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L. P. Aiello, for the Diabetic Retinopathy Clinical Research Network; Effects of Dilation on Visual Acuity Obtained by Electronic-ETDRS Visual Acuity Testing (EVA) in Diabetic Patients. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4527.
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To evaluate the effect of pupillary dilation on electronic-ETDRS visual acuity (EVA) in subjects with diabetes and to assess the suitability of post-dilation EVA as a surrogate for pre-dilation visual acuity (VA).
Pre-dilation standardized refraction and EVA measurements were performed according to DRCR.net protocol. Subjects underwent pre-dilation assessment of corneal clarity and pupil size. After dilation, pupil measurement, refraction, and EVA were repeated by an independent, masked examiner. Diabetic retinopathy (DR) severity level, extent of cataract, primary cause of visual loss, and post-dilation corneal clarity were evaluated for each eye.
129 eyes of 66 subjects with diabetes were examined. The median [lower, upper quartiles] pre-dilation EVA score was 69 [54, 86], Snellen equivalent 20/40-1 [20/80-1, 20/20+1], ranging from 0 to 95 [<20/800 to 20/12.5]. Pre-dilation VA was 20/40 or better in 62 eyes (48%), worse than 20/40 but 20/80 or better in 34 eyes (26%), and worse than 20/80 in 33 eyes (26%). Overall median post-dilation change in VA was -3 [0, -7] letters. A VA decline of ≥ 15 letters occurred in 9% of subjects overall. Although pre- and post-dilation VA were correlated, the VA change ranged from +12 to -25 letters. This effect was partially dependent on baseline VA. Of eyes with baseline VA ≥ 20/40 and 20/40 > VA ≥ 20/80, a ≥ 15 letter change was observed in 5% and 15% and a ≥ 5 letter change occurred in 31% and 53%, respectively. No substantial relationship was identified between change in VA and gender, race, lens status, phakic refractive error, educational level, DR severity level, or primary cause of vision loss.
In an optimized clinical trial setting using experienced examiners, there is a general decline in best corrected visual acuity after pupillary dilation. Although pre- and post-dilation VA are correlated, the wide range and large magnitude of VA change after dilation preclude the use of post-dilation EVA testing as a surrogate for undilated VA.
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