Worldwide, more and more people are suffering from myopia – or near-sightedness – and a lack of outdoor time may be to blame.
In Singapore, the military first brought the problem to light. Because military service is mandatory, they were in the unique position to evaluate virtually every citizen’s eyesight at about the same age. By the late nineties, the prevalence of myopia was nearly 80 percent.
In the U.S., a national survey completed in 2004 indicated that 42% of the population was myopic—up sharply from 25% 30 years earlier.
Many researchers assumed that an increase in screen time – televisions, computers, tablets and smart phones – was likely to blame for damaging eyesight, especially in young people. Yet studies have failed to prove a strong connection. Instead, a growing body of evidence suggests the problem is a lack of natural sunlight. Ambient light stimulates the release of dopamine in the retina, and dopamine reduces excessive eye growth – which causes myopia.
Indeed, in one study, children in Singapore were found to spend an average of only three hours outside per week, and 29 percent were affected by myopia. In Sydney, Australia, on the other hand, children spent nearly 14 hours outside per week, and myopia affected only 3 percent.
Population genetic differences may also be involved, but as global competition to excel academically increases, children in many countries spend more and more time in school and doing homework and less in natural sunlight.
Add this to the list of growing list of reasons to encourage kids to get outside and enjoy nature.
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Web Links
Myopia: The Evidence for Environmental Factors
Photo, taken August 28, 2011, courtesy of PhotoSteve101 (www.planetofsuccess.com/blog/) via Flickr.
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Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY.