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 occlusions usually occur because your arteries harden and cause a clot, much like a stroke. Blockages are more common in people with narrowed or damaged blood vessels, or those with chronic conditions that cause them. Such diseases include: atherosclerosis, which is a hardening of the arteries.