Retina blood vessels, coloured scanning electron micrograph (SEM). The retina is the lightsensitive membrane that lines the back of the eye. Blood vessels (orange, pink) radiate out from the optic disc, which is the area where the optic nerve and blood vessels enter the eye. Due to this, it has no lightsensitive cells and is the cause of the blind spot. This image was created using a resin cast, where resin was injected into the blood vessels and then the surrounding tissues were chemically digested, leaving this structure behind.