patient education > glaucoma

Glaucoma

Glaucoma is a group of diseases that can lead to damage to the eye's optic nerve and result in blindness. Open-angle glaucoma, the most common form of glaucoma, affects about 3 million Americans--half of whom don't know they have it. It has no symptoms at first. But over the years it can lead to loss of peripheral vision, sometimes progressing to tunnel vision with resulting visual handicap or disability.

What is the optic nerve?
The optic nerve is a bundle of more than 1 million nerve fibers. It connects the retina, the light-sensitive layer of tissue at the back of the eye, with the brain (see diagram). A healthy optic nerve is necessary for good vision.

How does glaucoma damage the optic nerve?
In many people, increased pressure inside the eye causes glaucoma. In the front of the eye is a space called the anterior chamber, between the clear cornea or front of the eye and the colored iris of the eye. A clear fluid flows continuously in and out of this space and nourishes nearby tissues.

The fluid leaves the anterior chamber at the angle where the cornea and iris meet. When the fluid reaches the angle, it flows through a spongy meshwork (trabecular meshwork), like a drain, and leaves the eye. Open-angle glaucoma gets its name because the angle that allows fluid to drain out of the anterior chamber is open. However, for unknown reasons, the fluid in this disease passes too slowly through the meshwork drain. As the fluid builds up, the pressure inside the eye rises. Unless the pressure at the front of the eye is controlled, it can damage the optic nerve and cause vision loss.

Who is at risk?
Although anyone can get glaucoma, some people are at higher risk than others. They include:

• Those of African descent over age 40.
• Everyone over age 60.
• People with a family history of glaucoma.
• Patients with history of trauma to the eye.

What are the symptoms of glaucoma?
At first, open-angle glaucoma has no symptoms. Vision stays normal, and there is no pain. As glaucoma remains untreated, people may notice they miss objects to the side and out of the corner of their eye. Without treatment, people with glaucoma may find that they suddenly have no side vision. It may seem as though they are looking through a tunnel. Over time, the remaining forward vision may decrease until there is no vision left.

How is glaucoma detected?
Most people think that they have glaucoma if the pressure in their eye is increased. This is not always true. High pressure puts you at risk for glaucoma. Not everybody with high eye pressure has glaucoma. Whether or not you get glaucoma depends on the level of pressure that your optic nerve can tolerate without being damaged. This level is different for each person. Although normal pressure is usually between 12 to 21 mm Hg, a person might have glaucoma even if the pressure is in this range. That is why an eye examination is very important.

To detect glaucoma, your eye care professional will do the following tests:
Visual acuity: This eye chart test measures how well you see at various distances.

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

Pupil dilation: This examination provides your eye care professional with a better view of the optic nerve to check for signs of damage. To do this, your eye care professional places drops into the eye to dilate (widen) the pupil. After the examination, your close- up vision may remain blurred for several hours.

Optic nerve photography: A baseline image of the nerve for baseline assessment and future comparison is important to monitor for possible disease progression. A combination of digital photography and special imaging with a special nerve imaging camera aids the doctors in their evaluation of the status of the optic nerve.

Tonometry: This standard test determines the fluid pressure inside the eye. There are many types of tonometry. One type uses a blue light to measure pressure. Another type is the "air puff," test, which measures the resistance of the eye to a puff of air.

Can glaucoma be treated?
Yes. Although you will never be cured of glaucoma, treatment often can control it. This makes early diagnosis and treatment important to protect your sight. Most doctors use medications for newly diagnosed glaucoma; however, new research findings show that laser surgery is a safe and effective alternative. You and your doctor may discuss which treatment options are best for your individual case.

Glaucoma treatments include:
Medicine: Medicines are the most common early treatment for glaucoma. They come in the form of eye drops and pills. Some cause the eye to make less fluid. Others lower pressure by helping fluid drain from the eye. Glaucoma drugs may be taken up to several times a day. Most patients tolerate the medicine(s) well, but some may experience side effects such as stinging, burning, redness, or even heart and breathing complications. For this reason, it is important for your eye doctor to know what your complete medical history, including all of your medications and allergies. Because glaucoma often has no symptoms, people may be tempted to stop or may forget to take their medicine. However, glaucoma is a chronic disease with no cure, and patients with glaucoma need to use their medicine.
Laser surgery (also called laser trabeculoplasty): Laser surgery helps fluid drain out of the eye. Laser surgery is performed in an eye care professional's office or surgery center. Before the surgery, our doctor will apply drops to numb the eye. As you sit facing the laser machine, your eye care professional will hold a special lens to your eye. A high-energy beam of light is aimed onto the meshwork inside your eye. You may see flashes of bright green or red light. The laser helps the fluid inside the eye drain better through the meshwork, resulting in lower eye pressure. Our doctors will check your eye pressure shortly afterward. They may also give you some drops to take home for any soreness or swelling inside the eye. You will need to make several follow up visits to have your pressure monitored.

Trabeculectomy surgery:
The purpose of surgery is to make a new opening for the fluid to leave the eye. Although our doctors may suggest it at any time, this surgery is often done after medicine and laser surgery have failed to control your pressure. Surgery is performed in an operating room in a surgery center or hospital. Before the surgery, your eye care professional gives you medicine to help you relax and then small injections around the eye to make it numb. The eye care professional removes a small piece of tissue from the white (sclera) of the eye. This creates a new channel for fluid to drain from the eye. But surgery does not leave an open hole in the eye. The white of the eye is covered by a thin, clear tissue called the conjunctiva. The fluid flows through the new opening, under the conjunctiva, and drains from the eye.

You must put drops in the eye for several weeks after the operation to fight infection and swelling. (The drops will be different than the eye drops you were using before surgery.) You will also need to make frequent visits to your eye care professional. This is very important, especially in the first few weeks after surgery.

Tube shunt (drainage implant) surgery: In some patients a different type of surgery may be the best option for controlling the eye pressure. This is a permanent implant that consists of a tube that shunts fluid from inside to eye to a separate part of the implant where the fluid drains into an artificial reservoir. This creates a new way for fluid to drain out of the eye and relieve the eye pressure. Keep in mind that while glaucoma surgery may save remaining vision, it does not improve sight. In fact, your vision may not be as good as it was before surgery.

Like any operation, glaucoma surgery can cause side effects. These include cataract, problems with the cornea, inflammation or infection inside the eye, and swelling of blood vessels behind the eye. However, if you do have any of these problems, effective treatments are available.

What are some other forms of glaucoma?
Although open-angle glaucoma is the most common form, some people have other forms of the disease.

In low-tension or normal-tension glaucoma, optic nerve damage and narrowed side vision occur unexpectedly in people with normal eye pressure. People with this form of the disease have the same types of treatment as open-angle glaucoma.

In closed-angle glaucoma, the fluid at the front of the eye cannot reach the angle and leave the eye because the angle gets blocked by part of the iris. People with this type of glaucoma may experience a sudden increase in which may lead to severe pain and nausea as well as redness of the eye and blurred vision. This is known as acute angle closure glaucoma, a medical emergency, requiring prompt examination and treatment. Closed-angle glaucoma can also develop slowly or gradually. This is known as chronic angle closure glaucoma. Both forms of closed-angle glaucoma require special laser treatment (peripheral iridotomy) to prevent progressive nerve damage and loss of vision.

In congenital glaucoma, children are born with anatomic defects in the eye that prevents the normal drainage of fluid. Children with this problem usually have obvious symptoms such as cloudy eyes, sensitivity to light, and excessive tearing. Surgery is usually the standard treatment. If surgery is done promptly, these children usually have an excellent chance of having good vision.

Secondary glaucomas can develop as a complication of other medical conditions. They are sometimes associated with eye surgery or advanced cataracts, eye injuries, certain eye tumors, or uveitis (eye inflammation). One type, known as pigmentary glaucoma, occurs when pigment from the iris flakes off and blocks the meshwork, slowing fluid drainage. A severe type of secondary glaucoma, called neovascular glaucoma, is linked to diabetes. Also, corticosteroid drugs used to treat eye inflammations and other diseases can trigger glaucoma in some people. All these types of glaucoma require examination and treatment based on a variety of individual factors for each patient.
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