Assessing macular pigment from SLO images

Abstract

To assess the spectral characteristics and spatial distribution of macular pigment by comparing relative retinal reflectance at four different wavelengths. A Rodenstock scanning laser opththalmoscope (SLO) with four spectral beams, 488, 544, 633 and 780 nm, was used to obtain images of the normal macula from five eyes of three normal subjects. The relative spectral reflectance was determined along a horizontal path extending from nasal to temporal retina through the fovea for each image. A comparison of this data provided an indication of the relative density and the actual spatial extent of macular pigmentation. There is an area of hyper-pigmentation obtained from averaging the data from all five eyes that extends from about 6 deg symmetrically into nasal and temporal macula surrounding a small zone of greater hyper-pigmentation that extends about 3 deg on each side of the fovea. The smaller central zone has a relatively high absorption for blue light and is considered to represent macular pigment. The larger less hyper-pigmented zone is considered to represent melanin in the retinal pigment epithelium. The circularly symmetrical hyper-pigmented central macula including the yellow macular pigment can be assessed by comparing different spectral images obtained from an SLO.