Abstract
We previously identified a deuteranope with a genetic defect believed to cause degeneration of all M-cone photoreceptors after foveal development is complete. Retinal photographs of the cone mosaic made with adaptive optics revealed lacunae, equal in size to one or more cones, which likely represent the loci of the missing cone class. Here we used adaptive optics to test whether this patient has corresponding microscotomas. Frequency-of-seeing curves were measured with 550 nm disks subtending either 0.75 or 7.5 arc minutes, flashed for 45 msec. Stimuli were randomly presented at any of 8 equally spaced loci 0.5 deg from fixation. A high data acquisition rate was achieved by randomly presenting 0 to 4 flashes per trial. By correcting for the eye's aberrations, adaptive optics produced retinal images of the small spot that were small enough to be largely confined within the typical cone diameter at this eccentricity. The patient's frequency-of-seeing for the small spots approached an asymptote of 74% detection, compared with 91% for control subjects, which is consistent with the fact that the gaps occupy 29% of the patient's cone mosaic. The differences in sensitivity, asymptote and slope between the patient and the controls for both the 0.75 arc minute spot and the 7.5 minute spot are accounted for by a model of detection incorporating the eye's corrected PSF, mosaic images, and eye movements. These results suggest that the gaps in the retinal images correspond to blind areas in the visual field.
Supported by NIH grants EY04367, EY01319 and EY14749. This work has been supported in part by the National Science Foundation Science and Technology Center for Adaptive Optics, managed by the University of California at Santa Cruz under co-operative agreement No. AST-9876783.