. </p>
<p>The dexamethasone implant is PBS approved for DMO in Australia but has never been evaluated in an Indigenous population. This is important because a possible side effect of steroid medications is increased pressure in the eye. If left untreated, this can lead to a condition called steroid-induced <a href="https://www.aao.org/eye-health/diseases/what-is-glaucoma">glaucoma</a>. </p>
<p>Glaucoma is thought to occur <a href="https://bjo.bmj.com/content/103/2/191.abstract?casa_token=XV8H0UCusPIAAAAA:CdA9CdW8b4XT2j5xn2NmpQRW2abVqgyftnqBfLl7ssce6jmgyxPQYwt-4_2kEDfOOBgcASlWOEd_">less commonly overall among Indigenous people</a>, suggesting differences in the physiology of eye pressure between Caucasian and Indigenous eyes. Additionally, the incidence of steroid-induced subtype glaucoma has never been studied among Indigenous people. This is particularly important for people in remote locations, since glaucoma is a “silent disease”, requiring regular check ups for detection and treatment. </p>
<p>The <a href="https://www.mja.com.au/journal/2015/203/1/facilitators-and-barriers-implementation-pragmatic-clinical-trial-aboriginal">historical barriers preventing this sort of research</a> include cultural and geographical factors, as well as a lack of endorsement from Indigenous health services and “staff champions”.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/458470/original/file-20220419-22-c414kc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="woman checks eyes of a second woman" src="https://images.theconversation.com/files/458470/original/file-20220419-22-c414kc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/458470/original/file-20220419-22-c414kc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=497&fit=crop&dpr=1 600w, https://images.theconversation.com/files/458470/original/file-20220419-22-c414kc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=497&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/458470/original/file-20220419-22-c414kc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=497&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/458470/original/file-20220419-22-c414kc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=625&fit=crop&dpr=1 754w, https://images.theconversation.com/files/458470/original/file-20220419-22-c414kc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=625&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/458470/original/file-20220419-22-c414kc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=625&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Kerry Woods, from the clan Plangermairreenner of the Ben Lomond people, is an Aboriginal eye health coordinator involved in the study. She said it gave her ‘insight to the treatments available for diabetic eye disease and the monthly injections required to manage this condition […] Working closely with patients I have the opportunity to yarn about the treatments and if they are happier with the new timeframe.’</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Not just what to research, but how</h2>
<p>At the <a href="https://www.lei.org.au/">Lions Eye Institute</a>, we sought to overcome these barriers with the <a href="https://clinicaltrials.gov/ct2/show/NCT04619303">OASIS Study</a> – a world-first clinical trial in ophthalmology to exclusively recruit Indigenous patients. </p>
<p>We framed our study around ten key factors for success including support from all participating Aboriginal Medical Services, free and safe treatment, free transport, appointment reminders, and cultural safety training for all trial staff. Wherever possible, study visits were performed within patients’ usual Aboriginal Medical Service. Study participants could have friends, family and staff members present. This helped communication and a sense of safety and trust.</p>
<p>Over two years, we recruited 38 Indigenous patients and 52 eyes (some patients had DMO in both eyes). Patients were recruited from both Perth and country Western Australia. On enrolment, they were randomly assigned to receive dexamethasone implant or an anti-VEGF agent called <a href="https://www.aao.org/eye-health/drugs/avastin">Avastin</a>. Follow up was performed for check ups and re-treatments. After 12 months, we analysed all our data, to compare the safety and effectiveness of the two drugs.</p>
<p><a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/ceo.14079">The results</a> showed patients who received dexamethasone implant gained four extra letters on a standard eye chart, equivalent to a 6.2% improvement in their vision. Those who received the anti-VEGF agent, meanwhile, lost 5.5 letters on average, representing an 8.9% decline. </p>
<p>Taken together, these results represented a 15% (9.5 letter) visual advantage for patients who received dexamethasone implant. In real world terms, this meant patients met the <a href="https://austroads.com.au/publications/assessing-fitness-to-drive/ap-g56/vision-and-eye-disorders/medical-standards-for-licensing-11">visual requirements for a private driver’s license</a>. Those who received the anti-VEGF agent did not. </p>
<p>This disparity was most pronounced in country towns, where dexamethasone implant had a 37% (24 letter) advantage over the anti-VEGF agent. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/457286/original/file-20220411-13-h1gbu6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map of WA with dot identifiers" src="https://images.theconversation.com/files/457286/original/file-20220411-13-h1gbu6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457286/original/file-20220411-13-h1gbu6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=750&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457286/original/file-20220411-13-h1gbu6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=750&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457286/original/file-20220411-13-h1gbu6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=750&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457286/original/file-20220411-13-h1gbu6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=943&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457286/original/file-20220411-13-h1gbu6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=943&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457286/original/file-20220411-13-h1gbu6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=943&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Trial participants came from all over Western Australia.</span>
<span class="attribution"><span class="license">Author provided</span></span>
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</figure>
<h2>Why it works</h2>
<p>As we suspected, the reason for the dexamethasone implant’s better performance related to its less frequent, hence more pragmatic, dosing regime. </p>
<p>Over 12 months, patients who were meant to receive four dexamethasone implant injections, received an average of 3.3 injections. This meant that, on average, they received 82.5% of their intended treatments.</p>
<p>Anti-VEGF patients, meanwhile, received 7.2 of their scheduled 12 injections. This equated to only 60% of their intended treatments, and reflects the difficulty of attending monthly appointments in the real world. Anti-VEGF patients had more than twice as many injections as dexamethasone implant patients, yet ended up with poorer vision.</p>
<p>Not all the results were positive. One third of patients who received dexamethasone implant developed high pressure in the eye – a recognised side effect of steroid injections. While not painful, this requires treatment with pressure-lowering drops and close follow up, to prevent <a href="https://www.aao.org/eye-health/diseases/what-is-glaucoma">glaucoma</a>. </p>
<p>Secondly, steroid injections speed up <a href="https://www.aao.org/eye-health/diseases/what-are-cataracts">cataract</a> formation (a clouding of the lens in the eye). This requires access to cataract surgery, which is not always simple to arrange in remote locations. Based on these caveats, we developed guidelines for the judicious use of dexamethasone implant among Indigenous patients, <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/ceo.14079">published in March</a>.</p>
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<strong>
Read more:
<a href="https://theconversation.com/a-new-way-to-keep-first-nations-people-with-dementia-connected-to-country-community-family-and-culture-171293">A new way to keep First Nations people with dementia connected to Country, community, family and culture</a>
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<h2>Reducing the burden, closing the vision gap</h2>
<p>While dexamethasone implants are not perfect, we believe the OASIS Study provides hope for reducing vision loss and the “burden of treatment” for Indigenous Australians with diabetes. </p>
<p>The ability to perform culturally safe clinical trials means new treatments may be similarly evaluated in the future, with consideration given to input from patients through <a href="https://findanexpert.unimelb.edu.au/scholarlywork/1415807-building-trust-and-sharing-power-for-co-creation-in-aboriginal-health-research--a-stakeholder-interview-study">community-controlled research</a>.</p>
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Read more:
<a href="https://theconversation.com/racism-is-a-public-health-crisis-but-black-death-tolls-arent-the-answer-176453">Racism is a public health crisis – but Black death tolls aren't the answer</a>
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<img src="https://counter.theconversation.com/content/180586/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>This study was funded by Allergan Australia Pty Ltd which produces the treatment Ozurdex mentioned in this article. None of the authors received personal payment. The funder had no role in study design, data collection, data analysis, data interpretation, or writing of the report. </span></em></p>Our study found a better way to treat eye problems in Indigenous communities – and some key considerations for undertaking culturally safe clinical trials.Hessom Razavi, Associate professor, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1751162022-01-21T13:10:06Z2022-01-21T13:10:06ZShort-sightedness is on the rise in both children and adults – new study<figure><img src="https://images.theconversation.com/files/441959/original/file-20220121-15-1u5hv5t.jpg?ixlib=rb-1.1.0&rect=23%2C0%2C3891%2C2617&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Short-sightedness is increasing worldwide. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/shortsighted-woman-holding-glasses-hand-white-1699397968">chali_studio/ Shutterstock</a></span></figcaption></figure><p>We’ve known for years now that <a href="https://www.nature.com/articles/519276a">rates of short-sightedness</a> (scientifically known as myopia) are rising globally. Some estimates even suggest that <a href="https://www.aaojournal.org/article/s0161-6420(16)00025-7/fulltext">half of the world’s population</a> will be short-sighted by 2050. In the UK and Europe alone, rates of short-sightedness have <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0146332">doubled in the last 50 years</a>. </p>
<p>But we still aren’t completely sure why these rates are rising so significantly – and who might be most at risk. This is what a recent study set out to understand. Looking at data from 107,442 participants aged 40-69, the researchers confirmed that rates of myopia have <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0260993">increased significantly</a> in the UK in all age groups – and showed that education level and ethnicity may also be linked to greater risk.</p>
<p>They found that there was a jump in the number of people with short-sightedness when they compared participants born between 1965-1970 with those born between 1939-1944 – going from 20% of the population having myopia to nearly 30%. They also found that a greater number of people were developing short-sightedness in adulthood. Those who developed short-sightedness in childhood were also shown to become highly short-sighted and at greater risk of developing <a href="https://www.sciencedirect.com/science/article/pii/S1350946212000444?via%3Dihub">serious eye conditions</a> in adulthood.</p>
<p>To get a better picture of whether certain groups were more at risk than others, the researchers compared participants by sex, ethnicity and education level.</p>
<p>While previous studies have found that women are <a href="https://iovs.arvojournals.org/article.aspx?articleid=2775369">more short-sighted on average</a> – particularly at <a href="https://iovs.arvojournals.org/article.aspx?articleid=2776744">younger ages</a> – others have <a href="https://pubmed.ncbi.nlm.nih.gov/10416931/">found no difference</a> between men and women. </p>
<p>This study found women had a 24% increased risk of developing myopia in childhood – but were 12% less likely to develop myopia in adulthood. It’s uncertain why this is – but it might be due to differences in lifestyle or the hormonal changes men and women experience. </p>
<p>Looking then at ethnicity, the researchers found that there was a higher prevalence of myopia in people who were Chinese. In fact, Chinese participants had a 240% greater risk of developing short-sightedness in childhood compared to white participants. Interestingly, all other ethnicities appeared to have a reduced risk of developing myopia in childhood – though this might be due to the fact that UK Biobank data has <a href="https://biobank.ctsu.ox.ac.uk/crystal/field.cgi?id=21000">fewer participants from ethnic minority backgrounds</a>.</p>
<p>These findings relate to what previous studies have shown, with research suggesting there’s a greater prevalence of <a href="https://pubmed.ncbi.nlm.nih.gov/28951126/">myopia in east Asia</a> and in people of <a href="https://pubmed.ncbi.nlm.nih.gov/23672971/">Asian descent</a>. One study looking at young men in Seoul found that almost <a href="https://iovs.arvojournals.org/article.aspx?articleid=2166142">97% of 19-year-olds were myopic</a>. Again, it’s not certain why this group has higher rates of short-sightedness. Some theorise it could be caused by <a href="https://iovs.arvojournals.org/article.aspx?articleid=2727314">lifestyle factors during childhood</a>, such as greater focus on education. </p>
<figure class="align-center ">
<img alt="University student with glasses reads his book." src="https://images.theconversation.com/files/441961/original/file-20220121-27-knp81v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/441961/original/file-20220121-27-knp81v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/441961/original/file-20220121-27-knp81v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/441961/original/file-20220121-27-knp81v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/441961/original/file-20220121-27-knp81v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/441961/original/file-20220121-27-knp81v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/441961/original/file-20220121-27-knp81v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Years in education was also linked to short-sightedness.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/focused-millennial-african-american-student-glasses-1079701271">fizkes/ Shutterstock</a></span>
</figcaption>
</figure>
<p>The researchers also looked at the impact that education had on short-sightedness. They found that the more years spent in education, the greater the risk a person had of developing short-sightedness in both childhood and adulthood. They also showed that the youngest participants (those born between 1965-1970) who had a university education were eight times more likely to develop myopia in childhood compared to those that had no formal education qualifications. Previous studies have also shown that people who spent more years in education are <a href="https://www.bmj.com/content/361/bmj.k2022.long">more likely to develop myopia</a>.</p>
<p>The nuanced relationship between ethnicity and education was also explored. Having no formal educational qualifications was linked with lower risk of becoming short-sighted, as expected. This was most visibly shown in Chinese participants, where having no qualifications did not change their risk of developing myopia. However, Chinese participants that had higher level qualifications (such as a University degree) had the largest risk of myopia across the whole study. </p>
<p>Although it’s clear that education has a large hand in the development of myopia, the direct cause is unknown. Some argue that <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0140419">more time spent reading</a> and <a href="https://pubmed.ncbi.nlm.nih.gov/31943280/">using screens</a> may be to blame. There’s now evidence even suggesting a link between home-schooling during COVID-19 lockdowns and <a href="https://jamanetwork.com/journals/jama/fullarticle/2784348">greater amounts of myopia</a> in <a href="https://jamanetwork.com/journals/jamaophthalmology/fullarticle/2774808">Chinese children</a> – potentially because more time is being spent indoors. </p>
<p>But the significant increase in short-sightedness is concerning for a number of reasons. For a person with myopia, having to wear glasses or contact lenses <a href="https://iovs.arvojournals.org/article.aspx?articleid=2127768">can be costly</a>. More significantly, it also puts them at greater risk of eye diseases – such as <a href="https://journals.lww.com/optvissci/FullText/2019/06000/Myopia_Control__Why_Each_Diopter_Matters.11.aspx">myopic maculopathy</a> and <a href="https://www.sciencedirect.com/science/article/pii/S1350946212000444?via%3Dihub">retinal detachments</a>, which can both permanently affect eyesight. Not only could this seriously impact a person’s way of life, it would also put a greater financial strain on healthcare systems. Short-sightedness in children is even more concerning, as they’re more likely to develop into severe myopia – which is more likely to lead to these eye problems as a result. </p>
<p>While you can’t change genetics – <a href="https://iovs.arvojournals.org/article.aspx?articleid=2727314">which is one of the causes of myopia </a> – there are a number of actions you can take to lower the risk of developing short-sightedness during childhood. Spending time outdoors has continued to demonstrate a protective effect against <a href="https://www.nature.com/articles/s41598-021-85825-y">developing short-sightedness</a>. But for children who may already be shortsighted, <a href="https://bjo.bmj.com/content/early/2021/03/17/bjophthalmol-2020-317664.info">specialised spectacles</a> and <a href="https://iovs.arvojournals.org/article.aspx?articleid=2727315">contact lenses</a> are available that have demonstrated success in reducing myopia progression.</p><img src="https://counter.theconversation.com/content/175116/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The study found 30% of adults born between 1965-1970 were short-sightedness.Neema Ghorbani Mojarrad, Lecturer in Optometry, University of BradfordSophie Coverdale, Optometrist and PhD Researcher, University of BradfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1718262021-11-25T04:21:36Z2021-11-25T04:21:36ZWhat is orthokeratology? And will it help slow the deterioration of my child’s eyesight?<figure><img src="https://images.theconversation.com/files/432109/original/file-20211116-21-1fbmxqn.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C2443%2C1616&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>If you or your child is short-sighted (struggles to see things further away) you might have heard about orthokeratology. </p>
<p>Also known as OK or ortho-k, orthokeratology has been around since the 1960s. However, it has gained interest recently for its ability to slow the progression of myopia (short-sightedness).</p>
<p>Orthokeratology involves wearing a specially-designed rigid contact lens overnight. Like a mold, the lens temporarily reshapes the eye while you sleep by gently changing the profile of the cornea (the eye’s clear, protective outer layer that acts like a powerful lens).</p>
<p>This creates a temporary change; when you wake up, you take the lens off and voilà! You can see.</p>
<p>It takes about a week of going through the cycle for the full effect to be reached but after that – assuming you wear them every night and take them off every morning – you should be able to get through your days without glasses or contact lenses. </p>
<p>And most importantly, there’s good evidence it can help slow the progression of myopia.</p>
<p>Like all treatments, however, orthokeratology has its pros and cons – and its risks need to be well understood before use. </p>
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<strong>
Read more:
<a href="https://theconversation.com/hidden-in-plain-sight-how-the-covid-19-pandemic-is-damaging-childrens-vision-158737">Hidden in plain sight: How the COVID-19 pandemic is damaging children’s vision</a>
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<hr>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/432114/original/file-20211116-25-1tk03qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/432114/original/file-20211116-25-1tk03qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/432114/original/file-20211116-25-1tk03qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/432114/original/file-20211116-25-1tk03qz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/432114/original/file-20211116-25-1tk03qz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/432114/original/file-20211116-25-1tk03qz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/432114/original/file-20211116-25-1tk03qz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/432114/original/file-20211116-25-1tk03qz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The orthokeratology lens temporarily reshapes the eye while you sleep.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>The pros</h2>
<p>Orthokeratology may be an appealing option:</p>
<ul>
<li><p>for people who want an alternative to glasses but find contact lenses either uncomfortable or not suitable (because, for example, they suffer from <a href="https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/dry-eye">dry eye</a>, work in dusty environments or enjoy water sports)</p></li>
<li><p>as an alternative to refractive surgery, also known as laser eye surgery or LASIK. Refractive surgery is permanent but orthokeratology is temporary; if you stop using the lenses, things go back to normal within a week</p></li>
<li><p>for parents of a child who might otherwise be wearing contact lenses at school; ortho-k allows a child to go to school without glasses or contact lenses, which can be lost or come loose during the day.</p></li>
</ul>
<h2>The cons</h2>
<p>The potential downsides include:</p>
<ul>
<li><p>the up-front costs are higher than daily wear contact lenses where the similar overall cost is spread over time</p></li>
<li><p>the effect wears off if you don’t use them every night</p></li>
<li><p>all contact lens use comes with a higher risk of eye infection than if you had no contact lenses at all.</p></li>
</ul>
<p>Some people might think orthokeratology has a higher infection risk than standard soft contact lenses. However, this is not supported by the research evidence. </p>
<p>A <a href="https://onlinelibrary.wiley.com/doi/10.1111/opo.12460">study in Japan</a> compared outcomes after 10 years of wear in children of either orthokeratology or soft contact lenses. It found there were no severe adverse events and the frequency of mild and adverse events were about equal between the groups. </p>
<p>If you get an infection from either a standard contact lens or orthokeratology lenses, it usually clears up with a course of antibiotics. However, it’s possible to get a rare infection called microbial keratitis, which has the potential to damage sight.</p>
<p>It’s not common. According to one <a href="https://journals.lww.com/optvissci/Abstract/2013/09000/The_Risk_of_Microbial_Keratitis_With_Overnight.6.aspx">study</a>, if you were to wear an orthokeratology lens every night for 1,000 years you are only likely to get one serious infection. </p>
<p>If you use sterile contact lens solutions and avoid tap water, orthokeratology lens-wearers will dramatically reduce their risk of eye infection. Tap water exposure to lenses or lens accessories greatly <a href="https://iovs.arvojournals.org/article.aspx?articleid=2124094">increases the risk of infection</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/432111/original/file-20211116-25-1fqf1ts.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A girl gets her eyes tested." src="https://images.theconversation.com/files/432111/original/file-20211116-25-1fqf1ts.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/432111/original/file-20211116-25-1fqf1ts.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/432111/original/file-20211116-25-1fqf1ts.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/432111/original/file-20211116-25-1fqf1ts.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/432111/original/file-20211116-25-1fqf1ts.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/432111/original/file-20211116-25-1fqf1ts.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/432111/original/file-20211116-25-1fqf1ts.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Slower myopia progression also means less frequent need for replacing glasses, which can save you money in the long run.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Reducing risk of devasting eye disease later in life</h2>
<p>It’s now projected <a href="https://www.aaojournal.org/article/S0161-6420(16)00025-7/fulltext">half the world’s population will by myopic by 2050</a>, and the World Health Organization has sounded the alarm, saying in one <a href="https://www.who.int/bulletin/volumes/98/6/19-240903.pdf">bulletin</a>:</p>
<blockquote>
<p>High myopia greatly increases the risk of macular atrophy, glaucoma and
other causes of severe vision loss, the incidence of which is not reduced by
wearing standard glasses.</p>
</blockquote>
<p>Slowing the progression of myopia reduces <a href="https://theconversation.com/hidden-in-plain-sight-how-the-covid-19-pandemic-is-damaging-childrens-vision-158737">risk of sight-threatening eye disease</a>. It also means less frequent changes in vision, which can save money in the long run from needing fewer changes to glasses.</p>
<p>Myopia progresses <a href="https://journals.lww.com/optvissci/Abstract/2012/01000/Myopia_Progression_Rates_in_Urban_Children_Wearing.7.aspx">faster in younger years</a>, so a myopia control prevention should be prescribed as early as possible. We don’t know exactly how orthokeratology slows myopia progression, but compelling <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0124535">research</a> shows it does.</p>
<p>If you’re considering orthokeratology for your child, you and your eye specialist need to strike a balance. The child must be old enough to be handle it – but wait too long and the the myopia control benefits it offers diminish. </p>
<p>Every child is different. Some are more able than others to contend with orthokeratology, or willing to wear it overnight. It can be uncomfortable at first, and some might find the idea of a contact lens too confronting. It cannot be forced.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/432113/original/file-20211116-13-1j6celv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/432113/original/file-20211116-13-1j6celv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/432113/original/file-20211116-13-1j6celv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/432113/original/file-20211116-13-1j6celv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/432113/original/file-20211116-13-1j6celv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/432113/original/file-20211116-13-1j6celv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/432113/original/file-20211116-13-1j6celv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/432113/original/file-20211116-13-1j6celv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Too much ‘close work’ can make myopia worse in children.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Review all the options</h2>
<p>Orthokeratology isn’t the only solution; there are also special lenses you can get for glasses and soft daily wear contact lenses that help slow progression of myopia. Seek advice from eye specialists to to review all the options. </p>
<p>I also recommend children do no more than two hours per day of leisure “close work” (meaning non-school work: close up screen time or book-reading) outside school hours. Parents can also teach kids the “<a href="https://www.mykidsvision.org/blog/the-visual-environment/">20-20 rule</a>” (for every 20 minutes of close work, take a 20 second break to look into the distance). Outside time (<a href="https://www.mdpi.com/1660-4601/16/14/2595">two or more hours per day</a>) is also crucial to healthy eye development in children.</p>
<p>What’s clear, however, is that all short-sighted children should be doing something to control their myopia. It’s not enough just to give a child standard single vision glasses to help them see, without doing more to help slow the march of myopia.</p>
<p>If right for your child, orthokeratology has one of the strongest research pedigrees for slowing progression of myopia.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-to-keep-your-contact-lenses-clean-and-what-can-go-wrong-if-you-dont-141117">How to keep your contact lenses clean (and what can go wrong if you don't)</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/171826/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Gifford is an Adjunct Senior Lecturer at the University of New South Wales and Adjunct Associate Professor at the University of Waterloo, Canada. He is co-founder of Myopia Profile, which educates optometrists and companies on research relating to vision, and MyKidsVision.org which provides parent focused research backed information on managing childhood myopia.</span></em></p>Orthokeratology involves wearing a specially designed rigid contact lens overnight. There’s good evidence it can help slow the progression of myopia. But like all treatments, there are risks, too.Paul Gifford, Adjunct Senior Lecturer, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1684892021-09-28T20:09:48Z2021-09-28T20:09:48ZCurious Kids: how does our DNA relate to our personality and appearance?<figure><img src="https://images.theconversation.com/files/423485/original/file-20210928-18-1gwfy8g.jpeg?ixlib=rb-1.1.0&rect=77%2C252%2C6402%2C4653&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><blockquote>
<p>How does our DNA relate to our personality and appearance? — Emma, age 9, Sydney</p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Hi Emma. Thank you for this great question!</p>
<p>Our body is made up of trillions of cells, each of which has a nucleus that holds our DNA. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/423476/original/file-20210928-26-2bh8nx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Human cell diagram" src="https://images.theconversation.com/files/423476/original/file-20210928-26-2bh8nx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/423476/original/file-20210928-26-2bh8nx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/423476/original/file-20210928-26-2bh8nx.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/423476/original/file-20210928-26-2bh8nx.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/423476/original/file-20210928-26-2bh8nx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/423476/original/file-20210928-26-2bh8nx.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/423476/original/file-20210928-26-2bh8nx.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Our DNA is contained within the nucleus in each cell in our body, much too small for our eyes to see!</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Our DNA is made up of more than 20,000 genes. You can think of genes as the the instructions which help decide what we look like, how our bodies work and even our personalities. </p>
<p>We get half our genes from our biological mother and the other half from our father. That’s why we don’t look exactly like our parents, but we may look a bit like them — and may also think and act similarly to them. </p>
<p>That said, each of us still has a unique collection of genes overall. That means no two people carry exactly the same genes, not even brothers and sisters. And that’s why each of us has a unique appearance and personality.</p>
<h2>What do our genes decide?</h2>
<p>Our genes help explain many parts of our appearance, like how tall we are and the colour of our eyes.</p>
<p>They also have a hand in our other skills, such as how fast we can run, how good we are at solving problems, and whether we enjoy talking to new people (rather than if we feel shy).</p>
<p>By studying a person’s genes, scientists can tell whether that person is more likely to have blue or brown eyes, without even seeing them.</p>
<p>They may also be able to tell that person how likely they are to develop certain medical conditions later in life, such as cancer or myopia (when you can’t see far-off objects as clearly).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/423479/original/file-20210928-26-19vv5g6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Glasses held out to focus on tree tops in the distance" src="https://images.theconversation.com/files/423479/original/file-20210928-26-19vv5g6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/423479/original/file-20210928-26-19vv5g6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/423479/original/file-20210928-26-19vv5g6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/423479/original/file-20210928-26-19vv5g6.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/423479/original/file-20210928-26-19vv5g6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/423479/original/file-20210928-26-19vv5g6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/423479/original/file-20210928-26-19vv5g6.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Myopia (also called ‘nearsightedness’) is the common eye condition where objects become blurrier the further away they are. Myopia doesn’t just happen to adults — kids can have it too! Luckily glasses can easily fix the problem.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-people-get-cancer-106069">Curious Kids: Why do people get cancer?</a>
</strong>
</em>
</p>
<hr>
<h2>Not everything is determined by genes and DNA</h2>
<p>Although genes are important, they’re not the only reason for why we look, think, feel and act as we do — or why we’re more likely to have certain diseases. While some traits such as <a href="https://www.nature.com/articles/s41433-021-01749-x">eye colour</a> are mainly determined by our genes, an eye injury can change someone’s eye colour. </p>
<p>Our habits, such as how much we eat and exercise, also have a big impact on who we are and what we look like. If you eat too much junk, you’ll probably get chubby and start running slower, regardless of the genes your parents gave you. </p>
<p>Our environment at home, school and/or work play a key role in shaping us, too. Take myopia. Before the discovery of the more than <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7145443/">400 genes for myopia</a>, scientists noticed children are at least three times more likely to be myopic if <a href="https://iovs.arvojournals.org/article.aspx?articleid=2162292">either one or both parents are</a>. They realised if someone has trouble seeing far-off objects, there’s a decent chance this is related to genetics.</p>
<p>At the same time, however, there is currently a surge <a href="https://pubmed.ncbi.nlm.nih.gov/26875007/">in myopia</a> happening around the world, with more people becoming myopic even though their parents are not!</p>
<p>Researchers discovered our environments and habits play a <a href="https://www.sciencedirect.com/science/article/pii/S1350946212000444?casa_token=k8_vRWGdaf8AAAAA:wDxO0QffQyxIruw4eQjThye7syHmpYo-LmFK82-19SkOZ50Wq7lqJ0udehfxt9-xfnWQZZHHBg">huge role in myopia development</a>. For instance, they found myopia (and the need to wear glasses) is more likely to happen among people living in cities rather than the country, and those who spend less time outdoors. </p>
<p>The way we perceive colour is also influenced by both our genes and environment. You might remember the social media trend of <a href="https://en.wikipedia.org/wiki/The_dress">#thedress</a> that went viral back in 2015.</p>
<p>The world was torn over whether the dress (below) is actually blue and black, or white and gold. Researchers later found the way we see colour in this dress is 34% related to <a href="https://jov.arvojournals.org/article.aspx?articleid=2599740">our genes</a> and 66% linked to environmental factors.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/423481/original/file-20210928-32-obctqn.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The dress that become a viral internet sensation in 2015." src="https://images.theconversation.com/files/423481/original/file-20210928-32-obctqn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/423481/original/file-20210928-32-obctqn.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/423481/original/file-20210928-32-obctqn.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/423481/original/file-20210928-32-obctqn.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/423481/original/file-20210928-32-obctqn.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/423481/original/file-20210928-32-obctqn.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/423481/original/file-20210928-32-obctqn.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Looking at this photo you will either see a dress that is blue and black, or white and gold. Amazingly, the answer is different for different people.</span>
<span class="attribution"><span class="source">Wikimedia</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-are-people-colour-blind-107599">Curious Kids: why are people colour blind?</a>
</strong>
</em>
</p>
<hr>
<h2>Genes and personality</h2>
<p>“Personality” describes the relatively stable ways in which people think, feel and act. And again, genes do a pretty good job of explaining why some people are more <a href="https://onlinelibrary.wiley.com/doi/pdf/10.1111/gbb.12439">outgoing and energetic, while others tend to be more moody and anxious</a>. </p>
<p>Our genes also help explain how smart we are. But one surprising finding is <a href="https://www.nature.com/articles/mp2014105">our genes have more of an effect on us as we age</a>. Among children, about 40% of the differences in intelligence scores are explained by genes. In young adults, this increases to about 60%, even though it’s the same genes that continue to affect intelligence. </p>
<p>This is most likely because <a href="https://pubmed.ncbi.nlm.nih.gov/23818655/">our genes can impact which environments we prefer</a>, and adults often act on their preferences.</p>
<p>For example, most adults do not get told when to go to bed at night! And adults who enjoy learning new things can choose to spend their time in libraries and art museums, or taking classes. In other words, adults can choose the environments and activities that best express their genes. </p>
<h2>The future is in your hands</h2>
<p>You can think of your genes as a way to understand yourself — but not as a way to make decisions. For example, just because someone’s parents may not have been able to go to university, they themselves can if they study hard.</p>
<p>Or, a person’s parents may be overweight, but that doesn’t mean they have to be. They can still join a sprint team if they’re willing to put in the effort.</p>
<p>Even though your DNA and genes shape a lot of your personality and appearance, remember: they <em>do not</em> determine your life story.</p><img src="https://counter.theconversation.com/content/168489/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Mackey receives funding through a National Health and Medical Research Council Practitioner Fellowship.</span></em></p><p class="fine-print"><em><span>Samantha Lee and Serena Wee do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Understanding your genes is a great way to understand certain things about yourself — yet, who we are is determined by so much more than just DNA.Samantha Lee, Adjunct Research Fellow, Centre for Ophthalmology and Visual Science, The University of Western AustraliaDavid Mackey, Professor of Ophthalmology, The University of Western AustraliaSerena Wee, Senior Lecturer in Work Psychology, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1623082021-06-16T10:21:16Z2021-06-16T10:21:16ZShort-sightedness is increasing in children – and researchers are still trying to understand why<figure><img src="https://images.theconversation.com/files/406519/original/file-20210615-15-7pq17y.jpg?ixlib=rb-1.1.0&rect=0%2C26%2C6000%2C3961&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Myopia is usually a lifelong condition.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/asian-child-kid-girl-wear-eye-1214506771">kornnphoto/ Shutterstock</a></span></figcaption></figure><p>Myopia is <a href="https://www.nytimes.com/2021/05/03/well/live/nearsightedness-myopia-children.html">on the rise</a>. In the UK, the number of children with myopia has <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0146332">doubled in the last 50 years</a>. Globally, it’s projected that by 2050 <a href="https://doi.org/10.1016/j.ophtha.2016.01.006">half of the world’s population</a> will be myopic.</p>
<p>Although myopia – also known as near-sightedness or short-sightedness – can <a href="https://iovs.arvojournals.org/article.aspx?articleid=2727314">run in families</a>, environmental factors, such as spending too much time indoors have a large influence. For most people, myopia develops from a mixture of both genetics and environmental factors. But while evidence shows that modern lifestyle factors contribute to myopia, scientists still aren’t entirely sure why. </p>
<p>For instance, research shows that the amount of time a child spends outdoors can play a significant role in their <a href="https://iovs.arvojournals.org/article.aspx?articleid=2727315">risk of developing myopia</a>. Not only do most studies show that children who <a href="https://iovs.arvojournals.org/article.aspx?articleid=2727315">spend more time outdoors</a> are less likely to develop myopia, studies requiring children to spend extra time outdoors during school hours have shown the <a href="https://iovs.arvojournals.org/article.aspx?articleid=2727315">rate of myopia onset decreased</a> compared with children who didn’t spend additional time outdoors.</p>
<p>But researchers still aren’t quite sure <a href="https://iovs.arvojournals.org/article.aspx?articleid=2772539#247195256">why this is the case</a>. <a href="https://link.springer.com/chapter/10.1007/978-981-13-8491-2_4">One theory</a> is that the higher levels of light outdoors releases more dopamine into our retinal receptors (the nerves that process light signals in the eye), <a href="https://iovs.arvojournals.org/article.aspx?articleid=2727313">thus protecting against myopia</a>. Another suggestion is that the greater amount of physical activity children typically get outdoors prevents myopia. But studies have now shown that this has <a href="https://iovs.arvojournals.org/article.aspx?articleid=2127681">little</a> <a href="https://www.sciencedirect.com/science/article/pii/S0014483513001061">effect</a>.</p>
<figure class="align-center ">
<img alt="Group of children playing football outdoors in the summer." src="https://images.theconversation.com/files/406523/original/file-20210615-3839-xeqvbw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/406523/original/file-20210615-3839-xeqvbw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/406523/original/file-20210615-3839-xeqvbw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/406523/original/file-20210615-3839-xeqvbw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/406523/original/file-20210615-3839-xeqvbw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/406523/original/file-20210615-3839-xeqvbw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/406523/original/file-20210615-3839-xeqvbw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">It’s still unknown why more time outdoors is good for eyesight.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/group-happy-schoolchildren-playing-football-together-1913590756">Iakov Filimonov/ Shutterstock</a></span>
</figcaption>
</figure>
<p>It’s also been suggested that the different patterns and details we see in outdoor versus indoor spaces might explain the increase in myopia. For example, one study suggests that the abundance of <a href="https://iovs.arvojournals.org/article.aspx?articleid=2770840">plain features and walls</a> in indoor environments is to blame. This may also be why myopia tends to be <a href="https://www.tandfonline.com/doi/full/10.1080/09286586.2019.1659979">more common in urban areas</a>, however, more research is needed to understand this.</p>
<h2>Modern lifestyles</h2>
<p>Nevertheless, modern lifestyles often require us to spend a lot of our time indoors. For example, children are spending longer in formal education thanks to increases in school leaving age and more people pursuing higher education, which evidence suggests <a href="https://www.bmj.com/content/361/bmj.k2022">can cause myopia</a>. Yet what aspects of formalised education are causing increases in myopia is still unknown. Prolonged reading, learning at close distances, time spent indoors and increased screen use might all be to blame.</p>
<p>While one study suggests reading at a distance <a href="https://iovs.arvojournals.org/article.aspx?articleid=2125070">closer than 25cm</a> may be a risk for developing myopia, reading probably only has a <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4618477/#:%7E:text=The%20findings%20from%20this%20meta,%2C%20than%20non%2Dmyopic%20children.">small effect</a> on developing myopia.</p>
<p>The effect of greater screen use on myopia in children also has <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/opo.12657">mixed results</a> – probably because estimating screen use and controlling it in a long-term experiment is difficult. Regardless, further research is needed to understand whether excessive screen use is to blame for higher rates of myopia, and why this is the case. </p>
<p>Given the risk factors for developing myopia, there are also concerns now that stay-at-home orders and home learning during the pandemic may have <a href="https://journals.lww.com/ijo/Fulltext/2020/68070/Will_COVID_19_pandemic_associated_lockdown.80.aspx">worsened children’s eyesight</a>. Although there has been no study yet looking at the effect on children in the UK, early results elsewhere suggest that the pandemic may cause more children to <a href="https://www.aaojournal.org/article/S0161-6420(21)00234-7/fulltext">develop myopia</a> – but it’s anticipated the <a href="https://jamanetwork.com/journals/jamaophthalmology/fullarticle/2774808">effects will be small</a>. Whether the pandemic will have caused permanent increases in myopia is also yet to be seen.</p>
<p>Currently, the best advice for limiting the risk of developing myopia is to increase time spent outdoors, <a href="https://ep.bmj.com/content/101/4/219">even by 40 minutes a day</a>.</p><img src="https://counter.theconversation.com/content/162308/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Neema Ghorbani Mojarrad does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Researchers are still uncovering how modern lifestyles may be causing this increase.Neema Ghorbani Mojarrad, Lecturer in Optometry, University of BradfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1601522021-05-06T18:12:42Z2021-05-06T18:12:42ZNocturnal dinosaurs: Night vision and superb hearing in a small theropod suggest it was a moonlight predator<figure><img src="https://images.theconversation.com/files/398999/original/file-20210505-17-16fmhv4.png?ixlib=rb-1.1.0&rect=32%2C9%2C1511%2C788&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fossils of _Shuvuuia deserti_ depict a small predatory creature with exceptional night vision and hearing.</span> <span class="attribution"><span class="source">Mick Ellison/American Natural History Museum</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Today, barn owls, bats, leopards and many other animals rely on their keen senses to live and hunt under the dim light of stars. These <a href="https://doi.org/10.1086/702250">nighttime specialists avoid the competition of daylight hours</a>, hunting their prey under the cloak of darkness, often using a combination of night vision and acute hearing.</p>
<p>But was there nightlife 100 million years ago? In a world without owls or leopards, were dinosaurs working the night shift? If so, what senses did they use to find food and avoid predators in the darkness? To better understand the senses of the dinosaur ancestors of birds, <a href="https://scholar.google.com/citations?user=kHIW_0cAAAAJ&hl=en&oi=ao">our team</a> of <a href="https://scholar.google.com/citations?user=6qODxwoAAAAJ&hl=en&oi=ao">paleontologists</a> and <a href="https://scholar.google.com/citations?user=m_p_Lc0AAAAJ&hl=en&oi=ao">paleobiologists</a> scoured research papers and museum collections looking for fossils that preserved delicate eye and ear structures. And we found some. </p>
<p>Using scans of fossilized dinosaur skulls, in a paper <a href="https://science.sciencemag.org/content/372/6542/610?intcmp=trendmd-sci">published in the journal Science on May 6, 2021</a>, we describe the most convincing evidence to date for nocturnal dinosaurs. Two fossil species – <em>Haplocheirus sollers</em> and <em>Shuvuuia deserti</em> – likely had extremely good night vision. But our work also shows that <em>S. deserti</em> also had incredibly sensitive hearing similar to modern-day owls. This is the first time these two traits have been found in the same fossil, suggesting that this small, desert-dwelling dinosaur that lived in ancient Mongolia was probably a specialized night-hunter of insects and small mammals.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/399011/original/file-20210505-23-hnil4h.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An artistic reconstruction showing _S. deserti as a small, feathered bipedal dinosaur with an owlish face." src="https://images.theconversation.com/files/399011/original/file-20210505-23-hnil4h.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/399011/original/file-20210505-23-hnil4h.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=848&fit=crop&dpr=1 600w, https://images.theconversation.com/files/399011/original/file-20210505-23-hnil4h.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=848&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/399011/original/file-20210505-23-hnil4h.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=848&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/399011/original/file-20210505-23-hnil4h.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1066&fit=crop&dpr=1 754w, https://images.theconversation.com/files/399011/original/file-20210505-23-hnil4h.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1066&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/399011/original/file-20210505-23-hnil4h.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1066&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Shuvuuia deserti</em> had acute hearing and low-light vision that would have allowed it to hunt at night.</span>
<span class="attribution"><span class="source">Viktor Radermaker</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Looking to theropods</h2>
<p>By studying fossilized eye bones, one of us, Lars Schmitz, had previously found that some small predatory dinosaurs <a href="https://doi.org/10.1126/science.1200043">may have hunted at night</a>. Most of these potentially nocturnal hunters were theropods, the group of three-toed dinosaurs that includes <em>Tyrannosaurus rex</em> and modern birds. But to date, fossils for only <a href="https://doi.org/10.1126/science.1200043">12 theropod species included the eye structures</a> that can tell paleontologists about night vision.</p>
<p>Our team identified four more species of theropods with clues for their sense of vision – for a total of 16. We then looked for fossils that preserve the structures of the inner ear and found 17 species. Excitingly, for four species, we were able to get measurements for both eyes and ears.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/399012/original/file-20210505-23-usv75o.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A close up photo of the skull of _S. deserti_ showing a large eye socket." src="https://images.theconversation.com/files/399012/original/file-20210505-23-usv75o.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/399012/original/file-20210505-23-usv75o.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=378&fit=crop&dpr=1 600w, https://images.theconversation.com/files/399012/original/file-20210505-23-usv75o.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=378&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/399012/original/file-20210505-23-usv75o.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=378&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/399012/original/file-20210505-23-usv75o.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=475&fit=crop&dpr=1 754w, https://images.theconversation.com/files/399012/original/file-20210505-23-usv75o.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=475&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/399012/original/file-20210505-23-usv75o.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=475&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The eye socket – and specifically the sclerical ring – of <em>S. deserti</em> shows an eye with a very large pupil capable of letting in large amounts of light.</span>
<span class="attribution"><span class="source">Mick Ellison/American Museum of Natural History</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Eye bones built for night vision</h2>
<p>Scleral ossicles are thin, rectangular bone plates that form a <a href="https://doi.org/10.1002/ar.24043">ring-like structure surrounding the pupils</a> of lizards as well as birds and their ancestors – dinosaurs. Scleral rings define the largest possible size of an animal’s pupil and can tell you how well that animal <a href="https://doi.org/10.1016/j.visres.2010.03.009">can see at night</a>. The larger the pupil compared to the size of the eye, the better a dinosaur could see in the dark.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/399017/original/file-20210505-19-1imtqg9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An owl skull with a cone like ring attached to the eye socket." src="https://images.theconversation.com/files/399017/original/file-20210505-19-1imtqg9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/399017/original/file-20210505-19-1imtqg9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=456&fit=crop&dpr=1 600w, https://images.theconversation.com/files/399017/original/file-20210505-19-1imtqg9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=456&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/399017/original/file-20210505-19-1imtqg9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=456&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/399017/original/file-20210505-19-1imtqg9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=573&fit=crop&dpr=1 754w, https://images.theconversation.com/files/399017/original/file-20210505-19-1imtqg9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=573&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/399017/original/file-20210505-19-1imtqg9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=573&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This owl skull clearly shows the large scleral ring that helps animals see in darkness.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Bubo_virginianus_8zz.jpg#/media/File:Bubo_virginianus_8zz.jpg">David J. Stang/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Since the individual bony ossicles of these rings fell apart after these animals died more than 60 million years ago, our team made scans of the fossils and then digitally reconstructed the eyes. Of all the theropods we examined, <em>H. sollers</em> and <em>S. deserti</em> had some of the proportionally largest pupils.</p>
<p><em>S. deserti</em>‘s pupil made up more than half of its eye, very similar to night-vision specialists that live today like geckos and nightjars. Our team then compared the fossils to 55 living species of lizards and 367 species of birds with known day or night activity patterns. According to the statistical analyses our team performed, there is a very high chance – higher than 90% – that <em>H. sollers</em> and <em>S. deserti</em> were nocturnal.</p>
<p>But those were not the only two theropods our team looked at. Our analysis also found a few other likely nighttime specialists – such as <em>Megapnosaurus kayentakatae</em> – as well as daylight specialists like <em>Almas ukhaa</em>. But we also found some species – like <em>Velociraptor mongoliensis</em> – with eyesight seemingly adapted for medium light levels. This might suggest that they hunted around dawn or dusk.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/399020/original/file-20210505-19-62si2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two white plastic molds on a black background both with an elongated vertical base splitting into a 'y' shape at the top." src="https://images.theconversation.com/files/399020/original/file-20210505-19-62si2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/399020/original/file-20210505-19-62si2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/399020/original/file-20210505-19-62si2q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/399020/original/file-20210505-19-62si2q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/399020/original/file-20210505-19-62si2q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/399020/original/file-20210505-19-62si2q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/399020/original/file-20210505-19-62si2q.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Molds of the inner ear canal from a barn owl (left) and <em>S. deserti</em> (right) are almost identical, suggesting that the small dinosaur had incredible hearing.</span>
<span class="attribution"><span class="source">Shivan Parusnath/Wits University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Incredible ears of a dinosaur</h2>
<p>In today’s nocturnal animals, <a href="https://doi.org/10.1002/bies.201600006">hearing can be as important as keen eyesight</a>. To figure out how well these extinct dinosaurs could hear, we scanned the skulls of 17 fossil theropods to decipher the structure of their inner ears and then compared our scans to the ears of modern animals.</p>
<p>All vertebrates have a tube-like canal called the cochlea deep in their inner ear. Studies of living mammals and birds show that the longer this canal, the <a href="https://doi.org/10.1098/rspb.2008.1390">wider the range of frequencies an animal can hear</a> and the better they can hear <a href="https://doi.org/10.1098/rspb.2008.1390">very faint sounds</a>.</p>
<p>Our scans showed that <em>S. deserti</em> had an extremely elongated inner ear canal for its size – also similar to that of the living barn owl and proportionally much longer than all of the other 88 living bird species we analyzed for comparison. Based on our measurements, among dinosaurs, we found that predators had generally better hearing than herbivores. Several predators – including <em>V. mongoliensis</em> – also had moderately elongated inner ears, but none rivaled <em>S. deserti</em>’s. </p>
<h2>The life of a nocturnal dinosaur</h2>
<p>By studying the sensory abilities of dinosaurs, paleontologists like us not only are learning what species roamed the night, but can also begin to infer how these dinosaurs lived and shared resources.</p>
<p><a href="https://doi.org/10.1126/science.abe7941"><em>S. deserti</em> had extreme night vision and sensitive hearing</a>, and this little dinosaur probably used its incredible senses to hunt prey at night. It could likely hear and follow rustling from a distance before visually detecting its prey and digging it up from the ground with its short single-clawed arms. In the dry, desert-like habitats of millions of years ago, it might have been an evolutionary advantage to be active in the cooler temperatures of the night. </p>
<p>But according to our analysis, <em>S. deserti</em> wasn’t the only dinosaur active at night. Other dinosaurs like <em>V. mongoliensis</em> and the plant-eating <em>Protoceratops mongoliensis</em> both lived in the same habitat and had some level of night vision.</p>
<p>Paleontologists currently do not know the full suite of animals that shared <em>S. deserti</em>’s extreme nocturnal lifestyle in the ancient deserts of Mongolia – it is rare to find fossils with the right bones intact that allow paleontologists to investigate their senses. However, the presence of a specialized night forager highlights that much like today, some dinosaurs avoided the dangers and competition of daylight hours and roamed under the stars.</p>
<p>[<em>Get the best of The Conversation, every weekend.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybest">Sign up for our weekly newsletter</a>.]</p><img src="https://counter.theconversation.com/content/160152/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonah Choiniere receives funding from the National Research Foundation of South Africa. </span></em></p><p class="fine-print"><em><span>Roger Benson receives funding from the European Research Council, National Environments Research Council and Leverhulme Trust. </span></em></p><p class="fine-print"><em><span>Lars Schmitz does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>By looking at the eye bones and ear canals of extinct dinosaurs, researchers show that a small ancient predator likely hunted at night and had senses as good as a modern barn owl.Lars Schmitz, Associate Professor of Biology, Scripps CollegeJonah Choiniere, Professor of Dinosaur Paleontology, University of the WitwatersrandRoger Benson, Professor of Palaeobiology, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1464322020-09-24T09:46:35Z2020-09-24T09:46:35ZParkinson’s disease can affect the eyes – here’s what we know so far<figure><img src="https://images.theconversation.com/files/359768/original/file-20200924-24-27yh42.jpg?ixlib=rb-1.1.0&rect=13%2C0%2C8661%2C5787&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Parkinson's is a motor disease which can affect eye movement.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/senior-looks-instrument-checking-eyes-ophthalmologist-372743563">Lucky Business/ Shutterstock</a></span></figcaption></figure><p>Parkinson’s disease is the <a href="https://www.thelancet.com/journals/laneur/article/PIIS1474-4422(18)30295-3/fulltext">second most common</a> neurodegenerative disease, affecting over <a href="https://www.parkinson.org/Understanding-Parkinsons/Statistics#:%7E:text=More%20than%2010%20million%20people,have%20Parkinson's%20disease%20than%20women.">10 million people worldwide</a>. It’s characterised by changes in movement, including tremors, and slower and more rigid movements. But researchers are also beginning to investigate other symptoms of <a href="https://theconversation.com/uk/topics/parkinsons-disease-30547">Parkinson’s disease</a> – including <a href="https://www.parkinson.org/Understanding-Parkinsons/Symptoms/Non-Movement-Symptoms/Vision-Changes">those involving the eye</a>. </p>
<p>Parkinson’s results from the degeneration of dopamine neurons in the brain’s basal ganglia – an area involved in voluntary movement. Though no cure exists for Parkinson’s, symptoms can be managed with drugs that replace dopamine.</p>
<p><a href="https://www.parkinson.org/Understanding-Parkinsons/Diagnosis">No single diagnostic test</a> exists for Parkinson’s as the blood-brain barrier (which protects the brain from pathogens roaming the bloodstream) and skull make it hard to assess the brain. As a result <a href="https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/how-parkinson-disease-is-diagnosed">subjective assessments of symptoms</a> are used to diagnose patients. </p>
<p>Given Parkinson’s is known to affect the body’s motor system, it’s perhaps not surprising it has been shown to <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5684125/">disrupt eye movements</a>. Promisingly, Parkinson’s may be diagnosed using technologies that already exist by showing subtle changes in eye movements and the thinning of specific layers in the retina. This may help measure the effectiveness of treatments and determine the progression of the disease. </p>
<h2>Changes in movement</h2>
<p>Studies investigating the effect of Parkinson’s on eye movements have focused on the rapid, ballistic movements of our eyes towards a stimulus (known as <a href="https://pubmed.ncbi.nlm.nih.gov/24113556/">saccades</a>). The opposite, <a href="https://www.sciencedirect.com/science/article/pii/S0042698913000357?via%3Dihub">antisaccades</a>, are voluntary movements of our eyes moving away from a stimulus. <a href="https://pubmed.ncbi.nlm.nih.gov/25600361/">Early studies</a> showed errors in antisaccades – whereby participants failed to look away from a light stimulus – are higher in those with Parkinson’s.</p>
<p><a href="https://www.jneurosci.org/content/35/38/13043">Another study</a>, which used <a href="https://www.michaeljfox.org/news/deep-brain-stimulation">deep brain stimulation</a>, found targeting the globus pallidus interna – the brain area partially responsible for conscious movement – reduced the number of antisaccade errors. Deep brain stimulation is the only surgical treatment for Parkinson’s disease. It works by directing electricity to precise regions of the brain. Stimulation targeting the subthalamic nucleus, an adjacent region, had no effect. Recently, <a href="https://www.nature.com/articles/s41598-020-61572-4">researchers found</a> stimulating the subthalamic nucleus increased antisaccade errors and delay both away from and towards a stimulus. </p>
<p>Though evidence from the small number of stimulation studies conflict, they highlight how Parkinson’s disease could <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6005881/">influence eyes movements</a>. </p>
<p><a href="https://n.neurology.org/content/94/15_Supplement/2174">A study from earlier this year</a> describes 85% of recently diagnosed Parkinson’s patients displaying rhythmic eyelid fluttering upon closing their eyes. These small changes in movement can be measured using webcams, virtually. However, larger studies are needed to investigate the potential of eyelid fluttering as a diagnostic tool.</p>
<h2>Retinal thinning</h2>
<p>Researchers have identified the abnormal accumulation of the protein <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3281589/">alpha-synuclein</a> in areas of the brain involved with voluntary movement in patients with Parkinson’s disease. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5122110/">Alpha-synuclein</a> is found throughout the brain, although its function is not yet well defined. It is thought to regulate the synthesis of dopamine, which in turn helps regulate movement.</p>
<p>Interestingly, a <a href="https://link.springer.com/article/10.1007/s00401-018-01956-z#Sec6">handful of recent studies</a> have found an accumulation of alpha-synuclein in the retinal tissue of Parkinson’s patients compared to healthy samples. The <a href="https://pubmed.ncbi.nlm.nih.gov/29737566/">amount of alpha-synuclein</a> found may even correlate with the severity of disease – though this potential disease indicator can only be detected using post-mortem tissue samples.</p>
<p>Optical coherence tomography (OCT) scans, which take cross-sectional images of the retina’s ten distinct layers, may allow researchers to detect retinal changes in living patients. These scans are fast, non-invasive, relatively cheap and easy to use.</p>
<p>A <a href="https://n.neurology.org/content/86/16_Supplement/P5.177">number</a> of OCT studies have so far shown retinal thinning in patients with Parkinson’s. Not only are dopamine neurons found in <a href="https://academic.oup.com/brain/article/132/5/1128/357681">specific regions of the retina</a>, the layers of the retina neighbouring these regions were <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4591751/">found to harbour alpha-synuclein</a>. <a href="https://www.nature.com/articles/s41598-019-48388-7">Studies show</a> retinal thinning does selectivity occur in these layers of the retina, potentially indicating the onset of early Parkinson’s disease.</p>
<figure class="align-center ">
<img alt="Man has his eyes tested using an OCT machine." src="https://images.theconversation.com/files/359769/original/file-20200924-23-iix4ij.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359769/original/file-20200924-23-iix4ij.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359769/original/file-20200924-23-iix4ij.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359769/original/file-20200924-23-iix4ij.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359769/original/file-20200924-23-iix4ij.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359769/original/file-20200924-23-iix4ij.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359769/original/file-20200924-23-iix4ij.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">OCT scans can show thinning of the retinal layers.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/slit-lamp-eye-oculist-doctor-control-1246634854">Parilov/ Shutterstock</a></span>
</figcaption>
</figure>
<p>Alongside diagnosing Parkinson’s, eye tests could also help track disease progression. <a href="https://cp.neurology.org/content/10/1/29">A study</a> involving 126 participants looked to see if OCT scans and simple visual chart tests in patients with Parkinson’s disease correlated with the risk of dementia (an algorithm was used to <a href="https://pubmed.ncbi.nlm.nih.gov/28629879/">calculate risk</a>). </p>
<p>Those with Parkinson’s disease who were calculated to have the highest risk of dementia fared worse on the sight tests. These patients also were found to have greater retinal thinning. These findings were not replicated in participants who had a similarly high dementia risk, but no Parkinson’s diagnosis.</p>
<p>However, this type of study has limitations. The number of patients involved and other factors – such as the medication they take – can affect the findings. Eye tests are also harder to perform on patients with the most severe symptoms.</p>
<h2>Big data</h2>
<p>As more patients are studied, more can be learned about Parkinson’s disease. Big data studies can be advantageous because Parkinson’s disease is <a href="https://www.thelancet.com/journals/laneur/article/PIIS1474-4422(18)30295-3/fulltext">relatively common</a> and eye scans are becoming increasingly routine. This allows researchers to analyse large numbers of OCT scans and retinal images already captured on patients with, and without, Parkinson’s.</p>
<p>Databases such as this exist, the largest being the <a href="https://www.moorfields.nhs.uk/news/moorfields-announced-new-health-data-research-hub">INSIGHT Data Hub for Eye Health</a>, which consist of <a href="https://www.insight.hdrhub.org/">millions of eye scans</a> alongside anonymised medical histories from over 250,000 patients. Population-based approaches, coupled with the use of machine learning (a type of artificial intelligence) and <a href="https://www.nature.com/articles/s41591-018-0107-6">deep learning</a> (a subset of machine learning), can sift through large databases, uncovering patterns. Researchers can use several eye scans from the same patient to <a href="https://link.springer.com/chapter/10.1007/978-981-10-4361-1_138">help investigate disease progression</a>.</p>
<p>An increasing body of evidence suggests that changes in eye movements and retinal structure result from the degeneration of dopamine, which is characteristic of Parkinson’s disease. Other <a href="https://pubmed.ncbi.nlm.nih.gov/27412389/">visual disturbances</a>, such as changes in rapid eye movement during sleep, motion perception, and colour vision, are also under investigation. Importantly, these changes can be detected non-invasively.</p><img src="https://counter.theconversation.com/content/146432/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chrystalina Antoniades receives funding from NIHR, Wellcome Trust, UCB- Oxford Collaboration grant, Merck Industry funding.</span></em></p><p class="fine-print"><em><span>Siegfried Wagner is funded by the Medical Research Council through a Clinical Research Training Fellowship. He also holds project grant funding from Fight for Sight and Alzheimer's Research UK. </span></em></p><p class="fine-print"><em><span>Pearse Keane and Salil Patel do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Parkinson’s disease may be diagnosed by looking for subtle changes in eye movements and thinning of retina layers.Salil Patel, NIHR academic clinical fellow and incoming PhD student, University of OxfordChrystalina Antoniades, Associate Professor of Neuroscience, University of OxfordPearse Keane, Professor of Ophthalmology, UCLSiegfried Wagner, Research Fellow, Ophthalmology, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1435232020-09-07T11:36:15Z2020-09-07T11:36:15ZThere’s no evidence that blue-light blocking glasses help with sleep<figure><img src="https://images.theconversation.com/files/352569/original/file-20200812-24-1i2zvox.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6000%2C3997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There is a lack of good clinical research on the advantages of blue-light filtering lenses. </span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>Health products, like detox teas and <a href="https://www.healthline.com/nutrition/detox-water-101">mood-boosting waters</a>, rely on a lack of neuroscientific knowledge to make their claims. Some of these claims are unsubstantiated, while others are completely made up.</p>
<p>My doctoral research investigates visual processing, but when I look at the big picture, I realize that what I’m really studying are fundamental aspects of brain anatomy, connectivity and communication. </p>
<p>One specific function of the visual system that I have studied during my degree is the blue-light detecting molecule, <a href="https://doi.org/10.1016/j.tins.2007.11.002">melanopsin</a>. In humans, melanopsin is seemingly restricted to a group of neurons in the eye, which preferentially target a structure in the brain called the suprachiasmatic nucleus — the body’s clock. </p>
<h2>Circadian rhythms</h2>
<p>This is where the (true) idea that blue light affects our sleep-wake cycle or circadian rhythm originates from. And also why many corrective lens producers have started cashing in on blue-light filtering glasses. The most common claims that go along with these lenses is that <a href="https://time.com/5752454/blue-light-sleep/">they will help restore our natural sleep-wake cycle</a>.</p>
<p>Blue-filtering lenses are marketed as a solution to so many other vision problems. There are claims that they <a href="https://www.cbc.ca/news/canada/marketplace-blue-light-lenses-hidden-camera-investigation-1.5364678">protect against a retinal disease called macular degeneration, decrease headaches and ward off eye cancer</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/NkJY9bgLyBE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A CBC Marketplace investigation into blue-light lenses.</span></figcaption>
</figure>
<h2>Blue-light complexity</h2>
<p>Ophthalmologists generally agree that there is “<a href="https://doi.org/10.1111/opo.12414">a current lack of high-quality clinical evidence to support a beneficial effect with blue‐blocking spectacle lenses for reducing eye fatigue, enhancing sleep quality or preserving macular health in the general population</a>.” </p>
<p>Similar to the workings of any biological system, melanopsin’s contribution to vision is more complicated than it is made out to be. </p>
<p>For example, melanopsin — like other light-sensitive molecules in our eyes — can result in neural activity outside of blue light specifically. Blue is simply where it is most sensitive. So, then, blue light does indeed affect our sleep-wake cycle, but so will other wavelengths of light, to a lesser extent. </p>
<p>But what is the real culprit of the effects of digital screen light on our sleep-wake cycle? Is it necessarily blue light alone or is the problem likely worsened by people commonly staying up late and using their devices? </p>
<p>The science seems to be on the <a href="https://doi.org/10.1111/opo.12406">side that is against any substantial effects of blue-light blocking lenses</a>. If you are staying up late anyway, blue-light blocking lenses aren’t proven to provide any help.</p>
<p>Research has shown that one likely cause for eye irritation and fatigue is the time we spend in front of our screens overall, which may <a href="https://doi.org/10.1097/opx.0000000000000157">decrease the amount of blinking we do</a>. </p>
<figure class="align-center ">
<img alt="Fatigued woman using laptop at night" src="https://images.theconversation.com/files/352571/original/file-20200812-24-ee9ria.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/352571/original/file-20200812-24-ee9ria.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/352571/original/file-20200812-24-ee9ria.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/352571/original/file-20200812-24-ee9ria.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/352571/original/file-20200812-24-ee9ria.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/352571/original/file-20200812-24-ee9ria.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/352571/original/file-20200812-24-ee9ria.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The amount of time we spend looking at screens — especially late at night — contributes to eye irritation and fatigue.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<h2>Filling the gap in clinical research</h2>
<p>The problem seems to be not only blue-light filtering lens sellers, but the way in which we talk about findings from research. </p>
<p>As of yet, there is no clinical evidence that supports the benefits of using blue-light filtering lenses. For now, this is another pseudoscience market that’s taken advantage of its consumer base — anyone who uses computers.</p>
<p>Expanding neuroscience literacy should be a public health goal: understanding how the brain and its partner organs — like the eye — work.</p>
<p>For now, keeping our eyes off screens at night and taking frequent breaks from screens is what will contribute most to our eye health and sleep hygiene.</p><img src="https://counter.theconversation.com/content/143523/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tareq Yousef receives funding from the Dalhousie University Department of Ophthalmology and Visual Sciences and has previously received funding from the Dalhousie University Faculty of Medicine and the Nova Scotia Health Research Foundation.</span></em></p>Some health products haven’t been tested for the benefits that they claim to produce. Blue-light blocking lenses are promoted as helping sleep cycles, but there is no evidence to support this.Tareq Yousef, PhD candidate, Medical Neuroscience, Dalhousie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1381932020-05-21T12:22:14Z2020-05-21T12:22:14ZIncreasing screen time during the coronavirus pandemic could be harmful to kids’ eyesight<figure><img src="https://images.theconversation.com/files/335514/original/file-20200516-138634-xtp6t0.jpg?ixlib=rb-1.1.0&rect=66%2C56%2C2066%2C1336&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">With online learning, children are staring at computer screens for more hours each day. </span> <span class="attribution"><a class="source" href="http://gettyimages.com">Christopher Furlong/Getty Images</a></span></figcaption></figure><p>The coronavirus pandemic is remaking the way children learn, and it could have an impact on their eyes. </p>
<p>With schools shifting to online lessons at home, children are spending more time in front of computer screens, and many parents are <a href="https://theconversation.com/forget-old-screen-time-rules-during-coronavirus-heres-what-you-should-focus-on-instead-135053">relaxing screen-time rules</a> for TV and video games to keep kids occupied while social distancing. In the midst of the crisis, many children are spending less time playing outdoors.</p>
<p>This combination – more screen time and less outdoor time – may actually harm children’s vision and put them at higher risk of developing myopia, or nearsightedness. That can lead to serious eye problems in the future, including some potentially blinding diseases.</p>
<p>As <a href="https://scholar.google.com/citations?user=DjdCWeYAAAAJ&hl=en">a health behavioral and policy professor</a> and <a href="https://medicine.umich.edu/dept/ophthalmology/olivia-killeen-md">an ophthalmology resident</a> interested in health promotion and eye care for children, we’re concerned about the impacts of decreased outdoor time and excess screen time on children’s eyes during the COVID-19 pandemic.</p>
<h2>What causes myopia?</h2>
<p>Scientists are still trying to understand how myopia, or nearsightedness, develops and progresses.</p>
<p>It occurs when the eyeball is too long or the eye’s focusing power is too strong, causing light rays to <a href="https://www.aao.org/eye-health/diseases/myopia-nearsightedness">focus in front of the retina</a> instead of on it, which creates a blurry image. While glasses or contact lenses can correct a child’s vision, research shows that having <a href="http://doi.org/10.1097/IAE.0000000000001489">severe myopia puts children at risk</a> for a number of eye problems down the road, including retinal detachment, glaucoma and macular degeneration.</p>
<p>Some factors in whether a child develops myopia, such as genetics, are beyond a parent’s control, but research shows that other risks can be reduced.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/336574/original/file-20200520-152298-ow2a1a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/336574/original/file-20200520-152298-ow2a1a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=675&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336574/original/file-20200520-152298-ow2a1a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=675&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336574/original/file-20200520-152298-ow2a1a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=675&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336574/original/file-20200520-152298-ow2a1a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=848&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336574/original/file-20200520-152298-ow2a1a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=848&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336574/original/file-20200520-152298-ow2a1a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=848&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In people with myopia, light focuses in front of the retina rather than on it, so distant objects appear blurry.</span>
<span class="attribution"><span class="source">Anurag Papolu/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>A review of <a href="http://doi.org/10.1371/journal.pone.0140419">25 years of research</a> found that working up close – like reading or using a tablet – increased the odds of myopia.</p>
<p>For example, a nationwide study in Taiwan found that after-school study programs with lots of closeup work were associated with an <a href="https://doi.org/10.1016/j.ophtha.2018.05.010">increased likelihood of nearsightedness</a> among children ages 7 to 12. A study of Chinese schoolchildren found that increased time spent working with the eyes focused on something <a href="http://dx.doi.org/10.1136/bjophthalmol-2019-315258">less than 20 centimeters away</a> was associated with myopia. Researchers in Ireland found that <a href="http://doi.org/10.1136/bjophthalmol-2018-313325">greater than three hours of screen time per day</a> increased the odds of myopia in schoolchildren, and investigators in Denmark found that the risk of myopia approximately doubled in <a href="https://doi.org/10.1111/aos.14242">Danish teenagers who used screen devices</a> for more than six hours per day.</p>
<h2>Getting outdoors matters</h2>
<p>Some studies now suggest that <a href="http://doi.org/10.1016/j.ophtha.2012.04.020">spending time outdoors</a> may be able to slow the onset and progression of nearsightedness.</p>
<p>In Taiwan, first grade students at schools with <a href="http://doi.org/10.1016/j.ophtha.2017.12.011">programs designed to increase their outdoors time</a> to 11 hours or more each week had less progression of myopia over one year compared to their peers. Similarly, in China, researchers found that <a href="http://doi.org/10.1001/jama.2015.10803">adding 40 minutes of outdoor activity</a> a day at school reduced the development of nearsightedness in six-year-old children over the next three years.</p>
<p>It is not clear why outdoors time protects against myopia, or why closeup work could make it worse. One theory is that <a href="http://doi.org/10.1038/s41588-018-0127-7">light intensity and time spent outdoors</a> regulates the <a href="https://doi.org/10.1016/j.exer.2006.09.018">release of dopamine in the retina</a>, which controls the growth of the eye. Other theories center on how <a href="https://www.ncbi.nlm.nih.gov/books/NBK470669/">viewing distances impact where the light is focused</a> on the retina; shorter viewing distances indoors may promote abnormal growth of the eye. </p>
<p>Although there is no consensus on how much time children need to spend outside or the importance of the light intensity they are exposed to, it is possible that more outdoor time can help to balance out more closeup work, as a <a href="http://doi.org/10.1016/j.ophtha.2007.12.019">study of children in Australia found</a>.</p>
<p>Childhood is an important time to think about myopia because myopic children tend to become more nearsighted over time. The <a href="http://doi.org/10.1111/opo.12305">age of myopia onset</a> is the most significant predictor of severe myopia later in life.</p>
<p><iframe id="ZX4Fu" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/ZX4Fu/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Globally, <a href="http://doi.org/10.1186/s12886-019-1220-0">rates of myopia have been rising</a>. The prevalence of myopia among children ages 6-19 years is estimated at around 40% in Europe and North America, and higher in Asia. By midcentury, researchers studying the trends have estimated that <a href="https://linkinghub.elsevier.com/retrieve/pii/S0161642016000257">about half the world’s population could be myopic</a>.</p>
<p>Such high rates of myopia also come with an economic burden. The <a href="http://doi.org/10.1016/j.ophtha.2018.10.029">potential lost productivity</a> resulting from myopia was nearly US$250 billion in 2015.</p>
<h2>Building an eye-healthy lifestyle at home</h2>
<p>Parents can help by carefully managing their children’s screen time to support educational use while limiting cartoons and video games. They can also encourage more outdoors activities while maintaining social distancing.</p>
<p>Having <a href="https://doi.org/10.1177/0009922813498152">clear rules, setting limits on screen time</a> and <a href="http://doi.org/10.1186/s12889-015-2337-6">parents’ communication style</a> have been associated with less screen time among children. <a href="http://doi.org/10.1186/1479-5868-10-89">Parental modeling</a> also influences how much time children spend watching TV. </p>
<p>The <a href="https://www.who.int/publications-detail/guidelines-on-physical-activity-sedentary-behaviour-and-sleep-for-children-under-5-years-of-age">World Health Organization recommends</a> that children under 5 spend one hour or less per day on digital devices, and children under 1 spend no time on digital devices. The <a href="https://higherlogicdownload.s3.amazonaws.com/AAPOS/d8bb1f42-47c4-46d5-82af-1582d9d6e8f5/UploadedImages/Documents/CEF-10-Things.pdf">Children’s Eye Foundation recommends</a> daily outdoor play, no screen time for those under age 2, a maximum of 1-2 hours per day for kids ages 2 to 5 and guided screen time with frequent breaks for kids over 5.</p>
<p>Parents and teachers can also check out helpful tips for eye health <a href="https://www.aao.org/newsroom/news-releases/detail/is-too-much-screen-time-harming-childrens-vision">from the American Academy of Ophthalmology</a>. Educators can find <a href="https://www.aao.org/museum-research-resources">resources</a> to prepare learning materials. Here are some recommendations: </p>
<ul>
<li><p>Take a 20-second break from closeup work every 20 minutes</p></li>
<li><p>Set a timer to remind kids to take those breaks</p></li>
<li><p>Keep digital media 18 to 24 inches away from the face</p></li>
</ul>
<p>As we plan the future of education in the age of COVID-19, schools and policymakers must consider children’s vision needs while designing new initiatives. Schools, teachers and parents can work together to incorporate eye health strategies and protect children as they learn online.</p>
<p>[<em>The Conversation’s newsletter explains what’s going on with the coronavirus pandemic. <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=upper-coronavirus-daily">Subscribe now</a>.</em>]</p><img src="https://counter.theconversation.com/content/138193/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shu-Fang Shih, Research Assistant Professor of Health Policy and Management, received funding from the Ministry of Education in Taiwan from 2013 to 2018 . </span></em></p><p class="fine-print"><em><span>Olivia Killeen does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>With online learning and social distancing, kids are spending more time staring at screens and less time outdoors. That can put them at higher risk of myopia and serious eye problems in the future.Shu-Fang Shih, Research Assistant Professor, Department of Health Management and Policy, School of Public Health, University of MichiganOlivia Killeen, Resident Physician in Ophthalmology, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1305182020-02-12T15:36:58Z2020-02-12T15:36:58ZWhen laser surgery turns into a nightmare, the toll can be enormous<figure><img src="https://images.theconversation.com/files/311695/original/file-20200123-162216-15qlynm.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1356%2C665&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Laser surgery is performed successfully in 95 per cent of cases but the operation can turn into a nightmare requiring complex treatments because it is a new, poorly documented field in medicine. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/">Shutterstock</a></span></figcaption></figure><p>It will soon be a year since Jessica Starr, a popular weatherperson on Detroit TV, took her own life. Her husband said she did so because of complications related to <a href="https://www.today.com/health/smile-surgery-husband-meteorologist-who-took-her-own-life-speaks-t151062">her recent laser refractive surgery</a>. </p>
<p>Such complications are not as rare as people think. <a href="https://www.nytimes.com/2018/06/11/well/lasik-complications-vision.html">The <em>New York Times</em></a> warned in 2018 of the potential effects on some patients. More recently, and closer to home, <a href="https://www.ctvnews.ca/health/lasik-md-patients-allege-nerve-damage-file-class-action-lawsuit-1.4697069">a class-action lawsuit was filed across the country</a>
against Québéc-based company Lasik MD. It is accused of failing to properly warn its clients of the risks associated with vision correction surgery.</p>
<p>Does this mean that the dream of getting rid of glasses while still improving vision should be forgotten? </p>
<h2>Improved technology</h2>
<p>Refractive laser surgery aims to change the profile of the cornea, the front and clear part of the eye, to correct common vision problems: nearsightedness, farsightedness and astigmatism. The idea is to eliminate the need for glasses. </p>
<p>Introduced in 1983 in Germany, the first North American procedure <a href="https://www.ncbi.nlm.nih.gov/pubmed/?term=kugler+wang+laser+applied+optics">was performed in 1985</a>. Since then, millions have been done. At that time, laser surgery was an advantageous alternative to <a href="https://www.ncbi.nlm.nih.gov/pubmed/2686058">a more imprecise technique, radial keratotomy </a>(KR). </p>
<p>The first laser technologies led to better, more stable, and more predictable results, but they were also associated <a href="https://www.ncbi.nlm.nih.gov/pubmed/31819355">with a number of complications</a>: intense pain during the procedure and in the days that followed, off-centre treatment leading to the perception of halos and glare, under- or over-correction requiring the need for retouching or a return to wearing glasses, permanent corneal fog or delayed healing of the corneal surface with increased potential for infection. </p>
<p>In order to improve this profile, and especially the patient’s comfort, a technique called LASIK (laser <em>in situ</em> keratomileusis) was developed in the 1990s. This time, the laser is applied once a flap of tissue, generated by incising the cornea with a small planer equipped with a blade, is lifted. The flap is then replaced without the need for sutures.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/310573/original/file-20200116-72756-1rpn42d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/310573/original/file-20200116-72756-1rpn42d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/310573/original/file-20200116-72756-1rpn42d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/310573/original/file-20200116-72756-1rpn42d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/310573/original/file-20200116-72756-1rpn42d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/310573/original/file-20200116-72756-1rpn42d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/310573/original/file-20200116-72756-1rpn42d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A patient and a team of surgeons in the operating room during ophthalmic surgery.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Complications remain</h2>
<p>All surgery carries risks. Serious incidents after <a href="https://www.newswire.ca/news-releases/protegez-vous-fevrier-2016---la-chirurgie-des-yeux-au-laser-sous-enquete-565633031.html">LASIK occur in only 0.1 per cent of cases</a>. But various complications affect between 10 and 30 per cent of patients undergoing surgery, compared to 7.7 per cent <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3777802/">after cataract surgery</a>. </p>
<p>While the majority of complications are minor and do not result in permanent consequences, a number of patients experience chronic, severe post-operative pain and/or visual problems, to the point where Morris Waxler, a former Food and Drug Administration expert, <a href="https://www.cbsnews.com/news/lasik-eye-surgery-retired-fda-adviser-says-procedure-should-be-taken-off-market/">is calling for a recall and suspension of its use pending further safety investigations</a>. </p>
<p>Regarding LASIK, <a href="https://www.canada.ca/en/health-canada/services/medical-procedures/laser-eye-surgery.html">Health Canada lists several potentially serious effects</a> that must be taken into account. </p>
<h2>A nightmare case</h2>
<p>Following laser surgery, the cornea is traumatized and must recover to restore normal function. In the case of LASIK, the cornea is cut at the level of the sensory nerves. These nerves protect the eye but also provide the feedback (biofeedback) necessary for the production of new tears. </p>
<p>In the absence of this feedback, the eye dries out and its surface can deteriorate. In the majority of cases, the cut nerves will return to normal function within four to six months. But for a number of patients, the episode turns into a nightmare. </p>
<p>Karen (not her real name) is one such patient I recently met. As a young, dynamic executive, she had opted for surgery for practical (work, sports activities) and esthetic reasons. Attracted by promotions and a tempting price, she went to a laser centre and was quickly examined by the staff. Even more quickly, she was given an appointment for surgery — the next day! Without thinking too much, she proceeded. </p>
<p>In the days and weeks that followed, her eyes began to hurt more and more —intense pain that felt like knives in her eyes, redness and sensitivity to light requiring her to wear sunglasses even indoors. She had difficulty sleeping. </p>
<p>The staff at the centre tried to reassure her, saying it would be temporary, that she is the only one to whom this happened, and that it would heal by itself. Weeks went by, without improvement. She asked to see the surgeon again. </p>
<p>The surgeon told her that her eye was healed and that nothing more could be done for her. His tone and attitude left Karen in great despair. She had feelings of rejection, of denial of what she was experiencing, of incomprehension. The situation affected her work. She began to consult other professionals, always being told that her eyes were perfect. No one seemed to understand.</p>
<h2>A puzzling condition</h2>
<p>Karen actually suffers from neuropathy. It is a disorder of the peripheral nerves that causes symptoms but is not associated with any visible pathology. Following LASIK, the nerves in the cornea remain permanently damaged, like bare electrical wires, or they regenerate but make poor connections. In either case, the nerves send a constant signal of pain to the brain. </p>
<p>After a few weeks/months, the pain becomes internalized (like pain emanating from a phantom limb) and the brain is therefore involved in making the symptoms chronic. Because no one really understands this condition, patients are dismissed and depression sets in as the condition worsens. </p>
<p>The lack of understanding of this case stems from the fact that it is a new field in ocular medicine that is poorly documented in the scientific literature. Treatments are complex and time-consuming. It is, in fact, necessary to create new normal nerve connections while breaking the bad ones, using medication such as cortisone, drops of autologous serum and dressing lenses made of amniotic membrane, etc. </p>
<p>The internalized stimulation must also be addressed, using oral medication prescribed by a specialized pain clinic. Antidepressants may also be helpful, but they usually have the effect of increasing dryness of the eyes, which is counterproductive. Psychotherapy is essential, with a professional trained in the treatment of chronic pain. Cannabis oil could help, in theory, but <a href="https://www.ncbi.nlm.nih.gov/pubmed/29513392">this approach is controversial</a>. </p>
<p>Karen lost her job due to frequent absenteeism and loss of productivity. Her treatments are expensive and are eating into her savings. The financial stress increases as the months go by and the light at the end of the tunnel is not always clear. The situation put great pressure on her marriage and her spouse has found it difficult to cope with the circumstances.</p>
<h2>What to know before deciding to have surgery</h2>
<p>To avoid an outcome like Karen’s, certain precautions can be taken. </p>
<p>First of all, it’s best to avoid making decisions on a whim. Get information from your own eye-care professional, the one who has known your eyes for a long time. Then, get at least two opinions — in different centres — before proceeding, and assess those interactions and the level of trust you feel. </p>
<p>Certain risk factors can reduce the effectiveness of the procedure. For example, many patients opt for surgery because they become intolerant to contact lenses, with uncomfortable and dry eyes at the end of the day. If this is the case, it is because the eye is already prone to dryness and surgery will only increase it. It is therefore necessary to consult your optometrist in order to treat this dryness <em>before</em> the operation, and wait until the surface of the eye is ready for surgery. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/310574/original/file-20200116-72760-4j291i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/310574/original/file-20200116-72760-4j291i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/310574/original/file-20200116-72760-4j291i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/310574/original/file-20200116-72760-4j291i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/310574/original/file-20200116-72760-4j291i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/310574/original/file-20200116-72760-4j291i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/310574/original/file-20200116-72760-4j291i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">If your eye is prone to dryness, surgery will only increase it. Therefore, dryness must be treated before surgery and then wait until the surface of the eye is ready for surgery.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Patients with chronic inflammatory diseases should avoid refractive surgery. These diseases include fibromyalgia, irritable bowel syndrome, Crohn’s disease, lupus and rheumatoid arthritis. Similarly, people with diabetes or severe and chronic migraines <a href="https://www.aafp.org/afp/2017/0515/p637.html">are considered poor candidates</a>. Finally, <a href="https://www.ncbi.nlm.nih.gov/pubmed/22081153">people with obsessive-compulsive disorders should also abstain</a>. For example, they may have the reflex to rub their eyes violently, which can dislodge the tissue flap.</p>
<p>Patients with severe myopia (>8D) as well as patients with large pupils (black part of the eye larger than five millimetres) are prone to the continuous perception of halos and glare after surgery.</p>
<h2>After the operation</h2>
<p>Once the operation has been performed, it’s important to ensure adequate professional followup. Demand to see an optometrist or ophthalmologist at every opportunity. Assistance personnel, even properly trained, are not legally authorized to diagnose your condition (saying that everything is fine is a diagnosis in itself). </p>
<p>It’s also important to never neglect regular eye health checkups. A severely near-sighted person, even after surgery, is still at risk of having a torn retina.</p>
<p>Laser surgery is performed successfully in more than 95 per cent of cases. To avoid chronic problems, it is important to be well assessed and well informed. </p>
<p>You only have two eyes and they are not replaceable. So take every precaution to ensure laser surgery is safe for you.</p><img src="https://counter.theconversation.com/content/130518/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Langis Michaud ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>Laser surgery is touted as a good way to get rid of eyeglasses, but not everyone is suited for it. Plenty of research should be done before taking the plunge.Langis Michaud, Professeur Titulaire. École d'optométrie. Expertise en santé oculaire et usage des lentilles cornéennes spécialisées, Université de MontréalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1223222020-02-05T04:05:06Z2020-02-05T04:05:06ZWhat is Charles Bonnet syndrome, the eye condition that causes hallucinations?<figure><img src="https://images.theconversation.com/files/313643/original/file-20200205-149772-7wauc8.jpg?ixlib=rb-1.1.0&rect=23%2C11%2C7796%2C4760&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">From shutterstock.com</span></span></figcaption></figure><p>Visual hallucinations, or seeing things that aren’t really there, can be frightening and distressing.</p>
<p>They may occur due to a large variety of physical and psychiatric conditions. But a lesser known cause is Charles Bonnet syndrome (pronounced <em>bo-nay</em>), named after the <a href="https://www.britannica.com/biography/Charles-Bonnet">Swiss scientist</a> who first described the condition in 1760.</p>
<p>Charles Bonnet syndrome (also called visual release hallucinations) refers to visual hallucinations in patients with severe vision loss due to eye, optic nerve or brain disease.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/311741/original/file-20200124-81341-jdmhd8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/311741/original/file-20200124-81341-jdmhd8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=739&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311741/original/file-20200124-81341-jdmhd8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=739&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311741/original/file-20200124-81341-jdmhd8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=739&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311741/original/file-20200124-81341-jdmhd8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=929&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311741/original/file-20200124-81341-jdmhd8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=929&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311741/original/file-20200124-81341-jdmhd8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=929&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The syndrome is named after Swiss scientist Charles Bonnet.</span>
<span class="attribution"><span class="source">Wikimedia commons</span></span>
</figcaption>
</figure>
<p>We don’t know the exact cause of Charles Bonnet syndrome. But the most commonly accepted theory is the loss of visual sensory signals to the brain (for example, when a person becomes blind) means the brain cannot put the brakes on <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1479-8301.2009.00288.x">excessive and unwanted brain activity</a>.</p>
<p>This leads the part of the brain responsible for the sensation of vision (the visual cortex) to fire signals inappropriately. The person in turn perceives they are seeing something in the absence of a true stimulus – a visual hallucination.</p>
<p>If these symptoms are affecting you, a friend or family member who has become blind in one or both eyes, it’s important to understand it’s not a sign of “going mad”.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-glasses-help-you-see-84363">Curious Kids: How do glasses help you see?</a>
</strong>
</em>
</p>
<hr>
<h2>What are Charles Bonnet hallucinations like?</h2>
<p>The hallucinations may be “simple” (such as lines, shapes, or flashes of light) or “complex” (such as formed images of animals, like butterflies). Simple hallucinations are much more common.</p>
<p>They may occur for seconds or minutes to hours or continuously, and the <a href="https://www.ncbi.nlm.nih.gov/pubmed/9091601">frequency ranges</a> from isolated episodes to multiple times a day. It’s normal for Charles Bonnet syndrome to <a href="https://pubmed.ncbi.nlm.nih.gov/24825847-negative-outcome-charles-bonnet-syndrome/?from_term=Cox+TM&from_cauthor_id=24825847&from_pos=1">last for years</a>; some people will experience symptoms for the rest of their lives.</p>
<p>The nature of Charles Bonnet hallucinations is highly variable. That is, people who are affected often don’t see the same thing repeatedly, and one person with Charles Bonnet syndrome will see different things from the next person.</p>
<p>Charles Bonnet hallucinations often have little or no emotional meaning, allowing affected people to <a href="https://www.ncbi.nlm.nih.gov/pubmed/8622335">recognise they are not real</a>. This is distinct from hallucinations associated with mental illness.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-age-related-macular-degeneration-59889">Explainer: what is age-related macular degeneration?</a>
</strong>
</em>
</p>
<hr>
<p>Other features of visual hallucinations unique to Charles Bonnet syndrome include:</p>
<ul>
<li><p>hallucinations only appear in the areas where vision is lost (for example, a person who is blind in their left eye will perceive hallucinations only in that eye)</p></li>
<li><p>hallucinations are more frequently seen with the <a href="https://www.ncbi.nlm.nih.gov/pubmed/8622335">eyes open than closed</a>, and may disappear when the person closes their eyes or looks away</p></li>
<li><p>hallucinations are more common in settings of <a href="https://www.ncbi.nlm.nih.gov/pubmed/8622335">sensory deprivation</a> (for example, at night time or in dim lighting, or during periods of inactivity).</p></li>
</ul>
<h2>Who is affected?</h2>
<p>Most people with Charles Bonnet syndrome are <a href="https://www.ncbi.nlm.nih.gov/pubmed/18983551">older adults</a> (usually over 70). This is probably because vision loss is most common in this age group. But any person of any age with acquired vision loss can develop Charles Bonnet syndrome.</p>
<p>The causes of blindness that lead to Charles Bonnet syndrome are usually macular degeneration, glaucoma, <a href="https://www.hollows.org/au/eye-health/diabetic-retinopathy?gclid=Cj0KCQiA2vjuBRCqARIsAJL5a-JKWwv0VqzUfB0BH7XZVpJzIKDMYh_5kfXTuPe13_CGEjkAd4OlnXAaAhV5EALw_wcB&gclsrc=aw.ds">diabetes</a>, <a href="https://www.visionaustralia.org/information/eye-conditions/stroke?utm_source=google&utm_medium=cpc&gclid=Cj0KCQiA2vjuBRCqARIsAJL5a-JO8Ty6cKPi-X8IkE7mWs90kZtUbz4UvwbewgvMyqgXYyybMfFTvVEaAp-pEALw_wcB">stroke</a> and injury – but any disease that leads to blindness may cause Charles Bonnet syndrome.</p>
<p>The syndrome does not occur in congenital blindness (people born blind from birth). </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/311743/original/file-20200124-81369-1sffd3q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/311743/original/file-20200124-81369-1sffd3q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311743/original/file-20200124-81369-1sffd3q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311743/original/file-20200124-81369-1sffd3q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311743/original/file-20200124-81369-1sffd3q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311743/original/file-20200124-81369-1sffd3q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311743/original/file-20200124-81369-1sffd3q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Charles Bonnet syndrome is most common in older people, but can present in anyone with acquired vision loss.</span>
<span class="attribution"><span class="source">From shutterstock.com</span></span>
</figcaption>
</figure>
<p>We currently have no conclusive data on how many Australians have Charles Bonnet syndrome, although <a href="https://www.ncbi.nlm.nih.gov/pubmed/18983551">one study</a> estimated more than 17% of people aged over 60 with impaired vision had it. In <a href="https://www.ncbi.nlm.nih.gov/pubmed/2314586">another study</a>, as many as 57% of participants with vision loss reported perceived visual hallucinations.</p>
<p>Importantly, it may be more common than estimated because of lack of reporting. That is, people who are affected may not report their hallucinations due to fear of psychiatric disease or of being perceived to be “going mad”.</p>
<p>Further, people who do report their symptoms may be <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3555593/">misdiagnosed</a> with psychosis or dementia.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-glaucoma-the-sneak-thief-of-sight-64807">Explainer: what is glaucoma, the 'sneak thief' of sight?</a>
</strong>
</em>
</p>
<hr>
<h2>Treatment options are limited</h2>
<p>Seeing a general practitioner (often in conjunction with a neurologist and/or geriatrician) is an important first step to exclude other causes of hallucinations. These could include dementia, physical neurological conditions (for example, a brain tumour), epilepsy and delirium due to infections or medications. Your doctor may order blood tests and/or brain imaging to rule these out.</p>
<p>Treatment for Charles Bonnet syndrome is very limited, but <a href="https://www.ncbi.nlm.nih.gov/pubmed/11711837">many patients report</a> reassurance is all they need, especially for infrequent hallucinations or those that don’t adversely affect quality of life. </p>
<p>Strategies to minimise the frequency and duration of hallucinations include frequent blinking or rapid eye movement, going to a lighter place or switching a light on, and increasing social interaction, which helps to counter inactivity.</p>
<p>For patients with debilitating symptoms, doctors may trial medications such as <a href="https://www.ncbi.nlm.nih.gov/pubmed/23676430">antidepressants</a>, <a href="https://www.ncbi.nlm.nih.gov/pubmed/23037678">antipsychotics</a> and <a href="https://www.ncbi.nlm.nih.gov/pubmed/27485168">antiepileptic drugs</a>, though their efficacy is variable and may be outweighed by side effects.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/scientists-have-found-how-to-make-people-hallucinate-and-how-to-measure-what-they-see-66842">Scientists have found how to make people hallucinate, and how to measure what they see</a>
</strong>
</em>
</p>
<hr>
<p>Hallucinations may disappear if the cause of vision loss can be corrected (for example, if severe cataracts were causing blindness and the patient has a cataracts operation).</p>
<p>Unfortunately though, generally the causes of vision loss that lead to Charles Bonnet syndrome can’t be treated.</p><img src="https://counter.theconversation.com/content/122322/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jason Yosar does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Charles Bonnet syndrome refers to visual hallucinations in people with acquired vision loss, and symptoms can last for many years.Jason Yosar, Associate Lecturer, School of Medicine, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1249442019-10-14T14:57:32Z2019-10-14T14:57:32ZCurious Kids: how can we see what we are imagining as well as what’s in front of us?<figure><img src="https://images.theconversation.com/files/296890/original/file-20191014-135501-1r4zgav.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6016%2C4016&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">You might be daydreaming, but your brain is hard at work.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/muslim-woman-holding-pen-handput-wireless-1503771215?src=AqmA4eYQgoN-AJNsjbJ_1A-4-27">February_Love/Shutterstock.</a></span></figcaption></figure><p><strong>How can we see what we are imagining but still see what’s in front of us? – Malala Yousafzai class, Globe Primary School, London, UK.</strong></p>
<p>This question gets right at the heart of a big issue for brain scientists. Say you’re daydreaming in class – you can have your eyes open and be aware of the colours and shapes in the classroom and the movement of your teacher and classmates, while at the same time “seeing” whatever you’re thinking of or imagining. </p>
<p>These two kinds of seeing are quite different, but they both happen in the same part at the back of our brain – the <a href="https://kids.kiddle.co/Visual_cortex">visual cortex</a>. Messages coming from different places can cause the visual cortex to become active, and whenever that happens, you “see” things. </p>
<p>To understand how this happens, imagine that you are a brain. You’re locked up inside a skull – a dark, silent vault. You’re in charge of a body, and you somehow need to know what’s going on in the world around you in order to guide this body successfully. </p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a>, which gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a>. We won’t be able to answer every question, but we’ll do our very best.</em></p>
<hr>
<p>One place the messages can come from is your eyes: light bounces off the objects around you and enters your eyes (if they’re open). The light is then focused onto <a href="http://thebrain.mcgill.ca/flash/d/d_02/d_02_cl/d_02_cl_vis/d_02_cl_vis.html">the retina</a> – a thin layer of light sensitive cells on the back of your eyeball. </p>
<p>The cells in the retina then send messages through the optic nerve, back towards the visual cortex. There, <a href="https://www.sciencedaily.com/releases/2019/09/190909123715.htm">different parts of the visual cortex</a> get to work decoding colours, edges and outlines and movements and faces. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/296866/original/file-20191014-135483-1utlkoo.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/296866/original/file-20191014-135483-1utlkoo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296866/original/file-20191014-135483-1utlkoo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296866/original/file-20191014-135483-1utlkoo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296866/original/file-20191014-135483-1utlkoo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296866/original/file-20191014-135483-1utlkoo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296866/original/file-20191014-135483-1utlkoo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296866/original/file-20191014-135483-1utlkoo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">How the brain sees.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/visual-projection-pathway-78253603">Alila Medical Media/Shutterstock.</a></span>
</figcaption>
</figure>
<p>The brain then puts all those visual messages back together again, allowing you to see what’s around you. </p>
<h2>Imagining things</h2>
<p>Remember, as far as the brain’s concerned, it doesn’t really matter where the messages are coming from – when the visual cortex is active, you are seeing. </p>
<p>So the messages could also be coming from other parts of your brain – and this is what happens when you see the things you imagine, remember or dream. </p>
<p>For example, sometimes hearing a song can make you remember where you were the last time you heard it. The sound can cause a cascade of activity in the brain: messages go from the parts of the brain that hear, to the parts that remember and eventually to the parts that see – and that’s how you experience a memory. </p>
<h2>Patterns and predictions</h2>
<p>That explains how your brain manages two different ways of seeing. But it takes a <a href="https://hypertextbook.com/facts/2001/JacquelineLing.shtml">lot of energy</a> for your brain to see what’s going on around you, based on the messages it gets from your eyes. So there’s another trick the brain uses for seeing, to help save itself some effort: it tries to predict what’s about to happen, based on your past experiences.</p>
<p>Even before babies are born, they’re already <a href="https://www.britannica.com/topic/infant-perception#ref321346">learning about the patterns</a> that exist in the world. As babies get older, they learn from these patterns to predict what’s going to happen next. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/296939/original/file-20191014-135501-2wszhj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/296939/original/file-20191014-135501-2wszhj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296939/original/file-20191014-135501-2wszhj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296939/original/file-20191014-135501-2wszhj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296939/original/file-20191014-135501-2wszhj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296939/original/file-20191014-135501-2wszhj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296939/original/file-20191014-135501-2wszhj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296939/original/file-20191014-135501-2wszhj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Learning every day.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/portrait-mom-cute-little-newborn-girl-1530181796?src=UlilVJ96S67OcEmeu7GP1A-1-29">PV Productions/Shutterstock.</a></span>
</figcaption>
</figure>
<p>For example, the first time a baby sees her dad goes around a corner, she might think he’s disappeared, and get upset. Then, when dad comes back, the baby might be surprised and happy. </p>
<p>But after this happens a few times, the baby starts to expect that her dad will come back from around the corner, and won’t be surprised anymore. </p>
<h2>Balancing act</h2>
<p>So, your brain is actually making up what you see all the time, based on messages from different places, as well as your expectations. </p>
<p>The brain keeps a delicate balance between these messages and expectations, to help guide you through the world, while also saving energy. </p>
<p>So if the teacher calls your name while you’re daydreaming in class, your brain quickly switches from imagining things, to paying close attention to the messages coming from your senses about what’s going on in the classroom. </p>
<hr>
<p><em>Children can have their own questions answered by experts – just send them in to <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, along with the child’s first name, age and town or city. You can:</em></p>
<ul>
<li><em>email <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a></em></li>
<li><em>tweet us <a href="https://twitter.com/ConversationUK">@ConversationUK</a> with #curiouskids</em></li>
<li><em>DM us on Instagram <a href="https://www.instagram.com/theconversationdotcom/">@theconversationdotcom</a></em></li>
</ul>
<p><em>Here are some more <a href="https://theconversation.com/topics/curious-kids-36782?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Curious Kids</a> articles, written by academic experts:</em></p>
<ul>
<li><p><em><a href="https://theconversation.com/curious-kids-why-is-the-sea-salty-124743?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Why is the sea salty? – Torben, aged nine, Sussex, UK.</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-why-do-i-have-boogies-and-why-does-my-nose-keep-replicating-them-122660?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Why do I have boogies and why does my nose keep replicating them? – Duncan, aged seven, Sydney, Australia.</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-could-humans-live-on-kepler-452-b-123786?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Can we live on Kepler 452-b? – Year Five, Globe Primary School, London, UK.</a></em></p></li>
</ul><img src="https://counter.theconversation.com/content/124944/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Niia Nikolova receives funding from The Leverhulme Trust.</span></em></p>Your brain balances messages coming from lots of different places to help you see, imagine, remember and dream.Niia Nikolova, Research Associate, University of Strathclyde Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1211612019-09-24T13:43:05Z2019-09-24T13:43:05ZThird of children who need glasses aren’t wearing them – and this may be impacting their academic, social and emotional learning<figure><img src="https://images.theconversation.com/files/291158/original/file-20190905-175691-12ftf32.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/download/success?u=http%3A%2F%2Fdownload.shutterstock.com%2Fgatekeeper%2FW3siZSI6MTU2NzcyNTUzOSwiYyI6Il9waG90b19zZXNzaW9uX2lkIiwiZGMiOiJpZGxfMTQ4NDY2Njk2MCIsImsiOiJwaG90by8xNDg0NjY2OTYwL2h1Z2UuanBnIiwibSI6MSwiZCI6InNodXR0ZXJzdG9jay1tZWRpYSJ9LCJaWEEwdkZZeVZ6QnF6bGlrQnI0R0RhcEdqVkEiXQ%2Fshutterstock_1484666960.jpg&pi=33421636&m=1484666960">POP-THAILAND/Shutterstock</a></span></figcaption></figure><p>It’s a problem many teachers are familiar with, a student apparently struggling in class, but in fact just suffering from something that’s easily fixed – vision problems – with an inexpensive pair of glasses.</p>
<p>It’s estimated that more than <a href="https://www.aop.org.uk/about-aop/media-centre/press-releases/2019/08/23/why-a-sight-test-tops-the-back-to-school-checklist">3.4m children aged four to 16</a> in the UK have been diagnosed with a vision problem. Indeed, vision screenings are carried out routinely in schools by the <a href="https://www.gov.uk/government/publications/child-vision-screening/service-specification">NHS</a> and glasses are free. </p>
<p>Approximately <a href="https://bmjopen.bmj.com/content/8/6/e021277">15%</a> of students fail the screening and a third do not obtain the glasses or the prescription needed, which can have an impact on their reading and mathematics achievement. But NHS rules prevent schools from receiving the results of the screening, which instead go into letters sent to students’ homes. </p>
<p><a href="https://bmjopen.bmj.com/content/8/6/e021277">Research shows</a> that in poorer, <a href="https://www.bioj-online.com/articles/abstract/10.22599/bioj.71/">high-poverty families</a>, or those where parents don’t read English, getting glasses isn’t always a priority. And so it seems students from the most disadvantaged backgrounds are the most likely to suffer from uncorrected vision problems. </p>
<p>Research in <a href="https://doi.org/10.1086/700631">China</a> and the <a href="http://dx.doi.org/10.1016/j.jaapos.2016.07.112">US</a> highlights that disadvantaged children are more likely to experience vision problems and less likely to receive the treatment and eyeglasses they need. <a href="http://dx.doi.org/10.1016/j.edurev.2017.12.001">Research</a> also suggests that interventions aren’t always implemented by schools in the way that’s <a href="https://doi.org/10.1016/j.tate.2017.11.010">intended</a>. </p>
<h2>Glasses in Classes</h2>
<p>Our new study, <a href="https://educationendowmentfoundation.org.uk/projects-and-evaluation/projects/glasses-in-classes/">Glasses in Classes</a>, aims to identify young children in a disadvantaged multi-ethnic community who need glasses and get them wearing them – with the aim of improving their academic, social and emotional learning long-term. It is the first ever UK study to examine the impact of a school-based intervention to support the wearing of glasses in young children and to measure subsequent improvement of the child’s academic and health outcomes. The research project is funded by the Education Endowment Foundation. </p>
<p>This large-scale randomised controlled trial involving 100 schools is part of a collaboration between the University of Nottingham, NHS Bradford Teaching Hospitals Foundation Trust and the University of Leeds. It will see reception year children (four- to five-year-olds) participate in vision screenings and academic achievement assessments. In half the schools, those who fail the eye assessment will be given glasses – along with a spare pair to be kept in school as needed. In the other schools, business-as-usual procedures will be followed. That is, parents will receive a letter. </p>
<p>In the treatment schools, there will be training materials for school staff, campaign materials for families, school-based systems to ensure children wear their glasses in school and spare glasses will be made available. Schools will also be able to find out the results of the vision assessments, and each school will have a designated lead for vision issues. Children who need follow up after their vision screening will have repeat vision and achievement assessments in 2020. </p>
<h2>Easily fixed</h2>
<p>Existing <a href="https://www.sciencedirect.com/science/article/pii/S1529183910002769">research</a> shows that the current system leaves some children – particularly those from high-poverty backgrounds – at a disadvantage in school. Vision problems left untreated result in some children having learning difficulty and needing remedial services – a major cost for school systems. </p>
<p>Indeed, more than <a href="https://educationendowmentfoundation.org.uk/tools/guidance-reports/preparing-for-literacy/">one in ten children</a> are estimated to have an undiagnosed common vision problem that affects their learning and development. Yet a quarter of four- to 16-year-olds have <a href="https://www.aop.org.uk/about-aop/media-centre/press-releases/2019/08/14/why-an-eye-examination-should-make-the-back-to-school-checklist">never been taken for a vision assessment</a> by their parents – many of whom say they waited for their child to show certain behaviours, such as sitting too close to the television, before taking them for a vision assessment.</p>
<p>But it’s a simple problem, easily prevented. And we hope our project could be the start of something that could make a huge difference to children’s lives.</p><img src="https://counter.theconversation.com/content/121161/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Professor Roisin P. Corcoran receives funding from the Education Endowment Foundation (Grant 1173696). Views expressed do not necessarily represent the Education Endowment Foundation's positions. </span></em></p>Research suggests that students from the most disadvantaged backgrounds are the most likely to suffer from uncorrected vision problems.Roisin P. Corcoran, Chair in Education and Professor, University of NottinghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1138782019-03-27T22:52:10Z2019-03-27T22:52:10ZGlaucoma: Vision’s silent killer<figure><img src="https://images.theconversation.com/files/264690/original/file-20190319-60956-1szd9hl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Glaucoma is an insidious disease that is sometimes confused with inattention or vision deteriorating with age, yet it can kill your eyesight and leave you blind. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/">Shutterstock</a></span></figcaption></figure><p>Like high blood pressure, glaucoma is a devious disease.</p>
<p>It develops without causing symptoms obvious to the average person yet its consequences are devastating: it can lead to blindness.</p>
<p>It affects six per cent of Caucasians over 70 years of age, with a significant increase every decade. Older African Americans are most affected, with a prevalence of 17 per cent while people of Asian origin appear to be <a href="http://www.dx.doi.org/10.1167/iovs.06-0299">relatively protected</a>, with the disease affecting only three per cent of their population.</p>
<p>Does this mean we should not be worried about glaucoma before we reach a venerable age? Certainly not, especially if it has affected a relative in the family, such as a father, mother, siblings or grandparents.</p>
<p>Ask Brian, who never saw it coming.</p>
<h2>Some alarm bells</h2>
<p>Brian’s name is fictitious in this case but he has a very real story. He is a 45-year-old Black man. He is healthy, doesn’t take any medication, and works as a forklift operator in a warehouse. Brian noticed that, in recent years, he had occasionally hit things with his machine but attributed these minor incidents to poor lighting or lack of attention. He didn’t take any action until his supervisor asked him to get a visual examination.</p>
<p>Brian thought it was a good idea, especially since he was finding it harder to read the purchase orders and other paperwork essential to his job. He had never been examined before and had never worn glasses. Since he was adopted, he wasn’t aware of eye diseases in his family.</p>
<p>He was fairly confident in his vision when he presented himself in January at a private clinic where I occasionally practice. To his surprise, I didn’t just make him read letters on a chart but performed several tests. He had to identify lights appearing in a large dome each time they showed up; a picture was taken of the inside of his eye and examined through a microscope.</p>
<p>Then the optometric diagnosis was made: Brian was suspected of having glaucoma, a term he had never heard before and which seemed quite frightening when said out loud.</p>
<p>It is a disease <a href="https://www.ncbi.nlm.nih.gov/pubmed/27898466">which is considered hereditary</a>, although several other forms may be contracted — for example after surgery or other trauma or due to the side-effects of medication. Without treatment, it is considered <a href="http://www.dx.doi.org/10.1001/jama.2014.3192">a disease that can blind you</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/262209/original/file-20190305-48444-14h579y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/262209/original/file-20190305-48444-14h579y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/262209/original/file-20190305-48444-14h579y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/262209/original/file-20190305-48444-14h579y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/262209/original/file-20190305-48444-14h579y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/262209/original/file-20190305-48444-14h579y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/262209/original/file-20190305-48444-14h579y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This is an image of the retina of the left eye of a 76-year-old woman who has glaucoma.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Narrowed field of vision</h2>
<p>While the symptoms can remain hidden until the disease is in its late stages, visible clinical signs can be detected when eye health is examined by a competent professional. Clinical signs can appear at any age but are more common after the age of 50.</p>
<p>By its nature, glaucoma is considered a progressive optic neuropathy, characterized by degenerating retinal ganglion cells and <a href="https://www.ncbi.nlm.nih.gov/pubmed/24825645">physiological changes in the optic nerve</a>. </p>
<p>In addition to age and ethnic origin, <a href="https://www.ncbi.nlm.nih.gov/pubmed/12049575">a significant risk factor</a> is increased <a href="https://www.ncbi.nlm.nih.gov/books/NBK532237/">“intraocular pressure”</a>. This may occur because of an overproduction of aqueous humour in the eye, or as a result of a restriction of the normal flow of the eye. An examination by an ophthalmologist or optometrist (depending on the jurisdiction) will determine which mechanisms are involved and help decide the most appropriate treatment. </p>
<p>Clinical tests also target the visual field, where glaucoma can most obviously show up. As the disease progresses, more nerve fibres are affected, resulting in a narrower field of vision for the patient. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/266188/original/file-20190327-139349-1hx5gsm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/266188/original/file-20190327-139349-1hx5gsm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/266188/original/file-20190327-139349-1hx5gsm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/266188/original/file-20190327-139349-1hx5gsm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/266188/original/file-20190327-139349-1hx5gsm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/266188/original/file-20190327-139349-1hx5gsm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/266188/original/file-20190327-139349-1hx5gsm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Commonplace accidents on the job can be important signs of vision loss.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Imaging tests are increasingly complemented by an analysis of nerve fibre and optic nerve layers using optical coherence tomography (OCT). By comparing a patient’s scan with a database matched for age and ethnicity, <a href="https://doi.org/10.1016/j.ophtha.2017.07.015">it may be possible to identify glaucoma attacks early</a> before there is any loss of visual field. Some OCT tests also let us get images of the structures of the eye that could have a negative impact on the circulation of aqueous humour, a fluid in the structure of the eye that supports the lens. </p>
<p>Finally, eye structures are examined using a biomicroscope (slit lamp), with specialized lenses or magnifying glasses (gonioscope).</p>
<p>In Brian’s case, his optic nerves had questionable appearances. Intraocular pressure was high, at 28 mm Hg in each eye. (Pressure below 20 mm Hg is usually considered normal.) All other eye structures were considered normal.</p>
<h2>Treatment options</h2>
<p>Once the diagnosis was confirmed, it was important for Brian to understand that no treatment will cure glaucoma, but we can slow its progression to limit the negative consequences on sharpness and field of vision. Once you have glaucoma, you have it for the rest of your life and complying with treatment is vital to maintaining vision.</p>
<p>Treatment usually begins with topical medications that either reduce the production of aqueous humour or promote its evacuation from the inside of the eye, or both. Some other drugs may also protect the optic nerve from damage caused by glaucoma. </p>
<p>Once drug treatment has been started, it should never be halted without the advice of a professional. Any side effects, such as redness, dry eyes or intense tingling must also be reported so they can be treated or prescriptions can be modified.</p>
<p>An ophthalmologist can also propose surgical or laser interventions at any time in order to <a href="https://www.ncbi.nlm.nih.gov/pubmed/28237137">better control the patient’s condition</a>. </p>
<p>Brian left the office surprised by his condition but feeling reassured about what will happen next. He realizes now that what he thought were commonplace accidents were actually important signs of vision loss. He will have to learn to adapt to this new reality and hope that his remaining vision will allow him to be able to continue to drive his forklift and his car.</p>
<p>He promised to talk to everyone around him, especially his children, about his disease so they can be examined and have it detected in time. Everyone over the age of 50 should be checked by an optometrist or ophthalmologist, as well as people of any age whose parents or relatives have glaucoma. </p>
<p>It’s the best way to keep this silent killer of vision at bay.</p><img src="https://counter.theconversation.com/content/113878/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Langis Michaud ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>Glaucoma is a serious disease which, if left untreated, can cause blindness. A professor of optometry explains the risks, process of diagnosis and available treatments.Langis Michaud, Professeur Titulaire. École d'optométrie. Expertise en santé oculaire et usage des lentilles cornéennes spécialisées, Université de MontréalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1115992019-02-12T22:48:25Z2019-02-12T22:48:25ZToo much screen time linked to an epidemic of myopia among young people<figure><img src="https://images.theconversation.com/files/258623/original/file-20190213-90497-18zyb99.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Today’s young people don’t play outside as much as their predecessors and are heavy users of electronics.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>Ask anyone about the benefits of technology and it probably won’t take them long to rhyme off a list of examples: it helps broaden your knowledge, connect with friends, both new and old, and allows you to see things you’ve never seen before.</p>
<p>But what about the drawbacks? Here’s a major one: increased screen time is hard on your eyes.</p>
<p>In fact, more and more young people are wearing glasses to correct their nearsightedness. This trend has prompted optical health experts to determine if the use of electronic devices such as computers, tablets and smart phones is leading to a deterioration in sight that is reaching epidemic proportions.</p>
<p>Let’s take the example of Pauline — although she could just as easily be a David or a Jason. She is 10 years old and a studious child, doing well in school. Like any young person her age, she loves to use her tablet computer to study or have fun. She’s on it two hours a day, plus weekends.</p>
<p>Pauline may be in for a change, however. She has recently been diagnosed with nearsightedness and her optometrist has strongly recommended that she — and her parents — limit her use of electronic devices and spend more time playing outside.</p>
<p>Pauline isn’t happy. She thinks it’s not fair.</p>
<p>But her case raises the question: what is the link between the use of electronic devices and the appearance of myopia?</p>
<h2>A public health issue</h2>
<p>Forty per cent of North Americans are affected by myopia. The number of cases <a href="https://www.ncbi.nlm.nih.gov/pubmed/18695106">doubled between 1972 and 2004</a> and continues to grow at a rate that <a href="https://www.ncbi.nlm.nih.gov/pubmed/24357836">qualifies the phenomenon as an epidemic</a>.</p>
<p>In Europe, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4504030/#sec2title">myopia is prevalent among 42.2 per cent of adults aged 25 to 29 years</a>, almost twice that of adults aged 55 to 59 years.</p>
<p>This suggests there is a real public health issue facing us — and not just the common problem of an error in the refraction of the eye which shows up as blurred vision when looking into the distance.</p>
<p>In fact, high amounts of myopia <a href="https://www.ncbi.nlm.nih.gov/pubmed/22772022">significantly increases the risk of major ocular health disorders </a>such as retinal tearing (21 times greater), glaucoma (40 times) or cataracts (six times).</p>
<p>An eye that becomes short-sighted becomes longer. The stretching is proportional to <a href="https://www.ophthalmologymanagement.com/issues/2012/july-2012/measuring-axial-length">the increase in myopia</a>. The more the eye stretches, the more the retina, which lines the inside of the eye, becomes thinner. Symptoms such as cracks, abnormal development of subretinal blood vessels and bleeding may appear.</p>
<p>Ultimately, the very nearsighted patient has a more than 50 per cent risk of spending the rest of his or her life legally blind — in other words living with vision reduced by 60 per cent. This means that the <a href="https://www.ncbi.nlm.nih.gov/pubmed/20363029">length of their eye exceeds 28 mm</a> (the normal length is 23 mm) or that <a href="https://www.ncbi.nlm.nih.gov/pubmed/?term=Tideman+JAMA+ophthalmol">the myopia levels exceeds six diopters</a>. (Diopters is a unit of measurement used to calculate eyesight — the further away from zero indicates a worsening in vision.) It is important to intervene before this happens to avoid these levels.</p>
<p>(In Canada, <a href="https://www.epso.ca/vision-health/general-interest/legal-blindness/">legal blindness is defined by a visual acuity of less than 20/200 </a>in the best eye with the help of glasses or contact lenses. A legally blind person therefore sees, at best, 20 times worse than a person with normal acuity.)</p>
<h2>What’s behind the epidemic?</h2>
<p>There are many causes of onset myopia. Genetics plays an important role but epigenetics — the environment in which the child evolves — is <a href="https://www.ncbi.nlm.nih.gov/pubmed/?term=Rong+Asia+Pacific+Pacific+J+Ophthalmol">a more important factor</a>.</p>
<p>And what has changed in our environment to explain the recent myopia epidemic? The impact of technology, which has seen a boom in recent years, is being closely examined.</p>
<p>For example, a rapid increase in visual problems has been noted since the introduction of the smartphone in 2007. While the device itself does not emit harmful radiation, it requires the user to read its screen at a distance of 20 cm rather than the normal distance of 45 cm to 50 cm. It has been suggested that this close distance <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4473431/">boosts the risk of developing myopia by eight times</a>, especially if both parents are myopic.</p>
<p>Ambient lighting also plays a role because <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4526691/">the use of fluorescents</a>, such as in classrooms, also promotes myopia. When a tablet is used in such an environment, the effect is multiplied tenfold.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/252534/original/file-20190104-32142-2rkjfs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/252534/original/file-20190104-32142-2rkjfs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=303&fit=crop&dpr=1 600w, https://images.theconversation.com/files/252534/original/file-20190104-32142-2rkjfs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=303&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/252534/original/file-20190104-32142-2rkjfs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=303&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/252534/original/file-20190104-32142-2rkjfs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=380&fit=crop&dpr=1 754w, https://images.theconversation.com/files/252534/original/file-20190104-32142-2rkjfs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=380&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/252534/original/file-20190104-32142-2rkjfs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=380&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Unlike paper books, tablet and computer screens emit blue light. The short wavelengths from blue light are perceived in front of the others by the eye, which generates a myopia stimulus.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Unlike books printed on paper, tablet and computer screens are optically associated with so-called chromatic aberrations. The shortest wavelengths (blue light) are perceived in front of the others by the eye, which generates a myopia stimulus. There is a dose and response effect here, suggesting that prolonged use leads to more negative effects.</p>
<p>Today’s young people don’t play outside as much as their predecessors and are heavy users of electronics. However, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3474591/">exposure to daylight has a protective effect against myopia</a>. These beneficial effects are decreased, but not negligible, <a href="https://www.ncbi.nlm.nih.gov/pubmed/30288926">during less sunny months</a> or when <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5599950/">myopia is already present</a>.</p>
<h2>Possible solutions</h2>
<p>The purpose of myopia treatment is to reduce the rate of progression of the dioptric, but above all to slow down the elongation of the eye. If, obviously, we cannot play with genetics, it is imperative to influence epigenetics and therefore the environment in which the child evolves.</p>
<p>Therefore, using any electronic media before the age of two should be avoided, <a href="http://pediatrics.aappublications.org/content/pediatrics/early/2011/10/12/peds.2011-1753.full.pdf">even if it’s only for a few minutes</a>. A limit of one hour per day should be the rule for those between two and five years of age and the emphasis should be put on educational sites or applications that promote interactions between the parent and child.</p>
<p>While school requests should be taken into consideration, the use of electronic media should continue to be limited as the child gets older. A maximum of one hour, besides school work, must be observed for good eye health. A two-minute break after every 30 minutes of device use will also lessen harmful effects and <a href="https://bmjopen.bmj.com/content/5/1/e006748">exposure to a device should be avoided at least one hour before sleep.</a></p>
<p>Children should also get a minimum of 45 minutes of daylight per day. They can get this by walking to school or participating in such activities as regular outdoor sports.</p>
<p>The next step is to ensure the co-ordination of both eyes, from far away but especially close up. An optometrist will need to perform an orthopic check-up and correct, by exercise or optical means, any anomaly that may have been detected.</p>
<p>Finally, optical correction must be chosen with the goal of slowing down the progression. In rare cases, glasses with anti-myopia lenses may be prescribed. They provide a <a href="https://www.ncbi.nlm.nih.gov/pubmed/26826749">deceleration rate of about 30 per cent </a>. Specialized contact lenses are often preferred and offer control ranging from 50 per cent to 80 per cent. The contact lens treatment is available from the age of seven, and will be periodically reassessed according to the child’s changing needs.</p>
<p>In short, myopia is not just a commonplace vision defect. It is a significant risk factor for serious eye disease. We must therefore do everything possible to slow its progress and protect our children’s vision — and that means also reviewing their relationship with electronic devices.</p><img src="https://counter.theconversation.com/content/111599/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Langis Michaud has received funding from: Johnson and Johnson, Bausch and Lomb, Cooper Vision and is a member of l'Association des Optométristes du Québec.</span></em></p>Myopia is a major risk factor for serious eye diseases. It has become epidemic among children, particularly because of their heavy use of electronic devices.Langis Michaud, Professeur Titulaire. École d'optométrie. Expertise en santé oculaire et usage des lentilles cornéennes spécialisées, Université de MontréalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1090392019-01-15T12:21:18Z2019-01-15T12:21:18ZHow our unconscious visual biases change the way we perceive objects<figure><img src="https://images.theconversation.com/files/253854/original/file-20190115-152977-e05sgo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/oop-something-went-wrong-close-picture-1255191481?src=Dq1JkImjXoW6GLOaL-eXjw-1-44">Roman Samborskyi/Shutterstock</a></span></figcaption></figure><p>As the old saying goes, beauty is in the eye of the beholder. But while we can appreciate that others might hold different opinions of objects we see, not many people know that factors beyond our control can influence how we perceive the basic attributes of these objects. We might argue that something is beautiful or ugly, for example, but we would be surprised to learn that the same object is perceived as a sphere by one person but as a cube by another. </p>
<p>The process of visual perception is a <a href="https://www.sciencedirect.com/science/article/pii/S0042698901001730">best guess</a> scenario. When we look at something, the brain uses visual cues –sensory signals that convey information – to help work out what that thing is. This means that our perception of the world is not a simple reflection of sensory information, it is an <a href="https://www.sciencedirect.com/science/article/pii/S0042698901001730">interpretation</a> of it. </p>
<p>Along with colour and motion, the perception of depth is very important to help us visually perceive things. Depth helps us to understand the shape of objects and their location relative to ourselves. We need to understand it to move around our environment and interact with objects. Imagine trying to pick something up if you don’t know what shape it is, or crossing the road if you can’t accurately perceive the distance of the cars. </p>
<p>To perceive depth, humans and animals rely on a number of brain processes and visual cues. One of these cues is shading information: we can perceive depth by simply interpreting the patterns of light and dark on the surface of objects, without needing to refer to any other information.</p>
<p>In order to perceive depth from shading patterns, we must either know or assume the position of the light source that illuminates the object. By default, if the light source is not apparent, we assume that the light comes from above the object. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/253625/original/file-20190114-43535-1en6bnm.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/253625/original/file-20190114-43535-1en6bnm.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=321&fit=crop&dpr=1 600w, https://images.theconversation.com/files/253625/original/file-20190114-43535-1en6bnm.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=321&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/253625/original/file-20190114-43535-1en6bnm.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=321&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/253625/original/file-20190114-43535-1en6bnm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=404&fit=crop&dpr=1 754w, https://images.theconversation.com/files/253625/original/file-20190114-43535-1en6bnm.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=404&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/253625/original/file-20190114-43535-1en6bnm.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=404&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The circle on the left is usually perceived as convex, while the circle on the right is usually perceived to be concave.</span>
</figcaption>
</figure>
<p>Look at the image to the right. The sphere on the left will most likely appear convex (protruding outwards). This is because it is lighter at the top, which reflects the patterns of light and dark that would be produced on a convex object if there was an overhead light source. The sphere on the right usually looks concave (recessed inwards) because it’s darker at the top. Again, if there was an overhead light source, a concave object would be darker at the top because the upward-facing portions of the object catch the light, and the downward-facing portions are obscured.</p>
<p>The light-from-above assumption isn’t very surprising, since we evolved in a world with an overhead light source – the sun. A less intuitive finding that scientists have made, however, is that light is assumed to originate from the <a href="https://www.nature.com/articles/nn0798_183">upper left-hand side of space</a>. We know this because, in the lab, people are generally faster to detect convex spheres from a group of concave spheres if the convex sphere is lit from the above-left, and they more readily <a href="https://jov.arvojournals.org/article.aspx?articleid=2193838">categorise these left-lit objects as convex</a>. </p>
<p>Experiments that measure electrical activity in the brain have also found that <a href="https://journals.lww.com/neuroreport/Citation/2003/05230/Neural_correlates_of_shape_from_shading.13.aspx">left-lit objects are more rapidly recognised</a> than those lit from other orientations. This is demonstrated in the image below. Both the upper and lower rows of circles contain one that is different from the others – <a href="https://www.biac.duke.edu/library/papers/2004_Neuropsychologia_Huettel.pdf">an oddball</a>. The oddball in the top row is lit from the above-left and it should “pop out” from the others, which have an exactly opposite shading pattern. The circles in the lower line also have an opposite shading pattern, but the oddball is much harder to detect because its shading pattern does not conform to our above-left expectations. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/253760/original/file-20190114-43535-133b7tv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/253760/original/file-20190114-43535-133b7tv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=285&fit=crop&dpr=1 600w, https://images.theconversation.com/files/253760/original/file-20190114-43535-133b7tv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=285&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/253760/original/file-20190114-43535-133b7tv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=285&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/253760/original/file-20190114-43535-133b7tv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=358&fit=crop&dpr=1 754w, https://images.theconversation.com/files/253760/original/file-20190114-43535-133b7tv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=358&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/253760/original/file-20190114-43535-133b7tv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=358&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The oddball sphere should pop out from among the others in the top line, but is much more difficult to see in the bottom line (it is the final circle in the sequence).</span>
</figcaption>
</figure>
<p>However, like the overhead light source assumption, the leftward light source bias exists outside conscious awareness. And not everyone experiences it. For example, people who read from right-to-left (such as Arabic or Hebrew readers) sometimes show rightward biases or <a href="https://jov.arvojournals.org/article.aspx?articleid=2193838">smaller left biases</a> than people who read left-to-right. Interestingly, people who have recently suffered a stroke in the right-hemisphere parietal lobe <a href="https://www.sciencedirect.com/science/article/abs/pii/S0278262609001821">typically demonstrate a rightward light source bias</a> too. This could indicate that the right parietal lobe – which is responsible for <a href="https://www.neuroskills.com/brain-injury/parietal-lobes.php">perceiving the physical environment and integrating</a> information from the senses, such as sight and hearing – is ordinarily responsible for orienting visual attention to the left side of space, because disrupting the normal function of that region shifts attention rightward. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/253624/original/file-20190114-43541-10a5i3y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/253624/original/file-20190114-43541-10a5i3y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=540&fit=crop&dpr=1 600w, https://images.theconversation.com/files/253624/original/file-20190114-43541-10a5i3y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=540&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/253624/original/file-20190114-43541-10a5i3y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=540&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/253624/original/file-20190114-43541-10a5i3y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=679&fit=crop&dpr=1 754w, https://images.theconversation.com/files/253624/original/file-20190114-43541-10a5i3y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=679&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/253624/original/file-20190114-43541-10a5i3y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=679&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The honeycomb stimulus: some people perceive the central hexagon as convex, others as concave.</span>
</figcaption>
</figure>
<p>The fact that a person’s culture or brain changes can result in subjective differences in perception means that some people will perceive concavity in certain images, whereas others will perceive convexity. The honeycomb image to the right is one example that we use experimentally to find out how someone perceives depth from shading. Some people will perceive the central hexagon as convex, while others (usually those with a left bias) as concave.</p>
<p>We all assume everyone perceives the world as we do, even if their impressions might be different from ours. It is difficult to imagine that some people might perceive three-dimensional depth differently from ourselves. But if our perception of something as basic as whether an object is convex or concave is not reliably the same across people and populations, how can we begin to judge the subjective experience? Biases in visual perception might explain some differences in aesthetic judgements, but if we can explain why different people have an opposite perception of the same thing, it could, ultimately, further our understanding of human cognition on a wider scale.</p><img src="https://counter.theconversation.com/content/109039/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Beverley Pickard-Jones received funding from the James Pantyfedwen Foundation in 2017.</span></em></p>We rely on depth to perceive objects, but not all of us see depth in the same way.Beverley Pickard-Jones, PhD Researcher, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1084892018-12-31T10:39:53Z2018-12-31T10:39:53ZCurious Kids: how do eyes grow?<figure><img src="https://images.theconversation.com/files/250453/original/file-20181213-178582-1b7j0lu.jpg?ixlib=rb-1.1.0&rect=9%2C0%2C6253%2C3652&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/extreme-closeup-young-woman-crosseyed-144570890?src=0-iqHIJ77V0YblVQ_8ZXGg-1-17">Shutterstock.</a></span></figcaption></figure><p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series for children of all ages, where The Conversation asks experts to answer questions from kids. All questions are welcome: find out how to enter at the bottom of this article.</em> </p>
<hr>
<blockquote>
<p><strong>How do eyes grow? – Annette, age seven, Stratford-upon-Avon, UK</strong></p>
</blockquote>
<p>Thanks for this brilliant question, Annette. Human beings’ eyes are quite unusual, because they are almost full sized when we are born. They do grow a bit bigger – but only by a few millimetres. But that’s not all that happens – when we are very young, our brains also learn to make images from the messages it gets from our eyes, and that’s how we learn to see.</p>
<p>Let’s start at the beginning: before we are born, we grow inside our mum’s body. We start life being <a href="https://www.ehd.org/virtual-human-embryo/">very tiny</a> – about the size of the top of a pin, or a full stop in a book. </p>
<p>Even though we start out very small, we are made up of special tiny building blocks called cells. </p>
<p>Every day, the number of cells gets bigger and bigger, and <a href="https://biologywise.com/cell-differentiation">different types of cell</a> start to form as well. </p>
<h2>The starting point</h2>
<p>Each different type of cell is <a href="https://www.bbc.com/bitesize/guides/zghqfcw/revision/4">the starting point</a> for the different parts of our bodies. So one type of cell might help to grow our ears, while another will help to grow our hearts, and so on.</p>
<p>There are three different types of cell that work to make our eyes. When we have been growing inside mum for about three weeks, our eyes start to be created. </p>
<p>After four weeks, special connectors called “nerves” start to grow, to connect our eyes with our brain. <a href="https://www.britannica.com/science/optic-nerve">These connectors</a> are very important, because they help our eyes to tell our brain about what we are seeing.</p>
<p>And by the time we have been growing inside mum for ten weeks, our eyes are fully formed, with all the parts they need in order to see. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/250454/original/file-20181213-178582-80cxoc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/250454/original/file-20181213-178582-80cxoc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=446&fit=crop&dpr=1 600w, https://images.theconversation.com/files/250454/original/file-20181213-178582-80cxoc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=446&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/250454/original/file-20181213-178582-80cxoc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=446&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/250454/original/file-20181213-178582-80cxoc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=560&fit=crop&dpr=1 754w, https://images.theconversation.com/files/250454/original/file-20181213-178582-80cxoc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=560&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/250454/original/file-20181213-178582-80cxoc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=560&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Growing in mum’s belly.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-rendered-medically-accurate-illustration-fetus-458874238?src=Y0iAQ1jxBeNyXqY3GJ68FA-1-5">Shutterstock.</a></span>
</figcaption>
</figure>
<p>At this stage, our whole body is about the size of a strawberry, so you can imagine how small our eyes must be. For the next 30 weeks or so, the baby will use energy from mum to grow bigger and bigger, until it is born.</p>
<h2>Learning to see</h2>
<p>When we are born, our eyes alone are about the size of a large raspberry. They don’t grow much bigger than that, and end up being about the size of a cherry. </p>
<p>In fact, when you think about how much bigger a grown up hand is than a baby’s hand, it’s clear that our eyes don’t have to grow very much at all, compared with the rest of our body. </p>
<p>What does change, though, is our sight. As soon as we open our eyes after we are born, they start to send signals along the nerves connecting to our brain. </p>
<p>But at first, we don’t see very well, and most things will look quite blurry. This is because our brain <a href="https://lookafteryoureyes.org/eye-care/children/stages-of-development/">needs to learn</a> how to turn information from our eyes into what we see. </p>
<p>As we get older, our vision gets better and better. When we are about eight weeks old, we can start to focus our eyes on the faces of people close to us. When we are three months old, we start to be able to follow things if they are moving around. </p>
<p>By five months old, we <a href="https://www.aao.org/eye-health/tips-prevention/children-vision-development">can see colours</a>, and by the time we are three years old, we can see things <a href="http://www.lea-test.fi/en/eyes/children.html">just as clearly</a> as most grown-ups.</p>
<p>It’s really important that we look after our eyes. We can do this by wearing sunglasses on bright days to protect our eyes from the sun, and by having our eyes checked over every year by an optometrist or eye doctor, so that we have clear sight long into adulthood.</p>
<hr>
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em>Please tell us your name, age and which town or city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question, but we will do our best.</em></p>
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<p><em>More <a href="https://theconversation.com/topics/curious-kids-36782?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Curious Kids</a> articles, written by academic experts:</em></p>
<ul>
<li><p><em><a href="https://theconversation.com/curious-kids-what-existed-before-the-big-bang-did-something-have-to-be-there-to-go-boom-103742?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">What existed before the Big Bang? – Ethan, age ten, Sydney, Australia</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-what-is-a-species-107402?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">What is a species? – Finlay, age four, London, UK</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-how-do-moths-eat-our-clothes-105978?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">How do moths eat our clothes? – Albie, age five, Australia</a></em></p></li>
</ul><img src="https://counter.theconversation.com/content/108489/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hannah Bartlett does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Our eyes don’t grow much at all – but when we’re very young, we still need to learn how to see.Hannah Bartlett, Reader in Optometry, Aston UniversityLicensed as Creative Commons – attribution, no derivatives.