Spectral and directional reflectance of the fovea in diabetes mellitus: Photoreceptor integrity, macular pigment and lens

Our aim was to assess the integrity of the photoreceptors in the fovea, and to measure the optical density of the macular pigment and the eye lens in patients with diabetes mellitus, and to compare the results with those of a group of healthy subjects. The directional and spectral properties of the light reflected from a 1.9 deg field centered on the fovea were measured simultaneously, in a single one second flash, with the Foveal Reflection Analyzer. The directional characteristics, i.e., the optical Stiles-Crawford effect, provided information on the integrity of the foveal photoreceptors. Model analysis of the spectral reflectance yielded optical densities of the macular pigment and the lens. The amplitude of the directional reflectance in diabetic eyes was significantly lower compared to controls (P<0.001). This indicates that the integrity of the photoreceptors in the fovea was altered in diabetics. Surprisingly, the directionality (a measure for the peakedness) was similar in diabetics and controls (P=0.3). The density of macular pigment was not different from that in controls (P=0.3). The optical density of the lens increased with age in both groups, but the rate of increase was larger in the diabetics (P<0.05). Possibly, the lens optical density increasing at a higher rate with age reflects changes preceding cataract formation.