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Jim M. Stringham, Paul V. Garcia, Peter A. Smith, Leon N. McLin, Jr., Brian K. Foutch; Sufficient Macular Pigment Optical Density for Optimal Visual Performance in Glare Conditions. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3638. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Presumably due to its optical filtering properties, macular pigment (MP) has been shown to improve visual performance in glaring light conditions. In previous work, trend lines indicate a benefit in glare task-related visual performance as a function of MP level. However, the point of diminishing returns for MP level with regard to visual performance in glare remains undetermined. This study sought to determine the optical density of MP at which visual performance benefits, for tasks involving glare, appear to asymptote.
Spatial profiles of MP optical density (MPOD) were determined, via heterochromatic flicker photometry, in twenty-six subjects aged 23-50 years. Three aspects of visual performance in glare were assessed: 1) photostress recovery, 2) disability glare, and 3) visual discomfort. Glare was delivered using bright white LEDs. For disability glare and photostress recovery the visual task consisted of identification of a 1o Gabor patch’s orientation. Visual discomfort was assessed with a rating scale.
MPOD at 30’ retinal eccentricity was found to span a range from 0.07 to 1.09. MPOD level was strongly associated with decreased photostress recovery time (r = -0.66; p = 0.001). When fit with an exponential function, however, an asymptote at approximately 0.60 - 0.70 MPOD was revealed. A similar finding was produced for disability glare contrast thresholds, where a linear relationship between MPOD and contrast thresholds was present (r = 0.549; p = 0.006), but a distinct asymptote in visual performance was determined at 0.6 MPOD. The relationship between visual discomfort and MPOD was linear (r = -0.607; p = 0.002) but did not appear to asymptote.
A critical level of MPOD near 0.6 - 0.7 was determined, below which visual performance appears to be compromised considerably for tasks involving photostress recovery and disability glare. For levels above 0.6 - 0.7 (despite a reduction in glare), additional MP appears to be superfluous for these tasks. By contrast, for visual discomfort it appears that higher MP translates, in a linear fashion, into lower estimated discomfort.
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