Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Glaucoma

What Is It?

Glaucoma is a common eye condition in which vision is lost because of damage to the optic nerve. The optic nerve carries information about vision from the eye to the brain. In most cases, the optic nerve is damaged when the pressure of fluid inside the front part of the eye rises. However, glaucoma-related eye damage can occur even when the fluid pressure is normal.

In the most common form of glaucoma, called primary open angle glaucoma, fluid circulates freely in the eye and the pressure tends to rise slowly over time. Gradual loss of vision is usually the only symptom. A less common form of the disease, called acute or angle closure glaucoma, develops suddenly and usually causes eye pain and redness. In this form of glaucoma, pressures rise quickly because normal fluid flow within the eye becomes blocked. This happens when a structure called the angle (where the iris and cornea meet) closes. Experts are uncertain why either form of glaucoma damages the optic nerve. In addition to open angle and angle closure glaucoma, there are rarer forms of the illness. They may be related to eye defects that develop before birth (congenital glaucoma) or to eye injuries, eye tumors or medical problems such as diabetes. In some cases, medications, such as corticosteroids, also can trigger glaucoma.

Glaucoma is the second leading cause of blindness in the United States, and the leading cause of blindness in African-Americans. It currently affects as many as 2.5 million Americans, but up to half of people with glaucoma don't know that they have the condition. Glaucoma tends to run in families and is five times more common in African-Americans than in Caucasians. The risk of glaucoma also increases with age in people of all ethnic backgrounds.