Why are we short-sighted?
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Myopia is among our most common complaints – but have we fundamentally misunderstood its origins and its treatment? David Robson squints at an answer.
When I was a teenager, my eyesight slowly began to fail and I had to wear spectacles. What began as tiny slithers of glass soon started to approach double-glazing. “Why is this happening?” I would ask my ophthalmologist as I squinted at the blurry shapes on the eyechart and he upped my prescription. His response was always the same: I could blame my genes and a love of reading.
A common concern is that glasses are making things worse – the answer is no
I had no reason to question him; it’s probably what your ophthalmologist told you, too, if you were diagnosed with short-sightedness. But recent research suggests those assumptions are quite wrong.
Many other things about the modern environment could be leading to poor eyesight. And, with just a few simple measures, our children may be prevented from the same blurry decline that has plagued our own generation.
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The idea that poor eyesight is primarily genetic had never really rung true for me, anyway. Without my glasses, I literally couldn’t tell a rock from a rhino. 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. If we had “short-sightedness” genes they have made it through the millennia regardless of their obvious disadvantages.
Ask an Eskimo
In fact, the experiences of the Inuit in Canada should have settled that question nearly 50 years ago. Whereas the older generation had next-to-no cases of short-sightedness, between 10-25% of their children all needed glasses. “That would never be possible with a genetic disease,” says Nina Jacobsen at Glostrup University Hospital in Copenhagen. 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. “Short-sightedness is an industrial disease,” says Ian Flitcroft at Children’s University Hospital, Dublin. 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.
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Part of that change would have been education and literacy – one of the most common explanations for short-sightedness. 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. Yet epidemiological studies suggest the effects are much smaller than once believed. “The more we studied it and measured the amount people read, the more the association seemed to vanish,” says Flitcroft. 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.
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