Mapping cone- and rod-induced retinal responsiveness in macaque retina by optical imaging

PURPOSE. To map the distribution of cone- or rod-induced retinal responsiveness by optical imaging from macaque retina. METHODS. The light reflectance changes in the posterior retina after a flash stimulus in anesthetized rhesus monkeys were measured by a modified fundus camera system equipped with a charge-coupled device (CCD) camera. The response topography of the optical signals was obtained in either light- or dark-adapted conditions. RESULTS. With infrared observation light, the whole posterior pole became darkened after the stimulus. The response topography in light- adapted conditions demonstrated a steep peak of darkening at the fovea, together with the gradual decrease of signal intensity away from the fovea toward the periphery. In dark-adapted conditions, the optical signal showed additional peaks along the circular region surrounding the macula at the eccentricity of the optic disc, together with the central peak at the fovea. A statistically significant positive correlation was obtained between the light reflectance changes in infrared observation light and the focal responses in multifocal electroretinogram (mfERG) at the corresponding retinal locations. CONCLUSIONS. The response topography in the retina, obtained by optical imaging, was consistent with psychophysical cone or rod sensitivity in humans and anatomic cone or rod distribution in humans and macaques. The cone- or rod-induced retinal responsiveness within the posterior pole region was noninvasively recorded within a short recording time.