Snubbing the outdoors for books, video games and TV is the reason up to nine in 10 school-leavers in big East Asian cities are near-sighted, according to a study published yesterday.
Neither genes nor the mere increase in activities like reading and writing is to blame, the researchers suggest, but a simple lack of sunlight.
Exposure to the sun’s rays is believed to stimulate production of the chemical dopamine, which in turn stops the eyeball from growing elongated and distorting the focus of light entering the eye.
“It’s pretty clear that it is bright light stimulating dopamine release which prevents myopia,” researcher Ian Morgan of the Australian National University said of the findings published in the Lancet medical journal.
Yet the average primary school pupil in Singapore, where up to nine in 10 young adults are myopic, spends only about 30 minutes outdoors every day — compared with three hours for children in Australia, where the myopia prevalence among children of European origin is about 10 percent.
The figure in Britain is about 30 percent to 40 percent, while in Africa it is “virtually zero” — in the range of 2 percent to 3 percent, Morgan said.
Children in East Asia “basically go to school, they don’t go outside at school, they go home and they stay inside. They study and they watch television,” the scientist said.
The most myopic school-leavers in the world are to be found in cities in Taiwan, China, Hong Kong, Japan, Singapore and South Korea, where between 80 percent and 90 percent are affected.
Of these, 10 percent to 20 percent have a condition called high myopia, which can lead to blindness.
“Most of what we’ve seen in East Asia is due to the environment, it is not genetic,” said Morgan, contrary to the common belief 50 years ago.
The researchers, collating the findings of studies from around the world, stressed that being a bookworm or computer geek does not in itself put you at risk.
“As long as they get outside, it doesn’t seem to matter how much study they do,” Morgan said. “There are some kids who study hard and get outside and play hard, and they are generally fine. The ones who are at major risk are the ones who study hard and don’t get outside.”