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 Open Angle Glaucoma

What causes open angle glaucoma?
How is open angle glaucoma treated?

Sometimes called chronic glaucoma, open angle glaucoma is the most common type of glaucoma, affecting 70 percent to 80 percent of those who suffer from the disorder. The other type of glaucoma is acute narrow angle glaucoma.

Open angle glaucoma is the leading cause of blindness among adults in the United States and is particularly dangerous because it can progress gradually and go unnoticed for years. The only way to detect the disease before it becomes a serious problem is with regular eye examinations that include a simple, painless pressure test. The disease usually affects both eyes.

Glaucoma is actually a group of diseases that are distinguished by an increase in pressure inside the eye that causes damage to the optic nerve and to the retina. Like the film in a camera, a healthy retina receives light rays from the front of the eye and transmits them through the optic nerve to the brain where they are turned into images. Damage to the retina or the optic nerve can result in serious vision loss and even blindness if not detected and treated early.

Open angle glaucoma typically occurs in patients over the age of 50, and the risk increases with age. African-Americans are at higher risk of developing the condition than Caucasians and, if there is a family history of glaucoma, the risk is up to six times higher than for the general population. Also, patients who are highly myopic (nearsighted), have diabetes mellitus, or have cardiovascular problems are at high risk of developing glaucoma.

Another form of open angle or chronic glaucoma is called low-tension glaucoma. Patients with normal eye pressure sometimes develop damage to the optic nerve that results in a loss of peripheral vision. This type of glaucoma can be detected by an examination of the back of the eye at the optic nerve head with an ophthalmoscope and by performing a test of the patient's peripheral vision capabilities known as a visual field test.

What causes open angle glaucoma?

Unlike narrow angle glaucoma, which is often caused by too small a space between the cornea and the iris, patients with open angle glaucoma have a gradual blockage of aqueous outflow despite a seemingly open space (chamber angle) in the front of the eye. Apparently as the eye ages, the drainage system can become clogged or the eye over-produces aqueous fluid, either of which causes pressure inside the eye to build to abnormal levels.

Open angle glaucoma is often referred to as "the thief in the night," because it can develop gradually and go unnoticed for years, slowly robbing the victim of his or her eyesight. Because there is usually no pain experienced over the months or years of development and no other apparent symptoms, the victim is unaware of the existence of this serious eye disorder.

How is open angle glaucoma treated?

Open angle glaucoma cannot be cured, but it can be controlled by lowering the pressure in the eye, with the use of eyedrops and/or oral medications. The eyedrops work by enhancing the drainage of fluid from the eye or by reducing the production of aqueous fluid in the eye. Normally, some form of these medications will have to be continued for the rest of the patient's life, and regular use according to a physician's instructions is absolutely necessary to control the disease.

If eyedrops and/or oral medications are not effective in controlling the internal pressure levels of the eye, there are several surgical procedures that might be employed at the discretion of an ophthalmologist. An argon laser trabeculoplasty involves laser treatment of the trabecular meshwork, a mesh-like structure inside the eye, which filters aqueous fluid and controls its flow into the drainage channels. If this is not effective, a surgical procedure known as a trabeculectomy may be used to remove a portion of the trabecular meshwork and subsequently lower the intraocular pressure. Both the trabeculectomy and the argon laser trabeculoplasty procedures have high rates of success.

The only way that chronic glaucoma can be detected is by regular eye examinations by an eye doctor, and treatment is effective when the disease is detected at an early stage.

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