Abstract
Purpose: :
To compare luminance matches made by minimum flicker and minimum motion photometry in the region of the macular pigment spectrum. To measure macular pigment optical density (MPOD) using motion photometry to determine the predictive relationship between the foveal and total retinal MPOD complements.
Methods: :
A Moreland anomaloscope was modified for flicker and for motion photometry. (1) Luminance matches were made for 14 wavelengths (430-560nm) against a 580nm comparison on a foveal field (diameter 2.2º) by 2 subjects using minimum flicker and minimum motion photometry under the same experimental conditions. (2) Measurements of MPOD retinal profiles were made by 35 subjects using minimum motion photometry (test 460nm, comparison 580nm). Two foveal fields (0.9º and 2.2º diameter) and 11 annular fields (eccentricities from 0.8º to 7.5º) were used.
Results: :
(1) The log luminance results obtained by the flicker and motion methods were linearly and highly correlated (slope = 1.03, r2 = 0.96) over a range of more than 1.5 log units. (2) Best-fit functions (exponential, gaussian or logistic) to the MPOD profiles were used to compute the total MPOD complement by numerical integration. Foveal relative MPOD was a poor predictor of total MPOD for either size of foveal field (r2 ≈ 0.2).The proportion of total MPOD in the foveal zone was greatest for subjects with the lowest total MP complement.
Conclusions: :
(1) Luminance matches made using the minimum flicker and motion paradigms are effectively identical. (2) There is no significant predictive relation between the foveal and total retinal MP complements. Eyes with a low total complement of MP have a greater proportion of it concentrated at the fovea.
Keywords: macular pigment • color vision • carotenoids/carotenoid binding proteins