THE PELLI-ROBSON LETTER CHART - NORMATIVE DATA FOR YOUNG-ADULTS

In the optic neuritis treatment trial (ONTT), we assessed contrast sen sitivity with the Pelli-Robson chart on 457 patients with acute optic neuritis. Mean age was 32.0 yr; 77% were women. To establish normal li mits for the age range of patients entered into the ONTT, we tested no rmal subjects with the chart. Contrast sensitivity on the Pelli-Robson chart and visual acuity on a retroilluminated ETDRS chart was assesse d in 140 normal volunteers in the age range of 18-45 yr using standard ized protocols. Contrast sensitivity scores corresponded to the lowest line in which at least two of the three letters were correctly identi fied and visual acuity scores to the LOGMAR conversion of the number o f letters correctly identified. The mean age of the 140 subjects was 3 2.3 +/- 7.4 yr; 74% were women. We calculated a normal limit based on the 95% confidence interval to most closely approximate line 15 (about 1.75 log units) for the Pelli-Robson chart and 0.08 for visual acuity . These data should be useful in planning research studies that assess contrast sensitivity with the Pelli-Robson chart and visual acuity in the 18-45 yr old age group.