Measurement of Visual Acuity With Lea Symbols and Lea Numbers: Comparison to Adult Standards

Abstract

Abstract: : Purpose: Lea Symbols and Lea Numbers are optotypes currently used to measure visual acuity in young children. However, performance on these tests has not been compared to recognized adult standards. The purpose of this study is to compare Log MAR visual acuity measured with Lea Numbers and Lea Symbols to Sloan and Landolt C charts in adults. Methods: 25 optometry students participated in this study. Best–corrected visual acuity of better than 20/25 was verified at the beginning of each session. Visual acuity of the right eye was tested at 4m, with each chart type presented in random order. A total of 4 measurements (two per session separated by 1 week) were obtained for each chart type. All charts were calibrated for testing at 4m and were of Log MAR design with 7 optotypes on each line (produced by Goodlite). The middle 5 optotypes were scored to ensure constant crowding. Statistical analysis was performed using regression analysis to control for the effects of order. As each subject contributed many data values to the analysis, robust techniques were employed to acknowledge the effect of clustering at the subject level. Significance criterion was set at p=0.01. Results: Mean Log MAR visual acuity was best for Lea Symbols (–0.156), followed by Sloan (–0.140), Lea Numbers (–0.125), Landolt C (–0.119). There was an average 1.8 optotype difference in performance between Lea Symbols and Landolt C. Lea Symbols acuity was not significantly different from Sloan (p = 0.143), but was significantly different from Landolt C (p<0.001). Lea Numbers acuity was not significantly different from either Sloan (p = 0.05) or Landolt C (p = 0.514). Conclusions: When tested in adults, Log MAR visual acuity obtained using both Lea Symbols and Lea Numbers compares well with recognized adult standards. Further testing is necessary to evaluate this relationship in the pediatric population.

Keywords: visual acuity • clinical (human) or epidemiologic studies: systems/equipment/techniques