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L. P. Aiello, for the Diabetic Retinopathy Clinical Research Network; Effects of Autorefraction, Pinhole Testing and Clinical Trial Protocol Refraction on Electronic-ETDRS Visual Acuity (EVA) in Subjects With Diabetes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4335.
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To assess the suitability of autorefraction (AR-EVA) and pinhole testing (PH-EVA) as surrogates for rigorous, clinical trial protocol refraction (DRCR-EVA) in assessing best-corrected EVA.
Both autorefraction and standardized DRCR.net refraction were performed for all eyes. Autorefraction could not be performed in 8% of eyes, all of which had DRCR-EVA equivalent to ≤20/40 (median DRCR-EVA [lower, upper quartiles]: 41 [21, 48]). EVA was measured utilizing each refraction and pinhole testing. The order of AR-EVA and DRCR-EVA was randomized, and subjects and examiners were masked to the origin of the correction.
216 eyes of 110 diabetic subjects were examined. The median DRCR-EVA score was 68 [51, 80] (Snellen equivalent 20/40 [20/70, 20/25]), ranging from 93-0 [20/12.5 - <20/800]. DRCR-EVA was not significantly different from AR-EVA (-1 letter [-4, 2], range -24/+27 letters P = 0.30), but did appear significantly better than PH-EVA (-3 letters [-9, 0], range -61/+18 letters, P = 0.003). Differences between AR-EVA, PH-EVA and repeat DRCR-EVA and the initial DRCR-EVA are shown in the table below. When eyes were stratified according to gender, age, race, pupil size, corneal clarity, lens status or DR severity, there were no subgroups in which AR-EVA or PH-EVA were superior to DRCR-EVA.
AR-EVA variability from DRCR-EVA is similar to the test-retest variability of DRCR-EVA while PH-EVA is worse. Variability is increased in eyes with worse vision. Given the substantial time and effort required to train and certify visual acuity examiners for study protocol refraction, further evaluation of AR-EVA as an alternative in clinical research and/or practice is warranted.
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