Glaucoma Basics

Glaucoma is a serious disease of the eye, in which intraocular pressure -- inside the eye -- is elevated and may damage the optic nerve, which connects the retina to the brain. This may lead to loss of peripheral vision and, if untreated, total blindness.

Nearly 67 million people worldwide have glaucoma, according to the Glaucoma Research Foundation. Even in developed countries, half of those who have it don't know it. Glaucoma is the second leading cause of vision loss in the world and is a leading cause of blindness in African Americans. Effective treatment of glaucoma depends on early detection. Most cases are detected during routine eye exams.

The exact cause of glaucoma is not known, but it is related to the production and removal of the fluid in the eye which is known as the aqueous humor. This is a transparent fluid that provides nutrition to the lens and cornea and transmits light rays to the retina at the back of the eye. Aqueous humor leaves the eye through a sieve-like tissue called the trabecular meshwork, and glaucoma is believed to be caused by changes in the meshwork that prevent aqueous humor from leaving the eye. The result is increased pressure within the eye. There may be no symptoms initially and there is no cure, although not all people with increased intraocular pressure have glaucoma.

Family history of the disease is a risk factor for glaucoma. African-Americans, diabetics and people with high blood pressure are also at increased risk. According to the Glaucoma Research Foundation, the disease is 6-8 times more likely to occur in blacks.

At-risk individuals may wish to have an annual eye exam after the age of 40. Diagnosing glaucoma before vision loss occurs will facilitate treatment. Because the optic system in humans has built-in redundancy of functions, it is possible to lose optic nerve tissue before losing sight.

Open-angle glaucoma is the most common form of the disease, affecting 3 million Americans. One percent of all Americans have the disease, according to the Glaucoma Foundation, and it occurs mainly in people over 50.

Normal (or low) tension glaucoma is characterized by progressive optic nerve damage and visual field loss even though intraocular pressure is normal.

Angle-closure glaucoma affects nearly half a million Americans and tends to be inherited. It is most common in people of Asian descent and people who are farsighted.

Acute angle-closure glaucoma occurs when pressure inside the eye increases suddenly, sometimes within hours, and is very painful. Eye sight can be permanently destroyed if untreated. These sudden, acute attacks often occur in a darkened room, such as a movie theater, or in other situations when the pupil is dilated. Stress and some drugs will cause the pupil to dilate, too. Sometimes a series of more minor attacks may occur.

Pigmentary glaucoma is largely inherited and is more frequent in men. It usually begins in the 20s or 30s and is more common among nearsighted individuals.

Exfoliation syndrome is most common among people of European heritage and occurs when material is deposited on the lens and iris and clogs the trabecular meshwork. According to the Glaucoma Foundation, exfoliation syndrome patients are six times more likely to develop glaucoma.

Finally, trauma-related glaucoma may occur from a chemical burn, a blow to the eye or a penetrating injury that causes a change in the eye's drainage system.

  Also see Dr. Robinson's HealthLink article on Diagnosis and Treatment of Glaucoma.

James C. Robinson, MD
Associate Professor of Ophthalmology
Medical College of Wisconsin
Froedtert & Medical College Eye Institute

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.