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.
In proliferative retinopathy, new, structurally unstable blood vessels grow on the surface of the retina. These unstable blood vessels cause frequent minor bleeding. The bleeding causes local irritation and scarring.Proliferative retinopathy can cause retinal detachment. This is a separation of the layers of the retina. It is one of the most serious consequences of proliferative retinopathy.The vitreous is the clear gel between the lens and the retina.