Discuss the structure of the retina, including any distinguishing "spots."

The retina consists of layers of cells, with the posterior layer containing the photoreceptors (rods and cones). Photoreceptors synapse onto bipolar cells, which in turn synapse onto an anterior layer of retinal ganglion cells, whose axons comprise the optic nerve. Also present are horizontal cells, which synapse with photoreceptors and bipolar cells, and amacrine cells, which synapse with bipolar and ganglion cells. Cones are sensitive to color and are most concentrated in a spot called the fovea. Another spot is the optic disk or blind spot, where the axons of all ganglion cells merge into the optic nerve, and where there are no photoreceptors.