Validity of a survey question as a measure of visual acuity impairment.

Survey questions are frequently used to collect data on the prevalence of vision difficulties. The 1971-1972 Health and Nutrition Examination Survey included both a question about "trouble with your vision even when wearing glasses or contact lenses," and clinical measurement of central distance visual acuity with usual corrective lenses. The question had low sensitivity for impairment of visual acuity, with variation by age and severity of impairment. Sensitivity analyses from other studies are reviewed. (Am J Public Health 1983; 72:93-96.)