Recently, a young woman asked me what I thought about laser treatment for shortsightedness.

She has to wear glasses all the time, and has had difficulties with contact lenses: being able to see without glasses obviously appealed to her immensely, so I was sympathetic.

But I couldn’t reassure her that laser treatment was safe, or that it would leave her with perfectly clear vision. There is a constant, though small percentage, of people who can’t see as well as they should afterwards – their vision is hazy – and glasses then don’t help very much.

A few years ago, the complication rate after laser surgery was quoted at around five per cent – one in 20 people treated. Now it is claimed that it is less, but I’m still not sure. The problem is that we can’t easily predict beforehand who is most likely to develop such complications.

So I chickened out and I referred her to an ophthalmologist who knows much more about the technique than I do. We are waiting for his assessment.

In the meantime, I worry about exposing eyes to the risk of surgery when, in most cases, wearing glasses or lenses pose far less risk. If a drug carried a five per cent risk of complications it would never be given a licence.

I don’t suggest that laser surgery should be avoided at all costs, just that people undergoing it should know precisely what might happen on the rare occasion it goes wrong.

In the meantime, is there anything you can do to help your eyes if you are shortsighted? Does exercising your eyes, for example, make them see better?

Sadly, claims that it can do so fail to understand the cause of shortsightedness. It is born in us, not the result of anything we do.

Basically, the fault with shortsightedness is that the eyeball is too long for its focal point, so that light is focused just in front of the retina – the screen at the back of the eye on which the light falls. That results in a blurred image.

Eye exercises can’t alter this structure: all they do is exercise the muscles around the eyes, which simply move the eyes around in their sockets. However, they do help to avoid eye fatigue, so that you feel more comfortable with, say, looking at a screen for hours on end.

Laser therapy alters the shape of the front of the eyes, correcting the focal point, so in theory – and for most people in practice – it can change short sightedness into normal vision. Glasses, of course, serve the same function.

In longsightedness the eyeball is too short, so that the focal point is behind the retina. Shaving the front of the eye with a laser would make it worse, by shortening the eyeball even further, so laser surgery isn’t recommended for it. If you are longsighted, glasses or lenses are the only reliable option.

So what’s the reasoning behind the recent news that the Chinese education authorities have asked their school pupils to exercise their eyes every day to prevent shortsightedness?

It seems that under a third of their primary school children have poor eyesight – mostly shortsightedness – yet by the time they are in university, that figure has escalated to more than eight in every ten. It is suggested that the deterioration is due to the many hours they have spent in schools reading and straining their eyes.

Our experts don’t agree with this. They say that shortsightedness is inherited, and that it worsens throughout childhood as the head – and eyes – grow. They don’t believe that the exercises will make any difference to their eyesight in the long run. Nor do our experts believe that sitting for hours close to a television screen will make us more shortsighted (or for that matter, longsighted).

But it can put a strain on the muscles of the eyes, especially if you are watching TV in the dark. It is better to have some lighting in the room, so that you aren’t looking at a small square of light against a black background. And it’s good to take your eyes away from the screen regularly, to give them a rest from the narrow field of focus.