Glaucoma affects 2 percent of the population, but many people don't know they have it until it is too late for effective treatment. There is no cure, and this disease that damages the optic nerve, which carries vision to the brain, is the second-leading cause of blindness.

Yet, despite those scary numbers, eye specialists have been treating glaucoma with variations of the same tools for decades: eye drops, which in the United States are the most commonly prescribed treatment; laser procedures, which are more popular abroad; and surgeries, some of which are based on techniques that most kindly might be called antique.

"There are different types of operations," said Dr. Joel Schuman, director of the UPMC Eye Center and professor and chairman of ophthalmology at the University of Pittsburgh School of Medicine. "Some of them have been around for a hundred years and some of them are very, very new and use technology that still has not been approved by the [Food and Drug Administration], so they are experimental ... [Others] have become available."

Two that have become available recently in Pittsburgh are the i Science canaloplasty and the Trabectome, NeoMedix's commercial name of the device used in the surgery called ab interno trabeculectomy (AIT). Both, unlike some of the early procedures, are minimally invasive.

To understand how they work, a brief explanation of the most common type of glaucoma is necessary.

The eye constantly produces fluid called aqueous humor that brings nutrition to the internal structure of the eye and takes waste to the blood vessels via the canal of Schlemm.

The canal in some ways functions like the rain gutters on a house, said Dr. Garry Condon, chairman of the ophthalmology department at Allegheny General Hospital. Atop it lies the trabecular meshwork, which Dr. Condon likens to the grating that keeps leaves out of the gutters. Like the gutter screens, the meshwork can get clogged, causing pressure to build up.

"If it is high enough, long enough, there is damage to the optic nerve," Dr. Condon said. "That is called glaucoma."

Glaucoma also can be caused by toxins in the nerve tissue damaging the optic nerve or by injuries, and babies sometimes are born with it, Dr. Schuman said, but the increased pressure of the clogged meshwork is the most common form and the kind seen most often in people 40 or over.

Eye drops lower that pressure either by reducing the amount of fluids made by the eye or by making it easier for fluids to leave the eye, Dr. Schuman said. It's like having a clogged drain in the house and either turning down the faucet or cleaning out the drain so the sink doesn't overflow.

"Laser stimulates the cells in the drain of the eye to work better and that helps lower the pressure in the eye," he said.

"When we do incisional surgery we're bypassing either a part or all of the drain of the eye and either building a new drain, removing the part where there's an obstruction or actually implanting a new drain," Dr. Schuman added. The two former are variations of the procedure known as a trabeculectomy; the latter is an implant. All three involve putting a hole in the white of the eye.

The canaloplasty and the AIT are much less invasive.

The former is similar to an angioplasty, said Dr. Robert Noecker, who is director of glaucoma services at the UPMC Eye Center and specializes in the canaloplasty.

A cut is made into the meshwork over the canal of Schlemm and a tiny catheter is inserted. "We stretch the canal, dilate it, then put a stitch or suture in so it stays open and the flow is easier," Dr. Noecker said. As in an angioplasty, the catheter is then removed.

"The size is only 200 microns, and 200 microns is a fifth of a millimeter," said Dr. Schuman, "so it's really finer than a hair." The surgery is done under a microscope.

"As a first procedure, it's probably one of the safest [operations]," Dr. Noecker said. "There's a fast recovery and predictable results. The reason I say that [it is so safe] is because you never enter the eye. The furthest you go is into the canal, so it has the lowest risk of infection. The canal is in the wall of the eye so the operation is never inside the eyeball.

"Because of that and because you're not leaving a hole, the chance of causing very low pressure is low as well. You've kept normal anatomy and tried to enhance how it works.

"And the other thing that's helpful is that it's easy to do in conjunction with cataract surgery."

Drs. Schuman and Condon prefer doing AIT with the Trabectome, which, Dr. Condon described as a "sophisicated, very small, microscopic tip on a device ... that allows us to remove the trabecular meshwork tissue" that is believed to be clogged. According to the Glaucoma Research Foundation, the incision is a mere 1/16 of an inch. After the clogged tissue is removed, the eye is irrigated with a saline solution to remove tissue debris. The eye recovers very quickly.

"It's simple, safe, the patient recovers rapidly and it leaves the door open for something else if it's not effective," Dr. Condon said.

Like the canaloplasty, the AIT can be done in conjunction with cataract surgery.

The two procedures are the shape of things to come.

"Conventional glaucoma surgery relied on a certain amount of healing without healing," Dr. Condon said, referring to surgeries that created new wounds by poking drainage holes into the whites of the eye.

"And so what we have been doing as technology has advanced, especially the last couple years, has been turning back to our indigenous drainage system ... [and] looking for ways to rejuvenate it rather than make a new hole in it."

The new emphasis is on clearing obstacles in the meshwork, he said.

"It unroofs that Schlemm's canal to provide more access of fluid to the outward pipes."

None of these surgeries can cure glaucoma.

"With glaucoma surgery, the purpose is to protect your vision, preserve the vision you have remaining," Dr. Schuman said.

The big trick, then, is diagnosing glaucoma early, since there are no symptoms until at least some vision has been lost.

"After the age of 40, people should be undergoing eye exams every two years to identify risk factors for glaucoma," Dr. Condon said.. "Then the frequency [of future exams] depends on that individual's characteristics of the eye and his risk profile."

Items in that risk profile should include age, whether the individual already has the disease and should be monitored, family history, how high is the eye pressure and, among other things, the thinness of corneas and race (African Americans have six to nine times the risk of developing glaucoma), he and Dr. Schuman said.

"The first step in a glaucoma exam is an examination of the eye from front to back," Dr. Condon added. It also should include a look at the optic nerve, ocular pressure reading, an exam of the drainage system and testing of the visual field.

If you're suspected of having glaucoma, you should have a more sophisticated examination that includes measurements of the shape and thickness of the nerve tissue in the back of the eye using modern technology, Dr. Schuman said. That allows specialists to follow patients over time using much better information than could be obtained from a standard eye exam alone.