Light sensitive layer of the eye. In vertebrates, looking from outside, there are four major cell layers: (i) the outer neural retina, which contains neurones (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.

This entry appears with permission from the Dictionary of Cell and Molecular Biology

(11 Mar 2008)