Hereditary diseases of the eye in a study of blind and partially sighted.

This study is based on an investigation of all blind and partially sighted persons living in the country of Hordaland, Norway with a population of 379 734. It was found that 1441 were visually impaired with a vision of 6/18 or less or 0.38% of the total population. There was a high frequency of hereditary diseases (29.6%). 336 had other family members with the same type of eye diseases, and 492 had someone in the family with an eye disease which differed from the one they had themselves. Blood relation between parents was found in 139 cases. Many large families with hereditary diseases, of which some are quite rarely seen, were discovered.