Glaucoma
Opening eyes to SLT for glaucoma

At a glance


• SLT is typically used as a secondary therapy, but should be considered an alternative first-line therapy for some early glaucoma patients
• 2 possible theories behind SLT mechanism: mechanical (altering meshwork fibers) and biological (local cellular trauma)
• Although advantages to SLT as primary tx (20-30% IOP reduction), doctors and patients still wary
• SLT, a procedure with 50% suc

From cost to compliance and beyond why many are opting for laser

Source: Karl Brasse, M.D., EyeLand Design Network

When it comes to glaucoma, for many patients in the United States the laser often lights the way, according to Michael Berlin, M.D., director, Glaucoma Institute of Beverly Hills, Los Angeles, and professor of clinical ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles.
“SLT is commonly used as a second-line therapy rather than a first-line therapy in many practices,” Dr. Berlin said. “However, many of us are realigning our thoughts and using SLT specifically as a first line therapy as an offering to patients because it has such a little downside and in a certain patient population is very effective in delaying the need for additional medications.”
Currently, there are two theories on how SLT works, according to Dr. Berlin. “There is a mechanical effect, which I subscribe to and there is a biological response that is a result of cellular responses to the trauma induced by the SLT,” he said.
The two theories are very different. “The biological is a response to local cellular trauma, which induces changes—metalloproteinases which change the structure of the intracellular meshwork allowing more poracity and allowing outflow to increase through the change in the extra cellular matrix,” Dr. Berlin said. “The mechanical theory is that we’re altering trabecular meshwork fibers such that they become mechanically more effective as they were in earlier times when they were controlling outflow attached to the ciliary muscle able to have an outflow response mechanically.” He likens this to taking a carpet and shaking it out so that the fluff is up again, allowing more fluid flow across it than it would if it were matted. “This is why we believe that it doesn’t last for a long time because eventually it becomes matted again,” Dr. Berlin said. “Eventually the chemical stimulus that causes the biological response decreases because the stimulus is no longer there and then the response wanes.”

Early option

There are, however, a bevy of advantages to using SLT as a first-line approach. “When used as first line therapy it can delay the necessity for medication treatment, which means that the cost, the daily compliance issues and the potential side effects of the drugs can be delayed or eliminated by a successful SLT lowering event,” Dr. Berlin said. “When used as second line therapy you’re again delaying or postponing the addition of a second medication, which once again involves compliance, cost and side effects.”He sees the SLT approach as putting the control squarely back in the surgeon’s hands. “The difference is that the surgeon has the control over the outcome versus the patient’s daily need to be responsible for their health care,” he said.
Reay H. Brown, M.D., clinical professor, Emory University, Atlanta, and president, Atlanta Ophthalmology Associates, Atlanta, agrees that for many open angle glaucoma patients SLT is an attractive early option. “I have always advocated that laser is an excellent option because it is low-cost, it does help some people and is very safe and it has been shown in a large multicenter trial more than 20 years ago to be at least as effective as medical therapy,” Dr. Brown said. “So, it has many pluses but it has not really ever been embraced by ophthalmologists.”
Despite the advantages some practitioners and patients are still leery of the procedure. “It takes more time to explain it to patients,” Dr. Brown said. “In addition, for some reason we have poisoned the water regarding laser treatment and so when we talk to patients about doing this, some feel like it indicates that they are going blind.” As a result, practitioners may end up with a very emotional patient who thinks that the only reason he or she has been urged to undergo this high-tech treatment is because they are going blind. “You think that you’re doing something that is going to be helpful to them and all of a sudden they’re crying in the chair and you have to try to reassure them,” he said. “Sometimes it’s difficult because there are emotional triggers that you’ve activated just by the word laser.”
Practitioners themselves can also be reluctant to recommend the laser early in the treatment course. “We did a survey for EyeWorld back about 10 years ago, which went out to the whole ASCRS membership,” Dr. Brown said. “We asked at what point they would recommend laser treatment and in general it was really after all medical therapy; very small percentage said that they would recommend it as initial therapy.” In that same survey, however, when asked if the practitioner was being treated for glaucoma him or herself when they would want to undergo laser therapy, the approach was much more popular. “I think that four times as many responders said that they would want it as initial therapy,” Dr. Brown said.
Garry P. Condon, M.D., associate professor of ophthalmology, Drexel University College of Medicine, Philadelphia, chooses SLT for relatively early glaucoma patients. “Patients who are candidates for this would be people who have anatomically open anterior chamber angles who need modest pressure reduction, although sometimes the pressure reduction with the SLT laser can be surprisingly substantial,” he said. “I think that it is now a form of therapy that has proven itself to be a first-line option for appropriate patients because I think that it has been well shown that the treatment is at least as effective as a single drop of the most effective medication that we have to lower intraocular pressure.”
Typically, Dr. Condon expects to seea 20% to 30-plus percent reduction in IOP in appropriate patients. “In my hands the SLT laser seems to be more effective than the older argon laser and it has been a very positive thing in my clinical practice for me,” he said. “The SLT seems to be more of a kinder, gentler form of laser treatment.”
There are relatively few complications with the SLT procedure. “I would say that the most common would be that it doesn’t work,” he said. “In my hands, I would suggest to a patient that they have a 75% to 80% chance of seeing a pressure reduction of 20%.”
Dr. Brown starts thinking of using SLT after patients have been on one drop. “I’ll initially try one drop and for most people I will recommend it next,” he said.
Dr. Berlin agrees that that this is best used relatively early in the glaucoma treatment pyramid. “Certainly a number of doctors use it as first line therapy,” he said. “Most use it in place of a second drug if at all and some will use it as sort of a third drug.” In some cases SLT is used as a stopgap measure. “It is often used to postpone or delay the necessity for trabeculectomy surgery if needed when cataract surgery is pending,” he said. “If you see a patient who will have cataract surgery soon and you need a little bit of pressure for a time we will try SLT and see if that will allow us the time until we’re going into cataract surgery, at which time we may or may not combine the cataract surgery with trabeculectomy.”

Considering complications

He finds that there are virtually no complications with SLT. “There are a small number of patients who have rebound pressure elevation and a very small number for whom the elevation is permanent,” he said. “The main issue occurs in pigmentary glaucomas in which case the treatment has to be modified to use lower energy settings and less tissue treatment in most segmental surgeries so that you don’t cause an inflammatory response.”
Dr. Condon agrees that it is the patients with pigmentary glaucoma that practitioners worry about most with SLT. “They’re the ones in whom often we would consider dialing down the amount of treatment that we actually give and not treat the entire 360 degrees in one sitting,” he said. “But typically we do treat the entire 360 degrees.” Dr. Condon warns that it is in these patients with pigmentary dispersion glaucoma that there are concerns about getting undesirable high pressure spikes immediately following the treatment. “Other things like a little redness, achiness, sensitivity to light are not uncommon, but they’re very self-limited and typically have not produced significant patient discomfort,” he said.
Dr. Brown finds that SLT is usually very benign. One concern he does have are possible future implications of using the approach. “The biggest drawback is whether it might have an impact on future angle-based surgical procedures such as canaloplasty or Trabectome (Neomedix, Tustin, Calif.) or whatever else is developed.” he said. “I don’t think that it will preclude these but may change how effective they are.” While Dr. Brown isn’t aware of any impact so far he points out that there hasn’t been a study that specifically randomized patients between those who have had previous laser treatment and those who have not.

The implant angle

Such shunts and other implants have not attained the popularity of the SLT procedure. “In general they are behind the laser because that is something that you can do in the office in five minutes with no risk,” Dr. Brown said.
Implants meanwhile can have a bigger impact on pressure but at a more profound risk. “In 20 years of doing laser trabeculoplasty I haven’t helped everybody but I don’t think that I’ve made a patient with open angle glaucoma and no other adverse factors worse,” Dr. Brown said. “I can’t begin to say that about surgical treatment.”
There is little comparison between SLT and shunts and implants, Dr. Condon finds. “Laser is as effective as the most effective eye drops that we have and it comes into play at the stage of disease when we’d be using eye drops,” he said. “If you asked me what’s the difference between an eye drop and a shunt I’d say a lot.”
Laser is extremely safe. “I tell patients that in fact it could be considered in some ways safer than an eye drop because it doesn’t get into your system or your blood stream,” Dr. Condon said. “It’s not going to slow your heart rate down like timolol can or cause an allergy like some other drugs can, or cause dryness to your eye or disrupt the ocular surface in any permanent way.”
Complications with shunts, however, are another story. “As soon as you pull out the knife and you got to the operating room and you’re talking about incisional transscleral drainage procedures like trabeculectomy and tube shunts you’re talking about potential devastating complications,” Dr. Condon said. “Fortunately these are not common, but some of these include bleeding, infection, late infection, tube erosion with tube shunts, corneal decompensation, double vision, discomfort, loss of vision, and blindness.”
Dr. Berlin agrees that SLT is akin to drop, while shunts are much more invasive. “Think of the SLT laser as the next drop that is going to be used, but it’s a single use drop that acts effectively for 3 to 5 years,” he said. “Going to tube shunts and other trabeculectomy procedures is a next step in the patient treatment regimen paradigm that changes a lot of postoperative behavior because you’re modifying their external environment.” Once a shunt is in place patients must remain vigilant for infection and injury. “ELT [excimer laser trabeculectomy] is sort of a bridge between them because it provides a surgical means of lowering pressure but doesn’t cause a change in the outer surface of the eye,” he said.
Meanwhile, Dr. Brown finds that the biggest problem with SLT laser treatment may be expecting more from this than is realistic. “The potential exists that we can persist too long in expecting something to happen that isn’t going to happen,” Dr. Brown said. He tries to emphasize for patients that while SLT can be helpful in some cases it is not a fix for glaucoma.
Overall, Dr. Brown views SLT as an appealing approach. “It has been said that a procedure that is 50% successful and that has essentially no risk is a very attractive procedure,” he said. “Even if the success rate in terms of improving the pressure 3- to 5-mm is only 50% that’s a very appealing outcome in a treatment that has very little risk.”

Editors’ note: Drs. Berlin and Brown have no financial interests related to their comments. Dr. Condon has financial interests with Alcon (Fort Worth, Texas), Allergan (Irvine, Calif.), iScience Interventional (Menlo Park, Calif.), Optonol (Neve Ilan, Israel).

Contact information

Berlin: 310-855-1112, Berlin@ucla.edu
Brown: 404-252-1194, reaymary@comcast.net
Condon:412-359-6298, garlinda@usaor.net