Glaucoma is an eye disorder in which an intraocular pressure that is too high for the health of the eye causes the optic disc to become cupped and atrophic and the visual field to develop characteristic nerve fiber bundle defects. The disease develops in two separate but related pathogenic stages. First, the drainage of aqueous humor from the eye becomes impaired, which causes the intraocular pressure to rise. Second, the high intraocular pressure, aided by other less well identified pathogenic factors, damages the optic nerve and produces the cupping and loss of visual field.