Presbyopia is an age-related problem, but not believed to be due to old or weak focusing muscles. Thoughts along these lines have suggested eye exercises or special diets, but such experiments are not fruitful, other than psychologically. The acceptable theory, is that decrease of accommodation due to age, is due to sclerosis, or hardening of the lens of the eye, such that focusing muscular effort gets Iess results. One of the problems in evaluating age-related focusing problems, is that most estimates are based on subjective factors, which involve too many variables, such as lighting, amount of rest, and so forth. A basic factor not considered by most people, is that any distance problem need be considered or corrected before one can adequately evaluate the closeup or reading problems. In other words, if the distance vision is not perfect, and can be corrected by glasses for myopia, astigmatism, or hyperopia, then the closer up vision is affected, more than just the age-related expectations. This brings up the subject of glasses, the usual treatment of presbyopia The reading problem added to any existing distance imperfection The near-sighted person wearing their glasses, experiences trouble reading also, and needs something different for reading than they do for distance. Same for the farsighted or astigmatic person. For most of us, who are emmetropic, there was no previous problem, and the eyes may continue to see quite well for distance without glasses. This makes the need for glasses, for the first time, perhaps even more surprising. The emmetropic situation exists in about forty per cent of the population, and therefore the largest group.