Comparison of human and monkey retinal photoreceptor sampling mosaics

We test the hypothesis that the diameters of foveal and near-foveal rods and cones for one well-studied human photoreceptor mosaic and one well-studied monkey photoreceptor mosaic (Macaca fascicularis) are scaled relative to focal length. We conclude that this hypothesis is not supported. Rather than being scaled proportionally, the sizes of the rods and cones, respectively, are nearly equivalent for both the human and monkey resulting in an effectively finer retinal grain for the larger human eye. Furthermore, the human rod density exceeds the monkey rod density beyond about 1 deg of retinal eccentricity. These results suggest that variation across primate species is reflected in retinal sampling strategies.