Comparison of international standard and diabetic retinopathy visual acuity chart in amblyopic children

Abstract

Objective To compare the two established visual acuity chart of the International Standard (IS) and the Early Treatment of Diabetic Retinopathy Study (ETDRS).Methods Test-retest reliability study.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 in every eye of each patient at random.As the main outcome measure,visual acuity was 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 0.11ogMAR (5 optotypes) and 100％ of retest scores were within 0.2 logMAR (10 optotypes).Reliability was high across on 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 was 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.Conclusions The ETDRS visual acuity chart has high test-retest reliability in Chinese amblyopic children.It suggests that the nonamblyopic,normal eye of amblyopic patients using IS chart behaves abnormally using ETDRS chart. Key words: Visual acuity ; LogMAR ; Child ; Repeatability ; Agreement ;