The cause-specific prevalence of visual impairment in an urban population: The Baltimore eye survey

Background: Whereas population-based data on the causes of bilateral blindness have been reported, little information is available on the distribution of causes of central vision loss less severe than the criteria used to define legal blindness. This visual impairment is responsible for a high proportion of eye care service use and results in important reductions in functional status. Methods: Data from the Baltimore Eye Survey were used to estimate the cause-specific prevalence of visual impairment (best- corrected visual acuity worse than 20/40 but better than 20/200) among black and white residents of east Baltimore who were 40 years of age or older. Eligible subjects underwent a screening examination at a neighborhood location and, for those whose best-corrected visual acuity was less than 20/30, a definitive ophthalmologic examination at the Wilmer Eye Institute. Results: The prevalence of visual impairment was 2.7% in whites and 3.3% in blacks; the age-adjusted relative prevalence (B/W) was 1.75 (P = 0.01). The leading causes of visual impaired eyes were cataract (35.8%), age-related macular degeneration (14.2%), diabetic retinopathy (6.6%), glaucoma (4.7%), and other retinal disorders (7.3%). Cataract, diabetic retinopathy, and glaucoma were more common as a cause of visual impairment among blacks, whereas macular degeneration was more frequent among whites. More than 50% of all subjects had the potential for improvement in vision with appropriate surgical intervention. Conclusion: Visual impairment is a prevalent condition among inner city adults 40 years of age or older. The distribution of causes suggests that improvements in the visual health of the population could be achieved with more effective delivery of efficacious ophthalmologic care.