Local density of human midget retinal ganglion cell receptive fields
63.423, Wednesday, 21-May, 8:30 am - 12:30 pm, Banyan Breezeway
Andrew Watson1; 1NASA Ames Research Center
The midget retinal ganglion cells of the human retina are thought to underly spatial pattern vision, and as such the spacing of their receptive fields imposes a fundamental limit on human visual spatial resolution. This spacing varies across the retina and increases rapidly with distance from the fovea. Modeling visual processing of extended or peripheral targets requires a quantitative description of this spacing across the visual field. Curcio and colleagues have provided estimates of the local density of cones (Curcio, Sloan, Kalina & Hendrickson 1990) and retinal ganglion cells (Curcio and Allen, 1990), as well as estimates of centrifugal displacements of foveal ganglion cells from their receptive fields (Drasdo, Millican, Katholi & Curcio, 2007), all in the same set of human retinas. In addition, Drasdo and Fowler (1974) have provided a model human eye that allows nonlinear mapping from anatomical coordinates in mm to visual field coordinates in degrees. We have combined these results (and a few plausible assumptions), to produce a new formula for midget retinal ganglion cell spacing as a function of position in the monocular or binocular visual field. The new formula does not depend on psychophysical results, extends to the full range of eccentricities, and is not confined to the four principal meridians. It is consistent with recent estimates of letter acuity for five observers viewing targets under adaptive optics conditions (Rossi and Roorda, 2010).