Does reading in poor light damage your eyes?

Winter is probably the best time to get round to reading a good book, especially by candlelight or the soft light of a bedside lamp. Children even like to hide under the covers with a pocket lamp. However, the joy of burying oneself in a book is often tempered by the fear that doing so might damage our eyes. Almost everyone's been told it at one time or another: "Put the light on, you'll damage your eyes!" But there's no need to worry – reading in the dark doesn't damage your eyes at all. However, if you need reading glasses, you should wear them.

Scientists still argue about this issue today: reading in poor light damages your eyes. But there's no reason to be concerned. There is currently no evidence at all to suggest that reading in poor light damages your eyes. However, one thing is clear: reading by light requires more strain on the eyes to make out the words. This makes reading more strenuous, and the eyes get tired more quickly, potentially resulting in red eyes and headaches. Despite this, the eyes themselves do not suffer from this process, according to a study by American scientists published in the renowned periodical British Medical Journal.

But why are our eyes not damaged by the extra strain? To understand this, we need to take a glance at how our eyes work. When trying to make out letters in weak lighting conditions, two particular parts of the eye are used: the ciliary muscle, which needs to keep the lens taught in order to read letters, and the photoreceptors themselves. In dim or poor light, the light-sensitive rods are particularly important. They require a special pigment, rhodopsin, also known as visual purple. The molecular structure changes when the ambient light is reduced. The result: reading in dim light is much more strenuous. However, it doesn't damage the eyes, as they can relax and recover as soon as they are closed.

So if you love reading a good book with the lights down low, there's no need to worry about your eyes. All the same, it's good to give your visual organs a break now and then, either by putting the book to one side for a moment and closing your eyes, or doing a little  visual workout. It only takes a few minutes, and then your eyes will feel refreshed and ready for action again. And parents don't need to worry about their kids when they read under the covers with a pocket lamp - at worst, it might be more difficult than usual to get them out of bed the next day!

But no matter whether the light is dim or bright, if you need to hold the book far away to make out the letters, you need to be wearing  reading glasses. As we get older, the lenses of our eyes lose elasticity, thus reducing their ability to curve, or "accommodate", meaning that they can no longer adjust to close distances. Those with this problem then find it difficult to focus at short range. To guarantee the best possible reading experience, it is important that you use reading glasses customised by an optician.