To assess the need for eye care in children and adolescents with severe mental deficiency, a cross-sectional study of the prevalence and causes of ocular defects amongst these individuals was conducted. Two hundred and sixty residents in a mental handicap unit were examined from January 1992 to June 1993. It was found that there was an unusually high prevalence of severe visual impairment (25%), refractive errors (24%), squint (8%) and a number of organic ocular diseases (8%). All the patients studied were non-verbal and 18% of them were deaf. Only 23 patients could walk. The results emphasize the need for establishing an efficient system to provide regular ophthalmic care for children with severe mental deficiency.