glaucoma

n. A disorder usually characterized by a buildup of pressure in the fluid (aqueous humor) inside the eye, which kills ganglion cells in the retinal nerve, causing loss of vision, and can cause total blindness if untreated. It is often caused by a blockage of the trabecular meshwork or Schlemm's canal, which carry fluid away from the eye into the circulatory system. It may also be caused by lessened blood flow to the retinal nerve ganglia. Glaucoma sometimes occurs in the absence of elevated interocular pressure, and its cause is not well understood. In acute glaucoma the blockage is caused by the pupil's dilating in a way which causes the iris to fold against the cornea and block the exit of the aqueous humor. This can cause blindness in a few days if not treated with eye drops which cause the pupil to constrict.