Could an increase in outdoor playtime for kids help reduce the need for eyeglasses later in life? According to a new study in China, it certainly might.

All around the world, kids are needing glasses earlier than ever before. The condition behind most of those eye doctor appointments is myopia, which is when you can see close objects clearly but things far away seem blurry. According to the National Eye Institute, more than 30 million Americans were diagnosed with myopia in 2010, and those numbers are predicted to rise sharply in the next few years.

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In China, almost 90 percent of high school graduates have been diagnosed with myopia in recent years and experts aren't sure why. So in a recent study, a team from the Zhongshan Ophthalmic Center in Guangzhou took a closer look at the effects of outdoor play on eyesight.

Researchers enlisted the help of 12 schools throughout China to take part. Half of the schools were asked to give their first graders an extra period of recess every day while the other half did not. In all, 1,900 first graders, aged 6 and 7, were evaluated over the course of the three-year experiment.

After three years, researchers found that 40 percent of the kids in the school who did not have extra recess developed myopia compared to 30 percent of the kids who did get the extra time outdoors. This means that about 45 minutes of extra outdoor play resulted in a 23 percent decrease in the development of myopia.

Some experts have speculated that it's exercise that's the key to better eye health. But other studies, in which kids were given extra recess but it was held indoors, found that exercise alone does not affect myopia rates.

It could be that when kids are outdoors, their eyes are forced to focus on things at varying eye lengths. That flower in the garden. Those trees at the end of the street. A bird flying high above.

The researchers aren't clear about why outdoor play helps reduce the risk of myopia for kids, but they do know that it does.

And what better reason is that to spend some extra time outside?