Some retinal diseases, such as diabetic retinopathy in its more advanced stages, and retinal vein occlusion, can cause ischemia in large areas of the retina. Retinal ischemia stimulates the growth of abnormal retinal vessels, which can cause severe ocular hemorrhages and, in some cases, certain forms of retinal detachment and glaucoma. In these cases, the ischemic areas are burned with thermal laser using a technique called panretinal laser photocoagulation.