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J. J. Vaidhyan, P. Lietzen, D. Ah-Kine Ng Poon Hing, A. Pathak, E. Ahonen, N. Quinn, S. Lyons, M. Leinonen, L. Hyvarinen, B. Moore; Comparison of Visual Acuity Measured With Lea Symbols and Lea Numbers to Adult Standards. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4853.
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© ARVO (1962-2015); The Authors (2016-present)
Lea Symbols (LS) and Lea Numbers (LN) are optotypes currently used to measure visual acuity (VA) in young children. However, performance on these tests has not been compared to recognized adult standards. The purpose of this study is to compare LogMAR visual acuity measured with Lea Numbers and Lea Symbols to Sloan letters (SL) and Landolt C (LC) charts in 2 populations of adults.
Group 1 consisted of 20 students at the Helsinki Polytechnic, Finland. Group 2 consisted of 25 optometry students at The New England College of Optometry (NECO), Boston, MA. LogMAR charts, calibrated for 4 meters (m) with 7 optotypes per line, were constructed for LS, LN, SL and LC optotypes by the Goodlite Co. and were used by both groups. The middle 5 optotypes were scored to ensure constant crowding. Group 1 had best-corrected Snellen VA of better than 20/16 and was tested binocularly. Group 2 had best-corrected Snellen VA of better than 20/25 and was tested monocularly. Four measurements (two per session separated by one week) were obtained for each chart. Repeated measures of ANOVA and multiple comparisons were utilized in the statistical analysis. Standard deviations were used to determine the variation within each group.
In Group 1, the mean LogMAR VA was better for LS -0.26 and LC -0.26 than for SL -0.22 and LN -0.22. In Group 2, the mean LogMAR VA was best for LS -0.13, followed by SL -0.12, then LN -0.10 and LC -0.10. There are significant differences between LC and LS (p<0.001) and LN and LS (p<0.001). The mean variation was 1.6 optotypes in Group 1 (range 1.4-1.8) and 4.2 optotypes for Group 2 (range 4.0-6.0).
In both groups of adults, LogMAR VA obtained with LS and LN compares well to that measured with adult standards. Although there were differences between optotypes, it is unlikely that they are clinically significant. Further testing is necessary to evaluate this relationship in the pediatric population.
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