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April 2008

 
Feature
When Glaucoma Progresses Experts Discuss the Incision Decision
By Miriam Karmel, Contributing Writer
 
 

Unlike cataract removal or retina reattachment, a decision to treat glaucoma progression with surgery is rarely straightforward.

Ask four glaucoma specialists when to move from eyedrops to the operating room and you’re likely to get eight different opinions, said Dale K. Heuer, MD, professor and chairman of ophthalmology at the Medical College of Wisconsin in Milwaukee. One thing, though, is clear. The reluctance to perform incisional surgery runs deep. Doctors resist it. Patients resist it. Some physicians never do surgery without trying medication. And some patients will try anything before agreeing to surgery.

There are many factors to consider before progressing to surgery, from the severity of the glaucoma to the patient’s age, ability to adhere to and/ or afford medication and coincident morbidities. The surgical procedure itself gives doctors and patients pause. Despite all the tweaking to perfect it, the gold standard trabeculectomy is risky. As Dr. Heuer explained, it’s not like cataract surgery, for example, which is so successful and which typically transforms the patient’s vision with minimal risk of serious complications. Similarly, retina surgeons faced with detached retinas have an easier decision. “If you don’t fix those, the vision will get worse,” he said. “Even the threshold for cornea transplant has been lowered. The decision to do glaucoma surgery, at least where pressure is not way off the map, is difficult.”

A RISK/BENEFIT RATIO. So when to resort to surgery? “When is a hard question to answer because some people do very well with medicines and some don’t,” said Douglas E. Gaasterland, MD, clinical professor of ophthalmology at Georgetown University. “When you’re sitting there in the chair with a patient, you can’t tell how they’re going to do with medication until they try them.”

The mantra has been and continues to be: medication first.

“Our standard approach to glaucoma is to begin with medical therapy and escalate by adding drops or using combined agents,” said Steven J. Gedde, MD, professor of ophthalmology at Bascom Palmer Eye Institute. “When that fails to adequately control IOP, traditionally we use laser trabeculoplasty. We reserve surgical intervention for patients who have inadequately controlled glaucoma, despite maximum tolerated medical therapy and appropriate laser treatment.”

The move toward surgery, as Dr. Heuer put it, comes “when the risk of continuing to observe outweighs the risk of doing surgery.” And what is that threshold? Determining the answer to that, Dr. Heuer said, “is more often art than science.”

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Reconsidering the Standard

Over the years, there have been challenges to the traditional stepped regimen of medication then laser trabeculoplasty. The Glaucoma Laser Trial (GLT) demonstrated that initial laser is at least as effective as medication.

And while doctors seldom, if ever, do glaucoma surgery before trying medication, a case has been made for surgery first—at least in newly diagnosed open-angle glaucoma patients with advanced visual field loss. The Collaborative Initial Glaucoma Treatment Study (CIGTS) found that lowering intraocular pressure with initial filtering surgery is as effective as medical therapy for inhibiting progression of visual field damage. In fact, surgery yielded a slightly greater reduction. The data derive from a subanalysis of the CIGTS data, reported by Paul Lichter, MD, and colleagues. It didn’t matter whether subjects with mild baseline visual field loss (mean deviation –2 dB or better) had surgery first or medication. But the subanalysis found that patients with more advanced visual field loss at baseline (mean deviation worse than –10 dB) fared better with initial surgery, compared with the medication-first group. The complete analysis has been submitted for publication.

OLD STANDARD STILL IN PLACE. Though the GLT and CIGTS studies showed that laser and surgical treatment were essentially equivalent to initial medical therapy, “They didn’t create a shift in the paradigm,” said Dr. Gedde. Medication continued to trump surgery as a first-line treatment. “I generally will give patients at least a trial of medical therapy,” Dr. Gedde said. “If they can be compliant and have access to medication, even people with advanced glaucoma will receive a trial with medical therapy.”

MAKING EXCEPTIONS. On the other hand, Dr. Gedde will consider surgical intervention as initial therapy in patients who have limited access to medications or who admit to poor compliance with other medications. Generally speaking, he said there is no magic IOP number—no cutoff point—that mandates surgical intervention. “You have to individualize to the patient,” Dr. Gedde said. “It requires judgment on the part of the clinician. It’s not easy to know when to pull the trigger.”

Marianne Feitl, MD, agrees. “ALT (argon laser trabeculoplasty), or SLT (selective laser trabeculoplasty), or surgical intervention has to be tailored to the individual patient, which is how we’ve always approached the issue,” she said. “There’s not been a huge shift in thought process about it.” Dr. Feitl is in private practice in Chicago.

“We’re inclined to use medications first, primarily because if you get into trouble, you can stop them,” Dr. Gaasterland said. “If you get into trouble with surgical intervention, it’s done. You can’t undo it,” he said. The result is, “We tend to be conservative.”

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Various Routes
SAME GOAL

Our glaucoma specialists do not disagree with each other’s essential goals for incisional surgery. But their particular strategies, concerns and patient criteria may very much affect how aggressively or frequently their threshold for surgery is reached.

Marianne Feitl, MD
In private practice with Arbor Centers for Eye Care in Chicago.

If there is too much scarring on the conjunctiva anteriorly, or if Dr. Feitl doesn’t think a trabeculectomy has a reasonable prognosis, she puts in a tube shunt 8 to 10 mm posterior to the limbus. Should trabeculectomy or tube shunt fail, then diode laser photocoagulation is an option. “We always try to temporize. It’s always worth trying medication, for at least a brief period of time.” Dr. Feitl selects patients carefully to avoid hypotony from antimetabolites.

Douglas E. Gaasterland, MD
Clinical professor of ophthalmology at Georgetown University.

“The guiding principle is we want to save vision as best we can,” Dr. Gaasterland said. “Most of the studies pay attention to eye pressure, but eye pressure doesn’t matter to the patient. What the patients care about is whether they can see the newspaper and read. Reduce the eye pressure from the level associated with damage and you can keep them that way. That’s the name of the game these days
—it has been forever.”

Steven J. Gedde, MD
Professor of ophthalmology at Bascom Palmer Eye Institute in Miami.

If a patient is developing glaucomatous damage despite apparent IOP control, Dr. Gedde considers that IOP measurements in a patient with an extremely thin cornea might be under true IOP. So he is sure to check central corneal thickness.

He is also mindful that the patient may be more compliant prior to office visits, and that diurnal fluctuations may mean that peak IOP measures may be occurring at times other than normal office hours.

Dale K. Heuer, MD
Chairman of ophthalmology, Medical College of Wisconsin and director, Froedtert and the Medical College of Wisconsin Eye Institute, Milwaukee.

Surgery first is an option in a patient with a mean defect worse than 10 dB, according to Dr. Heuer. “As a glaucoma specialist, I’ve had a little lower threshold for surgery,” he said, adding that the report (submitted for publication) from CIGTS “crystallized that for me.” But he said the decision to operate should be based on visual field testing, not on changes in GDx, HRT or OCT images. He also avoids surgery on ocular hypertensives or glaucoma suspects.

Andrew G. Iwach, MD
Associate clinical professor of ophthalmology, University of California, San Francisco, and executive director of the Glaucoma Center of San Francisco.

Dr. Iwach emphasized the uniqueness of each patient, and the importance of tailoring the results of studies to each patient’s clinical situation.

“All these studies report in averages and means. But we don’t treat averages or means. We treat individuals. Our job as clinicians is to determine an accurate risk assessment for that individual, drawing on studies and being aware that you need to customize the treatment.”

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Are We Too Conservative?

In patients with moderately advanced glaucoma, said Dr. Heuer, “We’re probably not operating enough.” Ophthalmologists are conservative because although trabeculectomy is safer than ever, he said, “It’s still not totally predictable, and it doesn’t always work, even when done well.”

THE FEARFUL PATIENT. Dr. Heuer, who has always been prone to operating when he sees moderate disease progression, is caught in a kind of catch-22 when it comes to early surgical intervention. On the one hand, he is talking to patients earlier about surgery. But he’s also very open with them about potential complications. As a result, he isn’t operating substantially more than in the past because many patients, after hearing the options, decide to stick with medication.

LASER BEFORE SURGERY. He’s not alone. “There are patients who will refuse to have surgery, even when we decided that medical therapy is not working,” said Dr. Feitl. They’ll try laser, and even oral carbonic anhydrase inhibitors, despite their potentially serious complications. “They’d still rather do that than have a surgical procedure.” She added that laser, though it doesn’t achieve pressures as low as trabeculectomy and doesn’t lower pressure much for about 15 percent of patients, is a good option after exhausting the prescription drug armamentarium. “If we do move on to needing a surgical procedure, patients and I are more comfortable knowing that we did try other reasonable avenues first.”

“Though laser trabeculoplasty doesn’t work as long as we’d like, it can buy time,” said Andrew G. Iwach, MD. “If that’s your objective and you have been able to avoid the more invasive step of trabeculectomy, you’ve done the patient a service.” Dr. Iwach is associate clinical professor of ophthalmology at the University of California, San Francisco.

LASER BEFORE DROPS? Dr. Iwach warned against rushing to surgery. “Glaucoma is, in general, a slow-moving disease, so you have the time to collect data, establish trends and then make a decision before you do something.” That’s where laser trabeculoplasty has a role, perhaps even more than eyedrops. “It can delay taking a patient to surgery. In some patients, it can delay the need for medication.”

Dr. Feitl agreed, noting that medication has a downside. Aside from cost and compliance issues, drugs can induce changes to the conjunctiva that may reduce surgical success down the road. She added that not doing surgery has its risks. “We have to tell patients that there’s a higher risk of losing your vision from uncontrolled glaucoma,” Dr. Feitl said.

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Each Patient Case by Case

“For some people, it’s going to be plain as day that you’ve got to do surgery. For some people it’s going to be a puzzle,” Dr. Gaasterland said. The obvious case involves a patient on maximum medication, with a high pressure and a deteriorating optic nerve or visual field. “The puzzling one is the one who’s not getting worse,” he said. That patient may have a pressure of 23, with a target pressure in the teens, but the visual field and optic nerve measures are holding steady. “You have a choice to escalate medication because they’re not yet on maximum treatment. That’s the person who you have to think about and decide about individually. Will they be able to adhere to a more complex medical schedule? Will more medication work? There is no easy guidance on this. It depends on the patient and the doctor.”

USE LOGICAL CRITERIA. Dr. Feitl’s criteria for operating include noncompliance and an inability to afford medication. Also, if a patient is getting worse, in spite of medical therapy, even if the pressure looks reasonable, “surgery is warranted because that approach may get a lower pressure,” said Dr. Feitl.

LOOK AT THE WHOLE PATIENT. There are no easy answers. “People like a cookie-cutter formula,” Dr. Iwach said. But a lot of patients fall into a gray area between monitoring and more aggressive treatment. That’s where being MDs comes in pretty handy, he said. Ophthalmologists have all the skills to assess the patient’s overall health and base treatment decisions on that information.

DON'T BE OVERLY CAUTIOUS. “It’s so individual, by patient, that it’s hard to articulate a precise point at which you’ll do surgery,” Dr. Heuer said. “What my colleagues and I struggle to realize is that in some of our patients we’re actually a little late to operate. With moderate to advanced glaucoma, we need to be a little more aggressive than most of us have historically been. At least with patients with advanced disease, we need to have a little lower threshold. We ought to operate more than we have.”

And clearly, doctors would operate more if they had a better surgery. “If we had the equivalent of clear cornea phaco with foldable IOL surgery, we would probably operate a lot sooner. But so far we don’t,” Dr. Heuer said.

Dr. Feitl, who has never treated a patient initially with incisional surgery, agrees. “If we had the perfect surgical procedure, with zero complications, I think we’d be doing a lot more surgery. But we haven’t got the perfect surgery yet.”
___________________________

Drs. Feitl, Gaasterland and Gedde report no related financial interests. Dr. Heuer has received consulting and speaker honoraria from Alcon, Allergan, Carl Zeiss and Pfizer. Dr. Iwach has served on speaker bureaus for Alcon, Allergan, Iridex, Ista, Lumenis, Merck and Carl Zeiss.
___________________________

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Trabeculectomy and the Fornix-Based Flap

If you could avoid creating an ischemic, localized bleb, would you be more inclined to do surgery earlier? Dr. Feitl said it’s probable. “We’d be more comfortable moving on to earlier surgical intervention,” she said, explaining that the benefits would outweigh the burden of patient adherence, the costs and the potential for localized and systemic side effects that are associated with medical therapy. “Traditionally, in the United States, surgery was considered a treatment of last resort because of the risk of infection,” Dr. Feitl said. “Some of the bias against surgery was in knowing that you often could end up with these ischemic, localized blebs.”

Trabeculectomy is still risky, but Dr. Feitl has adopted a surgical technique intended to create healthier blebs. The Moorfields Safer Surgery System, advanced by Peng T. Khaw, MD, PhD, involves a fornix-based flap with adjustable sutures and a diffuse application of antimetabolites. The resulting bleb is healthier appearing, flatter and more diffuse, as opposed to the elevated, ischemic and localized blebs that result from limbus-based flaps, Dr. Feitl said.

Dr. Heuer also has adopted the fornix-based flap, but he noted that Dr. Khaw’s technique involves two changes to the traditional surgery. One, he changed the flap technique. Two, he went from a local to more diffuse application of mitomycin C. “I think it’s more the latter that has changed the bleb morphology,” Dr. Heuer said.

Dr. Feitl stressed the importance of applying the antimetabolite over a large area. But she is so sold on Dr. Khaw’s technique that she no longer creates limbus-based flaps.

Dr. Khaw is a consultant ophthalmic surgeon at Moorfields Eye Hospital in London and professor of glaucoma and ocular healing at University College London. For a video presentation of Dr. Khaw’s surgical technique, “Advances in Trabeculectomy Surgery: The Moorfields Safer Surgery System,” go to http://aao.scientificposters.com/vodAbstract.cfm?id=25, click on “videos on demand” and type “Khaw” into the author field.

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