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David Hamilton; Effect of Decreased Lighting on Visual Acuity in Normal Subjects Donald C. Fletcher MD; California Pacific Medical Center Dept. of Ophthalmology and Smith-Kettlewell Eye Research Institute. Laura Walker Renninger; Smith-Kettlewell Eye Research Institute. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2752.
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Central field loss patients anecdotally report that more light improves their vision. In a recent study (Fletcher, Renninger, and Schuchard, 2012), it was reported that indeed acuity declines with lower light levels. The purpose of this study is to determine the extent to which light conditions affect visual acuity in normally sighted subjects.
Binocular Visual acuity was assessed on 20 normally sighted volunteers using their habitual correction. Initially a Snellen letter chart was viewed at one meter under ambient room light. Participants were tested a second time while wearing 4% transmission gray filter glasses (NOIR U23) over their spectacles or contact lenses. The acuity difference is reported as lines difference with decreased light.
Participants ranged in age from 22-70 (with a mean of 44.85 years). All patients displayed diminished visual acuity when 4% transmission glasses were worn. Lines difference ranged from 1 (31, F) to 7 (60, F) with the majority of patients falling in the 2-5 line range (mean: 2.95 lines, median: 2.5 lines). In Dr. Fletcher's patients, he observes a mean drop of about two lines (ambient room light vs. 4% transmission gray filter glasses.) My results are slightly more exaggerated, with almost a full additional mean line drop (2 vs. 2.95 lines.)
A significant reduction in visual acuity was noted with reduced lighting in this population of normally sighted healthy individuals. Providing adequate lighting conditions optimizes visual acuity for tasks such as reading. This is an inexpensive and easily administered test to evaluate visual performance under dim light conditions. Pathological conditions are often felt to decrease functional performance in subdued lighting. This data can serve as a baseline for comparisons.
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