Abstract
Purpose: :
To assess the cross-sectional correlation between MPOD and macular visual function measures obtained at baseline in White non-smoking volunteers of BMI ≤30.
Methods: :
Twenty subjects were enrolled, 18 of whom (age range: 50-66; M/F=7/11) were retained and completed the two required baseline visits. MPOD was measured at 0.5- and 2.0-deg of eccentricity according to a published method (Iannaccone et al. IOVS 2007; 48: 1458-65). The number of letters read on Pelli-Robson charts estimated contrast sensitivity (CS). The P50 amplitude of the pattern-reversal electroretinogram (PERG) to 45 minarc, 100% contrast, transient stimuli estimated overall macular function. Dark-adapted (DA) 650nm foveal cone sensitivity (DA-650 FCS) and DA 500nm parafoveal rod sensitivity (DA-500 PFRS) were measured at loci corresponding to MPOD estimates. Pearson’s coefficients, r, were calculated to estimate the correlation between MPOD and these variables. Non-normally distributed data were log transformed. MPOD was also expressed as a sum of 0.5- and 2.0-deg eccentricity (MPODtot).
Results: :
Measurements between eyes were highly correlated. Therefore, all correlations were investigated using the inter-ocular average for each measured variable. MPOD-0.5 was positively correlated to CS (r = 0.323). This correlation was considerably lower for MPOD-2.0 or MPODtot. MPOD-0.5 and MPODtot displayed a -shaped, curvilinear relation with PERG P50 amplitude (r = 0.698 and 0.715, respectively), with PERG tending to be largest for intermediate MPOD levels. MPOD-2.0 was unrelated to DA-500 PFRS, whereas MPOD-0.5 showed an inverse relationship with DA650-CFS (r = -0.430).
Conclusions: :
Cross-sectional analyses confirm that higher MPOD correlates with better CS, but also suggest that there is an optimal MPOD range within which PERG amplitudes are highest and that higher MPOD levels are associated with lower DA-650 FCS. Larger, biracial sample sizes and longitudinal studies of MPOD augmentation in response to dietary supplements remain necessary to verify these associations and change following supplementation.
Keywords: macular pigment • electroretinography: clinical • contrast sensitivity