An Evaluation of the M&S Technologies Smart System II for Visual Acuity Measurement in Young Visually-Normal Adults

Abstract

To compare visual acuity measures obtained with the M&S Technologies Smart System II (SSII) and the revised Early Treatment of Diabetic Retinopathy Study (ETDRS) charts in terms of accuracy and test-retest repeatability. Monocular visual acuities were taken in 57 young, visually normal adults on two separate visits in which both the SSII system and the ETDRS charts were tested in random order by two masked examiners. The eye to be tested throughout was chosen randomly at the initial visit. Measurements were made through an optimal phoropter correction, determined by a noncycloplegic refraction for a 10-foot distance. Both charts were presented at 10 feet, and were matched closely for luminance. The mean visual acuity in the group was -0.16 log minimum angle of resolution (MAR) for the ETDRS chart and -0.18 log MAR for the SSII, a small but statistically significant difference. A 95% confidence interval for the mean difference in visual acuity between the two charts was -0.033 log MAR to -0.003 log MAR. The test-retest repeatability was not significantly different in the two tests. The 95% limits of agreement for test-retest repeatability were -0.13 log MAR to +0.17 log MAR for the SSII and -0.12 log MAR to +0.13 log MAR for the ETDRS charts. The SSII can provide an accurate (mean difference<0.033 log MAR) and repeatable alternative to the ETDRS charts for visual acuity measurement in young, visually normal, well-corrected individuals.