Webster Dictionary(0.00 / 0 votes)Rate this definition: Freebase(0.00 / 0 votes)Rate this definition: Crenulation or Crenulation cleavage is a texture formed in metamorphic rocks such as phyllite, schist and some gneiss by two or more stress directions resulting in superimposed foliations.
Retinal artery occlusion. Retinal artery occlusion is a blockage in one of the small arteries that carry blood to the retina. The retina is a layer of tissue in the back of the eye that is able to sense light. Causes. Retinal arteries may become blocked when a blood clot or fat deposits get stuck in the arteries.
Several factors combine to bring on an occlusion. The usual situation is that the blood flow in a retinal vein is slowed down and a clot forms. The clot prevents blood from flowing freely. The blood is back logged and spills into the retina. The most common reason for slowed venous blood flow is a hardened artery (arteriosclerosis).