The rods and cones are not evenly distributed throughout the retina. In the graph on the left you
see that the density of cone receptors is very high in the center or foveal region (zero degrees) of
the retina. As one moves nasally or temporally away from the fovea the density of cones sharply declines.
Moving toward the periphery of the retina the density of rod receptors first increases (there are no
rods in the fovea (zero degrees) and then decreases in the eccentric part of the retina.Near 15 degrees nasal the receptor density of both the rods and cones is zero. This is the location of the optic disc where the axons of the ganglion cells, which make up the optic nerve, leave the retina and go to the lateral geniculate nucleus(LGN) in the center of the brain. The optic disc is also call the blind spot because if an image falls entirely within it the image is not perceived.
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