Assessment of functional vision performance: a new test for low vision patients.

Measures of functional vision are needed to assess elderly low vision patients, their success in using devices, and their ability to manage outside the treatment setting. A new test devised to measure functional ability through the performance of everyday tasks was administered to 94 patients who had acuities of 20/100 or worse in their better eye. Consisting of three versions and four subtests: spot reading, short-term text reading, identifying paper currency and clock reading, the test used standardized items and was timed. In a multiple regression model predicting test performance higher scores were associated with better near acuity (P = .002), higher education (P = .022) and higher levels of self-reported visual skills (P = .072). These predictors plus distance acuity, age and sex only accounted for 35 percent of the variance in test scores. Repeated administration of the test to a different group of 21 patients showed the test to be reliable (intraclass correlation = .85, P < .01) and to have no practice or version effects or differences between raters. This new test may be useful for natural history studies and clinical trials involving low vision patients but further evaluation of its sensitivity to change over time is required.