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 detachment usually happens because there's a tear (hole) in the retina. The most common cause of a tear is posterior vitreous detachment (PVD). Vitreous gel fluid flows through the tear, pools beneath the retina, and lifts the retina off the back of the eye.Retinal detachment can also happen without a retinal tear. Scar tissue buildup in the eye may pull on the retina. This is called traction.he most common cause of a tear is posterior vitreous detachment (PVD). Vitreous gel fluid flows through the tear, pools beneath the retina, and lifts the retina off the back of the eye. Retinal detachment can also happen without a retinal tear. Scar tissue buildup in the eye may pull on the retina.