The study defines people as severely visually impaired if they cannot read newspaper print, even with corrective lenses. Twelve percent of those aged 75 to 84 have severe visual impairments, compared with less than 1 percent of adults aged 18 to 44. The number of Americans of all ages with severe visual impairments in 1990 was 4.3 million, 1.7 percent of the total U.S. population. But an aging population means that this number should grow rapidly in the future, from 5.1 million in 2000 to 8.9 million by 2030, according to Neurohr's projections. Severe impairment is uncommon, but virtually everyone suffers some loss of visual acuity by age 65.
Many factors contribute to visual impairment, including a number of normal aging processes.
The first to strike many individuals is the loss of focusing ability at close range, otherwise known as farsightedness. This typically occurs at about age 45 and is caused by weakening eye muscles. It occurs when the lens is no longer flexible enough to change shape properly when focusing on close objects, says Dr. Bresnick of Rochester. The loss of focusing ability means that people aged 45 and older often have difficulty reading small print in telephone books, on packaging, and anywhere else it appears. They also may have difficulty reading complicated types of print.