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What is chronic glaucoma?

Glaucoma is an eye disease that involves abnormally increased pressure inside the eyeball, a condition called intraocular hypertension. The eye normally produces a clear fluid called aqueous humor that flows continuously through its chambers, providing nutrients and maintaining the round shape of the eyeball. The eye preserves a safe level of internal pressure by draining aqueous humor out through a special pathway. When too much of this fluid enters the eye or too little drains away, intraocular pressure rises.

As the pressure increases, it reduces blood supply to the optic nerve and causes nerve damage. Since the optic nerve relays signals from the eye to the brain, it is vital to sight, and any damage to the nerve leads to vision loss.

There are several different types of glaucoma, but chronic open-angle glaucoma is the most common. It is totally painless and tends to develop slowly. If regular checkups do not detect the increase in intraocular pressure, the disease may be present for years without the person being aware of it because damage begins at the edge of the visual field, affecting only the peripheral vision. If it is allowed to progress, however, the glaucoma can cause increasingly narrowed vision and, eventually, complete blindness.

Although chronic glaucoma can occur at any age, it is rare in children and young adults. The incidence rises after the age of 30, and the condition is most common in those over 60.

What causes chronic glaucoma?

Medical scientists do not fully understand all the causative factors leading to chronic glaucoma. Although the condition sometimes develops as a result of injury or a complication of some other eye disease, it usually strikes people who are in good health. Those

who are myopic (nearsighted) or who have diabetes are at greater risk, and blacks are affected more often than whites. Thus, scientists have concluded that heredity is a predisposing factor.

How is chronic glaucoma diagnosed and treated?

An eye specialist can diagnose glaucoma easily with a simple, painless test called tonometry, which measures eye pressure. Lifelong use of eye drops or a medicated implant that resembles a contact lens is necessary to control the condition.

What can I do myself?
The most important self-treatment entails faithful administration of medication. Also important are getting adequate rest, not smoking, and drinking large volumes of fluids.

When should I see my doctor?
Everyone over age 35 should have a tonometry test every year. Earlier or more frequent checkups may be recommended for people with a family history of glaucoma. Symptoms such as persistent blurring of vision, especially if it occurs in conjunction with other symptoms of glaucoma, require immediate attention.

What will the doctor do?
Most cases of glaucoma can be controlled with special prescription eye drops. Some of these medications slow the production of aqueous humor, while others help open the eye's drainage pathways. Therapy typically begins with the weakest available drug, pilocarpine, and frequent monitoring of intraocular pressure. If this does not achieve adequate control, increasingly stronger drugs will be tried until the glaucoma is brought under control. These drugs include timolol maleate, betaxaolol hydrochloride, epinephrine, dipivefrin, demecarium bromide, and echothiophate iodide.

In some cases, oral medications called carbonic anhydrase inhibitors may be prescribed to supplement the eye drops in an attempt to slow the production of aqueous humor.

If medication fails to control the

disease, or if it is diagnosed at an advanced stage, the patient may need laser treatments (known as trabeculoplasty) or eye surgery to improve drainage of aqueous humor.

The course of chronic glaucoma

Chronic glaucoma usually does not cause symptoms until irreversible eye damage has occurred. Once the optic nerve is damaged, however, it cannot be repaired. Therefore, any vision loss that occurs before the glaucoma is diagnosed and treated can­not be restored.

The speed at which intraocular pressure builds and nerve damage occurs varies significantly from person to person; some people lose their sight within weeks. In chronic glaucoma, however, vision loss usually occurs gradually over a period of years during which the symptoms may be so minimal as to go unnoticed.

Although peripheral vision loss occurs first, failure to control the disease with medication or surgery eventually leads to loss of central vision and blindness.

Glaucoma is rarely unilateral. This means that if both eyes are not affected simultaneously, the disease is likely to develop in the second eye sometime after it is diagnosed in the first.

Is chronic glaucoma dangerous?
Yes. It is the second leading cause of blindness in the United States, exceeded only by complications of diabetes. If chronic glaucoma is diagnosed and treated early, however, loss of vision can usually be prevented.