Glaucoma is a vision-robbing eye disease caused by damage to the optic nerve. This nerve carries information about vision from the eye to the brain. Glaucoma is a lifelong illness, but proper treatment can prevent loss of vision.
Glaucoma often stems from an increase in the pressure of fluid inside the front part of the eye. Sometimes, though, glaucoma-related eye damage occurs even when the pressure is normal.
Glaucoma is a leading cause of blindness in the United States. It currently affects more than 2.5 million Americans. Up to half of people with glaucoma don't know that they have the condition. Glaucoma tends to run in families. It is five times more common in African-Americans than in Caucasians. The risk of glaucoma also increases with age in people of all ethnic backgrounds.
In the most common form of glaucoma, called primary open angle glaucoma, fluid circulates freely in the eye and the pressure tends to rise slowly over time. Gradual loss of vision is usually the only symptom.
A less common form of the disease, called acute or angle closure glaucoma, develops suddenly and usually causes eye pain and redness. In this form of glaucoma, pressures rise quickly because normal fluid flow within the eye becomes blocked. This happens when a structure called the angle (where the iris and cornea meet) closes.
In addition to open angle and angle closure glaucoma, there are rarer forms of the illness. They may be related to eye defects that develop before birth (congenital glaucoma) or to eye injuries, eye tumors or medical problems such as diabetes. In some cases, medications, such as corticosteroids, also can trigger glaucoma.
Although open angle glaucoma and acute glaucoma both cause blindness, their symptoms are very different.
Open angle glaucoma. Vision fades away so painlessly and gradually that most people do not realize they have a problem until substantial damage has occurred. Symptoms include:
- loss of peripheral vision—vision at the edges—usually in both eyes
- tunnel vision—vision that has narrowed so you see only what is directly in front of you, like looking through a railroad tunnel.
If glaucoma is not treated, even this narrowed vision disappears into blindness. Once gone, areas of lost vision cannot be restored.
Acute (closed angle) glaucoma. Symptoms of this type of glaucoma occur suddenly. They include:
- blurred vision
- pain and redness in the eye
- severe headache
- halos around lights at night
- a haziness in the cornea (the clear front portion of the eye in front of the pupil)
- nausea and vomiting
- extreme weakness.
Open angle glaucoma is often detected during a routine eye examination. When looking at the back of the eye (the fundus) using a special telescope, the health care provider may notice changes in the appearance of the optic nerve. If glaucoma is suspected, its presence can be confirmed with one or more tests:
Tonometry measures the pressure inside the eye. This may be done by pressing an instrument against your eyeball, or by blowing a puff of air against your eye. Eye pressure is measured in millimeters of mercury, commonly abbreviated as "mmHg." Normal eye pressure is between 8 mmHg and 22 mmHg. Although high pressure inside the eye is often a sign of glaucoma, not everyone with high pressure will develop glaucoma, and not everyone with glaucoma has high pressure.
Visual-field testing is usually done with an automated machine. You look into the machine and press a button when you see a blinking light. The machine then draws a picture of where you are able to see the blinking lights.
Optical coherence tomography. This technique uses a laser to measure the thickness of the nerve fibers in the retina. Glaucoma causes loss of these nerve fibers.
Angle closure glaucoma usually is diagnosed in a person who has developed a red, swollen eye and difficulties with vision. The eye pressure is usually quite high. Some people may be told by their eye doctor that they are at risk of angle closure glaucoma because their angle looks narrow.
Although glaucoma usually can't be prevented, regular eye exams can identify it in its earliest stages and treatment started to prevent, or limit, vision loss.
In the United States, treatment of open angle glaucoma usually begins with prescription eye drops that lower the pressure inside the eye.
As an alternative to eye drops, laser surgery can ease pressure inside the eye. This procedure is called laser trabeculoplasty. A high-intensity beam of light is aimed at openings in the eye's drainage system. The light widens the openings, letting fluid drain out of the eye more easily.
Some people need conventional eye surgery to lower pressure inside the eye. This is done in an operating room. Intravenous medication is given to help you relax. Numbing medication is applied on and around the eye. The surgeon creates a new opening to improve fluid drainage from the eye.
With both types of glaucoma surgery, eye pressure almost always decreases. But it may not go low enough. Some people need repeat surgery and/or must continue taking glaucoma eye drops.
Acute glaucoma must be recognized and treated within 24 hours to prevent loss of vision. Treatment usually begins with laser treatment to make a new opening in the iris that allows fluid to drain. This often cures the problem, but it sometimes is necessary to use eye drops long-term or to perform additional surgery.