Abstract
Ten million or so Americans have some visual disability, of whom perhaps half a million are legally blind with corrected vision of less than 20/200 in each eye. Another million or so have visual impairment such that despite wearing glasses they cannot read a newspaper.1 Precise data regarding the prevalence and cause of visual problems do not exist. To attempt to generate such data, between 1979 and 1983 the National Eye Institute performed a study to determine whether it could obtain “estimates of the prevalence, by cause, of visual acuity impairment in persons 25 years of age or older.”2 The study concluded that such estimates could not be reliably obtained, largely because people were unwilling to be examined (P. F. Palmberg, personal communication).