Visual function tests, eye disease and symptoms of visual disability: a population-based assessment

Purpose: To examine associations between eye disease and tests of visual function with self-reported visual disability. Methods: The Blue Mountains Eye Study is a cross-sectional census-based survey of eye disease in two postcode areas in the Blue Mountains, west of Sydney, Australia. Of 4433 eligible residents, 3654 (82.4%) participated. Subjects had a detailed eye examination, including tests of visual acuity, contrast sensitivity, disability glare and visual field. Lens and retinal photographs were taken and graded according to standardized protocols for presence of cataract, early and late age-related maculopathy, glaucoma, diabetic retinopathy, retinal vein occlusion and other eye diseases. An interviewer-administered questionnaire included questions about perception of visual disability. Results: Scores on all tests of visual function significantly decreased with age (P < 0.0001). This decrease persisted for all tests except disability glare after excluding subjects with identifiable eye disease. The presence of one or more eye diseases was significantly associated with all (self-reported) measures of visual disability (trouble driving at night, difficulty recognizing a friend across the street, reading a newspaper or recognizing detail on television); mixed cataract (cortical and nuclear, or posterior subcapsular and nuclear) was associated with trouble driving at night and difficulty recognizing a friend across the street. A 10-letter (two-line) decrease in best corrected or presenting visual acuity was significantly associated with all self-reported measures of visual disability, as was a two-step decrease in contrast sensitivity. A five-point increase in points missing in the visual field was weakly but significantly associated with all self-reported measures of visual disability except trouble driving at night. Conclusions: Visual function declines with age. Impaired visual function was strongly, and eye disease relatively weakly associated with reports of visual disability.