Macular pigment optical density correlates inversely with intraretinal light scatter in support of a polarization-dependent glare-reduction mechanism

Macular pigments are thought to protect the retina from photo-oxidative stress and enhance visual performance by filtering short-wavelength light. Their role in mitigating intraretinal light scatter remains uncertain. This study examined whether the spatial distribution of macular pigment optical density (MPOD) relates to retinal light scatter, consistent with a glare-reduction function. Mie scattering theory, with parameters consistent with retinal cellular components, was used to model the scatter properties of biologically realistic particles. Inner retinal backscatter and MPOD were then measured from 0°–10° eccentricity in forty-eight healthy eyes using dual-wavelength autofluorescence and spectral-domain OCT. Modelling confirmed that oblique intraretinal scatter is highly linearly polarized and, whilst substantially less than forward scatter, considerably exceeds backscatter in intensity, and that OCT-measured backscatter is supported as a proxy for
intraretinal oblique scatter. MPOD was inversely correlated with OCT-defined retinal backscatter, with the strongest correlation within 0–2° eccentricity (R = −0.83, p <0.001). The preferred orientation of macular pigment molecules within the radial macular architecture is optimal for absorption of polarized short-wavelength light scattered obliquely from the parafoveal retina into the fovea. This polarizationdependent mechanism provides a unifying framework linking the entoptic
phenomena of Maxwell's spot, Haidinger's brushes, and Boehm's brushes.