Comparison of best corrected visual acuity estimates between a custom-made digital chart and the ETDRS chart

To compare best corrected visual acuity (BCVA) measurements obtained using a digital visual acuity chart with those from the gold-standard Early Treatment Diabetic Retinopathy Study (ETDRS) chart and to assess differences in measurement variability and examination time.

Altogether 42 subjects (≥ 55 years) were examined using both charts on two separate occasions. BCVA was recorded in logMAR. Examination time was recorded. Subjects were stratified into four visual acuity classes. A nested analysis of variance (ANOVA) was used to analyze systematic differences and variance components.

A statistically significant difference in BCVA between the charts was found, but the 95% confidence interval (CI) for the mean difference (Digital - ETDRS: -0.03 ± 0.04 logMAR) was below the 0.1 logMAR resolution threshold. No significant interaction was observed between chart type and acuity class. The digital chart significantly reduced examination time by an average of 50 sec (95% CI: ±21). Variance was highest between testing occasions compared with that between-subject and for interaction between chart type and subjects.

The digital chart provides clinically equivalent BCVA estimates compared to the ETDRS chart, with shorter examination time. Its use in routine clinical settings is supported.