Glaucoma

Definition

Glaucoma refers to a group of disorders that lead to damage to the optic nerve, the nerve that carries visual information from the eye to the brain.

Alternative Names

Causes

Glaucoma is the second most common cause of blindness in the US. There are four major types of glaucoma:

• Angle-closure (acute) glaucoma
• Congenital glaucoma
• Open-angle (chronic) glaucoma
• Secondary glaucoma

All four types of glaucoma are characterized by increased pressure within the eyeball, and therefore all can cause progressive damage to the optic nerve. Open-angle (chronic) glaucoma is by far the most common type of glaucoma.

The front part of the eye is filled with a clear fluid called the aqueous humor. This fluid is constantly made in the back of the eye. It leaves the eye through channels in the front (anterior) chamber of the eye, and eventually drains into the bloodstream. The channels that drain the aqueous humor are in an area called the anterior chamber angle, or simply the angle.

Angle-closure (acute) glaucoma is caused by a shift in the position of the iris of the eye that suddenly blocks the exit of the aqueous humor fluid. This causes a quick, severe, and painful rise in the pressure within the eye (intraocular pressure). Angle-closure glaucoma is an emergency. This is very different from open-angle glaucoma, which painlessly and slowly damages vision.

If you have had acute glaucoma in one eye, you are at risk for an attack in the second eye, and your doctor is likely to recommend preventive treatment.

Dilating eye drops and certain systemic medications may trigger an acute glaucoma attack if you are at risk.

Congenital glaucoma often runs in families (hereditary). It is present at birth, and is the result of the abnormal development of the fluid outflow channels in the eye.

In open-angle glaucoma, the cause is essentially unknown. An increase in eye pressure pushes on the junction of the optic nerve and the retina at the back of the eye, reducing the blood supply to the optic nerve.

Open-angle glaucoma tends to run in families. Your risk is higher if you have a parent or grandparent with open-angle glaucoma. People of African descent are at particularly high risk for this disease.

Secondary glaucoma is caused by:

• Drugs such as corticosteroids
• Eye diseases such as uveitis
• Systemic diseases