Retina

About the Retina

The retina is the light sensitive tissue lining the back of the eye, approximately 0.5 mm thick. It has ten layers. Photoreceptors are in the outermost layer, farthest from light. Rods approximately 120 million provide night and peripheral vision, achromatic. Cones approximately 6 million provide color and detailed central vision, concentrated in the fovea. Light passes through the retina to reach photoreceptors, activating opsins rhodopsin in rods, photopsins in cones, triggering phototransduction cascade that hyperpolarizes the cell. The fovea centralis is the area of sharpest vision, containing only cones and no blood vessels. The macula lutea surrounds the fovea, containing lutein and zeaxanthin. The optic disc is the blind spot, where optic nerve exits. The central retinal artery and vein supply the retina. Diabetic retinopathy is a leading cause of blindness. Age related macular degeneration AMD destroys central vision. Retinal detachment is a surgical emergency.