Macular pigment density assessed by directional fundus reflectance

Light radiated from foveal photoreceptors was analyzed in the eye's pupil at 470 nm and 532 nm. The reflectance of the inner limiting membrane was then measured at 6 deg from the fovea for the same wavelengths, allowing us to determine the macular pigment (MP) density D(dir) using the directional reflectance technique. In addition we measured the MP density D(nd) using the nondirectional reflectance technique (26 subjects). The mean values of D(dir) and D(nd) were 0.419+/-0.097 and 0.195+/-0.042 D.U., respectively (sample field of 2 deg). They were highly correlated (p<0.0001). Comparison of D(dir) and D(nd) implies that 57+/-12% of the light reflected from the fovea comes from layers anterior to MP at 470 nm. The mean directionality factors rho that we have measured at 470 nm and 532 nm were equal to 0.239+/-0.028 and 0.210+/-0.028 mm(-2), respectively. They were correlated (p<0.0001) and followed the spectral dependence suggested by Marcos.