The pigmentation and geometry of the primate fovea are prominent features thought to be associated with high acuity. We propose to measure the spatial distribution of the macular pigment in the foveal region and relate it to the width of the fovea, especially the avascular zone. Entoptic phenomena caused by macular pigmentation, retinal vasculature, and foveal geometry will be studied in the same subjects. Visual acuity at different eccentricities within the fovea will be measured in human subjects with dense or slight pigmentation and small or large avascular zones. This will test whether the pigmentation and foveal size are tightly linked with visual acuity. The macular pigment will be visualized in vivo in human and monkey eyes by monochromatic fundus photography and the pigment density distribution will be estimated. The avascular zone of the fovea will be measured by fluorescein angiography in the same monkey eyes and a few human eyes for which pigment measures were made. Some of the monkey eyes that were photographed will be excised and the Pigment density will be measured by microspectrophotometry and densitometry to establish the limits of precision of the in vivo technique. Two-dimensional plots of the pigment distribution will be obtained by image analysis. This project will combine the resources of three different laboratories in the Boston area. The long-term objectives of the project are to characterize the natural variations in macular pigmentation and foveal geometry that occur in a representative population of normal human subjects. Our research will establish techniques to estimate macular pigmentation and foveal size in vivo. It will link physical measurements with entoptic phenomena. These phenomena may be useful in obtaining information about the state of the macula in older patients with poor optic media. The availability of the methodology will also make it possible to study whether particular types of foveal pigmentation or foveal geometry are associated with the development of macular degeneration or other disorders of the macula.
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