The prevalence and causes of bilateral and unilateral blindness in an elderly urban Danish population. The Copenhagen City Eye Study

Abstract

Purpose: To study the prevalence and causes of bilateral and unilateral blindness in an elderly urban Danish population.

Methods: Data originated from a Danish epidemiologic cross-sectional random sample population eye survey conducted during the years 1986-1988. The population consisted of 1,000 inhabitants aged 60 to 80 years in Copenhagen. The participants underwent an extensive ophthalmologic examination. A participation rate of 96.9% was achieved. Any blindness was defined as best-corrected visual acuity (VA) worse than 0.05 (the WHO criteria) and VA of 0.1 or worse (the National criteria (NC) of blindness).

Results: The prevalence rates of bilateral and unilateral blindness were, respectively, 0.53% and 3.38% according to WHO, but 1.06% and 4.44% using NC. Bilateral blindness rose significantly with age (p=0.02). According to NC, age-related macular degeneration (AMD) was the leading cause of bilateral blindness, accounting for 60% of all blind persons. Glaucoma, myopic macular degeneration, cataract and retinitis pigmentosa were jointly the second most common cause, each accounting for 10% of all bilaterally blind persons. Diabetic retinopathy was not a cause of bilateral blindness. Amblyopia was the most frequent, AMD the second most frequent, and diabetic retinopathy was among the third most common cause of unilateral blindness accounting for, respectively, 28.60%, 16.66% and 9.52% of all unilateral blindness.

Conclusions: Blindness was associated with increasing age. A calculation indicates that among Danes aged 60 to 80 years 7,736 are bilaterally blind and 35,503 suffer from unilateral blindness. This study highlights AMD as the most important cause.