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Being outdoors lowers risk of nearsightedness

January 12, 2009 | 11:01 am

Outside1Spending two or three hours outdoors each day appears to lower a child's risk of developing nearsightedness, although researchers can't explain why.

A study published in this month's issue of the journal Optometry and Vision Science reviewed several large studies examining nearsightedness, or myopia, in large populations. The studies agreed that the risk of myopia drops in children who spend more time outdoors. A child's chances of becoming myopic if he or she has two myopic biological parents are about 6 in 10 for children who spend zero to five hours a week in outdoor activity. But the risk drops to two in 10 when outdoor activity exceeds 14 hours a week.

It doesn't seem to matter much what children are doing outside. The studies did not find that sports or physical activity played a role. In fact, participating in either active or passive activities outdoors had a protective effect on vision while sports played indoors did not have this effect.

Myopia affects about one-third of U.S. adults.

The authors of the analysis say they cannot explain why outdoor time lowers the risk of nearsightedness. It could be related to more time spent on distance viewing or to being in sunlight.

-- Shari Roan

Photo credit: Ricardo DeAratanha/Los Angeles Times