retinae

Retinae are the light-sensitive neural tissues lining the inner back surface of the eye. In vertebrates they form part of the central nervous system and consist of several cellular layers, including photoreceptors (rods and cones), bipolar cells, ganglion cells, and the horizontal and amacrine interneurons. Photoreceptors convert light into electrical signals that are processed by retinal circuits and transmitted to the brain through the optic nerve.

The outer retina contains photoreceptors and the retinal pigment epithelium, which supports photoreceptor function and the visual cycle. The inner retina contains the neural layers that relay and refine visual information via bipolar, amacrine, and ganglion cells. The macula, with the fovea centralis at its center in humans, provides high-acuity, color vision. The optic disc is the point where ganglion cell axons exit the eye to form the optic nerve and lacks photoreceptors, creating the natural blind spot. The retina receives blood supply from the central retinal artery and vein for the inner layers, while the outer retina near the pigment epithelium is nourished by the choroidal circulation.

Developmentally, retinae arise from the neural ectoderm as an outgrowth of the optic vesicle and organize into a layered neural tissue with synaptic circuits. The retina transduces light into neural signals that are mapped in the brain’s visual cortex for perception.

Common retinal disorders include retinitis pigmentosa (progressive photoreceptor degeneration), age-related macular degeneration (macular damage affecting central vision), diabetic retinopathy (microvascular changes), and retinal detachment. Treatments vary by condition and can involve medications, laser therapy, or surgical interventions.