Aug. 3, 2012 -- Spending more time outside may help protect children's eyesight.
New research suggests that increasing the amount of time children spend outdoors may reduce the risk of developing myopia, or nearsightedness.
Although nearsightedness is easily corrected, researchers say there is currently no widely used method to reduce the risk of developing the condition or slow its progression.
Researchers say that encouraging children to spend more time outside may be a new way to protect their eyesight and reduce the risk of myopia. Their findings would need to be confirmed by further studies.
The results also suggest that environmental factors, like the amount of time spent in front of TVs or reading books, may help explain rising rates of myopia in certain groups.
"Even though a substantial proportion of myopia cases can be explained by inheritance, this does not exclude strong environmental influences being the driving force behind the rapid increases in the prevalence of myopia over time, especially in East Asia," researcher Justin Sherwin, of the University of Cambridge in the U.K., and colleagues write in Ophthalmology.
Outside Time Protects Eyes
In the study, researchers reviewed a total of 23 studies on myopia in children and teens up to 20 years old.
Using information from seven studies that included population-wide data on the risk of nearsightedness, they estimated the impact of spending time outdoors on the risk of myopia.
"We found a significant protective association between increasing time spent outdoors and prevalent myopia in nearly 10,000 children and adolescents," write the researchers. "Each increase in hours per week of time spent outdoors was associated with a 2% reduced odds of myopia."
Another three studies that followed children over time showed that increasing the amount of time they spent outdoors slowed the progression of myopia.
"The overall findings indicate that increasing time spent outdoors may be a simple strategy by which to reduce the risk of developing myopia and its progression in children and adolescents," they write.
Researchers stress that these studies were observational and can only show an association between time spent outside and the risk of myopia, not a cause and effect. Future randomly controlled studies are needed to confirm the role of outdoor time in the development of nearsightedness.
They say there are a variety of potential explanations for the protective effect of spending time outside on eyesight.
For example, spending time outdoors may help protect against myopia by increasing the release of dopamine in the eye in response to sunlight. Or, as stated, it may reduce the amount of time spent on other work requiring near vision, like watching TV or reading.