Can reading in poor light ruin your eyesight?
Not that this imprecation ever keeps budding young bookworms from discovering if the hero prevails and the smugglers get their desserts, or whatever. Perhaps, if your vision has dimmed, you occasionally curse your youthful self for taking such a cavalier and, well, short-sighted attitude. If so then you can relax a bit because the consensus is that poor light doesn’t make a permanent difference to eyesight.
The brain does respond to low light by rejigging the eye and this can lead to painful eye strain but this seems to be a strictly temporary effect.
If you’re short sighted, though, don’t let the younger you off the hook just yet. There is a controversial theory that reading in poor light can lead to short sight — not because of the light, but because of the reading.
Good, you’re still here. That means you haven’t thrown down the magazine in disgust and sworn of the written word forever. You realise that the benefits of reading easily compensate for any myopia (though, to be fair, glasses or contact lenses help a lot too).
The idea here is that focusing a lot on near objects makes the eye permanently adapt for near vision at the expense of distance vision. The body may achieve this by allowing the eye to grow longer than it normally would.
Part of the support for this use-abuse theory comes from the popular observation that intelligent people tend to be short sighted, which is backed up by some more rigorous research. The proposed link isn’t direct. It’s assumed that intelligent people seek — or are encouraged to seek — more things to read. Intelligence itself doesn’t lead to myopia, but the act of reading (or performing any close work) does — assuming the theory is true. Further support comes from the observations of Eskimo populations that became much more short-sighted once Western education became widespread.
The causes of myopia aren’t yet well understood, so we’ll have to wait for the facts before reading can be “blamed” for ruining eyesight.. But poor light, at least, seems to be an innocent bystander.