Spatial order in short-wavelength-sensitive cone photoreceptors: a comparative study of the primate retina

We compared the spatial distribution of short-wavelength-sensitive (SWS or blue) cone photoreceptors in the retinas of eight primate species. The regu larity of the SWS cone array was quantified with a statistic (packing facto r) that varies between a random distribution (0) and a triangular array (1) . We find wide variability among species, with packing factors varying betw een 0.06 and 0.3. The SWS cone array in at least two New World monkey speci es is indistinguishable from a random array. The SWS cone density gradient across the retina was measured in the capuchin monkey Cebus apella. and the squirrel monkey Saimiri sciureus. Both species show a peak density of 5000 -8000 cells/mm(2) at the fovea and a 50-fold central-peripheral density gra dient. In contrast to the wide variation in local regularity, the spatial d ensity and the topography of SWS cones are well preserved across primates. (C) 2000 Optical Society of America [S0740-3232(00)00303-3].