The retina can be damaged by diseases affecting the blood supply. Both arteries and veins supplying the retina may become clogged or obstructed, analagous to a stroke in the brain. This can lead to blindness by robing the retina of oxygen and nutrients. Changes in the blood vessels can be seen with diabetes, hypertension and atherosclerosis. By examining the retina we can often diagnose these diseases. Common blinding diseases involving the blood vessels are retinal artery occlusions "above" and retinal vein occlusions "right".