On Wednesday, May 7, 2003, at 08:03 PM, John Kozubik wrote:
Eyeglasses have become common only in the past 100 years (and arguably in the past 60 years, about since the time visits to eye doctors became common). While there have been jokes about "four eyes" not breeding, because they can't get dates, neither this theory nor the converse appear to have any correlation with actual breeding patterns. Do more kids today need glasses than 100 years ago? Than 500 years ago? Than 5000 years ago? An interesting question, but claims that the past 60-100 years of eyeglass wearing have caused some major change in genetics seems to be a stretch.
Another possibility is that a large population of those with corrected vision had their vision slowly degraded by the early applications of the correction. I have no experience with vision correction, but I know anecdotally that most people with corrected vision need their corrections strengthened throughout their lifetime. In reality, their sight problem may have stabilized (or even improved) very early on in the absence of treatment. Thus, our perception of what sight abilities the average person in the United States has might be artificially deflated by early and aggressive treatment.
And equally anecdotally, my prescription has changed very little since when I was 14, when I first got glasses. I am now 51 and I can easily wear my glasses from 20 years ago as a backup pair. (Somewhere I have my old John Lennon-style glasses from _32_ years ago, and they are close to my current prescription.) Wearing glasses has not worsened my vision, and I doubt strongly that _not_ wearing glasses would improve my vision...though it might make me squint and strain and pull my eyes the way the girls in high school used to do to see the blackboard. I don't see any evidence that wearing glasses weakens eyes...the issue of vision correction is primarily one of eyeball shape, not the muscles which can, through squinting and straining, improve vision. Most people become nearsighted if they are young and lose their 20-20 vision. Some become farsighted. I see no evidence that those who become nearsighted when they are young would keep their good vision if only they skipped getting glasses. (I did notice a very large fraction of the girls in my high school squinting and using their fingers to pull their eyes, this to avoid wearing glasses. Perhaps this is why so many of them did so poorly in class? The several girls who did well in our school all wore glasses. The cheerleaders didn't, except for one, but they all got pregnant shortly after graduation and worked for Piggly-Wiggly and various banks, as tellers.) If you have some real evidence that wearing glasses is the cause of poor vision, I'm all ears, so to speak. --Tim May "Stupidity is not a sin, the victim can't help being stupid. But stupidity is the only universal crime; the sentence is death, there is no appeal, and execution is carried out automatically and without pity." --Robert A. Heinlein