The retina is the layer of tissue in the back of the eye that receives visual information from the world and helps transmit it to the brain. Arteries and veins supply the retina; disruption of this blood flow can cause the retina or optic nerve in the eye to be cut off from essential nutrients and oxygen, resulting in loss of vision. The severity of vision loss depends on the location and type of these blockages. When this happens, it's important to have both an eye exam as well as a visit with your primary care physician to evaluate for high blood pressure, carotid artery disease, or other cardiovascular problems that may be responsible for the blockage. Retinal vascular occlusions can be broken down into two major categories: artery occlusions or vein occlusions.