Urban Eyes Too much time spent indoors may be behind a surge in nearsightedness

Rogers Hornsby, one of the best hitters ever to swing a baseball bat, had a reputation for being standoffish. Teammates complained that he didn’t socialize, even balking at attending movies — prime entertainment during the 1920s. Sitting in a dark theater watching a bright screen made it difficult to hit a baseball, Hornsby used to say. Hard to argue with a guy who reportedly had terrific eyesight and who finished three seasons with a batting average better than .400.

Hornsby might have been onto something that scientists are only now coming to embrace: Too much time spent indoors may contribute to nearsightedness, also called myopia.

Nearsightedness has increased steadily in North America and Europe in recent decades, with one-third of adults in the United States now nearsighted. That figure alone is cause for concern. But the rise of myopia in East Asia is downright alarming. Recent studies of young men in Seoul and college students in Shanghai find that more than 95 percent are nearsighted. Increases also have shown up across other urban centers in the Far East.

Studies first uncovered a link between myopia and limited outdoor time during childhood just a few years ago. At the time, many researchers were taken aback. The notion that child’s play might promote normal eye growth seemed almost magical.

“Certainly, before five years ago, I don’t think anybody had taken much notice of how much time people spent outdoors,” says Jeremy Guggenheim, an optometrist who has researched myopia in Wales and is currently at Hong Kong Polytechnic University. He believes the findings offer a “new and exciting direction” for research.

It’s tantalizing to think that time spent outdoors early in life might fend off the need for eyeglasses, contact lenses or laser surgery in many people. But, Guggenheim notes, it is not yet clear to what extent outdoor exposure can cut risk or how it does so. Some scientists say the benefit could come from exposure to natural light, a relaxation of the eye gained from viewing things at a distance or the visual tableau that reaches the eyes’ peripheries while outdoors. Or it could be a mix of all those factors.

“There are great open questions, and that keeps us from making strong recommendations,” says Donald Mutti, an optometrist at Ohio State University College of Optometry in Columbus.

Aside from spending time outdoors, a person’s other behaviors might matter too. The higher myopia rates documented today coincide with a whole generation of children raised on computers, video games and, especially in the Far East, intense pressure to achieve in school. Some researchers cite a long-debated theory linking myopia to excessive reading or other “near work.”

http://www.sciencenews.org/view/feature/id/347738/description/Urban_Eyes