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.
Retinal vein occlusion occurs when one of the tiny retinal veins becomes blocked by a blood clot. This means that blood cannot drain away from the retina as easily and there is a backlog of blood in the blood vessels of the retina.This can lead to a build-up of pressure in the blood vessels.etinal vein occlusion occurs when one of the tiny retinal veins becomes blocked by a blood clot. This means that blood cannot drain away from the retina as easily and there is a backlog of blood in the blood vessels of the retina.