Vision - Retinal Eccentricity

The area of the retina on which light is focused influences visual acuity, which is sharpest when the object is projected directly onto the central fovea—a tiny indentation at the back of the retina comprised entirely of cones. Acuity decreases rapidly toward the retina's periphery. It was initially believed this was because cones decrease in number moving out from the retina, disappearing altogether at the retina's periphery where only rods exist. However, recent studies indicate it may result from the decreasing density of ganglion cells toward the retina's periphery.