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What Is It?

More than 2 million adult Americans suffer from glaucoma, making it one of the leading causes of blindness. It usually appears in middle age and seems to have a genetic component: one out of five sufferers has a close relative with the condition.

It is a common misconception that the eyeball is a closed tank of fluid. On the contrary, the inside of the eye continuously produces and drains a water-based fluid called aqueous humor. As new fluid is produced by cells inside the eye, excess fluid normally drains out through a drainage passageway called the trabecular meshwork. An imbalance between the production and drainage rates of aqueous humor leads to a build up of pressure on retina, located at the back of the eye. Persistent high pressure on the delicate nerve fibers along the innermost layer of the retina results in permanent vision loss.

Glaucoma has long been called "The Thief of Sight" because there can be significant damage to the eye before the problem is identified. Glaucoma damage is irreversible. At first, the outer areas of the visual field (peripheral vision) are lost. Untreated glaucoma may eventually lead to blindness.

Types of Glaucoma

There are several types of glaucoma - all of which share a common outcome: irreversible damage to delicate retinal nerve fibers. These fibers transmit visual images from the eye to the brain and there are over 1 million fibers in each healthy eye. These nerve fibers collectively form the optic nerve. The most common type of glaucoma is called chronic open-angle glaucoma, accounting for about 90% of cases. The precise cause of this type of glaucoma is not well understood. In chronic open angle glaucoma, vision loss occurs very gradually and much of the person's eyesight can be affected before he or she notices a change. Both eyes may be affected at the same time, but one eye is often worse than the other.

Acute closed-angle glaucoma is less common. Sudden blurred vision with pain and redness may occur, usually in one eye first. In closed-angle glaucoma, the flow of aqueous is blocked and can't move between the chambers of the eye, causing a sudden rise in the intraocular pressure. Just like in open-angle glaucoma, the high pressure permanently damages retinal nerve fibers. Acute closed-angle glaucoma is a medical emergency and needs immediate medical care to restore normal aqueous outflow, reduce pressure and prevent permanent damage to the eye.

Congenital glaucoma is rare. It is present in some infants at birth or within the first few years of life. Infants with glaucoma usually have cloudy eyes that are sensitive to light and have excessive tearing. Severe vision loss and even blindness may occur if the problem is not diagnosed and treated early. When a similar type of glaucoma occurs between age 3 and adulthood, it is called juvenile glaucoma.

Secondary glaucoma is a broad category of glaucoma problems usually associated with another eye disease or disorder, such as a very mature cataract, uveitis (inflammation inside the eye), bleeding, eye tumor, or an eye injury. People with diabetes can develop abnormal blood vessels inside the eye, making them susceptible to neovascular glaucoma, a particularly severe form of the disease.