Macular Pigment Optical Density and Measures of Macular Function: Test-Retest Variability, Cross-Sectional Correlations, and Findings from the Zeaxanthin Pilot Study of Response to Supplementation (ZEASTRESS-Pilot)

We report on the short-term test-retest baseline variability in macular function tests in ZEASTRESS-Pilot participants (n = 18), on their cross-sectional correlation with macular pigment optical density (MPOD), and on the effects of four months (FUV4) of 20 mg/day zeaxanthin (ZX), followed by a four-month washout (FUV8; n = 24, age 50-81 years old). Outcomes included: MPOD at 0.5 and 2.0 deg eccentricity (MPOD-0.5 and -2.0); contrast sensitivity (CS); pattern-reversal electroretinogram (PERG) amplitude; dark-adapted 650 nm foveal cone sensitivity (DA650-FCS); and 500 mn parafoveal rod sensitivity (DA500-PFRS). All measures of macular function showed close test-retest correlation (Pearson's r range: 0.744-0.946) and low coefficients of variation (CV range: 1.13%-4.00%). MPOD correlated in a complex fashion with macular function. Following supplementation, MPOD-0.5 and MPOD-2.0 increased at both FUV4 and FUV8 (p ≤ 0.0001 for all measures). Continued, delayed MPOD increase and a small, but significant (p = 0.012), CS increase was seen at FUV8 only in females. PERGs increased significantly at FUV4 (p = 0.0006), followed by a partial decline at FUV8. In conclusion, following ZX supplementation, MPOD increased significantly. There was no effect on DA-650 FCS or DA-500 PFRS. Both CS and PERG amplitudes increased following supplementation, but the effect varied between males and females. Additional studies appear warranted to confirm and characterize further these inter-gender differences.