Interventional Glaucoma: Selective Laser Trabeculoplasty (SLT) And Minimally Invasive Glaucoma Surgery (MIGS)

A Roundtable Discussion Of Nondestructive Interventional Treatments For Open-angle Glaucoma 

VIDEO SOURCE: Ellex Medical on YouTube 

At ASCRS 2018 in Washington, DC, a group of surgeons experienced in interventional glaucoma therapies sat down to discuss the roles of selective laser trabeculoplasty (SLT) and microinvasive glaucoma surgery (MIGS) for treatment of open angle glaucoma (OAG).

Iqbal Ike K. Ahmed, MD, FRCSC, introduces this roundtable discussion of different paradigms in glaucoma therapy, with Mahmoud A. Khaimi, MD; Mark J. Gallardo, MD; David Richardson, MD; Nathan M. Radcliffe, MD; and I. Paul Singh, MD.  

SLT and MIGS: An Interventional Approach

Dr. Ahmed: I want to keep it pretty open to start, just talking about your current treatment paradigms for OAG. Tell me your thoughts.

Inder Paul Singh, MD: I think it depends on your target pressure, of course, but maintaining the patient’s quality of life is always key for me. How can I get pressure down, maintain the pressure long term, and maintain a high quality of life? To meet those goals, I try to minimize patients’ reliance on drops, thereby avoiding all of the various compliance issues we face. I tend to use SLT as a first line, if possible, and now also offer MIGS procedures earlier than I would offer traditional glaucoma surgeries, in an effort to minimize the impact of compliance in this long-term disease. Drops are always there as an adjunct as needed.

Mark J. Gallardo, MD: I agree—minimizing medication reliance is critical. In fact, when I encounter a glaucoma patient with mild to moderate disease with a visually significant cataract, I use that as an opportunity to manage both the patient’s cataract and glaucoma. Unlike in the past, when I would rarely couple a cataract surgery with our more invasive filtration procedures in such patients, I now almost always automatically couple the patient’s cataract surgery with a glaucoma surgery—a MIGS procedure. I do this because of the proven safety and efficacy in both IOP and medication reduction, and minimal additional recovery compared to cataract surgery alone.

Dr. Ahmed: We can draw from a few categories of glaucoma therapy. We have medications, interventional therapies like SLT and MIGS, and more traditional surgeries such as trabeculectomy and tube shunt. Tell me about how you use SLT and MIGS in conjunction with each other in your practice.

Mahmoud A. Khaimi, MD: My treatment paradigm is to go to SLT as primary therapy, and then use a MIGS procedure like ABiC with the iTrack microcatheter after that. If the disease progresses, my next steps would be perhaps SLT again, and then maybe some other MIGS, pushing back filtering and tube surgeries to later stages. In this paradigm, medication has actually fallen to kind of an adjunct in between those treatment stages. I think that’s the way we’re heading.

David D. Richardson, MD: I agree with that. I think that, at least here in the United States, it has always been an issue with medical/legal acceptability to go straight to a procedure instead of starting with medication. The safety profile of SLT is so great, I would argue that it’s actually a safer first option than many of the medications. We talk about, for example, the beta-blockers as being a potential problem because they can have an impact on older patients. I actually had a younger, athletic patient end up in the emergency room because of his reaction to beta-blockers. So medications not only carry issues of adherence and cost, even with generics, but also health risks. I’ve never had a patient go to the emergency room after SLT. Never.

The safety profile of SLT is so great, I would argue that it’s actually a safer first option than many of the medications.

—David D. Richardson, MD

Dr. Singh: You’re right. And I’d add that there is the medications’ toxicity to consider as well. Also, most of our medications also divert fluid away from the natural outflow. The ability of SLT to maintain the flow through the trabecular meshwork (TM) as well as the canal and distal channels means we can maximize the flow through the natural outflow systems as early as possible. That not only lowers pressure but also has the potential to prime the area for use of MIGS at a later time. Using SLT and MIGS earlier is very important to increase compliance, minimize toxicity, and improve the flow for long-term effect.

Dr. Ahmed: It sounds like most of you are using SLT early in the treatment paradigm, and in your experiences, patients are receiving that option quite well. Other than thinking about it as a primary therapeutic response, how do you feel about using SLT as an indicator of response to MIGS?

The ability of SLT to maintain the flow through the trabecular meshwork as well as the canal and distal channels means we can maximize the flow through the natural outflow systems as early as possible. That not only lowers pressure but also has the potential to prime the area for use of MIGS at a later time.

— Inder Paul Singh, MD

Dr. Singh: This is something that my colleagues and I have studied. Recently, we conducted a retrospective analysis of our first iStent Trabecular Micro-Bypass Stent (Glaukos) cases with at least a 1-year follow-up. We found that patients had done well overall. When we analyzed the subset of patients who had previous SLT, we found those with historically a good response to SLT had better IOP reduction and were on less postoperative medications than the patients who historically did not have a response to SLT.

These outcomes made us reexamine SLT as a possible diagnostic tool and provided our first inkling that we needed to examine the location of future MIGS treatment. SLT works at the TM, right? So, if it works well, we can conclude that the flow is probably good in the canal and distal channels. If it does not work well, then there might be some downstream resistance.

Now a positive SLT outcome leads me to think a trabecular bypass might be sufficient as well as ABiC with iTrack, while a poor effect of SLT leads me to conclude that the patient might have better results if we focused not just on the TM, but rather on the entire outflow pathway, including the distal channels, which would lead me to rely on a procedure like ABiC with iTrack. We are still studying the outcomes to determine if this is an accurate predictor.

Dr. Khaimi: Whether SLT works or it doesn’t, I still do ABiC with iTrack afterward because I think it’s a little bit more powerful than other MIGS options and it comprehensively treats everything. So, perhaps we weren’t able to open up the TM very well with SLT, but with ABiC viscodilating so much of the canal, I think it opens up the TM well. To me, SLT is a good indicator of whether ABiC will be effective afterward, but if SLT doesn’t work, that doesn’t keep me from doing ABiC.

Dr. Singh: I agree with you. I think that’s one of the most important points. I probably wouldn’t do a TM bypass-only device after unsuccessful SLT. That’s where I think ABiC with iTrack can really help out in those patients.

Nathan M. Radcliffe, MD: We’re moving toward standalone MIGS procedures, and SLT is sort of the grandfather of standalone glaucoma interventions. A patient who did well with that SLT intervention is sort of psychologically primed to think, “I trusted Dr. Radcliffe. He told me there would be a laser, that I would recover very nicely, and that it could work. It worked. That was 4 years ago. Now things have changed with my glaucoma, and he’s recommending ABiC. I’ll do it.” Our patients are buying into this paradigm. As we gain experience and confidence with SLT, we’ll feel more confident in offering these safe, standalone MIGS procedures. The end result is that we’re changing the overall paradigm to what Dr. Ahmed has called interventional glaucoma laser, that I would recover very nicely, and that it could work. It worked.

I don’t think that we can do ALT anymore because we’re doing MIGS as a first-line surgical treatment now. There’s a big theme of rejuvenation in glaucoma now. SLT achieves that, and then we’re rejuvenating the TM a little bit more with ABiC with iTrack. So, unlike ALT, SLT’s nondestructive nature does not preclude future MIGS treatment options.

— Mahmoud A. Khaimi, MD