Neurophysiology Practice Test 2026 – Complete Guide on Cell Types and Signals

The nutrient supply to the retina comes from a vascular layer called the choroid, which lies between the sclera and the neural retina. The choroid contains a dense network of blood vessels, especially the choriocapillaris, that deliver oxygen and nutrients to the outer retina and the retinal pigment epithelium. The neural retina itself relies on its inner retinal circulation for some blood supply, but the outer retina depends primarily on the choroid. The sclera is the tough outer coat and isn’t a source of nutrients for the retina, and the lens is avascular and nourished by the surrounding fluids rather than providing nutrients to the retina. So the layer that supplies nutrients and is not part of the neural retina is the choroid.