An occlusion is a blockage that occurs in a blood vessel as a result of debris in the bloodstream, inflammation, or high blood pressure. Within the arteries of the retina, occlusions most often occur due to clots that dislodge from another vessel in the body and flow into a smaller artery of the retina. 

A cilioretinal artery occlusion causes cells of the macula to be deprived of oxygen and nutrients, and immediate and drastic central vision loss occurs. Any kind of arterial occlusion (or resulting sudden vision loss) should be regarded as an emergency, as only prompt removal of the blockage will restore vision. 

Cilioretinal arteries are small arteries arising from the ophthalmic arterial circulation that give additional blood supply to the macular area. Only 14% of people have this type of artery, so a cilioretinal artery occlusion is very rare. 

If an arterial occlusion is not found and removed quickly, vision loss will be permanent. There are, however, ways to lessen the chance that a future occlusion will occur. Most people who have an occlusion in an artery of the retina have high blood pressure, high cholesterol, diabetes, or some form of vessel disease. When proper steps are taken to control blood pressure, cholesterol, and blood sugar, the occurrence of another occlusion is much less likely.