Validation of an automated-ETDRS near and intermediate visual acuity measurement

Background The aim of this study was to determine the repeatability of an automated-ETDRS (Early Treatment Diabetic Retinopathy Study) near and intermediate visual acuity measurement in subjects with normal visual acuity and subjects with reduced visual acuity. The agreement of automated-ETDRS with gold standard chart-based visual acuity measurement was also studied. Methods Fifty-one subjects were tested (aged 23 to 91 years; 33 subjects with normal visual acuity: 6/7.5 or better; 18 subjects with reduced visual acuity: 6/9 to 6/30). Near and intermediate visual acuity of one eye from each subject was measured with an automated tablet-computer system (M&S Technologies, Inc.) and Precision Vision paper chart in a random sequence. Subjects were retested one week later. Repeatability was evaluated using the 95 per cent limits of agreement (LoA) between the two visits. Results Average difference between automated-ETDRS near visual acuity and near visual acuity by paper chart was 0.02 +/- 0.10 logMAR (p > 0.05). Agreement of near visual acuity between automated-ETDRS and paper chart was good, with 95 per cent LoA of +/- 0.19 logMAR. Furthermore, automated-ETDRS near visual acuity showed good repeatability (95 per cent LoA of +/- 0.20). Mean difference between automated-ETDRS intermediate visual acuity and intermediate visual acuity by paper chart was 0.02 +/- 0.10 logMAR (p > 0.05). Agreement of intermediate visual acuity between automated-ETDRS and paper chart was good, with 95 per cent LoA of +/- 0.20 logMAR. In addition, automated-ETDRS intermediate visual acuity had good repeatability (95 per cent LoA of +/- 0.16). Conclusion Automated-ETDRS near and intermediate visual acuity measurement showed good repeatability and agreement with the gold standard chart-based visual acuity measurement. The findings of this study indicate the automated visual acuity measurement system may have potential for use in both patient care and clinical trials.