Glaucoma

What is glaucoma?

Glaucoma is a disease of the optic nerve — the part of the eye that carries the images we see to the brain. The optic nerve is made up of many nerve fibers, like an electric cable containing numerous wires. When damage to the optic nerve fibers occurs, blind spots develop. These blind spots are usually not apparent to the person until the optic nerve is significantly damaged. If the entire nerve is destroyed, blindness results.

Early detection and treatment by your ophthalmologist (Eye M.D.) are the keys to preventing optic nerve damage and blindness from glaucoma.

Glaucoma is a leading cause of blindness in the United States, especially for older people. But loss of sight from glaucoma can often be prevented with early treatment.

What causes glaucoma?

A clear liquid called aqueous humor circulates inside the front portion of the eye. To maintain a healthy level of pressure within the eye, a small amount of this fluid is produced constantly while an equal amount flows out of the eye through a microscopic drainage system (fig. a). (This liquid is not part of the tears on the outer surface of the eye.)

Because the eye is a closed structure, if the drainage area for the aqueous humor — called the drainage angle — is blocked, the excess fluid cannot flow out of the eye (fig. b). A build up of fluid within the eye causes the eye pressure to increase, damaging the optic nerve.

What are the different types of glaucoma?

Primary open-angle glaucoma: This is the most common form of glaucoma in the United States. The risk of developing primary open-angle glaucoma increases with age. The drainage angle of the eye becomes less efficient over time, and pressure within the eye gradually increases, which can damage the optic nerve. In some patients, optic nerve damage occurs at "normal" eye pressure. Treatment is designed to lower the eye pressure.

Typically, open-angle glaucoma has no symptoms in its early stages and vision remains normal. As the optic nerve becomes more damaged, blank spots begin to appear in the field of vision. You typically won't notice these blank spots in your day-to-day activities until the optic nerve is significantly damaged and these spots become large. If all the optic nerve fibers die, blindness results.

Closed-angle glaucoma: Some eyes are formed with the iris (the colored part of the eye) too close to the drainage angle. In these eyes, which are often small and farsighted, the iris blocks the aqueous humor's access to the drainage angle, resulting in elevated eye pressure.

Symptoms of angle closure may include:

• blurred vision;
• severe eye pain;
• headache;
• rainbow-colored halos around lightsl
• nausea and vomiting

This is a true eye emergency. If you have any of these symptoms, call your ophthalmologist immediately. Unless this type of glaucoma is treated quickly, blindness can result.

Unfortunately, two-thirds of those with closed-angle glaucoma develop it slowly without any symptoms prior to an attack.

Who is at risk for glaucoma?

Your ophthalmologist considers different factors in determining your risk for developing glaucoma.

The most important risk factors include:

• elderly;
• elevated eye pressure;
• amily history of glaucoma;
• African or Spanish-American ancestry;
• farsightedness or nearsightedness;
• past eye injuries;
• thinner central corneal thickness;
• systemic health problems, including diabetes, migraine headaches, and poor circulation.

Your ophthalmologist will weigh all of these factors before deciding whether you need treatment for glaucoma, or whether you should be monitored closely as a glaucoma suspect. This means your risk of developing glaucoma is higher than normal, and you need to have regular examinations to detect the early signs of damage to the optic nerve.

How is glaucoma detected?

Regular eye examinations by your ophthalmologist are the best way to detect glaucoma. A glaucoma screening that checks only the pressure of the eye is not sufficient to determine if you have glaucoma. The only sure way to detect glaucoma is to have a complete eye examination.

During your glaucoma evaluation, your ophthalmologist may:

• measure your intraocular pressure (tonometry);
• inspect the drainage angle of your eye (gonioscopy);
• evaluate whether or not there is any optic nerve damage (ophthalmoscopy);
• test the peripheral vision of each eye (visual field testing, or perimetry).

Photography of the optic nerve or other computerized imaging may be recommended. Some of these tests may not be necessary for everyone. These tests may need to be repeated on a regular basis to monitor any changes in your condition.

How is glaucoma treated?

As a rule, damage caused by glaucoma cannot be reversed. Eyedrops, laser surgery and surgery in the operating room are used to lower eye pressure to help prevent further optic nerve damage. Treatment of glaucoma requires a partnership between the physician and the patient. The patient may use medications regularly to maintain lower eye pressure and continue follow up visits. The physician must monitor each patient to ensure the pressure is low enough to stabilize the disease.

Medications
Glaucoma is usually controlled with eyedrops taken daily. These medications lower eye pressure, either by decreasing the amount of aqueous fluid produced within the eye or by improving the outflow of aqueous through the drainage angle.

Never change or stop taking your medications without consulting your ophthalmologist. All medications can have side effects or can interact with other medications. Therefore, it is important that you make a list of the medications you regularly take and share this list with each doctor you see.

Laser Surgery
Laser surgery treatments may be recommended for different types of glaucoma.

In open-angle glaucoma, the drain itself is treated. The laser is used to modify the drain (trabeculoplasty) to help control eye pressure.

In closed-angle glaucoma, the laser creates a hole in the iris (iridotomy) to improve the flow of aqueous fluid to the drain.

What is your part in treatment?

Treatment for glaucoma requires teamwork between you and your doctor. Your ophthalmologist can prescribe treatment for glaucoma, but only you can make sure that you follow your doctor's instructions and take your eyedrops. Once you are taking medications for glaucoma, your ophthalmologist will want to see you more frequently. Typically, you can expect to visit your ophthalmologist every three to four months. This will vary depending on your treatment needs.

Loss of vision can be prevented

Regular medical eye exams may help prevent unnecessary vision loss. Recommended intervals for eye exams are:

Age 20-29: Individuals of African descent or with a family history of glaucoma should have an eye examination every three to five years. Others should have an eye exam at least once during this period.

Age 30 -39: Individuals of African descent or with a family history of glaucoma should have an eye examination every two to four years. Others should have an eye exam at least twice during this period.

Age 40-64: Every two to four years.

Age 65 or older: Every one to two years.

July 2003

© Copyright 2003 American Academy of Ophthalmology ®