High eye pressure, as occurs in individuals with untreated open-angle glaucoma, can predispose to this by tending to collapse the blood vessel from the outside. When the blood vessels to the eye are partially or completely blocked, the surrounding structures in the eye are starved for nourishment and oxygen. In response to this, they make certain chemicals which lead to the formation of new blood vessels, a process known as neovascularization. Most often this occurs first in the back of the eye on the retina. As these new blood vessels grow, the iris is pulled against and becomes adherent to the trabecular meshwork, permanently blocking the drainage path.
Treatment is directed toward two goals.
First, eye pressure needs to be lowered immediately to prevent it from further damaging the optic nerve. Initially, this is done through use of medications that reduce the amount of aqueous humor which flows into the eye. Eye drops, particularly beta-blocking agents, and a pill, such as acetazolamide, are most effective in this regard. Second, it is necessary to treat the eye and eliminate the neovascularization. This is particularly important if the glaucoma is recognized early so that the drain is not completely blocked.