| Summary: | Background: Reverse high-contrast (white-onblack) visual acuity has been shown to improve visual acuity in older patients and patients with pathology under photopic testing. In this study, we investigated whether reverse contrast results in improved visual acuity at mesopic light levels. Methods: Monocular visual acuities (logMAR) were assessed at four different light levels (1 photopic {94 cd/m2} and 3 mesopic {3 cd/m2, 0.75 cd/m2, and 0.38 cd/m2}) in 47 visually normal subjects (27.4±9.3 years). Visual acuity was assessed using an E-ETDRS algorithm, in standard and reverse contrast, at 3 m. Repeated measures ANOVA with post-hoc Tukey testing was used to analyze the data across the light levels. Results: The mean standard contrast visual acuity was -0.07±0.06 under the photopic condition, 0.06±0.08 at 3 cd/m2, 0.17±0.08 at 0.75 cd/m2, and 0.28±0.09 at 0.38 cd/m2. For reverse contrast, it was -0.08±0.06 under the photopic condition, 0.01±0.07 at 3 cd/m2, 0.12±0.08 at 0.75 cd/m2, and 0.22±0.09 at 0.38 cd/m2. There was a significant improvement in visual acuity using reverse contrast under all mesopic light levels (p<0.001), but not under photopic conditions (p=0.15). Conclusions: At mesopic light levels, there were significant differences between standard and reverse contrast. The use of mesopic reverse-contrast visual acuity could be another way to detect subtle changes in visual acuity. Reversecontrast presentations under low lighting conditions may be advantageous for a patient's visual acuity.
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