WEBVTT - Why Are So Many People Nearsighted?

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<v Speaker 1>Welcome to brain stuff from how Stuff Works. Hey, brain stuff,

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<v Speaker 1>Lauren vogelbamb here there's a myopia epidemic going on. In

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<v Speaker 1>n seventy two, about of Americans aged twelve to fifty

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<v Speaker 1>four were diagnosed with this condition, which is also called

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<v Speaker 1>near sightedness. But today some forty of young Americans are

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<v Speaker 1>receiving the same diagnosis. And that's nothing compared to Asian countries,

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<v Speaker 1>where of high school kids are now near sighted. In seal,

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<v Speaker 1>ninety six point five percent of nineteen year old males

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<v Speaker 1>are myopic, and researchers say that by the year twenty

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<v Speaker 1>fifty five billion people will be wearing glasses to combat

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<v Speaker 1>near sightedness. That's more than half the people in the world.

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<v Speaker 1>How did this happen so fast and so many people.

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<v Speaker 1>While intuitively you might think it has something to do

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<v Speaker 1>with all the time we spend staring at computer or

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<v Speaker 1>smartphone screens, it's not so cut and dried. The rise

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<v Speaker 1>and near sightedness started happening before the prevalence of those

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<v Speaker 1>screens and has been studied at least since the nineteen sixties.

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<v Speaker 1>The latest research reveals that the world's rising myopia rates

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<v Speaker 1>stem from spending too much time indoors in general, Several

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<v Speaker 1>studies show the less time children spend outdoors, the more

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<v Speaker 1>likely they are to develop myopia. This could explain the

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<v Speaker 1>much higher myopia rates in Asian countries, where a stronger

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<v Speaker 1>focus on education keeps kids indoors for more hours than

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<v Speaker 1>children living in most other parts of the world. We

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<v Speaker 1>spoke with Dr Adam Clarin, a Florida optometrist. He said

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<v Speaker 1>the progression of the number of myopic patients has risen

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<v Speaker 1>too fast to be explained by genetics alone. Unfortunately, the

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<v Speaker 1>data is not conclusive enough to determine what parts of

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<v Speaker 1>being outside is protective against myopia. Is that the sunlight,

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<v Speaker 1>is it looking at distant objects, or is it something

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<v Speaker 1>we're not even thinking about. Near sightedness is caused by

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<v Speaker 1>an elongated eyeball. Normally, the light that flows into your

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<v Speaker 1>eyes focused directly on the surface of the retina, but

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<v Speaker 1>if your eyeball is a bit too stretched out, the

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<v Speaker 1>lens will focus the lights slightly in front of the

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<v Speaker 1>retina instead, resulting in blurry vision. The hypothesis about myopia

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<v Speaker 1>that's gaining the most traction says that when the neurotransmitter

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<v Speaker 1>dopamine is released into the retina. It prevents your eyeball

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<v Speaker 1>from elongating and blurring your vision, and light is what

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<v Speaker 1>stimulates this release of dopamine. Normally, a pair of glasses

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<v Speaker 1>or contact lenses is all that's needed too sharpen your vision. However,

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<v Speaker 1>of those with the condition have a heightened form called

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<v Speaker 1>high myopia. People with high myopia are at a risk

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<v Speaker 1>for developing cataracts, glaucoma, torn or detached retinas, and even blindness.

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<v Speaker 1>Although no one knows how much time spent outdoors is

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<v Speaker 1>enough to forestall myopia, one researcher at the Australian National

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<v Speaker 1>University in Canberra estimated the amount at three or more

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<v Speaker 1>hours per day. It's also possible that strong indoor lights

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<v Speaker 1>could help, but Dr roheat Varma, director of the University

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<v Speaker 1>of Southern California I Institute, told us via email that

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<v Speaker 1>even if the myopia boom is not directly related to

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<v Speaker 1>children spending more time indoors looking at a screen quote,

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<v Speaker 1>these are two sides of the same coin. Spending more

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<v Speaker 1>time indoors equates to spending less time outdoors, especially during

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<v Speaker 1>the day. Researchers are still trying to determine the real

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<v Speaker 1>fix for the myopia epidemic. Dr Claarin said other studies

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<v Speaker 1>have shown that a low dose of atropine eye drops

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<v Speaker 1>can also slow the progression of myopia. These studies are

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<v Speaker 1>completely unrelated to the studies on being outdoors, so there's

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<v Speaker 1>obviously more than one mechanism at play. Hopefully, continuing research

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<v Speaker 1>will shed some light on this growing problem. Today's episode

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<v Speaker 1>was written by Bellinie redz Kien McManus and produced by

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<v Speaker 1>Tyler Clang. For more on this and lots of Far

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<v Speaker 1>Side of topics, visit our home planet, how Stuff works

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<v Speaker 1>dot com.