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.
Causes of retinal migraine. Retinal migraine is caused by the blood vessels to the eye suddenly narrowing (constricting), reducing the bloodflow to the eye. Afterwards the blood vessels relax, bloodflow resumes and sight returns. Usually there are no abnormalities within the eye and permanent damage to the eye is rare.