The circadian system is responsible for regulating a ton of
Glasses, contacts, and laser surgery equal big business for optometrists. Nowadays, the options available to nearsighted people run far and wide. With so many corrective methods available, it’s easy to disregard blurry vision as anything but a mere inconvenience.
Back in 2001, the British Journal of Opthamology estimated that about 75% of young adults in East Asian countries were nearsighted. Yet nearsightedness is on the rise. A new study in the Nature journal provides some sobering statistics:
(1) Up to 90% of teenagers in East Asia currently experience blurry distance vision. The worst affected country is South Korea;
(2) In the United States and Europe, about 50% of teens and young adults currently qualify as nearsighted;
(3) By the year 2020, approximately 1/3 of the Earth’s population (or 2.5 billion people) will need vision correction for nearsightedness. This number will be a sharp increase from the current 1.6 billion myopic people in the world.
Why is the number of nearsighted children and young adults increasing at such a rapid rate?
The traditional scapegoat for nearsightedness is “close work” such as homework and staring too long at books. Like many of you, my own mother used to lecture me about reading in the dark. A new culprit was uncovered by the Nature journal, which says empirical data doesn’t support the “close work” theory — at least, the theory doesn’t support the rapid increase in nearsightedness. A better explanation was uncovered (via Nature) by the Ohio State University College of Optometry. Professor Donald Mutti followed over 500 children with healthy vision. Their daily habits were studied, including “sports and outdoorsy stuff,” which was “an afterthought” when the study began.
Five years later, Mutti and his staff discovered that 20% of their group developed nearsightedness. The unfortunate ones were those who also spent the least amount of time outdoors. A parallel study of children in Sydney, Australia discovered similar results: “Based on epidemiological studies, Ian Morgan, a myopia researcher at the Australian National University in Canberra, estimates that children need to spend around three hours per day under light levels of at least 10,000 lux to be protected against myopia. This is about the level experienced by someone under a shady tree, wearing sunglasses, on a bright summer day.” In Australia, where most children spend plenty of time outdoors, only about 30% of teenagers are nearsighted.
The conclusion: Children who spend less time staring at video games and books indoors are less likely to develop myopia. Spending about 3 hours per day outdoors seems to be the ideal strategy. The downside: More time in the sun presents other risks like skin cancer. (Always a tradeoff.)