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Posted Apr 16 2010 12:00am

          Glaucoma is optic nerve damage that leads to progressive, irreversible loss of vision.  It is often, but not always, associated with increased eye pressure. The optic nerve is the main nerve to the eye (located in the back of the eye) that is responsible for transmitting electrical impulses to the brain.  Damage usually occurs as a result of elevated pressure of the fluid (aqueous humor) in the eye. This damage results in gradual visual changes and then loss of vision.  When there is a problem in the drainage, the fluid builds up in the eye and presses against the optic nerve (called intraocular pressure or IOP), resulting in glaucoma.  This increased fluid pressure actually pushes the optic nerve back into a ‘cupped’ or concave shape.  If the intraocular pressure remains too high for too long, the extra pressure damages parts of the optic nerve.  Almost 3 million people in the United States and 14 million people worldwide have glaucoma.  Glaucoma is the third leading cause of blindness worldwide and the second leading cause of blindness in the United States, where it is the leading cause of blindness among blacks and Hispanics.  In the United States, about one third of glaucoma occurs with eye pressures within the average range, a condition called low-tension glaucoma.

          There are many forms of adult and childhood glaucomas; however, most glaucomas fall into two categories: open-angle or closed-angle glaucomas.  Open-angle glaucoma is more common.  In open-angle glaucoma, the drainage canals in the eyes become clogged gradually over months or years.  Pressure in the eye rises slowly because fluid is produced at a normal rate but drains sluggishly.  Closed-angle glaucoma is less common than open-angle glaucoma.  In closed-angle glaucoma, the drainage canals in the eyes become blocked or covered because the angle between the iris and cornea is too narrow. The blockage can occur suddenly or slowly.  If the blockage occurs suddenly, pressure in the eye rises rapidly.  If the blockage occurs slowly, the pressure in the eye rises slowly like in open-angle glaucoma.

          Open-angle glaucoma is painless and causes no early symptoms.  The most important symptom of open-angle glaucoma is the development of blind spots, or patches of vision loss, over months to years.  The blind spots slowly grow larger and coalesce.  Peripheral vision is usually lost first.  Vision loss occurs so gradually that it is often not noticed until much of it is lost.  Because central vision is generally lost last, many people develop tunnel vision.  They can see straight ahead perfectly, but become blind in all other directions.  If glaucoma is left untreated, eventually even tunnel vision is lost, and a person becomes totally blind.  In closed-angle glaucoma, eye pressure can rise rapidly and people typically notice an abrupt onset of severe eye pain and headache, redness, blurred vision, rainbow-colored halos around lights and sudden loss of vision.  They may also have nausea and vomiting as a response to the increase in eye pressure.  Acute closed-angle glaucoma is considered a medical emergency, because people can lose their vision as quickly as 2 to 3 hours after the appearance of symptoms if the condition is not treated.  People who have had open-angle or closed-angle glaucoma in one eye are likely to develop it in the other.

          There is no cure for glaucoma, but it can be controlled.  Ophthalmologists use medication and surgery to prevent further vision loss.  These treatment methods are used to bring the intraocular pressure under control.  Nearly all glaucoma can be treated successfully with topical medications (applied directly to the eyes, such as eye drops or eye ointments) or oral medications (taken by mouth).  While glaucoma cannot be prevented, the earlier it is diagnosed the better.  Recommendations for early detection include having a test every two to four years if you are between the ages of 40 and 65.  If you are 65 of age or older, have a family history of glaucoma, are of Black or Asian ancestry, have diabetes or a chronic inflammatory disease, have had a previous, serious eye injury or if you are taking steroids, it is suggested that you have a test every one to two years.

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