Repeatability of ETDRS visual acuity in children

Abstract

PURPOSE. To evaluate repeatability of the best corrected log minimum angle of resolution (MAR) Early-Treatment Diabetic Retinopathy Study (ETDRS) acuity in a group of 6- to 11-year old children with myopia. METHODS. Best corrected monocular visual acuity (VA) of a subset of children (n = 86) enrolled in the Correction of Myopia Evaluation Trial (COMET; mean spherical equivalent refractive error -2.35 D with no more than 1.25 D astigmatism) was measured at baseline and 1 month later with ETDRS logMAR charts. Children started with logMAR 0.4 (6/15 or 20/50) and read each letter on all subsequent lines until they missed all letters in 1 line. RESULTS. At baseline, the mean best corrected logMAR VA was 0.003 ± 0.076 (6/6 or 20/20 ± 3.8 letters) in the right eye and 0.008 ± 0.059 (6/6 or 20/20 ± 2.95 letters) in the left eye. The signed difference between VA measured at baseline and that measured at 1 month was not significantly different from zero in either eye. Repeatability was not associated with age, but a small, statistically significant association with gender was detected in the left eye, with boys approximately 2 letters more variable than girls. The K statistic (agreement within 1 line) was good to excellent. CONCLUSIONS. Based on the 95% limits of agreement, the criterion for a statistically significant change in VA is no more than ±0.15 logMAR (or ±8 letters). This value is similar to those reported for adults and indicates that logMAR VA provides a repeatable measure of acuity in children.