Age-specific prevalence and causes of bilateral and unilateral visual impairment in older Australians: the Blue Mountains Eye Study

Purpose: To report age-specific prevalence and causes of bilateral and unil ateral visual impairment in a representative older Australian population. Methods: Participants in the Blue Mountains Eye Study (n = 3654) underwent a detailed eye examination. Any visual impairment was defined as best-corre cted visual acuity (VA) of 6/12 or worse, moderate impairment as VA 6/24-6/ 60 and severe impairment as VA worse than 6/60 (the Australian definition f or legal blindness). Bilateral visual impairment was defined from the bette r eye and unilateral impairment from the worse eye. Proportional causes for visual loss were determined by the examining ophthalmologist. Results: Prevalence of bilateral and unilateral visual impairment was stron gly age related. Corresponding bilateral and unilateral visual impairment p revalence rates were, respectively, 0.6% and 3.6% for persons aged 49-59 ye ars, 1.1% and 8.2% for ages 60-69, 5.4% and 20.1% for ages 70-79, and 26.3% and 52.2% for persons aged 80+ years. Overwhelmingly, age-related maculopa thy (ARM) was the predominant cause of bilateral blindness (13/17) and of m oderate to severe bilateral visual impairment in persons aged 70+ years. Ho wever, cataract was the most frequent cause of mild bilateral visual impair ment among persons aged 60+ years. Amblyopia was the most frequent cause of mild or worse unilateral visual impairment in persons aged 49-59 years. Ca taract was the most common cause of mild unilateral visual impairment in pe ople aged 60+ years, while ARM and cataract were jointly the most frequent causes of moderate to severe unilateral visual impairment in people aged 70 + years. Conclusions: These findings indicate that around half of visually impaired persons aged 60 years or over had cataract, a cause amenable to treatment.