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Glaucoma

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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. Damage to the optic nerve causes vision loss, which may progress to blindness. Most people with glaucoma have increased fluid pressure in the eye, a condition known as increased intraocular pressure.

Alternative Names:
Open angle glaucoma; Chronic glaucoma; Closed angle glaucoma; Congenital glaucoma

Causes, incidence, and risk factors:

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

• Open angle (chronic) glaucoma
• Angle closure (acute) glaucoma
• Congenital 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 anterior (front) 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.

In open angle glaucoma, the channels in the angle gradually narrow with time, making it hard for the fluid to drain properly. The buildup of fluid causes increased pressure in the eye. This increased 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.