Short-sightedness is caused by excessive growth of the eyeball, making it more difficult for the lens to focus an image on the retina, but dopamine seems to put the brakes on this and keep it in a healthier shape.Īlternatively, it could be a question of colour. A more widely accepted idea is that sunshine triggers the release of dopamine, directly in the eye itself. Perhaps it is because sunlight stimulates the production of Vitamin D, which is responsible for a healthy immune system and brain, and might also regulate eye health. Study after study, from Europe, Australia, and Asia, have all found that people who spend more time outside are far less likely to get short-sighted than people whose lives are mostly confined within four walls. Instead, many now argue that it is the time spent indoors, rather than reading per se, that matters most. One large study following the progress of children in Ohio appeared to show no correlation at all with reading, though we should not yet rule out the effect completely, says Jacobsen. “The more we studied it and measured the amount people read, the more the association seemed to vanish,” says Flitcroft. Yet epidemiological studies suggest the effects are much smaller than once believed. At first the evidence seemed to be strong: just look at the sea of glinting specs in any university lecture theatre or academic conference, and you would seem to find proof of a link. Part of that change would have been education and literacy – one of the most common explanations for short-sightedness. Our genes may still play a role in deciding who becomes short-sighted, but it was only through a change in environment that the problems began to emerge. “Short-sightedness is an industrial disease,” says Ian Flitcroft at Children’s University Hospital, Dublin. Over that same period, the Inuit had started to leave their traditional lifestyles of hunting and fishing for a more Western way of life – a far more likely cause of their decline. “That would never be possible with a genetic disease,” says Nina Jacobsen at Glostrup University Hospital in Copenhagen. Whereas the older generation had next-to-no cases of short-sightedness, between 10-25% of their children all needed glasses. In fact, the experiences of the Inuit in Canada should have settled that question nearly 50 years ago. If we had “short-sightedness” genes they have made it through the millennia regardless of their obvious disadvantages. So shouldn’t my ancestors have been removed from the gene pool as they groped and squinted their way through the savannah? Yet short-sightedness is something of an epidemic 30-40% of people in Europe and the US need glasses, and the figure has risen to as much as 90% in some Asian countries. Without my glasses, I literally couldn’t tell a rock from a rhino. ![]() The idea that poor eyesight is primarily genetic had never really rung true for me, anyway.
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