Screening for impaired visual acuity in middle age in general practice.

Screening for impaired distant visual acuity was one component of a controlled trial of multiphasic screening in middle age carried out in two general practices. The prevalence of impaired visual acuity (6/18 or worse in the better eye) at the initial screening in 1967 was 9.6% overall, ranging from 5.9% in people aged 40-49 years to 16.3% in those aged over 60. The question "Do you have difficulty seeing distant objects?" had a low sensitivity and high specificity, rendering it unsatisfactory for use in mass population screening for visual impairment. The prevalences of impaired visual acuity in the screening and control groups at the survey in 1972 showed no significant differences in any age group. Mass screening for defects of visual acuity in the course of a multiphasic examination is thus unlikely to reduce the prevalence of impaired distant visual acuity in the community.