Evaluation of the Test-Retest Reliability of the Electronic-ETDRS Visual Acuity Tester

Abstract

Purpose: To evaluate the intervisit and intravisit test-retest reliability of the Electronic-ETDRS Visual Acuity tester (EVA) in healthy subjects with uncorrected vision, and in comparison with visual acuity (VA) assessments using standard Early Treatment Diabetic Retinopathy Study methods (S-ETDRS).

Methods: Volunteers performed VA assessments with two instruments: laptop EVA tester (Model 11-WIN; Jaeb Center for Human Research, Tampa, FL), and standard ETDRS vision chart (Precision Vision, La Salle, IL) in each of two visits using the worse seeing eye without the use of corrective lenses. During Visit 1, volunteers performed VA assessments using the EVA tester twice and S-ETDRS once. During Visit 2 (≥7 days after Visit 1), volunteers performed VA assessments using the EVA tester once and S-ETDRS once. Response measures included VA (ETDRS letters), subjective comments, and adverse effects.

Results: Thirty-one subjects with median baseline uncorrected VA of 75 letters (range: 18-95 letters as measured by S-ETDRS) participated and 30 volunteers completed both visits. In intervisit comparisons, the median absolute difference of VA scores for EVA and S-ETDRS were 3.3 and 3.0 letters, respectively; intervisit scores were highly correlated (r²=0.93 and 0.87, respectively). Seventy-four percent of patients had an intervisit absolute difference of ≤0.1 logMAR. In an intravisit comparison, the median absolute difference of VA scores using EVA was 2.0 letters; intravisit exams were highly correlated (r²=0.96). Overall preference for the instruments was nearly equal with 43% (13/30) of subjects preferring EVA. The most frequent subjective comments with the use of EVA were that the random/dynamic presentation of letter sizes increases accuracy (n=17) and the screen of the computer laptop is too bright and/or has too much glare (n=15). Volunteers commented that the S-ETDRS chart is easier to read (n=9) and is more comfortable because of familiarity (n=8).

Conclusions: Results suggest that EVA and S-ETDRS are both reliable instruments to measure VA within one visit and across two visits in a small sample of healthy volunteers with uncorrected vision. There was no clear overall subjective preference between instruments. Further research, including larger study populations and in patients with ocular disease, is needed to verify these results.

Keywords: 465 clinical (human) or epidemiologic studies: systems/equipment/techniques • 754 visual acuity