Thursday, July 7, 2011

Playing outdoors in the sun reduces the risk of myopia in children

Too much time spent indoors can damage eye development. In the 70s, 25 percent of Americans were nearsighted. Today that number has risen to 42 percent. This appears to be due to our modern lifestyle and too much time spent indoors under artificial lights.

In the past people spent more time outdoors in natural sunlight. Today people do not go out and hunt for their food, children spend the day indoors at school; even face to face conversation by teens is done with texting or over email. People don`t sit on the back porch anymore and stare off into the distance.

Researchers suspect that when the eyes of a child are developing bright outdoor sunlight helps the eyes maintain the correct distance between the lens and the retina, which keeps vision in focus. When children spend too much time indoors with dim indoor lighting, their eyes do not grow correctly. Instead, the distance between the lens and the retina becomes too long, causing far-away objects to look blurry.

A study done in 2008 compared children of Chinese ethnicity living in Sydney, Australia with those living in Singapore. Children in Australia spent an average of 14 hours per week outside while those in Singapore spent about three hours per week. The rate of nearsightedness in Singapore was 29%, nearly nine times higher than that of the children studied in Sydney. Kathryn Rose, a visual disorder researcher, believes what is missing is retinal dopamine, a stimulator of eye growth whose release is motivated by light. When there is a lack of dopamine, there is excessive eye growth which can result in nearsightedness.

It was once believed that "near work" such as reading was the culprit of nearsightedness, but new evidence strongly suggests that what children need is more outside time. Since myopia develops early, children should get into the habit now of spending more time outdoors in natural light to protect their eyesight. Even reading outside will do the trick. Kathryn Rose suggests 10-14 hours per week at the bare minimum.

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