Glaucoma is a group of eye disorders that cause blindness by harming the optic nerve, the large nerve that is responsible for vision. In glaucoma, optic nerve damage is related to pressure changes in fluid circulating inside the front portion of the eyeball. In many patients, this damage occurs when the eye's internal fluid pressure is abnormally high, but it can also occur when the internal pressure is measured as "normal."
Fluid circulating inside the front portion of the eye is produced by a structure called the ciliary body, which is located behind the iris (the colored portion of the eye). This fluid circulates through the opening of the pupil, passes into the space between the iris and the cornea, and eventually drains out of the eye through a mesh of tissue called the angle, the site where the cornea and iris meet. In glaucoma, the normal passage of fluid through the angle either is reduced (causing open-angle glaucoma) or suddenly stops (causing acute glaucoma), and fluid pressure inside the eye increases. This increased fluid pressure injures the nerve fibers and the eye's large optic nerve and causes blind spots. It may lead to blindness in advanced cases.
Glaucoma is a leading cause of blindness in the United States. It tends to run in families and currently affects about 3 million Americans. Although the illness is five times more common in African-Americans than in Caucasians after age 40, the risk of glaucoma increases with age for persons of all ethnic backgrounds. Chronic glaucoma, which affects 1 percent to 2 percent of Americans older than 40, is much more common than acute glaucoma.
Although open-angle glaucoma and acute glaucoma both cause blindness, their symptoms and onset are very different.
Open-angle glaucoma - In this form of glaucoma, the loss of vision occurs so gradually it is rarely noticed. However, as eye damage progresses, you may eventually find that you have lost substantial areas of your peripheral vision, especially the field of vision near your nose. As larger areas of your peripheral vision fade, you may develop 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 glaucoma (closed-angle glaucoma) - Symptoms of acute glaucoma occur suddenly and may include blurred vision, halos around lights at night, a haziness in the cornea (the clear front portion of the eye in front of the pupil), pain and redness in the eye, headache, nausea and vomiting, and extreme weakness.
Treatment of open-angle glaucoma usually begins with prescription eyedrops. These medicines lower pressure inside the eyeball, either by causing the eye to produce less fluid or by helping fluid to drain more effectively. As an alternative to medication or when medication fails to control glaucoma, laser surgery can be done. This surgery, also called laser trabeculoplasty, uses a laser to widen the openings in the eye's drainage network. If medication and laser surgery are unsuccessful, conventional eye surgery may be necessary to make a new opening for fluid to leave the eye.
Acute glaucoma must be treated early to prevent loss of vision. Treatment usually begins with laser treatment to make a new opening in the iris that allows the angle to open. This is often curative, but in some eyes it is necessary to use eyedrops long-term. Surgical treatment is occasionally used, as well as medications to decrease production of eye fluid and to help clear the angle.
Always call your doctor immediately if you notice any loss of vision, especially if you have symptoms of acute glaucoma. Acute glaucoma is sight-threatening medical emergency that requires immediate treatment to prevent blindness. If you suspect that you have acute glaucoma, call for medical assistance day or night, or go to the nearest emergency room.
If you are older than 40, especially if you are African-American, schedule an eye examination with your doctor every two years, even if you have not noticed any change in your vision.
Open-angle glaucoma - Proper treatment greatly reduces the risk of vision loss in persons with chronic glaucoma. However, if chronic glaucoma remains untreated, permanent blindness can occur.
Acute glaucoma - If an episode of acute glaucoma is treated early, vision in the affected eye may return to a level that is almost the same as what it was before the episode began. If acute glaucoma is neglected, you can become blind in the affected eye within two days or less.