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Spending two or three hours playing outdoors each day can reduce(減少)a child's chance of becoming short-sighted(近視), research shows.It challenges the belif that short-sightedness is caused by computer use, watching TV or reading in weak light.
Australian government researchers believe that sunlight is good for people's eyes.They compared the vision(視力)and habits of 100 seven-year-old children in China and Australia.In all, 30% of the Chinese children were short-sighted.This percentage was ten times higher than Australian children.
Both groups spent a similar amount of time reading, watching TV and playing computer games.However, the Australia children spent an average of two hours a day outdoors, 90 minutes more than the Chinese children.
Professor Ian Morgan said, “Humans are naturally long-sighted, but when people begin to go to school and spend little or no time outdoors, the number of short-sighted peoplegets larger.We are also seeing more and more short-sighted children in cities all around the world-and the main reason may be that city children spend less time outdoors.
Daylight can be hundreds of times brighter than indoor light.But why does playing outside prevent us from becoming short-sighted? Scientists believe that natural light has a special chemical(化學(xué)物質(zhì))which stops the eyeball from growing out of shape and prevents people from becoming short-sighted.
So go outdoors.It doesn't matter if that time is spent having a picnic or playing sports.
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