Purpose: To evaluate the effect of pupillary dilation on electronic-ETDRS visual acuity (EVA) in diabetic subjects and to assess postdilation EVA as a surrogate for predilation VA.
Methods: DRCR.net-protocol refraction and EVA were measured before and after dilation in diabetic subjects by independent, masked examiners.
Results: In 129 eyes of 66 subjects, the median (25th, 75th percentiles) predilation EVA score was 69 (54, 86) (Snellen-equivalent 20/40(-1) [20/80(-1), 20/20(+1)]). Predilation VA was >or=20/20, <20/20 to 20/40, <20/40 to 20/80, and <20/80 in 29%, 19%, 26%, and 26% of eyes, respectively. Median EVA change postdilation was -3 letters (-7, 0). The absolute change in EVA score was >or=15 letters (>or=3 ETDRS lines) in 9% of eyes and >or=10 letters (>or=2 ETDRS lines) in 19% of eyes. Extent of change (range +12 to -25 letters) was associated with baseline VA. No relationship was identified between EVA change and gender, race, lens status, refractive error, DR severity, or primary cause of vision loss.
Conclusions: In an optimized clinical trial setting, there is a decline in best corrected EVA after dilation in diabetic subjects. The large range and magnitude of VA change preclude using postdilation EVA as a surrogate for undilated VA.