Glaucoma is the term applied to a group of eye diseases that gradually result in loss of vision by permanently damaging the optic nerve, the nerve that transmits visual images to the brain. The leading cause of irreversible blindness, glaucoma often produces no symptoms until it is too late and vision loss has begun.

An elevation in the pressure within the eye (the intraocular pressure, or IOP) is generally, but not always, associated with the development of glaucoma, although additional factors are also likely to play a role in its development. The optic nerve fibers inside the eye are damaged, resulting in vision loss that begins in the peripheral fields of vision. Glaucoma usually affects both eyes, but one eye may be more severely affected than the other.

There are many kinds of glaucoma. The most common form of glaucoma involves blockage in the drainage canals of the eye, so that fluid builds up within the eye and causes the increased IOP. This type of glaucoma, known as open angle glaucoma, usually progresses slowly over many years.

Another kind of glaucoma, called closed angle glaucoma, typically has a sudden (acute) onset. In this type of glaucoma, the angle in the front of the eye where the drainage canals are located is not as wide as it should be and the edge of the iris bunches up over the drainage canals when the pupil enlarges.

Secondary glaucoma can also occur after an eye injury, in the presence of inflammation or tumor of the eye area, or with advanced cases of cataracts or diabetes. The heavy use of steroids, for example with a steroid inhaler for asthma, is also associated with an increased risk of glaucoma.

Regular glaucoma checkups include two routine eye tests: tonometry and ophthalmoscopy. The tonometry test uses a special device to measure the pressure within the eye. Ophthalmoscopy is used to look at the inside of the eye, especially the optic nerve. If one of these tests is abnormal, further testing may be required to confirm a diagnosis of glaucoma. Additional tests may include visual field testing (perimetry) to map the field of vision and gonioscopy, a procedure to examine the anatomy of the drainage area of the eye.

Although anyone can develop glaucoma, certain groups of people are at particular risk. African-Americans are six to eight times more likely to develop glaucoma than Caucasians. People over 60 years of age and anyone with a family history of glaucoma are also at increased risk.

The American Academy of Ophthalmology's recommended intervals for eye exams are:

• Age 20-29: Individuals of African descent or with a family history of glaucoma should have an eye examination every three to five years. Others should have an eye exam at least once during this period.
• Age 30-39: Individuals of African descent or with a family history of glaucoma should have an eye examination every two to four years. Others should have an eye exam at least twice during this period.
• Age 40-64: Every two to four years.
• Age 65 or older: Every one to two years.

There is presently no cure for glaucoma. Glaucoma may be treated with medications (most commonly in the form of eye drops) or with surgery. The specific aims of treatment are to help drain fluid from the eye, prevent excess fluid production within the eye, and maintain normal pressure in the eye.

The long-term objective of treatment is to keep the glaucoma under control and to retain as much vision as possible.

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