Although not ideal, there are many occasions when reading by a dim or poor light becomes a matter of necessity. Perhaps there’s been a power-cut and you’re urgently inspecting the fuse box by way of a shaking match, or perhaps you’re a considerate bedfellow who reads by awful light in order not to disturb your sleeping other half.

It’s fortunate, then, that there is no evidence to suggest that reading by bad light is detrimental to the health of your eyes. It can tire them certainly, due to the fact that they need to work harder, but you’ll suffer no long-term negative effects. That’s because your eyes are clever enough to be able to adapt to different levels of light – as soon as you walk into a room.

When light is low, your eye adjusts itself in a number of ways. Firstly, the rod and cone cells on the retina begin to produce more light-sensitive chemicals. These chemicals detect light, convert it into electrical signals and then transmit those signals to the brain. Secondly, anyone looking at you might notice that your pupils have become enlarged, and this is because the iris recognises the fact that good light is in short supply, so it relaxes somewhat, allowing your eye to open wider. By doing this your eyes are essentially making a bid to collect as much light as possible!

Reading in poor light tends to frustrate eyes by sending mixed messages. On the one hand, the muscles want to relax in order to absorb as much light as possible, but on the other they’re trying to focus on the words on the page and soak up the detail. This, of course, makes focusing difficult, and over a long period of time they will inevitably become tired, as any muscle would. Any feeling of tiredness, however, is temporary, and if you find that you are experiencing any lasting symptoms we’d recommend that you get your eyes checked out by a professional. You could have an underlying problem such as nearsightedness.

So, reading in poor light is not so detrimental after all, but try not to do it too often!