PARIS: Snubbing the outdoors for books, video
games and TV is the reason up to nine in ten school-leavers in big East Asian
cities are near-sighted, according to a study published on Friday.
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 told AFP of the findings published in The Lancet medical journal.
Yet 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 percent.
The
figure in Britain was about 30 to 40 percent and in Africa "virtually
none" -- in the range of two to three percent, 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," the scientist said.
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
percent were affected.
Of
these, 10 to 20 percent 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," 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," explained Morgan.
"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."
The
scientist said 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.
"The
amount of time they spend on computer games, watching television can be a
contributing factor. As far as we can tell it is not harmful in itself, but if
it is a substitute for getting outside, then it is," said Morgan.
He said
ways must be found to get children to spend more time in reasonably bright
daylight without compromising their schooling.
"It
is going to require some sort of structural change in the way a child's time is
organised in East Asia because there is so much commitment to schooling and
there is also a habit of taking a nap at lunchtime, which is from our
perspective prime myopia prevention time."
-AFP/ac
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