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Comparative Study
. 2003 Feb;135(2):194-205.
doi: 10.1016/s0002-9394(02)01825-1.

A computerized method of visual acuity testing: adaptation of the early treatment of diabetic retinopathy study testing protocol

Roy W Beck  1 , Pamela S Moke, Andrew H Turpin, Frederick L Ferris 3rd, John Paul SanGiovanni, Chris A Johnson, Eileen E Birch, Danielle L Chandler, Terry A Cox, R Clifford Blair, Raymond T Kraker
Affiliations
Comparative Study

A computerized method of visual acuity testing: adaptation of the early treatment of diabetic retinopathy study testing protocol

Roy W Beck et al. Am J Ophthalmol. 2003 Feb.

Abstract

Purpose: To develop a computerized method of visual acuity testing for clinical research as an alternative to the standard Early Treatment for Diabetic Retinopathy Study (ETDRS) testing protocol, and to evaluate its test-retest reliability and concordance with standard ETDRS testing.

Design: Test-retest reliability study.

Methods: Multicenter setting of a study population of 265 patients at three clinical sites. Visual acuity was measured with both the electronic visual acuity testing algorithm (E-ETDRS) and standard ETDRS protocol (S-ETDRS) twice on one eye of each patient. E-ETDRS testing was conducted using the electronic visual acuity tester (EVA), which utilizes a programmed Palm (Palm, Inc, Santa Clara, California, USA) hand-held device communicating with a personal computer and 17-inch monitor at a test distance of 3 meters.

Results: For the E-ETDRS protocol, test-retest reliability was high (r = 0.99; with 89% and 98% of retests within 0.1 logMAR and 0.2 logMAR of initial tests, respectively) and comparable with that of S-ETDRS testing (r = 0.99; with 87% and 98% of retests within 0.1 logMAR and 0.2 logMAR of initial test, respectively). The E-ETDRS and S-ETDRS scores were highly correlated (r = 0.96 for initial tests and r = 0.97 for repeat tests). Based on estimates of 95% confidence intervals, a change in visual acuity of 0.2 logMAR (10 letters) from a baseline level is unlikely to be related to measurement variability using either the E-ETDRS or the S-ETDRS visual acuity testing protocol.

Conclusions: The E-ETDRS protocol has high test-retest reliability and good concordance with S-ETDRS testing. The computerized method has advantages over the S-ETDRS testing in electronically capturing the data for each tested letter, requiring only a single distance for testing from 20/12 to 20/800, potentially reducing testing time, and potentially decreasing technician-related bias.

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