Abstract
Purpose: :
Retinal screenings for diabetic retinopathy via digital photography are becoming more common in a variety of clinical settings. Protocols for these screenings differ, but most involve some type of visual acuity measurement. The Vanderbilt Ophthalmic Imaging Center assesses visual acuity with the Optec 800, a portable, inexpensive instrument comprised of a reduced, illuminated ETDRS chart. The present study tests the validity of the portable Optec instrument against the full–size, illuminated Early Treatment of Diabetic Retinopathy Study (ETDRS) chart.
Methods: :
Using a prospective design, data from 37 patients (72 eyes) were evaluated. The following data were recorded for each patient: age, gender, ocular history, presence and type of refractive correction. Patients were randomized, performing either the ETDRS or Optec 800 test first, while always starting the test with the right eye. Patients were instructed to read each letter individually until an entire line of letters had been incorrectly identified. Performance was recorded using single letter scoring, and a total correct score was calculated for each eye on each test.
Results: :
There was no statistically significant difference in performance between the Optec 800 and the illuminated ETDRS (P=0.09). The average of differences was –1.2, indicating that patients missed approximately 1.2 more letters on the Optec 800 versus the ETDRS, which is not clinically relevant. Additional factors such as gender, age, and test performed first did not affect performance between the two methods. No statistically significant adaptation or fatigue trend was found between right eye (tested first) and left eye.
Conclusions: :
There is no difference in performance between the Optec 800 vision screener and the illuminated ETDRS chart for our sample size. The study indicates that the Optec 800 instrument provides a similar visual acuity measurement as compared with the ETDRS chart, and therfore the Optec 800 may prove useful for other screening protocols.
Keywords: visual acuity • clinical (human) or epidemiologic studies: systems/equipment/techniques