An eye for a book

It’s quite hard, growing up as a bookwormy kid. It’s rock and a hard place, Scylla and Charybdis (bookwormy, see?). On the one hand, you get called ‘Data’ by your friends’ older brothers, who go around repeating ‘Need more input… Need more input.’ On the other, you get told by your friends’ parents that if you keep reading your Terry Pratchett books when the light gets bad, it’ll hurt your eyes. I assume this experience is pretty typical.

Eyes, in fact, get top billing in a fair few old wives’ tales; certainly more than do livers or gall bladders. Presumably that’s because while no one can really see how their gall bladder is doing, changes in the function of your eyes are pretty obvious. So if someone notices that, say, a kid who reads after dark a lot later needs glasses — or a kid who sits too close to the telly, or spends too much time locked in the bathroom with a copy of the Littlewoods catalogue — then they assume that thing A caused thing B.

A few of the myths we can fairly simply debunk. If masturbation caused blindness, there would be a global pandemic. Since a large percentage of teenage boys make it to adulthood in full possession of their eyesight, we can rule that one out.

Watching telly up too close is also, probably, not a problem. An article in Scientific American suggested that, in fact, the myth might have the causal arrow backwards — children who sat close to the telly did so because they couldn’t see it well when further away. If your child is pressed up against Peppa Pig, then it might be worth getting their eyesight checked, but not, most likely, because the telly is causing it.

The more difficult question arises with the idea that reading in dim light causes blindness. It’s always a complicated problem teasing out these sort of causal relationships, because — as in so many of these situations — you can’t force a group of children to not read in order to compare them to the ones who do and see who has better eyesight after 15 years. There are natural experiments — compare children who read lots with ones who read less, and then try to work out, with careful analysis. But there doesn’t seem to have been much research done, at least that I can find.

What there has been, interestingly, is a 2007 study by Rachel Vreeman and Aaron Carroll, published in the BMJ, into what medical myths were most prevalent among medical professionals. Among others — that your fingernails continue to grow after death; that eating turkey makes you drowsy — was the low-light claim.

What the researchers found was that while reading in low light can strain your eyes in the short term, there was little evidence that it caused long-term damage. ‘The majority consensus in ophthalmology…’, it says, ‘is that reading in dim light does not damage your eyes.’

There was one review, by Douglas Fredrick, from 2002 and also in the BMJ, which suggested that the idea that ‘the idea that the way in which we use our eyes early in life can affect ocular growth and refractive error is gaining scientific credence’. He notes that in a study in the 1960s of 1,200 Eskimo people in Alaska, the local level of myopia was strikingly different among those who had grown up with little contact with the western education system, before the second world war, and those who grew up after. None of those 56 or above had myopia; 8 per cent of those 30 and up did; and 59 per cent of their children did.

Further, he points out that ‘people whose professions entail much reading… (lawyers, physicians, microscopists, and editors)’ are more likely to have myopia than the rest of the population. The usual claim is that more intelligent people are more likely to have myopia, but Fredrick suggests that link has been confounded by the fact that more intelligent people tend to read more.

Vreeman and Carroll are unswayed by that argument, pointing out, first, that ‘hundreds of online expert opinions conclude that reading in low light does not hurt your eyes’, and second that although myopia has increased over recent centuries, that doesn’t necessarily square with the fact that artificial light has become cheaper and more available, so fewer people have to read in dim light these days. Another group has pointed out that the Inuit myopia claims are somewhat confounded by the fact that the children in the study were those brought to the clinic by parents who were worried about eye problems, and so were not a representative sample.

As always with these complex issues, it’s hard to give a definitive answer. Probably, there’s no causal link between reading under the covers with a dying torch and losing your eyesight, but it would be foolhardy of me to rule it out. But more importantly: these days, does it matter? Pretty much everyone wears glasses or contact lenses anyway, and they’re affordable and available; the skill of reading is hugely important to life chances; and frankly, glasses look good. Just check out my byline picture. If you’re stopping your child from reading when they’re actively trying to, out of concerns that they might need glasses later, I suggest you have your priorities backward.