Comparison Of International Standard And Diabetic Retinopathy Visual Acuity Chart In Amblyopic Children

PURPOSE:To compare two established visual acuity chart:the International Standard(IS) visual acuity chart and the Diabetic Retinopathy Study(ETDRS) visual acuity chart.DESIGN:Test-retest reliability studyMETHODS:Visual acuity was measured monocularly on both eyes of 79 amblyopic patients aged 4 to 10 years from one clinical site.Both IS and ETDRS chart were presented twice on every eye of each patient at random.As the main outcome measure,visual acuity of both visual acuity charts were measured twice.Visual acuity test results were converted to logarithm of minimal angle of resolution(logMAR) units for analysis.RESULTS:Test-retest reliability of ETDRS chart was high and for both right and left eyes,97%of retest scores were within 0.1logMAR(5 optotypes) and 100%of retest scores were within 0.2 logMAR(10 optotypes).Reliability was high across the age range of 4 to 10 years. Based on 95%confidence level estimates,a change in visual acuity of 0.2 logMAR(10 optotypes) from a previous acuity measure is unlikely to result from measurement variability.Test-retest reliability of IS chart was lower,92%of retest scores were within 0.2 logMAR,95%confidence level was from -0.21 to 0.19 logMAR.The agreement of IS and ETDRS visual acuity chart was not high. 66%of difference scores were within 0.1 logMAR and 90%within 0.2 logMAR.95%difference lied between -0.3 and 0.11 logMAR.The difference of two charts in mild and severe amblyopic group increased.CONCLUSION:The ETDRS visual acuity chart has high test-retest reliability in Chinese amblyopic children.We suggest that IS chart yields better visual acuity performance compared with ETDRS.