“The retina is the back part of your eye with the cells that respond to light. The cells are known as photo receptors and come in two varieties: rods and cones. Rods are very sensitive to light, shapes and movements and cones are not as sensitive, but they control the perception of color.
Like a digital camera, the retina does basic optical processing like edge detection and enhancement and color separation. It transmits images through the optical nerve and then your brain returns the inverted image to its correct right side up.”
Jennifer Hicks, Forbes, 29 January 2013