Short-sightedness (Myopia) due to lack of Sun
Baku, May 4 (AZERTAC). Snubbing the outdoors for books, video games and TV is the reason up to nine in ten school-leavers in big East Asian cities is near-sighted, according to a study.
Neither genes nor the 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," says researcher Ian Morgan of the Australian National University, lead author of the study published in The Lancet medical journal.
The average primary school pupil in Singapore, where up to nine in ten young adults are myopic, spent only about 30 minutes outdoors every day - compared to three hours for children in Australia where the myopia prevalence among children of European origin is about 10 per cent.
The figure in Britain was about 30 to 40 per cent and in Africa "virtually none" - in the range of two to three per cent, according to Morgan.
More than other groups, 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," says Morgan.
The most myopic school-leavers in the world are to be found in cities in China, Taiwan, Hong Kong, Japan, Singapore and South Korea, where between 80 and 90 per cent were affected.
Of these, 10 to 20 per cent had 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," says 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.
Morgan says children who spent two to three hours outside every day were "probably reasonably safe". This could include time spent on the playground and walking to and from school.
Other news in this section
