Contributor: Gordon K. Klintworth
Central retinal artery occlusion is an important occlusovascular disease of the retinal circulation. It has many causes including atherosclerosis, giant cell arteritis, retinal embolism [embolism - retina] and various types of arteritis. Emboli causing central retinal artery occlusion often lodge in the optic nerve within the central retinal artery in the lamina cribrosa. The lumen of the central retinal artery may become totally or partially occluded by an arteriosclerotic plaque usually at the lamina cribrosa. Atherosclerosis within the central retinal artery may extend into the main branches of the central retinal artery near the optic nerve head, and even into more distant branches. An acute central retinal artery occlusion may be precipitated by hemorrhage beneath an atheromatous plaque. When the central retinal artery becomes occluded the inner retina becomes ischemic and pale and the resultant retinal ischemia eventually causes atrophy of the inner retinal layers. With the loss of retinal ganglion cells the axons of the retinal ganglion cells degenerate, the nerve fiber layer of the retina becomes atrophic and the optic nerve undergoes degenerative changes leading to optic atrophy. Many cases of central retinal artery occlusion result from an embolus. Sources of retinal emboli include air [embolism - air]. Air emboli may be identified within the retinal blood vessels even when they are too small to cause significant ishemia. Neurons of the retina are extremely susceptible to hypoxia and coagulative necrosis of the inner retinal layers often follows acute central retinal artery occlusion. Intracellular edema causes retinal pallor in the acute stages of the retinal ischemia and this is especially prominent in the macula. Emboli causing central retinal artery occlusion often lodge in the optic nerve within the central retinal artery in the lamina cribrosa. The lumen of the central retinal artery may become totally or partially occluded by an atherosclerotic plaque usually at the lamina cribrosa. Emboli of the central retinal artery most often originate from fragmentation of atheromatous plaques of the larger arteries, with formation of calcific or platelet-fibrin emboli. Unusual emboli to the central retinal artery are portions of intravascular neoplasms that have broken lose. This includes a cardiac myxoma [myxoma - heart] in the atrium or ventricle, which may be a manifestation of Carney syndrome.