Spatial Mapping of Macular Pigment Optical Density and Its Relationship to Contrast Sensitivity and Glare Disability

This dissertation explored the relationship of the macular pigment optical density (MPOD) spatial profile with measures of contrast sensitivity (CS), glare disability (GD), relative glare disability (RGD) and intraocular light scatter. A novel device capable of measuring MPOD across the central 16 degrees of retina along 8 principle meridians using customized heterochromatic flicker photometry (cHFP) at eccentricities of 0, 2, 4, 6 and 8 degrees was built. MPOD was calculated as both discrete and integrated values at all measured retinal loci. CS was measured using vertical grating stimuli of 3, 6 and 9 cycles per degree (cpd) also presented at 0, 2, 4, 6 and 8 degrees eccentricity. GD was calculated as a difference in CS between glare and no glare conditions (CSNo Glare – CSGlare) using the same vertical grating stimuli presented at the same eccentricities. RGD [(CSNo Glare – CSGlare) / CSNo Glare] was calculated to isolate the glare attenuation effects of MPOD by controlling for CS variability among the subject sample. Intraocular scatter was assessed through a direct compensation method using a commercially available device. Statistical analyses of the discrete and integrated MPOD associations with CS, GD, RGD and intraocular scatter were evaluated. The cHFP identified reliable MPOD spatial distribution maps demonstrating a 1st order exponential decay curve as a function of increasing eccentricity. Foveal MPOD revealed the highest correlation coefficients with RGD using 9cpd stimuli. These results are consistent with the glare attenuation effects of MP at higher spatial frequencies. Further support may be seen from the significant correlations found between corresponding parafoveal MPOD measures and both GD and RGD at 2 and 4 degrees of eccentricity using 9cpd stimuli with greater MPOD being associated with less glare disability. All calculated measures of foveal MPOD shared similar significant correlation coefficients with both GD and RGD using 6cpd and 9cpd stimuli. Discrete and integrated measures of MPOD were similar in regards to their association with glare attenuation effects across the macula. Quartile analysis of the highest and lowest foveal MPOD values demonstrated significant differences in intraocular scatter which indicate MPOD may minimize scattered intraocular short-wavelength light