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retina

light sensitive layer of the eye. In vertebrates, looking from outside, there are four major cell layers: (i) the outer neural retina, which contains neurons (ganglion cells, amacrine cells, bipolar cells) as well as blood vessels, (ii) the photoreceptor layer, a single layer of rods and cones, (iii) the pigmented retinal epithelium (PRE or RPE), (iv) the choroid, composed of connective tissue, fibroblasts and including a well vascularised layer, the chorio capillaris, underlying the basal lamina of the PRE. Behind the choroid is the sclera, a thick organ capsule.

In molluscs (especially cephalopods such as the squid) the retina has the light sensitive cells as the outer layer with the neural and supporting tissues below.

See: retinal rods, retinal cones, rhodopsin. The light-sensitive membrane covering the back wall of the eyeball; it is continuous with the optic nerve.The interior lining of the vertebrate eye that contains photoreceptors cells (sensitive to light) in the form of 'rods' and 'cones' that can distinguish the various colours in light.