The Nearsightedness Epidemic

The Nearsightedness Epidemic


When you hear about epidemics, it usually
has to do with some frightening virus like HIV or Ebola. So when scientists in the know start talking
about an epidemic of nearsightedness, it probably sounds … strange. I mean, how can something that isn’t infectious
or contagious become an epidemic? And yet: The prevalence of nearsightedness
in the US is pushing 40 to 50% among young people. And that’s nothing compared to parts of
East Asia — particularly Singapore, China, Japan, and Korea — where nearsightedness
among high-school-age children is at 80% or more. Is it because kids these days have too much
homework? Or is technology to blame? Are iPads ruining our children?! New research suggests the cause of nearsightedness
might not be peering too closely at your homework … but neither is it all up to genetics. And that might be a good thing, because there’s
a potential prevention out there that’s universal, and free. The antidote to nearsightedness might be good
old-fashioned sunlight. Nearsightedness, or myopia, is a condition
in which your eyeball is elongated. When light enters an eyeball that’s too
long, the lens focuses light in front of the retina instead of right on its surface. This creates an image that’s blurry if you’re
looking at anything farther away than your outstretched arm. Myopia is easily corrected with glasses, contacts,
or surgery. But in extreme cases, what eye doctors call high myopia, it carries a risk
of severe eye problems, like glaucoma, retinal detachment, and cataracts. Nearsightedness has always been around to
some extent. Astronomer Johannes Kepler blamed his near-sightedness
on all of the writing and calculations he did up close, and for centuries that’s been
the conventional wisdom. For a long time, peering too closely at written
material, termed near work, has been blamed as the cause of nearsightedness. Near work typically includes things like reading
and writing. Watching TV doesn’t count, because it’s far enough away, and even using
a computer isn’t as hard on your eyes. Things like smartphones and tablets are new
enough that it’s hard to say whether they should be included in the definition, but
nearsightedness has been on the rise since before they became mainstream, so they’re
probably not at fault either way. But while extensive studies have had a hard
time ruling out near work entirely, they also have a hard time establishing a firm link. So, most scientists no longer think near work
is directly responsible for nearsightedness. But In the 20th century, we learned that there’s
a certain amount of genetic influence on nearsightedness. If your parents are nearsighted, you might
be, too. But that genetic influence isn’t really
straightforward. It involves a few dozen genes, each of which only contributes a fraction
of the overall story. Plus, a study of an Inuit community in Alaska
back in 1969 showed that nearsightedness can spread way too fast for genetics to explain. At one point, only 2 out of 131 people in
that community were nearsighted — that’s one and a half percent. But the prevalence rose to nearly fifty percent
in their children and grandchildren! Genetics couldn’t possibly be responsible
for such a rapid spread. This led scientists to conclude that, while genes have some influence,
the main cause of nearsightedness must be something in our environments. And it must be something that’s dramatically
increased in recent times. While near work itself doesn’t seem to be
the culprit, there does seem to be a link between nearsightedness and education. One study, published in October 2015 by researchers
from Cardiff University in Wales, found that firstborns are more likely to be nearsighted
than later children. About 10% more likely, to be specific, which
certainly doesn’t account for the skyrocketing prevalence, but it might provide a clue. When the researchers adjusted the data to
account for how much education the participants had had, the effect diminished, which means
that it was the education of the subjects that made the difference. The scientists suggested it was a result of
so-called “parental investment.” First-time parents who make their oldest kid hit the
books might be a little more relaxed by the third one. As a result, firstborns who spent
more time studying ended up being more likely to be nearsighted. Another study, by researchers from Sun Yat-sen
University in China, compared the rates of nearsightedness in two neighboring Chinese
provinces. They looked at schoolchildren in Shaanxi,
a middle-income province, and comparatively poor Gansu province. The prevalence of myopia among kids from the
wealthy province was roughly twice that of the poor province. The researchers couldn’t
fully explain this difference, but higher math scores were associated with higher rates
of nearsightedness. So it certainly looks like education correlates
with nearsightedness, but how is this happening? And if it’s so easy to correct, why worry? Well the fact is, about 20% of people with
nearsightedness end up having high myopia. For example, more than 90% of 19-year-old
men in Seoul, South Korea have myopia. So that means nearly 20% of that population is
at risk for those serious complications we mentioned, which can lead to blindness. Having this many people at risk of serious
eye problems is a major public health concern. And eyeglasses will certainly help, so getting
glasses to kids who need them is a big priority — or, at least, should be — in these countries. But still that’s not going to address the
underlying problem. Why are so many people throughout the industrialized world nearsighted,
when our ancestors didn’t have this problem? And why is the situation especially dire in
Asia? The best guess anyone has is that it’s related
to the particular emphasis placed on education by many East Asian cultures. China has a do-or-die college entrance exam
that makes the SAT look like a walk in the park. Kids as young as 10 spend hours every
day doing homework. If education is a factor in nearsightedness,
that’s where it’s going to show up. To tease out the effect of cultural environment,
Australian researchers from the University of Sydney looked at 6 and 7 year old ethnic
Chinese children living in Sydney and Singapore. The kids’ parents had similar rates of nearsightedness–around
70%–in both study groups. But in the kids themselves, the difference
was stark. Only 3.3% of kids in the Australian group were nearsighted, compared to 29.1%
in Singapore. And the children in Sydney actually did more
near-work activities, like reading and homework, than the kids in Singapore, so that couldn’t
possibly be the cause. The only difference between the two groups
of children that could account for the difference in myopia was how much time they spent outside. The kids in Sydney spent more than 13 hours
a week outside, the kids in Singapore only 3. This seems almost hard to believe. Can sunlight
really prevent you from becoming nearsighted? Scientists and public health officials would
really like to know. But, nothing in epidemiology is ever simple. In order to figure out if natural light can
treat myopia, we need two things: Rigorous evidence that sunlight really works, and a
scientific reason–a mechanism–for it to have that effect. Fortunately, within the last few years, researchers
have made progress toward both. Experiments in animals, including chicks and
rhesus monkeys, have shown that light can protect against myopia. Researchers in Germany first tried to induce
myopia in a set of chicks using special goggles, so that all the other variables could be controlled.
Then they exposed two groups to different lighting conditions, with one group being
raised under bright light that was meant to simulate sunlight, and others under normal
laboratory lighting. Turns out, the onset of myopia was slowed
in the group raised under bright lights, by around 60%. Then the researchers focused their attention
on a substance produced by your own brain that’s known to influence proper eye development:
the neurotransmitter dopamine. In another experiment, the researchers injected
the chicks with a chemical that blocked dopamine. Without the dopamine, the protective effect
of sunlight disappeared. So it’s believed that dopamine is released
into your eyes as a result of bright light. This chemical is at least partly related to
your body’s day/night rhythm — it’s involved in the switch body undergoes from from low-light
nighttime vision to daytime vision. And it’s what lets bright, natural light signal to
your body that it’s daytime. So, researchers now think that this dopamine
cycle is needed for healthy eye development throughout childhood. If it’s disrupted, like by spending all
your time indoors in dim light, your eyeball starts to become elongated, and myopia results. This light-dopamine hypothesis is currently
the best theory for how sunlight can help your eyes develop. Best part is, sunlight is free, and it’s
an easy thing to try to see if it keeps kids from becoming nearsighted. A few studies have even looked into using
sunlight as preventive medicine. One of the biggest studies looked at primary
school children at 12 schools in Guangzhou, China. They were divided into two groups of
six schools each, with about 950 children in each bunch. The control schools didn’t change their
daily routine, but the other schools added a 40-minute outdoor activity period. Then
the researchers tracked the kids for three years. By the end of the trial, the incidence rate
of myopia in the group that spent more time outside was 30%, compared to 39.5% in the
control group. The reduction was actually less than what
the researchers expected. But still, preventing myopia in young kids is worthwhile, they say,
because the longer it progresses, the worse it gets. The most difficult thing about using sunlight
as medicine might just be convincing parents to send their kids outside more. In the Chinese study, the schools sent the
kids outside for an extra 40 minutes, but parents were also asked to send their kids
outside even more on their own time. But as far as the researchers could tell,
the parents kind of…didn’t do that. And they think more than 40 minutes is needed
to achieve the most beneficial effect. So, it seems like a victory for sunlight.
I mean, it isn’t established for sure — many studies have shown that vision quality benefits
simply from going outside, rather than bright light per se. So it could be that the effect comes from,
say, playing more sports rather than sunlight. But researchers are calling for more studies
to better establish the link, and the data so far look promising. In the meantime, fresh air and sunlight as
a clinical intervention is a pretty appealing idea. In the end, it doesn’t seem like video games
or smartphones are to blame for the nearsightedness epidemic. But neither are books and homework.
And, thankfully, it’s not a terrifying virus that’s causing the epidemic of nearsightedness. Rather, it might be an overwhelming cultural
tendency to stay indoors. So if you want to keep your kids from becoming
nearsighted, maybe sign them up for soccer. Sports: they’re good for you. Who knew? Thanks for watching this episode of SciShow,
which was brought to you by our patrons on Patreon, like Carsten Steckel and Glen Knowles!
Thank you both! If you want to help us make more content like this, just go to patreon.com/scishow.
And don’t forget to go to youtube.com/scishow and subscribe!

100 thoughts on “The Nearsightedness Epidemic

  1. People don’t get out enough (light aside, your eyes will always focus farther out than an indoor space), and now they spend a high percentage of their time staring at something less than arm’s length from their eyes when they do go out.

  2. People should stop breeding with random ppl. Lol. Get a complete medical and genetic work so you know if your kid is gunna have a defect.

  3. If you watch any Twitch.TV esports game where the audience is in some Asian country, look at how basically everyone of them is wearing glasses; it's ridiculous!

  4. does higher depression/stress rates play into this? depression would lower the amount of dopamine released into the body. or is the dopamine released into the eye region non reliant?

  5. What if it isn't necessarily the light, but the far focus? You are more likely to have to see 30-40' on a constant basis. So like any muscle, if you don't use it you lose it?

  6. How bout having one nearsighted eye and one farsighted…also with different astigmatisms… Can sunlight fix my legal blindness

  7. Huh. I was outside most of time in warm weather, and at least 3 hrs a day in the winter. I'm extremely nearsighted. I can only see clearly about 5 inches in front of my face.

    Makes me wonder if it might've been a lot worse if I hadn't been outdoors so much.

  8. I believe they were correct with the educational theory. Nearsightedness doesn't only make anything further than your outstretched arm increasingly blurry; it also makes your near vision more detailed and magnified, giving you a more insightful view of what's really important, and more accurate observations of what really matter. I've had this idea since childhood when I was always in the sun…

  9. Being singaporean, im pretty sure that singapore kids spend more or at least equal amount of time as the sydney kids doing near work. After school, kids have alot of homework to do and spend alot of time watching tv or playing video games at home. Perhaps the study is nt accurate about the amt of time the kids spend doing near work.

  10. What about babies getting outside with their families? You didn't even mention how important is to take a walk with the baby every day.

  11. Every single day at the very least 1 h better 2 h natural daylight. Of that every morning in between 6 am and 9 am 20 – 30 minutes natural daylight. If in your region it's winter and the sun raises later, adjust accordingly.
    A strong daylight lamp in the morning can help but is not a true replacement.

  12. Literally every single person in my family is either nearsighted or farsighted EXCEPT FOR ME, and I virtually NEVER go outside.

  13. Do children in northern European countries, where there is limited sunlight during the winter, suffer more from near-sightedness?

  14. Its the yearly pupil dilation is the cause of the problem. I noticed the change the first time my eyes were dilated and since then my eye sight over the years so i soread out my eyes getting dilation.

  15. Wearing glasses worsens eyesight. Audiobooks could help.
    Using sunlight to heal eyes is not new. This information has been around for a long time.
    Sungazing helps depression and fatigue.
    Watch the sunrise and sunset.

  16. You list all these things, video games, studying, watching tv, etc., as things that don't cause nearsightedness, but they are the cause of keeping kids inside

  17. You can ;earn to contract and relax the orbital muscles that control eye movement. They can reshape the eye ball to focus near and far. We are not allowed to know this because it's top secret military national security and there are billions being made selling glasses that are ruining peoples lives that's just good business. .

  18. I spent all day playing outside as a child and I've been myopic since I was 5. They need a better answer for this. They need to look into nutrition.

  19. What if its because when you're outside you have to see further than when youre inside, so the eyes dont develop as well

  20. Maybe it's not being outside that matters as much as focussing on the far distance for more often?
    Much more common when you're outside but not simply being outside.

  21. My parents made me play lots of sports when I was young. I developed nearsightedness early and it got progressively worse. Now that I'm older I'm a computer scientist and spend most of my days staring at screens. My eyes get tired sometimes but my overall vision has remained stable for 5-10 years.

  22. Surprised they didn't mention the focal distance of outside vs inside. Your eyes need exercise. Focusing 10 ft away all day inside vs much greater lengths outdoors is probably the real reason for the difference

  23. My eyes are so bad. I can't really even read a book without glasses. By the time it's close enough to be in focus, it strains my eyes.

  24. You would to know why?
    1. Small room (singapore people lives in small houses / apartment)
    2. LED lamps joined with
    3. LED screen

    Eventhough I afford buying amoled screen phone, but no thanks

  25. I spent a million hours outdoors!! I'm 51 and wear glasses for both distance and reading. Although many times I don't wear glasses to read, use cell and can see quite a lot without glasses. Weird
    But real close up, I can't see details like I used to, eg, cooking etc. But sometimes I do. My retina is thinner than normal.

    My daughter has perfect vision. She's no longer teen. Not much outdoor time, though…

  26. My thought is in the hertz coming out of the wall and the condition of the light bulbs. We here in US have 60 hertz. That's 60 strobes of off and on per second. So its not like we view solid light inside. My theory is that the constant strobe affect is damaging our eyes. The sun does not strobe so that makes sense being outside is healthier. The should do research on candle or solid light vs. light bulbs next. Or lack of light bulb light. Just my 2 cents 🙂

  27. I had my nearsightedness cured with cataract surgery at age 53.  I Wish I had known about the sunlight cure as a boy when I was swatting indoors to be top of the class when the other kids were outside playing.  I also wish I had known that the hard contact lenses I used to wear to correct it probably caused the premature onset of the cataracts; although opthalmologists have denied this.

  28. There may be some truth to these theories. I've been wearing glasses due to myopia since I was 8, but my little brother has 20/20 vision. Let's see:

    First born? Check.

    Pressured to focus more on academics? Check.

    Placed in piano lessons instead of sports? Check.

    Rarely went outside as a kid? Check.

    My little brother is the complete opposite of all of the above. That's a shame. I'm in my 30s now and my eyes are just getting worse and worse. I'll likely be legally blind once I hit 62.

  29. Horseshit.. I'm 52.. there was no video game or cell phones when I was a kid, we had 1tv in the house and I only watched it on Saturday mornings… I was outside CONSTANTLY.. I hated being stuck inside.. I was on my bike, or in the pool, climbing trees, frying bugs, finding toads and newts etc.. I had friends that I talked to in person and knew what they Really looked like.. Not some animated, pretend screen pic.. AND I was the neighborhood paperboy… So I was out in the dark at 430 am and have excellent night vision to this day… But I was nearsighted at 10 and had to get glasses.. I have worked jobs outside my entire life.. I believe I have had sun exposure.. By the age of 38 I was -8 and -8.5 and couldn't read print unless it was at my nose without glasses.. I finally had Lasik and it was and is fantastic.. I still work mostly outdoors and I fish and shoot and skate… (These are called "Outside activities" kids…believe it or not..)
    I can also say that most all of my predecessors on both sides and additionally, cousins.. had some kind of vision issues.. my grand parents were born in the 1800's and lived on farms.. they were outside a lot. So, unless it's the opposite of this video and being caused by cosmic rays and chlorine.. I must continue to believe it's genetics thanks…

  30. I started thinking about this and remembered a study about the Sun and vitamin D production, that we need to be out in bright sunlight in order to produce vitamin D. I wonder if they considered giving vitamin D supplements to myopia sufferers? It's an easy enough experiment to do.

  31. I'm myopic, so is my brother. Neither of our parents are but our paternal grandmother is very short-sighted. We were both book worms, but I also spent a lot of time outside. I think for us it was mostly just genetics.

  32. Maybe what is making the difference is the lack of "far work" or looking to places far from yourself, if you never look to anywhere no more distant than a few meters (what usually doesn't happen with people who play outside) there's no wonder why this epidemic is happening.

  33. I have scar tissue over my pupil on my left eye. Took a metal belt buckle to the cornea as a child. You know why human eye's suck? Because robot visual sensors are awesome.

  34. So what caused the increase in myopia in the Inuit population? Were the younger generations living a different lifestyle than their grandparents?

  35. Lmao I have nearsightedness and barely passed high school but all my four older brothers don’t have near sightedness

  36. I don't believe that. I spent lots of time outside as a kid ( born in 1954) and am still a very outdoorsy person. I wore glasses in First Grade at the age of 7. By high school I couldn't see a foot in front of my face without glasses. I was a voracious reader from the time I was 3 (yeah, I was 3 when I started to read). So there is something about school that is damaging the eye. Florescent lighting?? I know that study with the Inuit. I homeschooled my three kids and all of them finally started wearing very mild glasses in their 20's. Mild, as in it just clears things up a little so is more comfortable. So, who knows? Be interesting to find out.

  37. Interesting video… except for the end where he recommended sports. Jesus said in Mark 10, Mark 11, and in Luke 22 that 'he who would be greatest among you must be servant of all, and last of all.' There is no reconciling that statement and the life of Jesus Christ with what's going on in a competitive sports game. God calls us to love one another, to serve one another 24/7. Outdoor recreation would have been a better recommendation.

  38. Ive been working outside, in the blistering sun, since August and I am developing near-sightedness because of it. I am confident because I have had 20/20 vision all of my life and only recently my eyes have been getting blurry.

  39. Optometrists account for a lot of this. Look at the stats on eye specialists (i.e.opthamologist) and think of the incentive of Optometrists-notice when the Inuit started needing glasses and when Optometrists had access to their tribes.

    Note all the weasel words used here: "may be, seems to, could be, indicates, seems, etc." A long winded screed that really says little new from some hipster with ear plugs who probably still doesn't need to shave every day.

  40. When I was younger my brothers,sister and i where always outside. I am nearsighted so idk if sun really played a role. I was the only one to need glasses I was also first born. But I have heard incubators creating pressure on developing eyes could be a cause and I was the only one born 2 months premature which is much more common in today's age with technology at keeping baby's alive. Skull development of course would effect how the eye is shaped as we grow into our bodies and i didn't need glasses for about 8 years or so I remember haveing very good eye sight for a short time.
    In my 30's I can see within 12 inches of my face and everything els is a blur.

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