DIRECT MEASUREMENT OF HUMAN-CONE-PHOTORECEPTOR ALIGNMENT

We have developed an imaging reflectometer to measure cone-photorecept or alignment. One makes measurements by bleaching the cone photopigmen t and imaging the distribution of light returning from the retina, whi ch is illuminated from a small source imaged in the plane df the eye's pupil. If the source is near the optimal entry pupil position as dete rmined psychophysically, the distribution of light returning from the retina is peaked, and the magnitude of the peak depends on the locatio n of the source in the pupil. of the eye. If the source is far from th e optimal entry pupil position, then there is no measurable peak. The location of the peak varies across individuals and coincides with the reported location of best visibility of the measuring light and with p revious psychophysical and reflectometric measurements of the Stiles-C rawford peak. The source of this directionality must arise either from the photoreceptors or from behind the photoreceptors because the peak is not present if measurements are made when the cone photopigments h ave high optical density.