Why do so Many Korean Children Wear Glasses?

Korean Children Glasses TV(Source: LG전자; CC BY 2.0)

Update, April 2009: In hindsight, I didn’t cover this subject thoroughly enough here, leaving some questions unanswered. For a more comprehensive overview, see this article I wrote for the Korea Times.

Update 2, June 2013: And for a much more up-to-date overview, see this article I wrote for Busan Haps.

If I’d been asked this question yesterday, then I too would have answered that it was because they were always hunched over their books, or staring at computer screens. But the surprising result of this Australian study was that those are only correlated but not causative factors.

In fact, it’s because they don’t get enough exposure to sunlight.

I confess, before I read the details of the survey, I was very sympathetic to such a result: young Korean women, for instance, have among the lowest Vitamin D levels in the world because of avoiding the sun for the sake of light skins, and given how the required behavior and body images that lead to such extremes are inculcated very early in Korean children’s lives, then if a lack of sunlight does indeed lead to myopia (short-sightedness) I’d wager money on rates being higher among Korean teenage girls than boys. Not much higher, no, but I’d still expect a statistically significant difference between them.

But technically the study never looked at Korean children specifically. And while Korea certainly shares other developed East Asian countries’ skyrocketing rates of myopia among children — virtually all my middle-school students wear glasses or contact lenses, and I bet yours do too — I was confused when I heard that the study was primarily based on Singaporean children.

How on Earth do children that live on the equator not get enough sun?

Actually, partially it’s precisely because they live there. As head researcher Dr. Ian Morgan explains in an Australian radio interview, the heat meant that:

The children in Singapore were spending about three hours a week outside, so very, very limited periods of time outside, excluding the school hours. Basically they went to school, they went home, they did their homework and then they watched television and that was life.

But this issue of climate wouldn’t apply so much to children in other East Asian countries, where the same education culture of going to school during the day and then cram schools in the evenings prevails, although that does also mean that they’re not outdoors much of course. But how to tease apart the effects of that lifestyle from a lack of sunlight specifically? Things like diet, and, say, the not insignificant fact that Korean children get the least sleep in the world, would presumably have some effect too.

Here’s the key part of the radio interview that reveals how and why researchers did that. Without it, basic summaries of the study like this and this that are all over the news wires are good introductions, but raise more questions than answers really:

DR IAN MORGAN:….we have been able to compare the prevalence of myopia in Chinese kids in Singapore, as compared to kids of Chinese origin growing up in Sydney. And at the age of six, the kids in Singapore — the Chinese kids in Singapore are ten times more myopic than the kids of Chinese origin in Australia.

INTERVIWER: But did the Singaporean children spend more time in near-work activity than the Sydney children?

DR IAN MORGAN: If anything, they spent a little bit less and this is what led in part to us looking for what other factors could be important. And the striking difference that came across was that these kids — remember they’re matched for age and they’re matched for ethnicity, they’re all of Chinese origin. The kids of Chinese origin in Sydney were spending a lot more time outdoors than the kids of Chinese origin in Singapore.

For more details, including the debunking of alternative theories that there is some genetic susceptibility to myopia among East Asian populations, and why it is specifically light intensity that is important, then I highly recommend reading the radio interview in full.

I don’t have the time to translate anything myself unfortunately, but it’ll be interesting to see how the Korea media interprets the results of this study. While it would be just one of a very long list of serious social and health problems among young Koreans resulting from Korea’s after-school institute or hagwon (학원) culture, and so unlikely to lead to any huge changes overnight, all the various English-language articles on the study point out that governments across the region already do have serious concerns about the issue. So, this may well provide just enough of a shove for Korean schools to, say, provide more outdoor physical education and field trips for students. Granted that it’s rather cold at the moment though!

15 thoughts on “Why do so Many Korean Children Wear Glasses?

  1. When I worked in Korea, about 70-80% of the students in my class wore glasses, and I had always wondered about it myself. Interesting find!

    I knew it couldn’t be the reading factor, because the idea that too much reading causes myopia has been discounted in most studies. (Not to mention that myself and others around me read a lot, and in *gasp* non-fluorescent-lit rooms!)


    1. Alex: I’m curious: do you find the same in Japan?

      Brian: Before I clicked on the link I thought that you were referring to the original 2 paragraph article in the KT that got me writing the post, but I can’t find that anywhere and it may even be too small to be worthy of placing on the site (but what newspaper website doesn’t have a readily identifiable “international” section for me to look in? sheesh!). Now that I’ve clicked on it though, then yeah, that is indeed interesting timing, and come to think of it, a few years ago I definitely saw a Korean documentary about new buildings placing a school in shadows for much the day, and it was probably this one. I tried to find some videos and photos via Naver, but although I found the odd no news report none are actually naming the school, so probably there deliberately aren’t any unfortunately.

      Thanks for passing it on though.


  2. James: Not so much in Japan. It may be the area I live in, though (a bit rural). I think that “out here” kids tend to spend less time in cram schools than in the larger cities.


  3. Alex, Given that Japan and Korea and so on do have huge problems with children’s myopia like the various articles mentioned, then it probably is just the rural area you live in. I never noticed children wearing glasses so much when I worked in the Korean countryside from 2000-2003 either.

    Come to think of it, one of those articles mentions that part of the problem isn’t so much the lifestyle per se, but that there’s so few places for urban children to spend outdoors these days. Reminds me of a I think Time or New York Times article from many years ago about the the sheer impossibility of a Tokyo kid finding somewhere to kick a soccer ball around on a Saturday morning!

    Having children now, the availability of many many public parks for them to run around in in New Zealand, as opposed to no parks at all here in Busan and merely small sand playgrounds of schools to walk in endless circles around instead, is one of the first things we noticed on a much overdue trip back last year, and one not insignificant reason why we must eventually move there for their sake.


  4. Thank you for a highly informative post, James. I became aware of the problem of vitamin D deficiency and its assorted ill effects on health just a couple of years ago. A former sunscreen fanatic, I now make sure to get brief daily exposure to the midday sun and take cod liver oil in the winter since vitamin D-inducing UVB rays do not penetrate the atmosphere when the sun is low in the winter sky past the Tropics of Cancer and Capricorn. Something like 88% of all African-Americans living in northern latittudes of the US are said to be deficient, some seriously. Most people don’t realize that the vitamin D in milk is synthetic and not well-absorbed by the body.

    I had never thought about vitamin D deficiency in Korea and its connection with eyesight. Learned something new!

    While living in Korea and China, I used to get horrible sinus infections every year and started getting bronchitis the last few years in Seoul. Have not had a single sinus or bronchial infection after returning to the US. The city where I live has an air quality rating of 98 out of 100.


    1. Thanks Songai, and you’re welcome, but actually the high rates of myopia are not caused by a Vitamin D deficiency due to the lack of sunlight. Here’s the part of the interview that explains:

      INTERVIEWER : So why does sunlight cut myopia rates, the science?

      DR IAN MORGAN : Well, there are at least three hypotheses there. The first one which has been a long-standing one is that if you go outside and you look off into the distance, then your eye muscles, your accommodation will relax and this will slow down your eye growth and hence you won’t become myopic.

      There are various reasons why this is not particularly convincing, particularly because we’re much less convinced these days about the importance of the reverse of long distance viewing, namely what we call near work, reading, writing etc.

      So, two other possibilities. One is that when you go outside, your pupil constricts. It gets narrower and if you think of that in terms of what a photographer’s doing with a camera, it increases the depth of field, de-focus is much less important in bright light.

      But we think the real reason may be that light intensity, and we know this from studies on experimental animals, that light intensity controls the release of a transmitter called dopamine, from the retina. And dopamine is known at least in certain circumstances to be able to inhibit eye growth. Now that’s not proven, but there’s a very plausible case for a pathway from light exposure to control of eye growth and, once again we’re working experimentally to confirm that that’s the pathway involved.

      Which is not to say that I don’t think that vitamin D deficiencies are a problem among Korean women in particular, nor that Koreans should really be thinking more about it…quite the opposite! I confess, I’ve been thinking about the subject ever since I worked in the construction industry part time while I was a student, because while NZ and Austalia’s 10% UV hole does rightfully mean that their “slip (on a t-shirt), slop (on sunscreen), slap (on a hat)” campaigns are heavily promoted in schools and the media, I often thought that their prescriptions for avoiding skin cancer were just a tad dogmatic to follow for someone working outdoors all day (e.g: “today at 12 pm your skin will start burning in 8 mins”…gee, thanks). These days, sometimes I have mild arguments with my wife about taking either of my daughters outside (one is 2.5, the other 5 months), because while I can understand and appreciate the Korean tradition of keeping young children indoors, and the fact that it is very cold at the moment too, they both really do still need some fresh air (and sunlight) occasionally!


  5. Thanks for the clarification, James. I confess that I skimmed your post and did not read the linked articles. On the subject of sun exposure and cancer. some studies have found that regular sun exposure is inversely correlated with the deadlier forms of skin cancer. The explanation is that vitamin D is protective and that regular exposure is less damaging to skin that irregular exposure, which risks sunburn.


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