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.
Retinal vessel occlusion. A retinal vessel occlusion is a blockage in the blood vessels of your eye that can cause sight loss. There are two types of retinal blood vessels, arteries and veins, and either of these can be affected by an occlusion. This information describes these two different types of vessel occlusion and their affect on vision.