Glaucoma is an illness caused by too much pressure in the eye (intraocular pressure, IOP). Normally, watery fluid (called aqueous humor) flows into and out of the eye. If this flow becomes blocked, pressure in the eye rises, causing glaucoma. Too much pressure can damage the eye nerve and cause vision loss. Glaucoma must be caught early to prevent this damage.
Average IOP is 16 millimeters of mercury (mm Hg). It’s considered to be elevated if it is above 21 mm Hg. Glaucoma is rare before the age of 40 and becomes more common with aging. Glaucoma affects more than 70 million people in the world. Women and people who are farsighted may have an increased risk of glaucoma. People who have a family history of glaucoma are more likely to develop it.
The two types of glaucoma are open-angle and closed-angle (angle-closure). In open-angle glaucoma, flow of fluid is blocked slowly (chronic condition). In acute closed-angle glaucoma, fluid flow is blocked suddenly; this is a medical emergency. The causes of open-angle glaucoma, the most common type, are not clear.
Open-angle glaucoma usually produces no symptoms early on. Later, loss of side vision (or peripheral vision) may occur.
Closed-angle glaucoma can cause headache, halos around lights, loss of central vision, severe eye pain, sudden vision change, and vomiting.
Glaucoma is easy to diagnose. An eye specialist (optometrist or ophthalmologist) measures eye pressure with a painless test called tonometry. The specialist also tests whether vision is good, especially side vision, and looks inside the eye with an instrument (ophthalmoscope).
The test of side vision is the visual field test. It can show early damage to side vision, the first sign of glaucoma.
Treatment—eye drops and surgery—is aimed at lowering a high IOP to a more normal IOP.
Some people need only one or two different eye drops. These drops, however, can affect other parts of the body. For example, eye drops that are beta-blockers should be used carefully in people with asthma or breathing or cardiac problems.
Other people need laser surgery or other types of surgery. Laser surgery can be quite effective, but many people will need to continue using eye drops after surgery.
Other operations for glaucoma involve making a new drain to let aqueous fluid flow out faster, so IOP is lowered.
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