Yes, the world’s eyesight is getting worse: kids are getting more short-sighted while more older adults are becoming long-sighted.
Kids are getting more short-sighted: but reading isn’t to blame
Having myopia means that objects in the distance are blurry while everything close-up is easy to see. The soft crystal-clear lenses that sit in front of each pupil continually change shape to focus on what we are looking at: for up close work, it squashes into a peaked dome, and for looking in the distance it flattens into a shallow hillock-shape. Myopia occurs when the squidgy lens cannot stretch flat enough to bring distant objects into focus. Either the lens is too thick, or the eyeball is too big.
People who wear glasses have often been seen as smart, and there is some truth in it: academics and people with high IQ test scores are more likely to be myopic than those who lead a less bookish life. Hence, vision specialists have presumed too much time reading books and focusing on screens strains the lenses to fix them in a permanently squashed position. Or close-up work somehow stretches the eyeball to make it too large.
Recent research has shown that reading is almost certainly not the true cause, but lack of sunshine is. In Australia few kids have myopia – only 3% –but across the water in Singapore, 29% of children are short-sighted. Reading and computer work can’t explain Singapore kid’s bad eyesight because Australian children actually spend more time doing close-up work. The crucial difference is that Ozzie kids also spend four times as long playing outside (13 hours a week compared to just 3 hours in Singapore).
It seems that time in sunlight is vital for keeping eyes healthy, especially in children. No one is quite sure why. Time in the sun triggers the release of a substance from the back of the eye called dopamine – the same chemical that is lacking in Parkinson’s disease – that seems to help the eyes grow normally. Throughout the day, the eyeball also changes size – getting slightly bigger around midday and shrinking at night – suggesting that not getting out in the day and not sleeping at night somehow stops the eye developing normally.
More adults are getting long-sighted
As we get older, we find it increasingly difficult to focus on close objects – hence Granddad holds the newspaper at arm’s length to read it. Over time, the eye’s lenses get stiffer, making it more difficult for the lens to squash fully. About one fifth of the world is long-sighted (presbyopia) and it is estimated that more than half of adults in middle and lower-income countries over the age of 30 are long-sighted (have presbyopia).
Sadly, long-sightedness is an inevitable part of ageing and there is no known way of preventing it. As we live longer, it will become ever more common. For now, good nutrition, regular eye check-ups (especially if over 40), wearing sunglasses and staying generally healthy are your best bets. Either that, or don’t get old.
For kids, there are things simple things we can do: get them outside more. Schools may need to see the light and try new ways of teaching in the great outdoors. And for parents who find it impossible to tear their kids away from their screens, an alternative might be getting them to play on their phone or tablet in the garden. A good idea is to give them a brolly first.
Get advice on keeping healthy eyesight here (American Academy of Opthalmology).