A retinal artery occlusion occurs when the blood flow to the retina is stopped, causing a sudden loss of vision.

The retinal arteries deliver nutrients and oxygen to the eye.  When a retinal artery becomes blocked, that section of the eye can no longer create vision.  Common causes for a retinal artery occlusion include clots or other emboli that travel through the blood from the carotid artery or heart and get stuck in the retinal artery.  Sometimes, inflammation in the retinal vessels causes the blockage.  An artery occlusion will often cause sudden, painless blurry or dim vision.  This diagnosis is taken very seriously as it may preclude a more serious life-threatening condition such as a stroke in the brain or permanent vision loss in both eyes.