Occlusion of the central retinal artery. Fundoscopy image of the retina of the left eye of a patient with central retinal artery occlusion (CRAO). The retina is the light-sensitive layer at the back of the eye. In this patient, a variation in the blood vessel architecture includes what is known as the cilio-retinal artery. When this artery is present, the central vision will be preserved even in cases of CRAO. CRAO is where the flow of blood through the central retinal artery is blocked (occluded). A common cause is carotid artery atherosclerosis. If not treated, CRAO can lead to blindness.