title: A computerized method of visual acuity testing: adaptation of the early treatment of diabetic retinopathy study testing protocol.
abstract: 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.
authors.affiliation: Jaeb Center for Health Research, Tampa, Florida 33613, USA. rbeck@jaeb.org
authors.forename: Roy W
authors.initials: RW
authors.lastname: Beck
authors.forename: Pamela S
authors.initials: PS
authors.lastname: Moke
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Turpin
authors.forename: Frederick L
authors.initials: FL
authors.lastname: Ferris
authors.forename: John Paul
authors.initials: JP
authors.lastname: SanGiovanni
authors.forename: Chris A
authors.initials: CA
authors.lastname: Johnson
authors.forename: Eileen E
authors.initials: EE
authors.lastname: Birch
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Chandler
authors.forename: Terry A
authors.initials: TA
authors.lastname: Cox
authors.forename: R Clifford
authors.initials: RC
authors.lastname: Blair
authors.forename: Raymond T
authors.initials: RT
authors.lastname: Kraker
mesh_terms: 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*