Localized xanthophyll carotenoid abundance is associated with rod-mediated dark adaptation and cone-mediated visual acuity in aging and early and intermediate age-related macular degeneration (AMD)

Abstract

Purpose : In a center-surround model of parafoveal rod vulnerability and foveal cone resilience in aging and AMD, cones are sustained by two circulations and abundant Müller glia, for which xanthophyll carotenoid pigment is a marker. Rods depend on the choroid, as measured by efficiency of retinoid re-supply. We determined the association between imaging-based metrics for xanthophyll abundance and visual function measures in a cross-sectional study of adults ≥60 years old with and without AMD.

Methods : AMD severity was determined by 9-step Age-Related Eye Disease Study grading. Tests probed cones (best-corrected visual acuity (VA), contrast sensitivity), cones and rods (low luminance VA, low luminance deficit, mesopic light sensitivity), or rods only (scotopic light sensitivity, rod-mediated dark adaptation (RMDA)). From macular 2-wavelength autofluorescence images (Spectralis, Heidelberg), signal attenuation by xanthophyll optical density (MPOD) was estimated by a ratio of blue and green autofluorescence signal normalized at 9° for 3 metrics: mean MPOD in a 1° diameter fovea-centered disk, mean MPOD in a 2° diameter disk centered on the RMDA test spot 5° inferior to the fovea, and volume, integral of MPOD in a 4° diameter fovea-centered disk. Associations between vision and imaging measures were assessed using Spearman partial correlation coefficients adjusting for age.

Results : In 88 eyes of 88 subjects (mean age 74.9 years), mean foveal MPOD was 0.54±0.21, 0.65±0.21, and 0.68±0.20 in normal (n=32), early (n=22), and intermediate AMD (n=33) eyes respectively. Higher foveal MPOD was associated with better VA (r=-0.22, p=0.044) and worse low luminance deficit (r=0.23, p=0.029). Higher MPOD in the area of the RMDA test target was associated with faster RMDA (r=-0.30, p=0.005). No other significant associations between xanthophyll abundance and visual function were found.

Conclusions : In a small sample of subjects ≥60 years old with normal macular health, early AMD, or intermediate AMD, higher xanthophyll concentrations at foveal and parafoveal locations are both associated with better best-corrected VA and RMDA, respectively. Data will be interpreted in light of a hypothesis that considers HDL-mediated delivery of xanthophylls to foveal cells a driving force in high-risk drusen formation in central macula.

This is a 2020 ARVO Annual Meeting abstract.