Indoors time short-sighted

Short-sightedness among young people has doubled over the past 50 years, and the cause is thought to be teenagers being taught indoors and using computers.

A study found 23 per cent of British 12- and 13-year-olds suffer from myopia compared with 10 per cent in the 1960s. Experts said the surge in short-sightedness was down to teenagers playing outside less because of screen time and intensive education.

Parents have been urged to make sure their children spend more time outdoors and researchers warn that sedentary lifestyles are bad for the eyes as well as the waistline. In east Asian countries with intensive education systems, up to 90 per cent of teenagers leave school shortsighted, and one Chinese city is experimenting with transparent classrooms to expose them to more sunlight.

‘‘Most short-sightedness comes on around 6 or 7 years of age, which is probably younger than in the 1960s. We’re getting shortsightedness at an earlier age and we’ve getting more of it,’’ said Professor Kathryn Saunders, of Ulster University, who carried out the latest survey.

British children are three times as likely to be short-sighted as Australians.

People with a degree are twice as likely to be myopic as those leaving education after primary school, according to research by Professor Chris Hammond of King’s College London, which leads researchers to suspect the rise in cases is linked to more time sitting in the classroom. One study found that 30 per cent of ethnic Chinese 6-year-olds in Singapore had myopia, compared with just 3 per cent from the same ethnic group in Australia.

‘‘The Sydney children spent two hours a day outside and in Singapore it was less than half an hour a day. That’s pretty compelling evidence,’’ Hammond said.

In Singapore ‘‘they’re living in an educational hot-house where kids are having competitive entry from the age of 4. If you have a very, very strong environmental stimulus, almost anyone can become short-sighted,’’ he added.

Professor Jeremy Guggenheim of Cardiff University agreed: ‘‘We’re worried about children starting education very young, doing homework all evening.

‘‘We need to be very careful because there’s a strong link between education and countries that are 80 to 90 per cent myopic.’’

Today’s 50-year-olds are twice as likely to be short-sighted as their parents, while the rate for those in their 20s is now above 40 per cent, Hammond found.

He argues that being surrounded by books and walls could lead to the eye growing longer as it struggles to focus on peripheral objects.

But Saunders believes the problem may be caused by a lack of sunlight, as vitamin D deficiency rises.