Figure 1

Structure of the retina. (a) Schematic organization of retinal circuits. The vertebrate retina consists of six major types of neurons - rod and cone photoreceptors, horizontal, bipolar, amacrine and ganglion cells. The rod and cone photoreceptors are specialized light-sensing neurons, which capture photons and transduce visual signals to the inner retina. The RPE serves as a barrier between the choroidal capillaries and the neural retina and is crucial for photoreceptor survival. Bipolar cells relay signals to the amacrine and ganglion cells through synapses in the inner plexiform layer. Ganglion cell axons project towards the optic nerve head and carry signals to the brain. (b) Ocular fundus photograph of a healthy retina showing retinal blood vessels, optic disc, macula (5 to 6 mm diameter), and fovea (central pit of the macula). Photograph provided by Dr Emily Chew (National Eye Institute, National Institutes of Health, Bethesda, MD).