Glaucoma: The Second-Leading Causeof Blindness in the U.S.

By Judith Lee and Gretchyn Bailey;reviewed by Dr. Vance Thompson
Your eye has pressure just like your blood, and when this intraocular pressure (IOP) increases to dangerous levels, it damages the optic nerve. This can result in decreased peripheral vision and, eventually, blindness. Glaucoma is similar to ocular hypertension but with accompanying optic nerve damage and vision loss.
Glaucoma affects an estimated 3 million Americans, with 120,000 blind due to the condition. Elsewhere in the world, glaucoma treatment is less available, and glaucoma ranks as a leading cause of blindness just about everywhere. Even if people with glaucoma do not become blind, vision can be severely impaired.
There are two major types of glaucoma: chronic or primary open-angle glaucoma (POAG) and acute closed-angle glaucoma. Other variations include congenital glaucoma, pigmentary glaucoma and secondary glaucoma.
Glaucoma Signs and Symptoms
Chronic glaucoma (primary open-angle glaucoma or POAG) is often called "the silent thief of sight" because you have no warning sign, no hint that anything is wrong. About half of Americans with chronic glaucoma don't know they have it. Glaucoma gradually reduces your peripheral vision, but by the time you notice it, permanent damage has already occurred. If your IOP remains high, the destruction can progress until tunnel vision develops, and you will only be able to see objects that are straight ahead.
An acute attack of narrow-angle glaucoma, also termed acute angle-closure glaucoma or acute closed-angle glaucoma, produces sudden symptoms such as eye pain, headaches, haloes 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.
Other signs include headaches, blurred vision, difficulty adapting to darkness, or haloes around lights. Chronic glaucoma normally develops after age 35.
Like POAG, normal-tension glaucoma (also termed normal-pressure glaucoma, low-tension glaucoma or low-pressure glaucoma) is an open-angle type of glaucoma that can cause visual field loss due to optic nerve damage, but in normal-tension glaucoma, the eye's IOP remains in the normal range.
Chronic narrow-angle glaucoma, like open-angle glaucoma, can be symptomless until vision loss occurs.

Open angle glaucoma is one of the most common forms of the disease.
Acute angle-closure glaucoma is a medical emergency. If the high pressure is not reduced within hours, it can permanently damage vision. Anyone who experiences its symptoms should immediately contact an ophthalmologist or go to a hospital emergency room.
It's difficult to spot signs for congenital glaucoma because the children are too young to understand. If you notice a cloudy, white, hazy, enlarged or protruding eye, consult your eye doctor. Congenital glaucoma occurs more in boys than girls.
Pigmentary glaucoma often exhibits no symptoms at all. You may notice some pain and blurry vision after exercise. Pigmentary glaucoma affects mostly white males in their mid-30s to mid-40s.
Symptoms of chronic glaucoma following an eye injury could indicate secondary glaucoma.


What Causes Glaucoma?
An increased IOP reading indicates a problem with the amount of aqueous humor (fluid) in the eye: either the eye is producing too much, or it's not draining properly. The drainage area is the angle formed between the cornea and the iris, which is why you see the word "angle" in the different glaucoma names.
In chronic glaucoma, the aqueous humor can't make it through meshwork in the eye to the drainage channel. Risk factors for this type of glaucoma include:
Age. In a major study, less than 1% of people age 60 to 64 had chronic open-angle glaucoma. Among people 10 years older, the prevalence more than doubled to 1.3%, and among those 80 to 84, it more than doubled again to 3%.
Certain medical disorders. Diabetes, extreme nearsightedness and previous eye surgery are risk factors for chronic open-angle glaucoma. Additionally, if you have a condition that requires the use of oral or inhaled steroids, particularly high doses for prolonged periods, that can increase your risk as well.
Ethnic background. Chronic glaucoma is four times more common in African-Americans than in whites. It also develops earlier: African-American risk starts to increase after age 45, white risk at age 60. Among whites, groups at higher risk include people with Scandinavian, Irish and Russian backgrounds.
Family history. Like so many diseases, glaucoma tends to run in families; different genes, however, are involved in different families.


The cause of normal-tension glaucoma is not known, but many doctors believe it is related to poor blood flow to the optic nerve. Normal-tension glaucoma is more common in those who have a history of vascular disease, are Japanese or are female.
Narrow-angle glaucoma occurs in less than 10% of glaucoma patients. In this form of the disease, aqueous humor cannot drain out of the eye due to very narrow drainage angles that are usually blocked by the iris. This condition can occur slowly and progressively, or very quickly.
Again, rapid closing of the angles, or acute angle-closure glaucoma, is a medical emergency. Optic nerve damage and vision loss will occur within hours if the angles are not opened to drain fluid and lower IOP. Acute angle-closure glaucoma may be triggered by anything dilating the pupil, resulting in more of the iris blocking the angles. Dim lighting, drops administered by your eyecare 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% of cases diagnosed by age one. These children are born with narrow angles or some other defect in the drainage system of the eye.
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 damages the drainage system.

Glaucoma Treatment
The best way to prevent vision loss from glaucoma is early diagnosis and treatment. See your eyecare practitioner at least every two years for a complete examination, including an IOP check. People at high risk for glaucoma due to high intraocular pressures, family history, ethnic background, age or optic nerve appearance may need more frequent visits to the eye doctor.
A test called a visual field may be performed on glaucoma suspects to detect peripheral vision loss. It 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 restore 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. These may not be used in people with heart conditions, because they can affect heart or lung function. There are other pressure-lowering drops besides beta-blockers that are known as alpha-2 agonists and prostaglandin analogs. Many of the drugs used for glaucoma interact with common medications. Patients should discuss these issues with both the family physician and the eyecare practitioner.