Visual acuity disturbance in subjects over 50 years of age in a population-based cataract survey

Visual acuity is still an essential examination item in cataract epidemiological studies, even though this parameter lacks objective reliability. A population-based epidemiological study was conducted in a rural area of Japan to find out the relationship between visual acuity levels and cataracts, the types of gradings of which were evaluated by an objectively reliable method through lens images, and to serve as a sample for researchers who perform epidemiological studies on cataract but lack the latest methodology. 863 participants above 50 years of age were examined and those previously diagnosed with ocular diseases which affect visual acuity were excluded from the analysis as much as possible. The mean visual acuity (LogMAR) in subjects in their 50s, 60s, 70s and over 80 years of age was 1.1, 1.0, 0.7 and 0.4, respectively. Both the mean and the distribution of visual acuity showed a statistically significant relationship to ageing (p < 0.01, p < 0.01). Both age and cataract grading showed a statistically significant relationship to visual acuity (p < 0.01), but there was no significant interaction effect between these two variables upon visual acuity. Visual acuity worsened remarkably with ageing in the eyes with grade III, whereas that of eyes with grades I and II remained fairly stable at a level of 0.7-1.0, except for those above 80 years of age. A fairly good visual acuity of 1.0, 0.8 and 0.7 remained in the eyes with pure cortical cataract of grades I, II and III, respectively, whereas those with mixed type cataract were 0.9, 0.6 and 0.3, respectively.