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    Understanding Glaucoma -- the Basics

    What Is Glaucoma?

    More than 3 million adult Americans have glaucoma, making it one of the leading causes of blindness in the U.S.

    The most common form, chronic open-angle glaucoma, generally appears in middle age and seems to have a genetic component: One in five people with glaucoma has a close relative with the condition. In chronic, open-angle glaucoma, sight begins to fade in the outer areas (peripheral) of the visual field; if untreated, tunnel vision and then blindness follow.

    Understanding Glaucoma

    Find out more about glaucoma:

    Basics

    Symptoms

    Treatment

    Prevention

    The inside of the eye continuously produces and drains away a fluid called aqueous humor. As fresh aqueous is produced by cells inside the eye, an equal amount must exit through a drainage passageway (trabecular meshwork). If not enough drains away, pressure will increase inside the eye. The effects of intermittent or persistent high pressure on delicate retinal nerve fibers and the optic nerve results in permanent vision loss.

    Glaucoma has long been called "the silent thief of sight," because there can be significant damage to the eye before the problem is discovered. Glaucoma damage is irreversible.

    Types of Glaucoma

    Glaucoma is a collection of diseases, all of which share a common outcome: irreversible damage to delicate nerve fibers and the optic nerve that sends information to the brain. The most common type of glaucoma outside of Asia is called chronic open-angle glaucoma, accounting for about 75%-90% of cases. There are multiple causes of this type of glaucoma. In chronic open-angle glaucoma, both eyes may be affected at the same time, but one eye is often worse than the other.

    Narrow or closed-angle glaucoma is less common and may occur suddenly -- usually in one eye first -- with blurred vision, a great deal of pain in the eye and head, and redness. In closed-angle glaucoma, the flow of aqueous is physically blocked by the iris from exiting the eye, which can cause  a sudden and severe rise in pressure inside the eye. Just like in open-angle glaucoma, the high pressure permanently damages the retinal and optic nerve fibers. Acute closed-angle glaucoma is a medical emergency and needs immediate medical care to restore normal aqueous outflow, reduce pressure, and prevent permanent damage to the eye and blindness.  Chronic angle closure glaucoma can, like open angle glaucoma, slowly and silently damage the nerve of the eye with elevation of eye pressure. This type of glaucoma is much more common in Asia; indeed in certain countries closed angle glaucoma is the more common type of glaucoma.

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