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Harvard Commentaries
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Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School


Don't Lose Sight of Glaucoma


July 02, 2014

National Eye Institute source image

 

Don't Lose Sight of glaucoma

Don't Lose Sight of Glaucoma

Information for People at Risk

 


What is glaucoma?

Glaucoma is a group of diseases that damage the eye's optic nerve that can lead to vision loss and blindness. However, with early detection and treatment, you can protect your eyes.

Open-angle glaucoma is the most common form of the disease.

What causes it?

Eye pressure is a major risk factor for optic nerve damage. In the front of the eye is a space called the anterior chamber. A clear fluid flows continuously in and out of the chamber and nourishes nearby tissues. The fluid leaves the chamber at the open angle where the cornea and iris meet. (See diagram below.) When the fluid reaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye.

In open-angle glaucoma, even though the drainage angle is "open", the fluid passes too slowly through the meshwork drain. Since the fluid builds up, the pressure inside the eye rises to a level that may damage the optic nerve. When the optic nerve is damaged from increased pressure, open-angle glaucoma-and vision loss—may result. That’s why controlling pressure inside the eye is important.

Another risk factor for optic nerve damage relates to blood pressure. Thus, it is important to also make sure that your blood pressure is at a proper level for your body by working with your medical doctor.

At the front of the eye, there is a small space called the anterior chamber. Clear fluid flows in and out of the chamber to bathe and nourish nearby tissues. In glaucoma, for still unknown reasons, the fluid drains too slowly out of the eye. As the fluid builds up, the pressure inside the eye rises. Unless this pressure is controlled, it may cause damage to the optic nerve and other parts of the eye and loss of vision.

Eyeball

Who is most likely to get it?

Glaucoma is a leading cause of blindness in the United States. Although anyone can get glaucoma, some people are at higher risk. They include:

  • African Americans over age 40
  • Everyone over age 60, especially Mexican Americans
  • People with a family history of glaucoma

What are the symptoms?

At first, there are no symptoms. Vision stays normal, and there is no pain.

Without treatment, people with glaucoma will slowly lose their peripheral (side) vision. As glaucoma remains untreated, people may miss objects to the side and out of the corner of their eye. They seem to be looking through a tunnel. Over time, straight-ahead (central) vision may decrease until no vision remains.

How is it detected?

Glaucoma is detected by exam that includes:

Visual field test. This test measures your peripheral (side vision). It helps your eye care professional tell if you have lost peripheral vision, a sign of glaucoma.

Dilated eye exam. In this exam, drops are placed in your eyes to widen, or dilate, the pupils. Your eye care professional uses a special magnifying lens to examine your retina and optic nerve for signs of damage and other eye problems. After the exam, your close-up vision may remain blurred for several hours.

Tonometry. This measures pressure inside the eye by using an instrument called a tonometer. Numbing drops may be applied to your eye for this test. A tonometer measures pressure inside the eye to detect glaucoma.

Pachymetry. This is the measurement of the thickness of your cornea. Your eye care professional applies a numbing drop to your eye and uses an ultrasonic wave instrument to measure the thickness of your cornea.

How can it be treated?

Immediate treatment for early-stage, open-angle glaucoma can delay progression of the disease. That’s why early diagnosis is very important.

Glaucoma treatments include medicines, laser trabeculoplasty, conventional surgery, or a combination of any of these. While these treatments may save remaining vision, they do not improve sight already lost from glaucoma.

Medicines:

Medicines, in the form of eye drops or pills, are the most common early treatment for glaucoma. Taken regularly, these eye drops lower eye pressure. Some medicines cause the eye to make less fluid. Others lower pressure by helping fluid drain from the eye.

Before you begin glaucoma treatment, tell your eye care professional about other medicines and supplements that you are taking. Sometimes the drops can interfere with the way other medicines work.

Glaucoma medicines need to be taken regularly as directed by your eye care professional. Most people have no problems. However, some medicines can cause headaches or other side effects. For example, drops may cause stinging, burning, and redness in the eyes.

Many medicines are available to treat glaucoma. If you have problems with one medicine, tell your eye care professional. Treatment with a different dose or a new medicine may be possible.

Because glaucoma often has no symptoms, people may be tempted to stop taking, or may forget to take, their medicine. You need to use the drops or pills as long as they help control your eye pressure. Regular use is very important.

Make sure your eye care professional shows you how to put the drops into your eye.

Laser surgery. Laser surgery called trabeculoplasty helps fluid drain out of the eye. Your doctor may suggest this step at any time. In many cases, you will need to keep taking glaucoma medicines after this procedure.

Laser trabeculoplasty is performed in your doctor’s office or eye clinic. Before the surgery, numbing drops are applied to your eye. As you sit facing the laser machine, your doctor holds a special lens to your eye. A high-intensity beam of light is aimed through the lens and reflected onto the meshwork inside your eye. You may see flashes of bright green or red light. The laser makes several evenly spaced burns that stretch the drainage holes in the meshwork. This allows the fluid to drain better.

Like any surgery, laser surgery can cause side effects, such as inflammation. Your doctor may give you some drops to take home for any soreness or inflammation inside the eye. You will need to make several follow-up visits to have your eye pressure and eye monitored.

If you have glaucoma in both eyes, usually only one eye will be treated at a time. Laser treatments for each eye will be scheduled several days to several weeks apart.

Studies show that laser surgery can be very good at reducing the pressure in some patients. However, its effects can wear off over time. Your doctor may suggest further treatment.

Conventional surgery:

Conventional surgery makes a new opening for the fluid to leave the eye. (See diagram on the next page.) Your doctor may suggest this treatment at any time. Conventional surgery often is done after medicines and laser surgery have failed to control pressure.

Conventional surgery, called trabeculectomy, is performed in an operating room. Before the surgery, you are given medicine to help you relax. Your doctor makes small injections around the eye to numb it. A small piece of tissue is removed to create a new channel for the fluid to drain from the eye. This fluid will drain between the eye tissue layers and create a blister-like "filtration bleb."

For several weeks after the surgery, you must put drops in the eye to fight infection and inflammation. These drops will be different from those you may have been using before surgery.

Conventional surgery is performed on one eye at a time. Usually the operations are four to six weeks apart.

Conventional surgery is about 60 to 80 percent effective at lowering eye pressure. If the new drainage opening narrows, a second operation may be needed. Conventional surgery works best if you have not had previous eye surgery, such as a cataract operation.

Sometimes after conventional surgery, your vision may not be as good as it was before conventional surgery. Conventional surgery can cause side effects, including cataract, problems with the cornea, inflammation, infection inside the eye, or low eye pressure problems. If you have any of these problems, tell your doctor so a treatment plan can be developed.

  • What research is being done?

    Through studies in the laboratory and with patients, NEI is seeking better ways to detect, treat, and prevent vision loss in people with glaucoma. For example, researchers have discovered genes that could help explain how glaucoma damages the eye.

    NEI also is supporting studies to learn more about who is likely to get glaucoma, when to treat people who have increased eye pressure, and which treatment to use first.

  • What can you do?

    If you are being treated for glaucoma, be sure to take your glaucoma medicine every day. See your eye care professional regularly.

    You also can help protect the vision of family members and friends who may be at high risk for glaucoma-African Americans over age 40; everyone over age 60, especially Mexican Americans; and people with a family history of the disease. Encourage them to have a comprehensive dilated eye exam at least once every two years. Remember that lowering eye pressure in the early stages of glaucoma slows progression of the disease and helps save vision.

    Medicare covers an annual comprehensive dilated eye exam for some people at high risk for glaucoma. These people include those with diabetes, those with a family history of glaucoma, and African Americans age 50 and older.

Image for NEI

National Eye Institute
National Institutes of Health
NIH Publication No. 91-3251

 

Current as of July 2, 2014
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