Various combinations of these changes in vision can occur. Nearly 2 million people are severely visually impaired and cannot read ordinary newsprint even with reading glasses, according to projections based on 1986 data from the National Center for Health Statistics. Another 6 to 9 million people have impaired vision that may interfere with their ability to perform some activities. About 77 percent of severely visually impaired people are at least 65 years of age. Eye diseases, eye injury or aging of the eye may disrupt normal visual function and result in low vision.
Visual complaints differ depending on which part of the visual system is damaged.
Inability to do an activity depends on whether the problem affects side vision, central vision or both. In this disease, there is a progressive breakdown of the macula-the central part of the retina that permits the greatest perception of detail and color. Activities requiring good central vision, such as reading, sewing or driving, are difficult for persons with this disease. On the other hand, since macular degeneration does not affect side vision, walking in familiar areas usually poses few problems. Other eye conditions also may cause low vision.