Visual acuity in a community-dwelling Japanese population and factors associated with visual impairment

The aim of this study was to describe the distribution of visual acuity and investigate the predictors of visual impairment in a Japanese population.

Best-corrected visual acuity was measured in 2263 subjects aged 40-79 years randomly selected from a local community. Relations between visual impairment and possible risk factors were investigated.

Among these subjects, 41 individuals (1.8%) were identified as visually impaired (best-corrected visual acuity in the better eye <0.5). Both sexes in the older age groups had a higher frequency of visual impairment (Mantel-Haenszel chi-square test: P<0.001). A multiple logistic regression indicated that an increase in age of 10 years [odds ratio (OR) 3.9; 95% confidence interval (CI) 2.3-6.7] and myopia (OR 2.9; 95%CI 1.4-6.0) were independent risk factors for visual impairment. Individuals with the highest level of education (college or higher) had a lower risk of visual impairment (OR 0.1; 95%CI 0-0.7) compared to individuals with the lowest level of education.

As expected, visual impairment increased with advancing age, although the prevalence of visual impairment in our population was lower than in other surveys. Racial and regional differences and differences in study design may be responsible for discrepancies between surveys. It is noteworthy that myopia was a significant risk factor for visual impairment, although the reasons for this association are uncertain and need further investigation.