Macular Pigment: Its Associations with Color Discrimination and Matching

Abstract

Macular pigment (MP) acts as a prereceptoral filter which selectively absorbs short wavelengths. It has the potential to alter color vision but the literature is conflicting on whether it does and, if so, to what extent, possibly reflecting differences between color mechanisms and color tests. This study was designed to identify and investigate relationships, if any, between MP optical density (MPOD) and color sensitivity using a battery of techniques to quantify the color vision of color-normal observers. Color vision was assessed with the Farnsworth-Munsell 100-Hue test (FM100), Moreland match on the HMC anomaloscope, and a customized short wavelength automated perimetry (SWAP) technique at the foveola and at 1, 2, 3, 4, and 5° eccentricity. MPOD spatial profile was measured using customized heterochromatic flicker photometry. Total error scores and % partial error scores on the FM100 were uncorrelated to MPOD. Moreland matches showed a significant long wavelength shift with MPOD at between 1 and 3° (at 1.75°, r=0.489, p<0.001). Sensitivities on customized SWAP (cSWAP) using foveal targets were significantly inversely correlated with MPOD at both 1.75° (r=-0.461, p<0.001) and 3° (r=-0.393, p<0.001). Partial correlation analysis suggests that none of these findings can be attributed to age effects within the range 18 to 40 years. Our findings suggest that dietary supplementation to increase MPOD is unlikely to adversely affect hue discrimination. The association of MPOD with cSWAP may be a temporally limited effect to which the visual system normally adapts. We suggest that cSWAP may provide a clinical tool for assessing short-wavelength foveal sensitivity.