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.
Ocular causes. 1  Vitreous haemorrhage: may also present as sudden floaters. 2  Central retinal artery occlusion presents with painless, almost instantaneous reduction of vision in one eye. 3  Central retinal vein occlusion frequently presents with loss of vision or blurred vision, often starting on waking.