means The light-sensitive layer of tissue lining the back of the eye, where incoming images are converted into nerve signals sent to the brain.

from From Medieval Latin retina, almost certainly built on Latin rete, meaning 'net' — the early anatomists who named it saw a fine, net-like web of tiny blood vessels spread across the eye's inner surface. So the screen at the back of your sight is, etymologically, a net cast for the light.