Children who regularly spend time outside may be less likely than their peers to develop nearsightedness. Previous studies have found that children who spend more time outside during the day tend to have better distance vision than those who favour indoor activities. The reasons are not yet clear, but children's physical activity levels did not seem to be a factor. Researchers from America surveyed parents of 191 children who were 13 years old, on average, and tested the children's vision annually. Overall, it was found, children who developed myopia spent an average of 8 hours outside per week, compared with nearly 13 hours among non-myopic children. Nearsighted children also watched more TV, but there was no such correlation with time spent reading, studying or using a computer. The researchers speculate exposure to sunlight may play a role, as may the fact that being outside often makes kids focus on objects at a distance. Animal studies suggest that this affects eye development in a way that helps prevent nearsightedness, or myopia. On the other hand, there was no strong evidence that near-work like reading or using a computer raised children's risk of nearsightedness. In two other studies researchers from Australia and Singapore found similar connections between outdoor time and lower myopia risk. Lower rates of near-work did not explain the link, and the Singapore study found no evidence that children who read a lot were at greater risk of nearsightedness. However further studies are needed to find out why outdoor time might affect children's visual development.
Optometry and Vision Science
February 2009