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Potential role of macular pigment in preserving rod-dominated dark adaptation in the older eye
Laura Patryas
In: British Congress of Optometry and Vision Science; 16 Sep 2011-16 Sep 2011; Aston University, Birmingham. 2011.
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Abstract
Purpose: To characterize the rate of scotopic sensitivity decline with age using cathode-ray-tube (CRT)-based dark adaptometry and compare the results with the macular pigment optical density (MPOD). Methods: Thresholds were measured following a minimum of 30% bleach, using a white 1° stimulus (flickering at 1 Hz), presented 11° below fixation on a CRT monitor. MPOD was measured using MPS 9000 based on heterochromatic flicker photometry. 33 subjects were divided into two groups: older (≥45, n = 16) and younger (<45, n = 17). Results: Rod recovery (slope of S2) was 0.04 log10 units min-1 (p < 0.001) slower in the older (0.19 ±0.03 log10 units min-1) compared with the younger group (0.23 ±0.03 log10 units min-1). Faster rates of S2 were correlated with lower thresholds (r = 0.49, p < 0.005). The average MPOD for the whole group was 0.37 ±0.21. Subjects with lighter irides had on average 40% lower MPOD compared with darker irides. There was a weak relationship between MPOD and final threshold and MPOD and rate of S2. The rate of S2 recovery for the lower 10th percentile of MPOD was significantly slower compared with the upper 10th percentile (p = 0.037). Conclusion: Dark adaptation abnormalities in normal ageing may be related to structural changes in the Bruch’s membrane/Retinal Pigment Epithelium complex subsequent to oxidative stress. Macular pigment is a powerful antioxidant therefore augmentation of MPOD could have beneficial effects on scotopic vision in the elderly. Longitudinal, placebo-controlled intervention studies are needed to explore this possibility.