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


METHODS
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.
Beck
Roy W
RW
Jaeb Center for Health Research, Tampa, Florida 33613, USA. rbeck@jaeb.org
Moke
Pamela S
PS
Turpin
Andrew H
AH
Ferris
Frederick L
FL
SanGiovanni
John Paul
JP
Johnson
Chris A
CA
Birch
Eileen E
EE
Chandler
Danielle L
DL
Cox
Terry A
TA
Blair
R Clifford
RC
Kraker
Raymond T
RT
D000293:Adolescent; D000328:Adult; D002648:Child; D002985:Clinical Protocols; D003930:Diabetic Retinopathy / Q000175:diagnosis; D003936:Diagnosis, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014786:Vision Disorders / Q000175:diagnosis; D014787:Vision Tests / Q000295:instrumentation / Q000379:methods*; D014792:Visual Acuity / Q000502:physiology*