# glasses **URL:** \ **Category:** Factual Questions\ **Created:** [June 1, 2000, 12:40am UTC](https://boards.straightdope.com/t/glasses/21061 "2000-06-01T00:40:21Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Wood\_Thrush](https://avatars.discourse-cdn.com/v4/letter/w/b38774/32.png) [@Wood\_Thrush](https://boards.straightdope.com/u/Wood_Thrush)\ **Post date:** [June 1, 2000, 12:40am UTC](https://boards.straightdope.com/t/glasses/21061/1 "2000-06-01T00:40:21Z")
In class today, we had a discussion in class about glasses, specifically why so many people wear them. Here’s much of what the teacher said. It’s paraphrasing, not an actual > [@](#): > > The reason so many people wear glasses is that we have wars. We don’t send people who wear glasses to fight wars. The people out on the battlefield die and cannot pass on their “good eyesight” genes. The people back home, however, do not die and become a larger percent of the population and therefore may pass on their genes for “bad eyesight.” These are my problems with this hypothesis, in no particular order:[ul] [li]Just because someone dies doesn’t mean their genes are out of the genepool. They could’ve had children before they died.[/li][li]Wars have been around forever, or at least since before glasses were invented. One would think that now, since we have widely available correction devices such as glasses, _more_ people with bad eyesight would be on the battlefield.[/li][li]Women, until fairly recently, never were on the battlefield, and they carry half of all genes. Now, we know myopia is not an inherintly male disorder.[/ul][/li]What’s the straight dope? ---
**Author:** ![UncleBeer](https://avatars.discourse-cdn.com/v4/letter/u/977dab/32.png) [@UncleBeer](https://boards.straightdope.com/u/UncleBeer)\ **Post date:** [June 1, 2000, 1:02am UTC](https://boards.straightdope.com/t/glasses/21061/2 "2000-06-01T01:02:45Z")
> [@](#): > > We don’t send people who wear glasses to fight wars. I think I’d also strongly question this statement. As far as I know, there are no eyesight restrictions for the average G.I. Air Force pilots, sure, but not G.I.'s. I’ve never been in the military, but I worked for a defense contractor for 13 years and met many EM’s and officers with glasses. Hell, look at Colin Powell, he was Chairman of the Joint Chiefs of Staff and he wore glasses. I’ll see if I can find something over at the Army recruiting site. ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [June 1, 2000, 1:58am UTC](https://boards.straightdope.com/t/glasses/21061/3 "2000-06-01T01:58:21Z")
There’s been a significant increase in nearsightedness over the last 100 years or so, but nobody knows why. One study suggested that using nightlights in a child’s room when they were young increased the chances, but a later study failed to support it. The CNN website had an article about it about a month ago. Nobody suggested it had anything to do with war, though. Arjuna34 ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [June 1, 2000, 2:16am UTC](https://boards.straightdope.com/t/glasses/21061/4 "2000-06-01T02:16:57Z")
The increase in nearsightedness runs parallel with the amount of reading. People who go to school have a far higher incidence and nerds who read even more have an ever higher rate. The eye tends to adapt to the near distance. ---
**Author:** ![AWB](https://avatars.discourse-cdn.com/v4/letter/a/bb73d2/32.png) [@AWB](https://boards.straightdope.com/u/AWB)\ **Post date:** [June 1, 2000, 2:18am UTC](https://boards.straightdope.com/t/glasses/21061/5 "2000-06-01T02:18:31Z")
One theory that I’ve heard for the increase in glasses, contacts, etc., is that we read a lot more than our ancestors. Our eyes weren’t designed to focus on something 12-24 inches from our face for long periods of time. So our eyeballs distort to make reading easier. The consequence is that our far vision suffers. Myopia (near-sightedness) is far more prevalent than far-sightedness. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 1, 2000, 2:59am UTC](https://boards.straightdope.com/t/glasses/21061/6 "2000-06-01T02:59:33Z")
The reading theory has always made sense to me, too… On the other hand, there’s many folks (my mother comes to mind) who are too nearsighted even to read. Either there’s some other relatively common cause of myopia, or the eye has a tendancy to overadjust. ---
**Author:** ![Dystopos](https://avatars.discourse-cdn.com/v4/letter/d/e79b87/32.png) [@Dystopos](https://boards.straightdope.com/u/Dystopos)\ **Post date:** [June 1, 2000, 3:09am UTC](https://boards.straightdope.com/t/glasses/21061/7 "2000-06-01T03:09:59Z")
> [@](#): > > \*\* > The increase in nearsightedness runs parallel with the amount of reading. People who go to school have a far higher incidence and nerds who read even more have an ever higher rate. The eye tends to adapt to the near distance. > \*\* Or maybe nobody worried about being nearsighted if they weren’t reading all the time? It’s not an ailment if you aren’t suffering. I can’t imagine that a tenth century turnip farmer would be so enfeebled by the kind of nearsightedness that now requires corrective lenses that he would seek treatment. Perhaps it would be more reasonable to consider lenses a tool rather than a medical appliance. ---
**Author:** ![Wood\_Thrush](https://avatars.discourse-cdn.com/v4/letter/w/b38774/32.png) [@Wood\_Thrush](https://boards.straightdope.com/u/Wood_Thrush)\ **Post date:** [June 1, 2000, 3:18am UTC](https://boards.straightdope.com/t/glasses/21061/8 "2000-06-01T03:18:04Z")
Thanks, dopers\*\*\*!\*\*\* Any sources, though? I can’t seem to find any. ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [June 1, 2000, 3:42am UTC](https://boards.straightdope.com/t/glasses/21061/9 "2000-06-01T03:42:26Z")
Here’s the cnn article about the study that suggested nightlights were a problem: [http://www.cnn.com/HEALTH/9905/12/children.lights/](http://www.cnn.com/HEALTH/9905/12/children.lights/) and here’s the cnn article later that said they weren’t: [http://www.cnn.com/2000/HEALTH/children/03/08/light.myopia.wmd/index.html](http://www.cnn.com/2000/HEALTH/children/03/08/light.myopia.wmd/index.html) Here’s a page from NERF (National Eye Research Foundation) which says myopia went from 2-9% of the population at the turn of the century to 35% today. From looking at the site, NERF appears to be dedicated to promoting eye-correction surgery, so their numbers may be inflated. This website [http://www.nb.net/~sparrow/myopia.html](http://www.nb.net/~sparrow/myopia.html) has some very good links to myopia info. I’d start with this one. Arjuna34 ---
**Author:** ![Steve-o](https://avatars.discourse-cdn.com/v4/letter/s/ecc23a/32.png) [@Steve-o](https://boards.straightdope.com/u/Steve-o)\ **Post date:** [June 1, 2000, 4:03am UTC](https://boards.straightdope.com/t/glasses/21061/10 "2000-06-01T04:03:07Z")
As to nightlights causing myopia in children… A couple of subsequent studies have been performed, and were unable to reproduce the initial study’s results. These subsequent studies suggest that nightlights do not cause myopia. [Here](http://www.sciencedaily.com/releases/2000/03/000309074442.htm) is a link to a little something I found on it. FYI, when I first heard of the initial study results, I did an informal poll of the people at my work (as did my wife), and what we found is that most people who wore glasses did have a nightlight, and those who did not wear glasses did not use a nightlight. Hmmmmm… ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [June 1, 2000, 4:38am UTC](https://boards.straightdope.com/t/glasses/21061/11 "2000-06-01T04:38:30Z")
Don’t I remember reading about this in one of David Feldman’s books? I wouldn’t actually pay money for them, so I don’t have them at hand. He talked about a study done to determine if there was a correlation between the amount of material read and myopia. The researchers concluded that they had failed to prove a correlation, but Feldman took that to mean they had proved there was no correlation. It’s things like this that make me steer clear of paying money for his books. It was a number of years ago I read the book, so I could be mistaken in the particulars. Anybody have the books? ---
**Author:** ![aramis](https://avatars.discourse-cdn.com/v4/letter/a/e68b1a/32.png) [@aramis](https://boards.straightdope.com/u/aramis)\ **Post date:** [June 1, 2000, 4:50am UTC](https://boards.straightdope.com/t/glasses/21061/12 "2000-06-01T04:50:21Z")
Just as an aside here, I’ve read that in the early days of North American settlement by Europeans, it was found that the average Native American had significantly better eyesight than the average European settler. I can’t vouch for the source (especially since I can’t remeber what it was), but if true it raises some interesting questions. That would seem to support the idea that good eyesight is heritable and so, while the teacher’s story is probably an exaggeration, the principle may be sound. Though the US military doesn’t consider mildly bad eyesight a reason to preclude service, there are a wide variety of other health and fitness characteristics that _are_ causes for exclusion. Hence the most fit, genetically speaking, are singled out for military service. And, since the majority of front-line soldiers – and so the majority of caualties – tend to be men in their late teens or early twenties, significant proportions of them have never fathered a child. Regarding that 13th century farmer referred to previously, in an agrarian – pre-eyeglasses – society, anyone with the kind of eyesight that many of us have now would probably not have survived long except with an exceptional degree of aid. ---
**Author:** ![Alphagene](https://avatars.discourse-cdn.com/v4/letter/a/8e7dd6/32.png) [@Alphagene](https://boards.straightdope.com/u/Alphagene)\ **Post date:** [June 1, 2000, 5:10am UTC](https://boards.straightdope.com/t/glasses/21061/13 "2000-06-01T05:10:43Z")
You might want to check out [this](http://www.newscientist.com/lastword/answers/lwa367body.html) site. It gives a few possible explanations as to why humans seem to have so many vision problems requiring glasses. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [June 1, 2000, 5:52am UTC](https://boards.straightdope.com/t/glasses/21061/14 "2000-06-01T05:52:31Z")
Why Native Americans are less likely to suffer myopia: Almost all Native Americans have type O blood. People with types A, B, and AB blood are roughly 2.5 times more likely to suffer myopia than those with type O. I mentioned this in the [Evolution of blood](http://boards.straightdope.com/sdmb/showthread.php?threadid=16053) thread about a month ago. Why type-O people should be relatively immune, I cannot say. I found a respectable source that mentions a “proposal” that links reading with myopia. From [Berkely](http://spectacle.berkeley.edu/class/opt10/answers.shtml) > [@](#): > > Q: In last week’s lecture on myopia, the lecturer said that there is a feedback mechanism to tell the eyeball to stop growing longer so that the person won’t be near-sighted but she did not know what the mechanism is. Can it be that if the muscles that adjust the lens are under constant contraction, the brain interprets this constant tension as the eyeball is too short and therefore tells the eye ball to grow longer? So, if one reads too much, the muscles are contracted often which let the brain to tell the eyeball to grow; as a result, the person becomes near-sighted. Does this sound like a reasonable hypothesis? > > A: I believe this is a proposed mechanism for the development of myopia. Good thinking. Because of this idea, many optometrists suggest to their nearsighted patients to take their glasses off when they read so that they don’t need to use those muscles which could stimulate more nearsightedness. In fact, I have heard of some optometrists giving their children bifocals so that their children don’t use their focusing muscles in order to reduce the probability of increased nearsightedness. ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [June 1, 2000, 2:07pm UTC](https://boards.straightdope.com/t/glasses/21061/15 "2000-06-01T14:07:57Z")
I always assumed that the increase in glasses-wearing was just due to more thorough screening and earlier detection of myopia, also increased (parental) awareness. Nowadays I sometimes see 3 and 4-year-olds wearing glasses. When I got my first glasses as a kindergartener back in the late 50’s, it was a nine-days wonder. “A 5-year-old with glasses!” Glasses were for Big Kids, who needed them to play the piano and do algebra. ---
**Author:** ![SuaSponte](https://avatars.discourse-cdn.com/v4/letter/s/67e7ee/32.png) [@SuaSponte](https://boards.straightdope.com/u/SuaSponte)\ **Post date:** [June 1, 2000, 9:35pm UTC](https://boards.straightdope.com/t/glasses/21061/16 "2000-06-01T21:35:40Z")
One probable reason for the increase in myopia in recent times is pure Darwinism. With the increased availability of glasses and other corrective methods, the myopic individual was much less likely to accidentaly step into that 50-foot hole. Instead, they (me included) can walk around the hole, go home, and have sex, breeding more myopic kids. While a little facetious, the above may apply to increases in several genetic or hereditary diseases. Why are there more hemophiliacs? Because with modern medicine, they are much more likely to survive into their reproductive years. V. ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [June 2, 2000, 1:04am UTC](https://boards.straightdope.com/t/glasses/21061/17 "2000-06-02T01:04:43Z")
It’s been a pretty quick increase in myopia for genetics to account for it- according the the citation I posted earlier, 3-9% at the turn of the century, and 35% today. Arjuna34 ---
**Author:** ![Wood\_Thrush](https://avatars.discourse-cdn.com/v4/letter/w/b38774/32.png) [@Wood\_Thrush](https://boards.straightdope.com/u/Wood_Thrush)\ **Post date:** [June 2, 2000, 2:08am UTC](https://boards.straightdope.com/t/glasses/21061/18 "2000-06-02T02:08:26Z")
You’ve all been very helpful. ---
**Author:** ![Danielinthewolvesden](https://avatars.discourse-cdn.com/v4/letter/d/ce7236/32.png) [@Danielinthewolvesden](https://boards.straightdope.com/u/Danielinthewolvesden)\ **Post date:** [June 2, 2000, 2:17am UTC](https://boards.straightdope.com/t/glasses/21061/19 "2000-06-02T02:17:57Z")
believe it or not, it is actually safer to be in the Armed services than at home, even during a war. Even with our high death count in WWII, a very small % of soldiers died. And those who stayed home were thought of pretty poorly, allowing “war heroes” to get their choice of the Ladies. So your teacher is full of it. ---
**Author:** ![Kamino\_Neko](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kamino_neko/32/34_2.png) [@Kamino\_Neko](https://boards.straightdope.com/u/Kamino_Neko)\ **Post date:** [June 2, 2000, 2:28am UTC](https://boards.straightdope.com/t/glasses/21061/20 "2000-06-02T02:28:40Z")
> [@](#): > > **Or maybe nobody worried about being nearsighted if they weren’t reading all the time? It’s not an ailment if you aren’t suffering. I can’t imagine that a tenth century turnip farmer would be so enfeebled by the kind of nearsightedness that now requires corrective lenses that he would seek treatment.** Except that nearsightedness isn’t really a problem for reading books, unless you’re so severely myopic that you’re nearly blind, in which case you’re going to have a lot of trouble doing just about everything. It would, however, be a problem for a hunter, if he used a spear, bow, or firearm, as he’d have a harder time seeing his prey. Or for a shepherd, as it would be that much harder to keep track of your flock, when the furthest members blend into a uniform blur of white. [Next page](https://boards.straightdope.com/t/glasses/21061.md?page=2)