Glaucoma is called the "thief of sight" because it can blind its victims painlessly and irreversibly. There are no symptoms until victims begin to lose their vision. Treatment can slow the progression of the disease but cannot reverse the damage.
Eye doctors are worried about an impending increase in the number of glaucoma patients. Those at highest risk are people older than 60, African Americans older than 40, and those with a family history of the disease.
"As our population ages, we have more people entering into the glaucoma age group," says Dr. Robert J. Fucigna, a Stamford, Conn., ophthalmologist. "We know that the baby-boomer African-Americans are at high risk today, and the Caucasian baby boomers will be coming into the risk pool in a few years."
Nearly 3 million Americans have glaucoma, one of the leading causes of blindness, according to the National Eye Institute. Black people are four times more likely to get the disease, indicating that it might have a genetic component.
Fortunately, there have been advances in both testing and treatment.
Glaucoma is easily detectable during a complete eye exam. Many people recall the air-puff test, in which the doctor directed a quick puff of air at the eye while the head was immobilized.
To check for glaucoma, doctors examine three things: pressure in the eye, the optic nerve at the back of the eye and peripheral vision. The air puff tested pressure.
Now, instead of the air puff, eye doctors use a small device called a tonometer that delivers a microburst of air that the patient can't even feel. The tonometer is about the size of a Magic Marker, says Fucigna. The small bursts more accurately measure pressure inside the eye.
At the front of the eyeball, there is a small space called the anterior chamber. Clear fluid flows in and out of a complex series of channels in the chamber to bathe and nourish nearby tissues. In glaucoma, for unknown reasons, the fluid drains too slowly out of the eye. As the fluid builds up, the pressure inside the eye rises. Unless this pressure is controlled, it damages the optic nerve and other parts of the eye and leads to blindness.
But "pressure is just part of the picture," says Dr. Gina F. Gladstein, a Greenwich, Conn., ophthalmologist. "In early glaucoma, 50 percent of patients have normal pressure. Just going into an eyeglasses store for a pressure check does a disservice. You must have a complete eye exam in which the optic nerves are examined thoroughly."
The only symptom of glaucoma is a gradual loss of peripheral vision, so the third part of the exam checks for that. This is important, too, says Gladstein, because people use their central vision 90 percent of the time -- for reading and looking at each other. So it's possible to lose a great deal of peripheral vision without even realizing it. The visual field test is called perimetry.
If the tests indicate that a person has glaucoma, treatment usually involves eye drops to ease the pressure, says Fucigna.
Sometimes, the beneficial effects of eye drops wear off, and the physician will prescribe a different type or combination of drops. Eventually, patients might face laser surgery to relieve pressure in their eyes. In this procedure, a high-energy beam of light is directed at the drainage meshwork, enlarging the holes.
If the effects of that wear off, they might face more complicated surgery -- a trabeculotomy, goniotomy or trabeculectomy. All of those involve cutting a hole in the anterior chamber so fluid can leave the eye.
The facts on glaucoma
* Glaucoma is a group of diseases of which open-angle glaucoma is the most common. The other types are acute glaucoma, requiring emergency treatment, and congenital glaucoma.
* About 3 million Americans have open-angle glaucoma -- but about half are unaware of it.
* Those at highest risk are anyone older than 60, blacks age 40 or older, and anyone with a family history of the disease.
* It is estimated that as many as 120,000 Americans are now blind from the disease.
Source: National Eye Institute, National Institutes of Health