Your eye has pressure just like your blood. When intraocular pressure (IOP) increases to dangerous levels, it damages the optic nerve. With very high pressure, or higher than normal pressure over a period of time, vision loss occurs, and blindness may follow. Glaucoma is similar to ocular hypertension but with accompanying optic nerve damage and vision loss. Glaucoma is the second-leading cause of blindness in the United States.

Causes

Glaucoma appears in several variations: chronic or primary open-angle glaucoma (POAG), acute, narrow-angle or closed-angle glaucoma, congenital glaucoma, pigmentary glaucoma and secondary glaucoma.

All five forms of glaucoma have one thing in common: a problem with the amount of fluid filling the chambers of the eye, called aqueous humor. The balance between aqueous humor production and fluid drainage may not be equal, or the drainage channels in the eye may be blocked or too narrow to allow for proper drainage of aqueous humor.

Primary open-angle glaucoma is the most common form of glaucoma, and it develops slowly over time, usually after the age of 35. POAG occurs when either too much aqueous humor is produced, or the fluid itself doesn't drain out quickly enough to maintain the correct fluid pressure within the eye.

Narrow-angle glaucoma occurs far less frequently than POAG, seen in less than 10 percent of glaucoma patients. In this form of the disease, aqueous humor cannot drain out of the eye due to very narrow drainage angles which are usually blocked by the iris. This condition can occur slowly and progressively, or very quickly. Rapid closing of the angles is called acute angle-closure glaucoma. This is a medical emergency, as optic nerve damage and vision loss will occur within hours if the angles are not opened to drain fluid and lower intraocular pressure.

Closed-angle glaucoma may also be triggered by anything dilating the pupil, resulting in more of the iris blocking the angles. Dim lighting, drops administered by your eye care practitioner during an eye examination or certain medications such as antihistamine/decongestant drops or cold medications may cause an acute angle closure attack.

Congenital glaucoma is a rare form of the disease affecting babies, with 80 percent of cases diagnosed by the age of one. These children are born with narrow angles or some other defect in the drainage system of the eye. Congenital glaucoma occurs more in boys than girls.

Pigmentary glaucoma, another rare form of the disease, is caused by pigment from the iris clogging the draining angles, preventing aqueous humor from leaving the eye. Over time, the inflammatory response to the blocked angle causes damage to the drainage system. Pigmentary glaucoma affects mostly white males in their mid-30s to mid-40s.

Secondary glaucoma develops after trauma to the eye that affects the drainage system. Injury, infection, inflammation, tumor or an enlarged cataract can precipitate secondary glaucoma.

African-Americans are at much higher risk for glaucoma than other demographic groups, with the disease occurring about six to eight times more often in African-Americans than Caucasians. Primary open-angle glaucoma is the leading cause of blindness for African-Americans. Diabetics are also at higher risk for the disease, with diabetics three times as likely to develop glaucoma as nondiabetics. Family history also plays a large role.

Symptoms

Glaucoma has been branded the "sneak thief in the night" because it creeps in so gradually to steal your vision. By the time you notice any warning signs, vision loss most likely has already occurred. With POAG, you may notice a gradual narrowing of your peripheral (side) vision, headaches, blurred vision, difficulty adapting to darkness or halos around lights.

These same symptoms following an eye injury could indicate secondary glaucoma. An attack of narrow-angle glaucoma produces sudden symptoms such as eye pain, headaches, halos around lights, dilated pupils, vision loss, red eyes, nausea and vomiting. These signs may last for a few hours, then return again for another round. Each attack takes with it part of your field of vision.

Symptoms for congenital glaucoma are difficult to ascertain because the children are too young to understand. If you notice a cloudy, white, hazy, enlarged or protruding eye, consult your pediatrician or eye care practitioner. Pigmentary glaucoma often exhibits no symptoms at all, or those affected may notice pain and blurry vision after exercise. Physical activity flushes pigment through the eye to the angles, where it becomes trapped. Aqueous humor builds up and causes an increase in intraocular pressure, followed by the pain and blurry vision.

Most Common Treatments

The best way to prevent vision loss with glaucoma is early diagnosis and treatment. See your eye care practitioner at least every two years for a complete examination including checking the pressures of your eyes. This can be done two ways: with an air-puff tonometer or a more sensitive applanation tonometer. People at high risk for glaucoma due to high intraocular pressures, family history, ethnic background, age or optic nerve appearance may need to be examined more frequently.

Another test called a visual field may be performed on glaucoma suspects. This test detects peripheral vision loss, one of the hallmarks of glaucoma. The painless visual field involves staring straight ahead into a machine and clicking a button when you notice a blinking light in your peripheral vision. The visual field test may be repeated at regular intervals for your doctor to determine the extent of vision loss.

Glaucoma treatment (for any form) entails decreasing aqueous humor production, increasing fluid drainage or a combination of the two. These treatments will not return any vision already lost to glaucoma.

Generally the first stage of glaucoma treatment is beta-blocker eyedrops, which will lower fluid production in the eye. Another choice is pilocarpine, eyedrops to constrict pupils and increase fluid drainage.

If eyedrops fail to decrease aqueous humor production or increase drainage, surgery may be necessary. This option also works for narrow-angle glaucoma attacks. A laser creates tiny holes where the cornea and iris meet in a procedure called trabeculoplasty to increase aqueous humor drainage. Another procedure called trabeculectomy creates an artificial drainage area in advanced glaucoma when optic nerve damage is present and intraocular pressures continue to soar.