Visual Acuity Testing Using Autorefraction or Pinhole Occluder Compared with a Manual Protocol Refraction in Individuals with Diabetes

Purpose: To compare visual acuity (VA) scores obtained after autorefraction or using a pinhole occluder to scores obtained after refraction according to a standard clinical research protocol. Design: Prospective, comparative case series Participants: One hundred and ten study participants (209 eyes) with diabetes mellitus and a broad range of diabetic retinopathy severity and visual acuity (VA). Methods: VA was measured after autorefraction by a Topcon KR-8000 autorefractor as well as after a Diabetic Retinopathy Clinical Research Network (DRCR.net) protocol manual refraction. The order of testing was randomized and examiners were masked to the source of each refraction. A second VA measurement, utilizing an identical DRCR.net manual refraction, was made in a subset of eyes (N = 144, 69%) in order to establish test-retest variability for comparison purposes. All eyes underwent VA testing using a pinhole occluder. Main Outcome Measures: Best corrected VA as measured by the Electronic Early Treatment Diabetic Retinopathy Study Visual Acuity Test© (E-ETDRS). Results: In all eyes, the median E-ETDRS VA letter score (EVA) obtained after manual refraction (MR-EVA) was 69 (Snellen equivalent 20/40), ranging from 4 to 93 (20/800 to 20/16). The median MR-EVA was slightly better than the median EVA obtained after autorefraction (AR-EVA), with a median difference (AR-EVA – MR-EVA) of −1 letter (25th, 75th percentiles: −4, 2 letters). The absolute difference between AR-EVA and MR-EVA was similar to the test-retest variability of MR-EVA alone. In contrast, MR-EVA was better than EVA obtained using a pinhole occluder (PH-EVA), (median PH-EVA – MR-EVA: −4 letters [−9, 0]), and had significantly less test-retest variability (P