The Epidemiology of Visual Disability Studies of Visually Disabled People in the Community

Review of the world literature on attempts to discover how many people are disabled by poor sight suggested that estimates of prevalence and cause have been constantly hampered by differences of definition, and the difficulties

inherent in equating reduced visual acuity with the hardship that it actually causes to each individual in his whole social environment. Attempts have been made to overcome these difficulties by population survey techniques

using both self identification alone and self identification followed by visual acuity measurement, but they have seldom covered whole populations and have

usually been constrained by the relatively low level of acuity by which most countries define their blind and partially sighted people. Other approaches, through registers and hospital records, though sometimes providing a more comprehensive picture of the diseases leading to poor sight, have not fully analysed the social and other processes leading to selection and have not therefore been able to provide population estimates of prevalence. On the other hand, purely social studies, while sometimes comprehensive, have always used a low level of sight - usually 'blindness' - as a starting point and have

tended to ascribe all hardship to the single cause without exploring the possible relationships with other disabling conditions.