Low-contrast visual acuity test for pediatric use.

Abstract

Single-letter flash cards were made at contrast values of 96%, 7% and 4% to compare high-, intermediate- and low-contrast visual performance in amblyopic children young enough to benefit from occlusion therapy. The single-letter format was intended to differentiate the effect of contrast on reading performance from any effects of nearby contours. Two groups of patients were tested: 37 children aged 3 to 8 years who had completed occlusion therapy and 15 children aged 4 to 8 years who were still receiving occlusion therapy. Their results were compared with the results of 45 control subjects aged 3 to 8 years. Three patterns of visual loss were identified in the patients: predominantly for high-contrast acuity, fairly uniform at high-, intermediate- and low-contrast levels, and, in two patients, loss at low- and intermediate-contrast levels with relative sparing at the high-contrast level. The incidence of high-contrast acuity loss was not significantly different between the two groups, but the proportion of children with no acuity loss at any contrast level was 54% in the group that had completed treatment, compared with 17% of those who were still receiving treatment.