IOVS 26(3), 11 (Abs.).

Perceptual consequences of the slightly nonregular arrangement of the photoreceptors in the fovea have recently been demonstrated by interferometric techniques (1). Gratings with spatial frequencies higher than the nominal Nyquist frequency of the foveal sampling array generate the perception of low frequency noise having the appearance of "zebra stripes." Noise in the photoreceptor pattern may also limit spatial position resolution in some hyperacuity situations. We have developed an algorithm for packing disks of varying size which can be used to generate model foveal sampling arrays. Each new disk is placed in contact with two that are already in place. The deviations from a perfect hexagonal array are assumed to result only from the varying sizes of the disks. The key parameter of the model is the coefficient of variation of the disk diameter. Measurements from photomicrographs of monkey foveas suggest that this parameter should have a value of 0.1.(2) Simulated foveal arrays using this value have spatial and spectral characteristics which are qualitatively and quantitatively like those of actual foveal arrays.

1. Williams, D'Zmura, and Lennie, ARVO Abs., 313 (1984).
2. Hirsh and Hylton, Vision Res. 24, 347 (1984).

Work supported by NASA Consortium Agreement NCA-OR345-301 with the Univ. of Calif., Irvine.