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 artery occlusion. Retinal artery occlusion is a blockage in one of the small arteries that carry blood to the retina. The retina is a layer of tissue in the back of the eye that is able to sense light. Causes. Retinal arteries may become blocked when a blood clot or fat deposits get stuck in the arteries.
Causes of retinal detachment are: 1  Tears or holes in the retina. 2  These may lead to retinal detachment by allowing fluid from the middle of the eye (vitreous gel) to collect under the retina. 3  A common cause of retinal tears is posterior vitreous detachment (PVD).