Blood vessels in the fundus affected by hypertension (high blood pressure) are narrow and appear quite bright. Rapid-onset or severe hypertension, which can cause strokes, may first be diagnosed when a patient seeks an eye exam for blurred vision caused by the disorder. Arteriosclerosis (hardening of the arteries) is a normal process of aging and poses no danger to vision. Central retinal artery occlusion and central retinal vein occlusion can cause sudden loss of vision in the affected eye when the blood supply to the retina is obstructed for longer than two hours, or if hemorrhaging occurs within the retina. Vision is then severely limited to light only and damage is virtually irreversible. Causes include hypertension, diabetes mellitus, narrowing of a carotid artery (the primary arteries supplying blood to the head), and blood disorders such as anemia, leukemia, and sickle-cell anemia.
Science EncyclopediaScience & Philosophy: Verbena Family (Verbenaceae) - Tropical Hardwoods In The Verbena Family to WelfarismVision Disorders - Refractive Errors, Hyperopia/presbyopia, Other Refractive Errors, Strabismus, Nonparalytic Strabismus, Paralytic Strabismus - Myopia, Astigmatism, Glaucoma, Secondary glaucomas, Degeneration of the macula, Retinal dystrophies