The Spatial Distribution of Macular Pigment Optical Density Following Lutein Supplementation

Abstract

Abstract: : Purpose: Macular pigment (MP), an accumulation of xanthophylls in the central retina, absorbs potentially harmful wavelengths of light before they reach the photopigments and outer limiting membranes and appears to serve as an antioxidant. Consequently, MP is thought to protect posterior ocular tissues from light induced insult. This possibility has led to several studies that investigated the effects of increased consumption of lutein, the main constituent of MP. Few intervention studies have reported changes in macular pigment optical density (MPOD) across the retina. The objective of the current project was to investigate changes in the spatial distribution of MP following lutein supplementation. Methods: MPOD was measured in 15 subjects at baseline and after consuming 30mg of lutein supplement daily for 4, 8, and 12 weeks. A free view densitometer was used to measure MPOD at four retinal loci: 20', 30', 60', and 120' eccentricity. For characterizing the spatial distribution MPOD, the subjects’ data were fit with Gaussian, Lorentzian, and Voigt functions. The coefficient of determination (COD) was used as a measure of goodness of fit and the area under the curves was taken to yield an integrated Gaussian MPOD (iGMPOD), integrated Lorentzian MPOD (iLMPOD) and integrated Voigt MPOD (iVMPOD). Results: Mean MPOD at baseline was 0.469 (SD=0.16), 0.391 (SD=0.16), 0.234 (SD=0.09), and 0.084 (SD=0.05) at 20', 30', 60', and 120' eccentricity, respectively. After twelve weeks of intervention, mean MPOD increased 0.115 at 20' (p < 0.001), 0.062 at 30' (p < 0.001), 0.041 at 60' (p = 0.01) and 0.007 at 120' (p = 0.17) eccentricity. The mean COD at baseline was higher for the Voigt function (R² = 0.983) than for the either the Gaussian (R² = 0.970) or Lorentzian (R² = 0.979) functions. The mean COD for each function did not change from baseline. After twelve weeks of intervention, iVMPOD increased approximately 24% (p = 0.005), whereas iGMPOD (p = 0.08) and iLMPOD (p = 0.07) increased approximately 12%. Conclusions: Significant increases in MPOD and integrated MPOD were observed after subjects consumed 30mg of lutein supplement for twelve weeks. The spatial distribution and deposition of macular carotenoids may be best described by a Voigt function.

Keywords: macular pigment • carotenoids/carotenoid binding proteins • retina