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J. C. Wong, M. Engles, B. R. Wooten, B. R. Hammond, Jr.; Testing the Visibility Hypothesis of Macular Pigment Using a Filter That Simulates Changes in Macular Pigment Density. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1704.
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The selective accumulation of the dietary carotenoids lutein (L) and zeaxanthin (Z) in an area so vital to visual performance (in and around the fovea) suggests these yellow pigments might influence visual function. One possibility is that these macular pigments (MP) could improve visibility (distance vision) by preferentially absorbing short-wave scattered light in the atmosphere ("blue" haze). This study represents a first test of the Visibility Hypothesis (Wooten and Hammond, 2002).
Five young healthy subjects were evaluated. MP optical density (OD) was measured using HFP. Visibility was assessed by measuring contrast sensitivity thresholds at 8 cycles/deg (CST) using an optical system that passed xenon-light through a series of sine-wave gratings. Blue haze was simulated using a ecologically valid broad-spectrum filter. Changes in MP density were simulated using a variable path length filter with an oil-based carotenoid solution that perfectly mimicked the absolute absorption spectrum of MP.
The average baseline CST was 0.004. Adding 0.25 OD of simulated MP lowered the average threshold to 0.003 (25%). An additional 0.25 OD decreased thresholds an additional 10% and the effect reached a plateau at about 0.50.
The largest improvement (about 25%) in contrast occurred with the initial, and relatively modest, addition of 0.25 OD units of simulated MP. This plateau may have been due to testing subjects who already had relatively high MP. We are testing additional subjects with low MP to investigate this possibility.
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