The fluid accumulates within the eye and causes the eye pressure to increase. If this happens over a short period of time, the patient may have sudden pain. If the blockage of the drain occurs more slowly, there may only be redness with some discomfort. In both situations, the eye pressure needs to be lowered if vision is to be saved. Neovascular glaucoma occurs in individuals in whom there is poor blood flow to the eye.
Blood provides much of the eye with nourishment, including oxygen, and removes wastes from it.
In addition, the clear aqueous humor, which nourishes some of the inner portions of the eye, can only be properly formed if there is an adequate blood supply. Blood flow in individuals with diabetes often is reduced in many parts of the body, including the eyes, particularly when the diabetes has been present for more than ten years. In other individuals, there may be a sudden blockage of an important blood vessel within the eye by a blood clot or other change. This tends to happen most often when there is high blood pressure in the body. 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.