- In the United States and Europe 25-40%
- In some developed Asian countries 70-90%
- In some indigenous populations from undeveloped countries 1-8%
The arguments regarding the cause of myopia are very heated and sway between Nature/Nurture. Twin Studies show a genetic predisposition to myopia, and literacy studies show extended near-focus to be the major contributing factor. No one really knows how genetics and environmental factors interplay, but surely, both sides of the equation contribute, and it probably varies on an individual basis.
The Internet is full of information about the causes of Myopia. In my opinion, this Wikipedia article about myopia is about the fairest comprehensive treatment for the lay person that I could find: http://en.wikipedia.org/wiki/Myopia
Some promoters of the Nurture school-of-thought go so far as to blame eye doctors and the optical industry for Myopia as part of a grand conspiracy. The Myopia Mafia causes an increase of myopia by prescribing glasses to correct the vision of children with myopia, is the crux of one argument. Another claims the problem is nutritional in nature and has a vitamin to fix it. These extreme and entertaining examples usually have their own product to sell (so BUYER BEWARE) and while espousing some truths, they fundamentally over-simplify the problem.
With today's technology, Myopia is a mere annoyance for most of us. In developed countries, it is easy to correct with glasses, contact lenses, or surgery using MINUS dioptric power--all of which use impressive new technologies. Stay tuned for upcoming articles on advances in lens and surgery technologies.
Because of the evidence that near stress induces myopia, there may be some things you can do. Children who spend more time outdoors and less time in front of TV, computers, or books tend to have less incidence of myopia. The problem is, we learn most of what we need to survive in today's world by reading and using the computer, so avoiding these activities to prevent myopia might cause other life-problems. And if not putting glasses on a nearsighted kid could prevent further myopic progression, would it make sense to keep your child in a constant state of blur? Like everything else, there is wisdom in balance.
Several alternative "cures" are out there, like "The See Clearly Method" and "Rebuildyourvision.com." You will often find them long on testimonials and short on credibility. We get patients who try these things occasionally thinking they will surprise us. So far, I haven't seen anyone with verifiable improvements to their refractive state via these programs.
I personally like to prescribe bifocals or progressives to myopic children who show signs of excessive accomodative convergence (misaligned eyes with close focus) or other signs of near stress. Some studies have shown a 40% reduction in myopic progression with bifocal use, and I seem to see that played out clinically in these cases of over-convergence.