Cause-specific prevalence of bilateral visual impairment in Victoria, Australia - The visual impairment project

Purpose: To study the cause-specific prevalence of eye diseases causing bil ateral visual impairment in Australian adults. Design. Two-site, population-based cross-sectional study. Participants: Participants were aged 40 years and older and resident in the ir homes at the time of recruitment for the study. The study was conducted during 1992 through 1996. Methods: The study uses a cluster stratified random sample of 4744 particip ants from two cohorts, urban, and rural Victoria. Participants completed a standardized interview and eye examination, including presenting and best-c orrected visual acuity, visual fields, and dilated ocular examination. The major cause of vision loss was identified for all participants found to be visually impaired. Population-based prevalence estimates are weighted to re flect the age and gender distribution of the two cohorts in Victoria. Main Outcome Measures: Visual impairment was defined by four levels of seve rity on the basis of best-corrected visual acuity or visual field: <6/18 <g reater than or equal to>3/60 and/or <10<degrees> greater than or equal to5 degrees radius field, moderate vision impairment; severe vision impairment, <6/60 <greater than or equal to>3/60 and/or <10<degrees> greater than or e qual to5 degrees radius field; and profound vision impairment <3/60 and/or <5 degrees radius field. In addition, less-than-legal driving vision, <6/12 <greater than or equal to>6/18, and/or homonymous hemianopia were defined as mild vision impairment. In Australia, legal blindness includes severe an d profound vision impairment. Results: The population-weighted prevalence of diseases causing less-than-l egal driving or worse impairment in the better eye was 42.48/1000 (95% conf idence interval [CI], 30.11, 54.86). Uncorrected refractive error was the m ost frequent cause of bilateral vision impairment, 24.68/1000 (95% CI, 16.1 2, 33.25), followed by age-related macular degeneration (AMD), 3.86/1000 (9 5% CI, 2.17, 5.55); other retinal diseases, 2.91/1000 (95% CI, 0.74, 5.08); other disorders, 2.80/1000 (95% CI, 1.17, 4.43); cataract, 2.57/1000 (95% CI, 1.38, 3.76); glaucoma, 2.32/1000 (95% CI, 0.72, 3.92); neuro-ophthalmic disorders, 1.80/1000 (95% CI, 0, 4.11); and diabetic retinopathy, 1.53/100 0 (95% CI, 0.71, 2.36). The prevalence of legal blindness was 5.30/1000 (95 % CI, 3.24, 7.36). Although not significantly different, the causes of lega l blindness were uncorrected refractive errors, AMD, glaucoma, other retina l conditions, and other diseases. Conclusions: Significant reduction of visual impairment may be attained wit h the application of current knowledge in refractive errors, diabetes melli tus, cataract, and glaucoma. Although easily preventable, uncorrected refra ctive error remains a major cause of vision impairment. Ophthalmology 2001; 108:960-967 (C) 2001 by the American Academy of Ophthalmology.