IMAGES OF CONE PHOTORECEPTORS IN THE LIVING HUMAN EYE

Though the photoreceptor mosaic has been imaged through the intact opt ics of the eyes of several species, it has not been clear whether indi vidual photoreceptors can be resolved in the living human eye. We have constructed a high-resolution fundus camera and have resolved cones w ith a spacing as small as 3.5 mu m in single images of the fundus. The high contrast of these images implies that almost all the light retur ning from the retina at this wavelength (555 nm) has passed through th e apertures of foveal cones. The average power spectra of our retinal images show that it is possible to recover spatial frequencies as high as 150 c/deg in eyes with normal optical quality, a conclusion that w as confirmed with estimates of the optical quality of these eyes obtai ned with a Hartmann-Shack wavefront sensor. These results emphasize th e superiority of the eye's optics over the spatial sampling limits of the retina when the eye's optical quality is optimized. They also show that it would be possible to routinely resolve retinal structures as small as photoreceptors in the normal living eye if its aberrations co uld be corrected.