Monday, August 31, 2015

The Real Reason Why You're Nearsighted

glassesWhen I was growing up, I was always led to believe that needing glasses was just something that happened to people. You were simply born to be nearsighted or farsighted, and that was all there was to it. To some extent this idea is true. Scientists have found genes that can be linked to these visual ailments, which are widely known to be passed down in certain families; but does that tell the whole story?

When you really think about it, it doesn't make a whole lot of sense. Conditions like myopia are incredibly common. Everybody knows somebody who needs glasses or corrective surgery. So you have to ask yourself, if vision problems are mostly genetic, and they're so common in children all over the world, why didn't natural selection weed this trait out of the gene pool?

You have to imagine that not being able to see properly would be so much more hazardous for our ancestors than it is for us. How could hundreds of millions of people be suffering from a genetic disease that just a few centuries ago, would have nearly been a death sentence? Honestly, this totally defies our notions of evolution.

Well it turns out that the scientific community is slowly changing its mind on the origins of childhood vision problems, specifically with myopia. Genetics still play a role, but the research that has been done over the past few years has revealed a new risk factor.

For starters, the vast numbers of people with myopia blows the whole genetics theory out of the water. But the countries that have it the worst, can give us a hint to its true causes.
East Asia has been gripped by an unprecedented rise in myopia, also known as short-sightedness. Sixty years ago, 10–20% of the Chinese population was short-sighted. Today, up to 90% of teenagers and young adults are. In Seoul, a whopping 96.5% of 19-year-old men are short-sighted.
Other parts of the world have also seen a dramatic increase in the condition, which now affects around half of young adults in the United States and Europe — double the prevalence of half a century ago. By some estimates, one-third of the world's population — 2.5 billion people — could be affected by short-sightedness by the end of this decade. “We are going down the path of having a myopia epidemic,” says Padmaja Sankaridurg, head of the myopia programme at the Brien Holden Vision Institute in Sydney, Australia.
So what do all of these countries have in common? They're all developed nations, or soon to be developed nations. But what do advanced nations have in common? Literacy and education of course. While all developed nations have a myopia problem, East Asians nations seem to have it at a much higher rate, and their children spend much more time studying and reading than ours do. The average teenager in Shanghai spends 14 hours a week doing homework, compared to 6 hours in the United States.

Studies across the planet have stumbled upon this phenomenon over and over again. Whenever a culture is exposed to the modern world, their myopia rates go through the roof, and it appears that the amount of time that a child spends reading and studying, has a strong effect on their vision. For a long time, it was believed that spending so much time focusing your eyes on nearby objects was hurting them, but after a while, it was realized that this also doesn't fully explain the myopia epidemic. Though it does seem to be related.
In the early 2000s, when researchers started to look at specific behaviours, such as books read per week or hours spent reading or using a computer, none seemed to be a major contributor to myopia risk. But another factor did. In 2007, Donald Mutti and his colleagues at the Ohio State University College of Optometry in Columbus reported the results of a study that tracked more than 500 eight- and nine-year-olds in California who started out with healthy vision. The team examined how the children spent their days, and “sort of as an afterthought at the time, we asked about sports and outdoorsy stuff”, says Mutti.
It was a good thing they did. After five years, one in five of the children had developed myopia, and the only environmental factor that was strongly associated with risk was time spent outdoors. “We thought it was an odd finding,” recalls Mutti, “but it just kept coming up as we did the analyses.” A year later, Rose and her colleagues arrived at much the same conclusion in Australia. After studying more than 4,000 children at Sydney primary and secondary schools for three years, they found that children who spent less time outside were at greater risk of developing myopia.
It was initially thought that exercise was playing a role, but that didn't hold up either. Eventually the scientists in these studies realized that sunlight was the greatest contributing factor. For some reason, exposure to light reduces the chance of becoming nearsighted, which has been subsequently demonstrated in both humans and animals.

So far it isn't 100 percent conclusive, but the evidence is mounting. The leading theory now is that when light reaches the eye, it stimulates the release of dopamine into the retinas, which apparently prevents the eyeball from elongating and causing myopia. They've tested this theory on chickens by injecting them with dopamine inhibitors, and have found that light no longer protects their vision.
Right now there doesn't seem to be any evidence that sunlight can cure myopia, but it does appear to either prevent it in most people, or at least stop it from progressing. So if you don't want your kids to become nearsighted, the best thing you can do for them is kick their butts outside and let them play for a few hours.

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  1. This is confusing to me, since it doesn't differentiate between nearsightedness (seeing up close well, but not things in the distance) and farsightedness, which I have suffered from since reaching my 40s (seeing things in the distance well, but not up close).

    Am I to understand that both (opposite) vision deficits are to be grouped together, for the purposes of this article -- or only nearsightedness?

    Nonetheless, I agree that vision problems which seem so wide-spread in the developed world, seem to be curious, since (as you said) this most likely was not the case for humankind for most of its history (i.e., poor vision is a contra-indicator for projecting a long life expectancy)!

  2. Like Deric Fiddleman, I would like to know if Scientists found this equally true for far sightedness. I have been told that looking both near and far as one can only do out of doors is another reason for improved vision. I don't know whether or not it is true but I was also told that the endorphins from the sun enter the brain and prevent depression. I know the sun gives us vitamin D. I know that staring directly at the sun is supposed to damage the eyes. I know that some proponents of sun gazing believe that it is beneficial to gaze/stare at the sun as it rises at dawn and sets at dusk. But I don't know what is true. What is the Science? Is there a doctor in the room? Or ANYBODY who really knows?

  3. The connection between sunlight and visual acuity seems sensible, but I think there are perhaps unrecognized co-factors. Or maybe they are recognized in some of the research but were not focused on in this article. (Pun intended)

    I am 65 y.o. and have been nearsighted since age 7. I grew up in Key West Florida, USA, from age 4 until age 20. Despite constant exposure to bright outdoor sunlight, by age 7 I needed plastic corrective lenses for mild myopia.

    My myopia steadily worsened with every exam until I was considered legally blind without my glasses, by age 20. At that time I moved upstate to north central Florida where the light is still very bright even though it isn't "coastal" bright. From then on my lifestyle included at least one full day of each weekend working outdoors, as well as an hour or so of yard work after my regular workday each and every day of my life, but my vision continued to worsen until about age 50.

    So, if sunlight is the answer, why did it not work for me? Two thoughts come to mind. First, once a person has a lens between his/her eyeball and the incoming sunlight, the sunlight may be refracted in some way that eliminates the theorized benefit of direct sunlight-- like looking at the sunlight through a window, from indoors. And second, diet, specifically the consumption of refined sugar and other simple carbs, may also affect visual acuity, with or without adequate outdoor direct sunlight. I suggest this second possibility because I know someone who at age 27 eliminated sugar and wheat from her diet, and who had a steady improvement in her myopia (which was only slightly less severe than mine) over the next 6 months as she lost weight and experienced a steady decline in her blood values for cholesterol, triglycerides, CRP and homocysteine. She now can even drive without her eyeglasses, and seldom ever wears them anymore.

    Along with my lifelong daily "diet" of sunlight taken through plastic lenses, I ALWAYS ate too much sugar, bread and pasta, until now. When I finally stopped eating sugar at age 65 due to being prediabetic, all sorts of things changed, including my eyes. Subsequent elimination of wheat produced even more profound effects, including almost total elimination of all pain from fibromyalgia and osteoarthritis and a marked lessening of allergic type symptoms like sneezing, drippy eyes, nose, hoarseness, itching etc.

    Now, at age 65, my vision hasn't changed much in a decade, except for worsening presbyopia and growth of cataracts. Although eliminating sugar and wheat cleared up a decades long problem with dry eyes and resulted in an improvement in the quality of my tear film, it hasn't yet resulted in the reversal of myopia that my young friend experienced. On the other hand, over the past two years as my yard work and thus my sunlight exposure has lessened, I have not seen a worsening of my myopia either.