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.
Retina Hole. You are probably wondering what is that and so was my husband. There are several different types of retinal tears caused by a PVD. An operculated hole is one of them. These holes are commonly caused by the vitreous pulling on the retina where the fibers are strongly attached and often occur with a PVD.