Prevalence of visual impairments:
Blindness affects approximately 45 million people world wide. Because of aging and population growth, this number is expected to double by the year 2020. Indeed, in the US alone, macular degeneration is responsible for low vision experienced by more than 15 million people.
The National Center for Health Statistics estimated that 4.3 million people in the US have difficulty reading the newspaper with their corrected vision -- a functional definition of perceived limitations termed Severe Visual Impairment as defined by Nelson and Dimitrova in the American Foundation for the Blind's Journal of Visual Impairment and Blindness of March, 1993. Importantly, an additional 2.3 million people have a disability that involves the loss of intermediate or distant vision only. From these statistics, we may conclude that a total of 6.6 million people are unable to read printed signs at normal viewing distance. Data from the Bureau of the Census put the figure for this same level of impairment at 9.7 million people (McNeil, 1993). There is another important way of looking at the demographics of blindness. Estimates of tested acuity classify 1.1 million people as Legally Blind which is defined as corrected acuity of 20/200 or less and a visual field of < 20 0 (Chiang, et al, The MilbankQuarterly, Vol. 70, No. 2, 1992).
Of course, there are other disabilities which prevent persons from reading print.
