Originally posted by: Jeff7
The only eye damage I've heard about concerning monitors might be from the effect of simply focusing too closely for too long a period of time. Human eyes never evolved to look at things really close for extended periods. We'd always be on the lookout for predators, food, or mates, most of which would not be 2 feet away for many hours at a time. Focusing up close for long periods may deform the eyes permanently, which is, in a way, an adaptation - the eyes are then able to focus up close more easily, but of course, we lose the ability to see things far away. Nature's just trying to be helpful.🙂
As for retina damage, I've heard nothing of that sort.
I was told this as a child also. I went from perfect vision to -5 diopters almost overnight, and the optometrist said it was because I read too much, read while lying down, and read in the dark.
I'm now doing my PhD work on accommodation (how the eye focuses from far to near and vice versa) and why we naturally lose it with age (a condition called 'presbyopia', which is why people need bifocals around age 40-45). In near vision, the ciliary muscle (the small, smooth muscle that encircles your lens) contracts, decreasing the amount of force on your lens. In distance vision, the muscle relaxes and puts tension on your lens, causing it to flatten. Thus, based on principles of biomechanics that I reviewed
here, one might expect the muscle to decrease its 'thickness' and, therefore, its 'strength' in someone who is constantly focused near. So, the old explanation is possible. However, the ciliary muscle is very strange compared to any other muscles in the body such that I don't really believe this is necessarily the case. If this were the case, then the person would still have good visual acuity at near distances (say, up to 10 feet or so) where the weakened muscle could stretch the lens. Instead, at -5 D, I can't see anything more than about 1 foot.
Stepping outside what I'm extremely familiar with, I believe the sudden onset of myopia or hyperopia (nearsightedness and farsightedness, respectively) are more highly correlated with age than reading techniques, duration, and frequency. The eye, as a rule, stops growing around age 13. The only tissue in the eye that continues growing is the lens, but it grows slowly and at a pretty constant rate throughout life in just about all species, so it is not likely linked to myopia/hyperopia. Instead, as the eye grows in the pre-teen years, the shape of the cornea may change dramatically. Since the cornea does most of the refracting for the eye, a small change in curvature can have a large impact on visual acuity. This is why LASIK and similar procedures alter the surface of the cornea to fix problems with visual acuity.
/semi-off-topic rant
I'll write more about the actual topic in a while when I get some more time.
😛
