My parents were right!! A spate of studies over the past decade has found that kids who spend more time outdoors are less likely to develop near-sightedness.
Outdoor time seems to protect kids even if they do a lot of "near work" (e.g., reading Goosebumps and Animorphs nonstop) and if their parents are myopic.
When I was a kid, my parents would always tell me to stop reading and go play outside. I would scoff: What kind of parents want their kid to stop reading? But maybe they had a point after all.
A team of Australian researchers recently reviewed major studies since 1993 of kids, myopia and time spent outdoors. They found more than a dozen studies, examining more than 16,000 school-age kids in total, that found children were more likely to be nearsighted or to develop nearsightedness if they spent less time outdoors. A few of the later studies also found that being outdoors protected even those kids who did a lot of near work or had myopic parents. The studies included kids living in Europe, the U.S., Asia, the Middle East and Australia.
The researchers did find three studies, comprising about 4,600 kids, where there was no association between nearsightedness and time spent outdoors. Of those three studies, one looked at a group of children that was predominantly myopic (83 percent of them were nearsighted) and spent very little time outdoors overall (just six hours a week, on average). Another study looked at younger children, aged six months to six years. Nearsightedness is rare in kids that young.
Scientists aren't sure yet why being outside prevents kids from becoming Miss Four-Eyes early in life. There is some evidence, from studies done in lab mice, that sunlight may trigger the production of the brain chemical dopamine, which in turn prevents eyes from growing elongated. Nearsighted eyes are overly elongated. However, some conflicting studies mean that scientists can't be sure this is what's happening in humans.
Scientists also aren't exactly sure how strongly outdoors time protects kids. Some studies have found a small protective effect, while others have found larger ones, the Australian reviewers report.