The incidence of primary open angle glaucoma in patients with central retinal vein occlusion is reported to be between 5.7 and 66%, while that of primary angle closure glaucoma is from 0 to 9%. (Corrected for the relative incidence of these two types of glaucoma in the general population, these rates are comparable). There appears to be a causal relationship between elevated intraocular pressure and central retinal vein occlusion, which does not correlate with the height to which the pressure is elevated. Other etiologic factors may be important, particularly arteriosclerosis. The association between elevated pressure and branch vein occlusion is less clear. Central vein occlusions occur in 3.5 to 5% of patients with primary open angle glaucoma. Similarly, central vein occlusions occur in approximately 3% of patients with ocular hypertension. It is recommended that ocular hypertensive patients over the age of 65 be treated to lower their pressure below 25 mm Hg.