The elastic quality of the lens capsule tends to lessen with time. People over 45 years of age are often unable to accommodate sufficiently to read the fine print in books and newspapers or on medicine bottles. Their eyes remain focused for distant vision. This condition is termed presbyopia, or farsightedness of age. Eyeglasses or contact lenses can usually make up for the eye's loss of refracting power.

Other visual problems result from eyeballs that are too short or too long for sharp focusing. If an eye is too short, light waves are not focused sharply on the retina because their point of focus lies behind it. A person with this condition may be able to bring the image of distant objects into focus by accommodation, but this requires contraction of the ciliary muscles at times when these muscles are at rest in a normal eye. Still more accommodation is needed to view closer objects, and the person may suffer from ciliary muscle fatigue, pain, and headache when doing close work.

Since people with short eyeballs are usually unable to accommodate enough to focus on the very close objects, they are said to be farsighted. Eyeglasses or contact lenses with convex surfaces can remedy this condition (hyperopia) by focusing images closer to the front of the eye.

If an eyeball is too long, light waves tend to be focused in front of the retina, and the image produced on it is blurred. In other words, the refracting power of the eye, even when the lens is flattened, is too great. Although a person with this problem may be able to focus on close objects by accommodation, distance vision is invariably poor. For this reason, the person is said to be nearsighted. Eyeglasses or contact lenses with concave surfaces that focus images farther from the front of the eye treat nearsightedness (myopia).

Still another refraction problem, astigmatism, reflects a defect in the curvature of the cornea or the lens. The normal cornea has a spherical curvature, like the inside of a ball; an astigmatic cornea usually has an elliptical curvature, like the bowl of a spoon. As a result, some portions of an image are in focus on the retina, but other portions are blurred, and vision distorts.

Without corrective lenses, astigmatic eyes tend to accommodate back and forth reflexly in an attempt to sharpen focus. The consequence of this continual action is often ciliary muscle fatigue and headache.