Glaucoma

Glaucoma is one of the leading causes of blindness in the United States. According to the National Eye Institute (NEI), nearly three million people have the disease.

Early detection and treatment can be the best way to control glaucoma. But in its early stages, there are often no symptoms, so regular eye exams are essential. (Read about "Eye Exams")

What causes glaucoma

Normally, our eyes (Read about "The Eye") are bathed with clear fluid, which flows in and out of the eye. At the front of the eye there is a small space called the anterior chamber. A clear fluid flows through this chamber and bathes and nourishes the nearby tissues. In the normal eye, the clear fluid leaves the anterior chamber at the open angle where the cornea and iris meet. When fluid reaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye. In most forms of glaucoma, this fluid starts to build up. The exact reason this starts happening isn't clear. But as the fluid increases, so does the pressure within the eye called intraocular pressure (IOP). As this happens, the optic nerve and other parts of the eye can be damaged. Glaucoma can also occur as the result of eye injury or inflammation, according to the Glaucoma Research Foundation. In addition, it can result from some medications or eye diseases. Glaucoma can also be present at birth.

Types of glaucoma

• Primary open angle - The most common form of glaucoma is primary open angle glaucoma. Sometimes, when the fluid reaches the angle, it passes too slowly through the meshwork drain, causing the pressure inside the eye to build. If the pressure damages the optic nerve, open-angle glaucoma - and vision loss - may result. Initially, NEI says that in this form of glaucoma, there are no symptoms and no pain. But gradually, the field of vision blurs and narrows until vision is lost permanently.
• Closed angle or narrow angle glaucoma - In closed-angle or narrow 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 have a sudden increase in pressure. According to NEI, this is termed acute closed angle glaucoma. Symptoms include severe pain and nausea as well as redness of the eye and blurred vision. This is a medical emergency. The patient needs immediate treatment to improve the flow of fluid. Without treatment, you can lose sight in that eye in as little as one or two days. Usually, prompt laser surgery can clear the blockage and protect sight.
• Low tension/normal tension - 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.
• Congenital - In congenital glaucoma, children are born with defects in the angle of the eye that slow the normal drainage of fluid. (Read about "Birth Defects") Children with this problem usually have obvious symptoms such as cloudy eyes, sensitivity to light and excessive tearing. Surgery is usually the suggested treatment, because medicines may have unknown effects in infants and be difficult to give to them. The surgery is safe and effective. If surgery is done promptly, these children usually have an excellent chance of having good vision.
• Secondary glaucomas - 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 eye inflammation. (Read about "Cataracts" "Eye Injury" "Eye Cancer")

Who's most at risk

Anyone can get glaucoma. But the National Eye Institute says some groups are at higher risk, including:

• African Americans over the age of 40 (Read about "Minority Health")
• anyone over the age of 60
• diabetics (Read about "Diabetes")
• people with a family history of glaucoma (Read about "Family Health History")

The Glaucoma Research Foundation says an eye exam every two years can help safeguard vision, especially if you fall into one of the high-risk groups. Eye care professionals will test how well you see at various distances, measure your side or peripheral vision, test the fluid pressure inside your eye, and check the optic nerve for signs of damage. There may be drops placed into the eye to dilate or widen the pupil to give the examiner a better view of the optic nerve. This can result in temporarily blurred vision.

To detect glaucoma, NEI says that your eye care professional will use tests that can include:

• Tonometry - This standard test measures the fluid pressure inside the eye.
• Optic nerve examination - In this test, nerves of the eye are examined to check for any changes that may indicate the beginnings of glaucoma.
• 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.
• Gonioscopy - This test can inspect the drainage angle.
• Pachymetry - This test measures the thickness of the cornea.

Although the most common form of glaucoma can't be cured, it can be controlled. NEI says there are several types of treatment options:

• Medications - This can be either in the form of eye drops or pills. Some drugs work to reduce pressure by slowing the flow of fluid into the eye. Others help to improve fluid drainage. For most people with glaucoma, regular use of medications can control the increased fluid pressure. But, the effect may not last, or there may be side effects. If this happens, the eye care professional may select other drugs, change the dose or suggest other ways to deal with the problem.
• Laser surgery - At the front of the eye, there is a small space called the anterior chamber. During laser surgery, a strong beam of light is focused on the part of this anterior chamber where the fluid leaves the eye. This results in a series of small changes, which makes it easier for fluid to leave the eye. Over time, however, the effect of laser surgery may wear off. In addition, patients who have this form of surgery may need to keep taking glaucoma drugs.
• Surgery - Surgery can also help fluid escape from the eye and thereby reduce the pressure. However, surgery is usually reserved for patients whose pressure cannot be controlled with eye drops, pills or laser surgery.

NEI says that surgery for glaucoma may increase the risk of developing cataracts. (Read about "Cataracts") As with any medical treatment, make sure you discuss all options as well as potential side effects with your doctor.

Related Information:

    Refractive Errors

    Retinitis Pigmentosa

    Glossary of Vision Terms