"It's definitely a hot area of research right now," says Lisa Jones-Jordan, PhD, a research associate professor at The Ohio State University College of Optometry. Jones-Jordan authored a study in 2012 analyzing the relationships between outdoor time and nearsightedness, one of three studies published in the past few years analyzing the relationship. Her work was recently highlighted in a cover story for the National Institute of Health's journal Environmental Health Perspectives. "They've all found similar results, in that children who spend more time outdoors are less likely to develop nearsightedness, and nearsighted kids do seem to be outside less."
Nearsightedness is reaching epidemic proportions in Asia, the journal found. For instance, more than 80 percent of the population of Singapore is myopic. And researchers have found that children in hot, humid regions of Asia who get outside less are more likely to suffer from the condition. It's also believed that the heavy cultural emphasis on education and its side effect of keeping kids inside to study has played a role. The exact protective mechanism, whether it's vitamin D from sunlight or some other aspect of being outdoors, is still being studied.
Save Your Eyes—Change Your Light Bulbs
Contrary to what you might think, nearsightedness can't be pegged to one particular cause. Genetics plays a role, but there really are no other scientifically confirmed known causes. Near work, such as spending a lot of time reading or sewing, has never been conclusively tied to vision problems, and neither has working at a computer for long hours. Even diet, says Jones-Jordan, hasn't been studied well enough for scientists to know for certain whether eating lots of carrots and spinach, like your mother and Popeye told you to, will do much to prevent nearsightedness. (Beta-carotene, the beneficial compound in carrots and spinach tied to eyesight, does help maintain healthy vision, but it seems to prevent vision problems only in children who are severely deficient in the vitamin.)
That's what makes this new research so intriguing, she says. Nearsightedness almost always develops when you're young. Though there are some instances in which adult onset of the disorder can occur, "usually by the time you're no longer a teenager, you'll be as nearsighted as you're going to be."
Unfortunately, because of that fact, spending time outside as a nearsighted adult is unlikely to improve your vision, and that's why researchers' focus has been on encouraging children to get outside as much as possible—to prevent the problem before it starts.