AURORA, Colo. -- Parents already know the benefits of getting kids outside to play when they're climbing the walls during the winter.

But playing outside actually has other benefits parents probably don't even know about. It can reduce a child's chances of becoming nearsighted.

"I think it's surprising," said Janee Pedersen. "It makes me want to have my children outside more than I do."

A recent study showed that nearsightedness in this country has increased 66 percent over the last 30 years.

But playing outside 14 or more hours a week can reduce the risk of nearsightedness in children by 40 percent.

The reasons why outdoor play has this benefit are yet unclear. But Dr. Michael Taravella from the University of Colorado School of Medicine has his theories.

"There are some retinal transmitters, dopamine in particular that is effected by light and that can inhibit eye growth," Taravella said. "Maybe it's Vitamin D related. I don't think they've even looked at that yet."

The primary risk factors for nearsightedness are genetics and the amount of time spent doing near-work, like reading or working at a computer.

But a study done at Ohio State University indicated that play might have the upper hand on both.

"They looked at genetic tendencies and found that the environmental factor, playing outdoors, seemed to override that tendency at least for mild degrees of nearsightedness," Taravella said. "Is that an exciting finding? Yes it is. It means that there are things that we may be able to do to modify nearsightedness."

That is good news for parent.

"Certainly on those colder days if we were on the edge of staying inside or going outside we would probably go outside knowing that information," said Justin Harper.