Putting SLT In Action
Experts share clinical pearls for successful glaucoma laser therapy.
Glaucoma specialists agree it's virtually impossible to monitor patients' compliance with glaucoma medications. What's more, even conscientious patients who are willing to overlook the potential side effects of IOP-lowering agents may have difficulty paying for several glaucoma medications, especially when they use other drugs they may consider more critical to their health and well-being.
These are just a couple of examples of why laser therapy is making major inroads as a first-line treatment for primary open-angle glaucoma (POAG).
SLT Indications and Outcomes
How can clinicians predict what patients are good candidates for SLT? James B. Wise, M.D., of Glaucoma and Laser Surgery Associates in Oklahoma City, foregoes SLT if a patient can control his IOP with a single drop of low-dose bimatoprost (Lumigan); otherwise, Dr. Wise is a strong advocate for SLT as primary therapy.
"SLT is an extremely safe option for patients who have issues with drug compliance or tolerance. This procedure usually produces a 6-mm Hg pressure drop, which is enough of a drop for most people," he says.
South Dakota glaucoma specialist, Monte Dirks, M.D., of Blackhills Regional Eye Institute in Rapid City, says that some of his patients have had "startling" results with SLT.
"I've been pleasantly surprised. We offer this procedure to any patient who's using multiple medications, as well as those who are on monotherapy but have tolerance problems or even compliance or cost issues," Dr. Dirks says. "I've used SLT as primary therapy for people who were unable or unwilling to use eye drops, and I've been very pleased with our success."
Laser surgery isn't a new innovation in glaucoma treatment, but many clinicians prefer SLT over argon laser trabeculoplasty (ALT).
Before he purchased his Selecta II Glaucoma Laser System, Dr. Dirks performed about 50 ALT procedures per year. Now he performs about 100 SLT procedures every month.
Dr. Wise also reports success with SLT, noting that everyone he's treated with this procedure has lower post-op IOPs. His "maximum rational medical therapy" technique uses SLT to increase trabecular outflow in conjunction with a long-acting aqueous suppressor and a prostaglandin, which increases uveoscleral outflow.
"All these agents have relatively independent actions, and I consider SLT an additive to the prostaglandins," he explains.
SLT's large beam size covers the entire trabecular meshwork, decreasing the time it takes to complete a 360° treatment.
When Dr. Wise started performing SLT, he treated only 180° of the inferior angle, but he now treats 360° in all patients.
"To some extent, I use SLT in the same way I used ALT to increase trabecular outflow," he says. "If you throw your outflow load on half the meshwork, I think it will eventually decompensate. Spreading the treatment load around 360° gives you a better chance of long-term control."
Dr. Wise modeled his SLT treatment plan on a similar ALT approach that has controlled IOP for as long as 20 years.
"I apply 1.1 to 1.2 millijoules of laser power, even for patients with darkly pigmented trabecular meshwork (TM). We want to break up the material that's clogging the trabecular meshwork, so to remove more material, we have to use more power," he says. Despite his seemingly aggressive strategy, Dr. Wise rarely sees post-op pressure spikes.
Another physician who's switched from treating 180° to 360° of the TM in all SLT patients is Robert J. Noecker, M.D., a glaucoma specialist and vice-chair of the department of ophthalmology at the University of Pittsburgh. (See "Setting SLT Nomenclature" for a discussion of treatment terminology.)
"Anecdotally, patients who received 180° treatments had a lower success rate than those who received 360° treatments," he says. "A lot of those patients returned for 360° treatment." Dr. Noecker has noted a higher rate of IOP spikes with this more aggressive treatment, but these usually resolve within an hour.
"I decide what power settings to use based on the clinical endpoint. I set the laser at one millijoule and do a few test shots to see what happens. If I get a big bubble, I back it down. If I get no reaction, I turn it up 0.1 millijoules," he explains.
Mark A. Latina, M.D., relies on SLT's positive risk/benefit ratio to protect his patients from years of noncompliance. "I offer SLT to my patients who don't use their IOP-lowering medications. The procedure is easy to perform, carries minimal risks and can lower patients' IOPs without the burden of extended medication use," says Dr. Latina.
In clinical trials,1 SLT reduced IOP by an average of 25% (about 6 mm Hg) from baseline levels. When used as a primary intervention, SLT maintains about 75% efficacy for at least 2.5 post-op years.2
Dr. Noecker knows he's using appropriate power setting when he sees little "champagne bubbles" in the anterior chamber. "We're not causing any coagulative necrosis, but we're far more aggressive than we were with our original parameters," he says.
And surgeons can afford to be more aggressive. "SLT won't cause coagulation, even if you use more than one millijoule of power," says Mark A. Latina, M.D., associate clinical professor at Tufts University School of Medicine in Boston. "You may see depigmented areas, but that's because the laser is actually blowing pigment out of the meshwork and fracturing melanin granules. But you won't get any coagulation," he stressed.
Brian A. Francis, M.D., of Doheny Eye Institute at the University of Southern California Keck School of Medicine in Los Angeles, typically performs 360° SLT treatments -- with some exceptions.
"I may do a 180° treatment on patients who have pigmentary glaucoma or very heavily pigmented angles to reduce the chance of pressure spikes," he says. "When I started doing SLT, I was using lower power settings because the clinical study recommendations were to use just enough power to achieve champagne bubbles and then back off until they were gone. Now, we want to see champagne bubbles in more than half the spots before backing down," he says.
Ronald L. Gross, M.D., professor of ophthalmology at Baylor College of Medicine Cullen Eye Institute in Houston, started using SLT later than some of his colleagues.
"When I first started, others had already moved on to 360° treatments. They said, 'titrate to the champagne bubbles,' so that's what I do. I usually need 1.0 to 1.1 millijoules of power -- whatever it takes to get a champagne bubble," he says.
Dr. Dirks, too, is a late adopter. However, unlike Dr. Gross, Dr. Dirks continues to use the original 180° parameter. "I start with one millijoule and titrate my level based on response," says Dr. Dirks. "I may shift to 360° in the future, depending on what kind of long-term outcomes I see." Fifteen months into his follow-up, none of Dr. Dirks' patients have needed retreatment.
|Setting SLT Nomenclature|
Physicians communicate best when they use consistent terminology to describe procedures. The participants in this roundtable discussion discovered they were using different words for similar procedures, specifically 180°, 360° and repeat selective laser trabeculoplasty (SLT). After some discussion, they agreed to adopt the system proposed by Brian A. Francis, M.D., for the remainder of the event.
Dr. Francis uses three distinct terms to describe repeat SLT:
Completion: 180° SLT followed by treatment of the remaining 180°, for a total 360° treatment area
Enhancement: 180° SLT followed by 360° SLT
Retreatment: 360° SLT followed by additional 360° SLT.
Patients treated with SLT develop few post-op adverse events, and when they do, they're usually confined to brief pressure spikes, eye discomfort or increased anterior chamber irritation.
"I've observed pressure spikes, but I've never had a case where these spikes were difficult to control," says Dr. Gross.
In the 3 years Dr. Wise has been performing SLT, remarkably few of his 600 patients developed adverse events. He can name only two patients, including one with pigmentary glaucoma, whose IOPs increased after SLT and who had to go on to filtering surgery.
Dr. Dirks pretreats all of his SLT patients with brimonidine (Alphagan) and avoids post-op steroids.
"Jorge Alvarado, M.D., recommends we let nature take its course, and give the eye time to stimulate some inflammation, so I don't want to suppress that," he says. "I have a 3% post-op complication rate -- 1% needed treatment for uveitis, 1% had pressure spikes and 1% developed ocular surface problems, either an abrasion or discomfort," he says.
Dr. Dirks even has had success treating angle recession with SLT. "I've treated the undamaged portion of the angle in about a half-dozen people, achieving the average 25% IOP reduction," he says.
Dr. Latina, too, has been successful using SLT to treat traumatic glaucoma with open angles and angle recession. "I've had no post-op spikes and no patients who had to go to filtering surgery," he says.
Dr. Francis reports pressure spikes, which usually resolve by the next post-op day, in 3% of his SLT patients. "I rarely prescribe post-op medications. About 10% of my patients have significant inflammation or complain of soreness or irritation at their 1-hour post-op pressure check. I give these patients nonsteroidal anti-inflammatory drugs (NSAIDs) to use three or four times a day as needed, usually for about 3 days," he says.
Like Dr. Dirks, Dr. Noecker uses brimonidine prior to SLT, but he also prescribes post-op NSAIDS to his patients. "Before I started using NSAIDS, my patients complained that their eyes felt achy during the first post-op week," says Dr. Noecker. "This ache was really their only complaint about SLT. We often see a lot of pigment in the anterior chamber in the first post-op hour, but it's relatively unusual to see inflammatory cells. I give my patients NSAIDs more for comfort than inflammation," he says.
Comparatively speaking, Dr. Noecker points out, ALT is a painful procedure. Patients report experiencing a "pin prick" sensation with ALT that doesn't occur with SLT. "Complaints about post-op pain vary from patient to patient, but SLT patients report a low level ache, at worse," he says.
Dr. Wise reported using steroids four times a day for 4 days after ALT, whereas with SLT he prescribes the nonsteroidal diclofenac (Voltaren) four times a day for 4 days. "Whether or not to suppress inflammation is an interesting question to which I've given a lot of thought, and I decided diclofenac represents a good middle ground," he says.
Expanding Treatment Horizons
Disease progression in glaucoma is directly related to patient compliance with therapy. In the hands of a skilled surgeon, SLT offers patients a safe, effective and less painful alternative to ALT and a more convenient solution than daily eye drops.
1. Latina MA, Sibayan SA, Shin DH, et al. Q-switched 532-nm Nd:YAG laser trabeculoplasty (selective laser trabeculoplasty): a multicenter, pilot, clinical study. Ophthalmology. 1998;105:2082-2088.
2. Nagar M, Howes F. Selective laser trabeculoplasty: a new approach to open angle glaucoma management. Poster presented at: Annual Meeting of the Academy of Ophthalmology; October 20-23, 2002; Orlando, Fla.