Don't look too closely

Sitting in front of a screen for hours can do irreparable harm to a child's eyesight. Kate Hilpern talks to the doctors trying to change our focus

"You'll ruin your eyesight watching all that TV," my mother used to tell me when I was a child. It turns out that she may have been right all along. The epidemics of short-sightedness in countries such as Japan and Singapore are due solely to changes in children's lifestyle, according to medical research. What's more, similar levels of myopia could soon be seen in many Western countries. "As kids spend more time indoors, on computers or watching TV, we are going to become just as myopic," says Ian Morgan of the Australian National University in Canberra.

"You'll ruin your eyesight watching all that TV," my mother used to tell me when I was a child. It turns out that she may have been right all along. The epidemics of short-sightedness in countries such as Japan and Singapore are due solely to changes in children's lifestyle, according to medical research. What's more, similar levels of myopia could soon be seen in many Western countries. "As kids spend more time indoors, on computers or watching TV, we are going to become just as myopic," says Ian Morgan of the Australian National University in Canberra.

While short-sightedness is on the increase in most places, it is no coincidence that it's rising fastest in the Far East, the researchers believe. Take Singapore, where 80 per cent of teenagers are myopic, up from 25 per cent just 30 years ago. Children there spend much time focusing on close objects, such as study books and computers for playing the ever-increasing number of games available. To compensate, the eyeball is thought to grow longer, so less effort is needed to see up close, but the elongated eye can no longer focus on distant objects.

Another study found myopia rates of 80 per cent in 14- to 18-year-old boys studying in schools in Israel where the reading of religious texts is emphasised. The rate for boys in state schools was 30 per cent.

Karla Zadnik of the Ohio State University College of Optometry in Columbus believes that parents may soon take action. "We may start to get parents cutting the time their children spend on the computer or watching television and encouraging them to spend more time outdoors." This could achieve more than they realise. Studies show that children who play sports are less susceptible to short-sightedness. Sport tends to involve more focusing on far, rather than near, objects - thus protecting the eye from abnormal growth. Also, studies of animals have found that light protects against myopia. Children who do become myopic are most likely to do so between the ages of eight and 12, Zadnik says. "The condition usually gets worse until about the age of 15 or 16, at which time the prescription steadies out. Some get a bit more myopic progression in their twenties or thirties, but it's nothing compared to what they experience at school age."

Less telly time and more visits to the tennis club mightn't be the only way to curb the onset of myopia. What children eat may also be relevant. A team of evolutionary scientists, led by Professor Loren Cordain of Colorado State University, found that a diet rich in sugar and refined starches, including white bread and cereals, can cause short-sightedness. They argue that these foods may affect the development of the eyes by stimulating the production of the hormone insulin. High levels of insulin are matched by a fall in levels of a similar chemical - binding protein-3 - thought to be involved in the growth of the eyeball and the lens.

Evidence of the trend may be seen in Inuit people and Pacific islanders: less than 1 per cent had myopia in the last century, but rates have rocketed, in some cases to 50 per cent. This has been blamed on the increase in reading after the rise of literacy and compulsory schooling. But reading does not explain why the incidence of myopia has remained low in communities that have adopted Western lifestyles but not diets, say the scientists. "In Vanuatu, they have eight hours of compulsory schooling a day, yet the rate of myopia in these children is only 2 per cent," says Cordain. The reason, she believes, is almost certainly that the Vanuatuans eat fish, yam and coconut rather than white bread and cereals.

There's more circumstantial evidence. Because being overweight or having adult-onset diabetes also involves having elevated insulin levels, you would assume that such people would be more likely to develop myopia. Studies have shown this to be the case. And changing diet cannot undo any damage already caused, says Cordain, although it may prevent further degeneration.

However, not everyone is persuaded by these theories. Christopher Hammond of St Thomas' Hospital in London points out that short-sighted children usually have short-sighted parents. And his latest study, launched last week, has identified the first gene to be associated with myopia. "Clearly, the increase in myopia in the Far East must be at least partly due to environmental influences," he says. "However, only the genetic argument can explain why the remaining 20 per cent of the people in the Singapore study are not myopic, when they had a similar education. Genes must be the protective factor."

He points to one of the most famous US myopia studies. "It showed that, while close reading was associated with myopia, by far the most important contributing factor was family. The children whose parents were not myopic had a 6 per cent prevalence of short-sightedness. The children who had one parent with myopia had an 18 per cent prevalence, and the children who had two myopic parents had a 33 per cent prevalence."

Peter Warren of the Association of Optometrists in London says: "I think we can only conclude that it is probably the case that if you have a genetic disposition to myopia, then you are much more likely to be susceptible to the environmental factors." He is keen to give precautionary advice to short-sighted parents. "That advice includes limiting the time spent by children on a computer. I also suggest that children always use a good light when reading, and have a balanced diet. Children should have plenty of time outdoors, but remember to protect their eyes from too much exposure to the sun."

Not surprisingly, pharmaceutical companies are trying to develop cures. So far, there is nothing that prevents short-sightedness, but there are products aiming to halt the progression in children. The one most likely to be widely available in the UK - and with least side effects - is Pirenzepine ophthalmic gel, which appears to slow the growth of the axial length of the eye.

Paul Lopez, the president of Valley Forge Pharmaceuticals (the US company conducting a clinical investigation of the use of the gel in children) says: "What we've seen in our trials to date is a 50 per cent reduction in the progression of myopia. It looks likely that the product will be available in the UK from around 2008 or 2009." But Hammond sounds a note of caution. "The gel is only shown to halve the rate of progression, not stop it altogether. And there are questions that can't yet be answered. For instance, are there any long-term side effects? If children stop using the gel at any point, would their eyes then play catch-up to those who never took it, or would they remain less short-sighted?"

He believes that behaviour during close work will be the next area of investigation. "Does it help for children to take breaks from reading or computer work by looking into the distance? This is an area that's only just starting to be properly examined. The results should be interesting."