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 vein occlusions typically occur in older patients with a history of high blood pressure and atherosclerosis. Other causes of retinal vein occlusion include vasculitis, clotting disorders, and medications such as oral contraceptive pills.
There are two types of retinal vascular occlusion. The type depends on which blood vessel is affected: Retinal artery occlusion . Retinal artery occlusion is a blockage of one of the retinal arteries, which are blood vessels that carry oxygenated blood from the heart to your retina.