Shortening the Early Treatment Diabetic Retinopathy Study visual acuity test utilizing a novel computer software: reproducibility in control and patient eyes

Purpose To describe and compare a method of computerized visual acuity (VA) testing software to the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. Methods Setting: Single tertiary institution. Study Population: Prospective study including right eyes of volunteers (N = 109) and patients (N = 126). Intervention: Subjects were tested in a random order twice with the ETDRS chart and twice with the VA software. For ETDRS, we calculated the final VA separately for each run, using four different test termination criteria (1-miss in a row, 2-miss in a row, 50% miss and per-letter). For software testing, we calculated final VA with a variety of number of letters presented. Main Outcome Measures: The main outcome measures were reproducibility and number of letters required to exceed ETDRS reproducibility. Results For ETDRS, the average number of letters presented was 55.1 +/- 9, 54.3 +/- 10, 53.1 +/- 10 and 70 for the 1-miss, 2-miss, 50% termination and per-letter criterion. The test-retest variability (TRV) of ETDRS was 0.29, 0.42, 0.17 and 0.141 for the 1-miss in a row, 2-miss in a row, 50% and per-letter termination criteria. For the software VA test, TRV was 0.202, 0.138 and 0.112 after presenting 6, 11 and 20 letters. The reproducibility of the software was equal to the ETDRS at 11 letters and thereafter surpassed. Similar results were achieved in the patient group. Conclusions This study demonstrates that by utilizing a VA testing software, based on advanced threshold testing algorithms we were able to duplicate, and surpass, the reproducibility of the ETDRS chart while presenting much fewer letters.