Comparison of static visual acuity between Snellen and Early treatment diabetic retinopathy study charts

The purpose of this prospective study was to compare the Static Visual Acuity (SVA) scores obtained with Snellen versus Early Treatment Diabetic Retinopathy Study (ETDRS) charts in a hospital-based Indian population. Six hundred and thirty eyes within the age group of 10 to 60 years were included in this study. They underwent the routine ocular examination. The distance visual acuity was checked simultaneously using a projected Snellen chart and ETDRS chart in both eyes under the standardized lighting condition. Snellen’s visual acuity was then converted to LogMAR and compared with the ETDRS charts. Six hundred and thirty eyes were included in the study. 54% were females and 46% were males. Mean value for Snellen Visual Acuity was 0.043 and that of ETDRS was 0.02365 LogMAR. The mean difference was 1 letter (0.0195 LogMAR) better on ETDRS chart when compared to Snellen chart. The results of this study suggest that for both clinical and research purposes, both Snellen and ETDRS can be used interchangeably.