Interocular differences in macular pigment density.

Interocular differences in the optical density of macular pigment were examined. Foveal and parafoveal sensitivities to lights of 460 and 530 nm were measured by heterochromatic flicker photometry for both eyes of ten subjects. These two wavelengths represent the maximum and minimum absorbance for macular pigment. Taking the difference in log sensitivity to the 460 nm light for the fovea and parafovea, after normalizing with respect to 530 nm, yields a measurement of the optical density of the macular pigment. Consistent interocular differences in macular pigment density were found for only two subjects, and these differences were less than 0.1. Other subjects frequently showed significant interocular differences on a given day but showed no consistent differences over the course of many days. In general, the amount of macular pigment measured for one eye was found to be essentially the same as that for the other eye. When measurements were averaged for the two eyes of each subject, significant differences in macular pigment density among subjects were found.