ORLANDO, Fla. October 24, 2011 A new analysis of recent eye health studies shows that more time spent outdoors is related to reduced rates of nearsightedness, also known as myopia, in children and adolescents. Myopia is much more common today in the United States and many other countries than it was in the 1970s. In parts of Asia, more than 80 percent of the population is nearsighted. The analysis suggests that more exposure to natural light and/or time spent looking at distant objects may be key factors. Today at the 115th Annual Meeting of the American Academy of Ophthalmology Dr. Anthony Khawaja of the University of Cambridge, will present a summary analysis of the evidence. The analysis was led by Dr. Justin Sherwin of the University of Cambridge.
The data included in the analysis was drawn from eight carefully selected studies on outdoor time and myopia in children and adolescents, representing 10,400 participants in total. Dr. Sherwin's team concluded that for each additional hour spent outdoors per week, the chance of myopia dropped by approximately two percent. Nearsighted children spent on average 3.7 fewer hours per week outdoors than those who either had normal vision or were farsighted.
Though the reasons aren't yet clear, the protective effect appears to result from simply being outdoors rather than performing a specific activity. Two of the eight studies examined whether children who spent more time outdoors were also those who spent less time performing near work, such as playing computer games or studying, but no such relationship was found in either study. The amount of time spent on near work is of interest to researchers as another potential cause for the recent uptick in nearsightedness.
"Increasing children's outdoor time could be a simple and cost-effective measure with important benefits for their vision and general health" said Dr. Khawaja. "If we want to make clear recommendations, however, we'll need more precise data. Future, prospective studies will help us understand which factors, such as increased use of distance vision, reduced use of near vision, natural ultra violet light exposure or physical activity, are most important."
Another question, Dr. Khawaja considered is whether boosting outdoor time might stop nearsightedness from getting worse. He cited a recent Chinese study, not included in Dr. Sherwin's analysis, of 80 nearsighted children between the ages of 7 and 11. Forty of them were assigned to spend less than 30 hours on near work and more than 14 hours on outdoor time per week. At the end of the two-year study, children in the intervention group were less nearsighted on average than the 40 control group children who did not follow the special schedule.
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American Academy of Ophthalmology