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Diana V Do, Neil M Bressler, Quan Dong Nguyen, Mostafa Saad Hanout, Susan B Bressler; Evaluation of Visual Acuity Measurements with Standard Luminance Compared with Low Luminance in Eyes with Geographic Atrophy from Age-related Macular Degeneration . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2821.
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Prior studies suggest low luminance (LL) best-corrected visual acuity (BCVA) may affect the prognosis of visual acuity loss in eyes with geographic atrophy (GA) due to age-related macular degeneration (AMD). In order to expand our understanding of the contribution made by LL BCVA in the management of eyes with GA, this study compares standard and LL BCVA in such eyes
Eligible eyes had the following: (1) BCVA letter score with standard luminance of 18 (approximate Snellen equivalent of 20/400) or greater on a retroilluminated Early Treatment Diabetic Retinopathy Study (ETDRS) chart following a protocol refraction and visual acuity measurement by a certified visual acuity examiner, (2) GA due to AMD with a minimum total diameter of 0.5 disc area within 3000 um of the fovea, and (3) no choroidal neovascularization. Study eyes underwent evaluation with standard and then LL BCVA. LL BCVA was measured by placing a 2.0-log-unit neutral density filter over the trial frame in front of the study eye and having the participant read the normally illuminated ETDRS chart using a different version of the chart. IBM SPSS v19.0 software was used to calculate means, standard deviations, and standard errors.
27 subjects (53%) were women and 44 (86.3%) were Caucasian. Mean age (+ standard deviation) was 80.5 (+ 7.4) years. At baseline, the mean (+SD) BCVA letter score with standard luminance (approximate Snellen equivalent) was 54.9 (20/80) + 19.5 (+ approximately 4 lines, assuming 5 letters per line). The mean LL BCVA letter score was 34.1 (20/200) + 18.9 (+ approximately 4 lines.). The difference between standard and LL scores averaged 20.9 (±14.1) letters, P<0.001. The mean total area of GA was 10.1 + 9.2 mm2 (3.9 + 3.6 disc areas) on digital color photos.
In this cohort, the average of the differences between BCVA with standard luminance and LL BCVA was substantial, although there was a wide variability of differences across the pairs of measurements. Additional studies with longitudinal data will be of value to determine the prognostic value of LL BCVA as well as the difference between standard and LL BCVA on the natural course and treatment outcomes in eyes with GA due to AMD.
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