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S. Saigal, M. J. Byrnes, P. Johnston, D. Sena, G. Torkildsen, A. Ingerman; Comparison of Photopic and Mesopic Visual Function in Early Dry AMD Patients and Healthy Controls. Invest. Ophthalmol. Vis. Sci. 2010;51(13):973.
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Deficits in visual function under mesopic illumination have been reported in subjects with early- stage dry age-related macular degeneration (AMD). In this study, we compared best-corrected visual acuity (VA), near visual acuity (NVA), and reading acuity (RA) under photopic and mesopic illumination in patients with early dry AMD and normal controls to assess the extent of AMD-associated mesopic vision loss.
Visual function in photopic and mesopic illumination was assessed in 15 eyes of 15 subjects (10 subjects with early dry AMD in the study eye (BCVA 20/40 or better) and 5 controls aged 60+ (BCVA 20/20 or better)) using 3 charts (ETDRS (VA), SKILL (NVA), and MNRead (RA)). Mesopic illumination was achieved by having the subject view the chart through neutral density filters for VA and RA, and by comparing performance using the light (white on black) and dark (black on grey) SKILL charts for NVA. Each test was repeated 3 times within 2 weeks. Reliability was assessed by fitting components of variance models and calculating intraclass correlation coefficients (ICC). The effect of subjects’ AMD status on VA, NVA, and RA under photopic and mesopic conditions was analyzed via two-factor ANOVA models. Models with and without AMD-luminance interactions were evaluated to determine the best fitting model.
ICC estimates ranged from 0.69-0.77 over all tests and luminances, indicating substantial reliability. Significant interactions between subjects’ AMD status and extent of vision loss under mesopic luminance were not observed (p=0.82 for VA, 0.24 for NVA, and 0.24 for RA). When analyzing the study population as a whole, the mean vision loss under mesopic illumination was 0.34, 0.80, and 0.27 logMAR units for VA, NVA, and RA, respectively (p<0.001).
Assessment of VA, NVA, and RA in early dry AMD patients and unaffected controls under photopic and mesopic luminance achieved reliable results. Significant vision loss under mesopic illumination (relative to photopic) was observed with VA, NVA, and RA charts in both subject groups. By each measure, the extent of vision loss under mesopic illumination was similar in early dry AMD patients and controls.
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