Despite centuries of warnings to “protect” our eyes from the sun, researchers around the world are now discovering the sun is actually the best protection we have against nearsightedness.
The number of people with nearsightedness or “myopia” has been on a sharp rise over the last couple of decades along with the number of hours young people spend in artificially lit indoors staring at screens.
By 2050, almost half the world will be nearsighted and require some form of corrective lens, up from a quarter of the global population in 2000. In China, as many as 90 percent of recent high school graduates are nearsighted, up from only 10 percent 60 years ago. Most of that increase happened in the last two decades.
Dozens of studies over the last decade suggest the solution is simple – spend more time outdoors in natural sunlight.
UVB rays — the rays responsible for sunburns — are particularly good at preventing short-sightedness, according to the latest of these studies published in The Journal of the American Medical Association Opthomology.
Researchers at King’s College London interviewed more than 3000 elderly Europeans about how much time they spent in direct sunlight at various stages of their lives and gave them eye exams. Those who had gotten the most sun in their youth were about 25 percent less likely to have developed myopia by middle age. UVB exposure between ages 14 and 30 showed the most benefit.
This new study adds to the growing body of research indicating a lack of direct sunlight may reshape the human eye and impair vision.
“People with myopia have long eyeballs, so there must be something in sunlight that affects how the eye grows, especially in childhood,” the study’s lead author Katie Williams told the New York Times.
A 2008 study, also published in JAMA Ophthalmology, compared 6 and 7-year-old children of Chinese ethnicity living in Australia and China. The rate of nearsightedness among the children living in China was nearly nine times that of children living in Australia. The parents of both sets of children had about the same rates of myopia, ruling out genetics as a significant factor.
The main difference between the two groups was the number of hours they spent outdoors. On average, the children in Australia spent nearly 14 hours per week outside, while the children in China spent just 3 hours per week outside.
“We hypothesize that another factor contributing to the differences in the prevalence of myopia may be the early educational pressures found in Singapore but not in Sydney,” the authors of the study wrote. In other words, the amount of time doing “near work” – reading, writing and computer work.
In response Taiwanese schools increased outdoor time to a minimum of two hours per day in 2010, resulting in significant reductions in the number of children diagnosed with myopia, and improvements in those who’d already developed it, according to a 2013 study.
A 2007 study by scholars at Ohio State University found that, among American children with two myopic parents, those who spent at least two hours per day outdoors were four times less likely to be nearsighted than those who spent less than one hour per day outside.
“The best prevention for myopia in children is more time outdoors,” Ohio State University researchers wrote in a report published last month by the National Eye Institute.
In a New York Times article titled “The Sun is the Best Opometrist” Princeton professor of molecular biology and neuroscience Sam Wang says he and other researchers suspect bright outdoor light helps children’s developing eyes maintain the correct distance between the lens and the retina, keeping their vision in focus.
“Dim indoor lighting doesn’t seem to provide the same kind of feedback,” Wang said. “As a result, when children spend too many hours inside, their eyes fail to grow correctly and the distance between the lens and retina becomes too long, causing far-away objects to look blurry.”
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