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.
The initial hypofluorescence may be due in part to focal ischemic areas, resulting in nonfilling of the choriocapillaris. (From Schatz H et al: Interpretation of Fundus Fluorescein Angiography, CV Mosby, 1978) FIG. 4. Retinal branch vein occlusion.