Less incidence of nearsightedness in kids who spend more time outdoors: Study

By Dr. Ananya Mandal, MDOct 26 2011

A new study finds that children who play outdoors often are smarter, leaner and stronger than kids more inclined toward indoor activities. They're less likely to suffer from nearsightedness, in which objects in the distance appear blurry.

The study was presented Monday at the American Academy of Ophthalmology’s yearly meeting. It took in the findings of eight studies that explored the relationship between outdoor time and myopia in more than 10,000 children. The researchers, led by Dr. Anthony Khawaja of the University of Cambridge, found that for every extra hour per week a child spent in outdoor activity, his or her likelihood of suffering from nearsightedness declined 2%. Compared with kids with normal eyesight or who were farsighted (meaning they had trouble focusing on things close up), children with nearsightedness spent an average of 3.7 fewer hours per week outside say researchers.

Khwaja said the reasons are not clear. Nearsightedness, or myopia, runs in families and has also been linked to a host of factors including the amount of time spent focusing on near objects, for example when reading, and levels of physical activity.

It could be the greater exposure to long-distance views, the effect of spending less time at close-up activities such as reading, Web-surfing or video-gaming, the physical activity that might come with outdoor play or the greater exposure to natural ultraviolet light.

Dr Justin Sherwin, study co-author, said the benefit from being outdoors could be linked to increased exposure to ultraviolet light. Myopia is caused by having longer eyes and some laboratory-based studies have indicated that chemicals affected by UV rays may control the length of the eye, meaning that a lack of sunlight could make them grow too much, he explained. He said, “It could be caused by not enough UV radiation, but it could also be spending less time looking into the distance or not enough physical activity.”

Prof Paul Foster, who supervised the project, added, “To be honest we do not know what causes people to become short-sighted, but they tend to read a lot more and to have higher academic achievement and we tend to assume it is because they are reading all the time. It might be something to do with relaxing the focusing mechanism in the eye and returning it to normal distance vision, and the wavelengths of light we are exposed to outside could also have an impact.”

Between 15 and 20 per cent of British people are short-sighted. In some parts of Asia, rates of myopia among children have jumped by 80%, and in the United States, kids today spend much less time outdoors than they used to. If the trend continues, some experts say, we'll have a generation of overweight, myopic kids unable to engage themselves in imaginary play and lacking in wonder.

One study comparing Chinese children living in different countries found that those in Australia had better vision on average than their peers in China and Singapore. The Australian group read as much and achieved the same results academically as those in other countries, but tended to spend more time outdoors.

More outdoor play and less close-up work may reduce rates of nearsightedness and may even reverse some nearsightedness - Khawaja cited one Chinese study showing that myopic kids ordered outdoors for extra hours weekly were on average less nearsighted after two years.

One recent study however found that for “lazy eye,” also known as amblyopia, playing video games brought improvement even for adults, whose amblyopia was thought to be more resistant to treatment.