The incidence of registered blindness caused by age-related macular degeneration

Abstract

Membership applications to the Danish Society of the Blind were used as a register source of legal blindness (visual acuity < or = 6/60). Based on application forms completed by specialists in ophthalmology 1585 subjects were recorded as blind in 1993. 1132 subjects (71.4%) had age-related macular degeneration. Only 5% of the registered subjects with age-related macular degeneration were below 70 years of age. The median age was 82, equal for both gender. A female overrepresentation of 2.8:1 was found. Five-year age-specific incidence rates demonstrated an exponential rise of registered blindness due to age-related macular degeneration from age 60 to 90. A decline in incidence after the age of 90 is assumed to reflect underregistration of very old persons. This tendency of non-registration was particularly pronounced in elderly males. Estimated prevalence rates of registered blindness due to age-related macular degeneration increased 100-fold from the age group 60-64 to the age group 80-84. The age specific incidence rate for the age group 60-99 years was 140:100,000 for females and only 66:100,000 for males. The corresponding incidence rate for both sexes was 108:100,000. It is still a matter of dispute whether 'true' prevalence rates of blindness are higher in females than in males. The sex difference seems not to be explained by differences in 'visual impairment threshold of registration' among the registered persons.