ABiC™ In The Spotlight
A Roundtable Discussion Of Nondestructive Interventional Treatments For Open-angle Glaucoma
VIDEO SOURCE: Ellex Medical on YouTube
Dr. Ahmed: Let’s focus on one of the MIGS: ABiC with iTrack. We’ve all used this system, and I think there is increasing interest in the procedure. Could a few of you describe how ABiC works, in terms of its mechanism of action and how it lowers pressure?
Dr. Richardson: I describe ABiC to my patients as essentially angioplasty for the eye. We take a drainage system that has been stopped up and we expand it, rejuvenating the natural outflow. Patients get that, because they all understand what angioplasty is.
One of the things that I like about ABiC with iTrack is how we approach it. I take a step-wise approach with MIGS. First I want to use SLT to get the TM working better. If the improvement is not enough, then I want to make sure that the outflow system is truly open by using ABiC with iTrack. The next step, in my opinion, is placing a stent, so we’re creating a communication pathway. So that’s the step-wise approach that I take, and patients understand that. You’ve got an obstruction, you’ve got a drainage system behind that, and then sometimes you have to open it up. It’s nice, because it’s a very simple, straightforward, easily understood discussion to have.
Dr. Khaimi: That’s truly the epitome of interventional glaucoma therapy. The mechanism with ABiC is viscodilation of Schlemm canal, which might be collapsed or have herniated TM in it. We’re also creating intratrabecular fractures and beams that allow aqueous to flow through diseased TM and out through the conventional outflow pathway.
There are a lot of pretty revolutionary MIGS options, but I like to start off with ABiC first. There is a misconception that it only works on the canal distally. I think that ABiC comprehensively treats all outflow channels, which is why it is my first go-to MIGS procedure. I don’t have the diagnostic capability to know where the obstruction is located or what level of resistance exists, so I like to start off with a MIGS that addresses everything. The other advantage is that ABiC doesn’t burn any bridges. I can do any other procedure afterwards because it isn’t destructive, and I don’t have to worry about a device.
Dr. Richardson: We were talking earlier about SLT being a diagnostic tool. ABiC with iTrack has the same potential. If it doesn’t work, then there’s no point in going in later and putting in a stent or a scaffold. A failed ABiC is telling you this system is not capable of being reopened. Fortunately, that’s quite rare, but if we’re looking at a step-wise approach, I would not place a stent in a patient who does not respond to ABiC. Instead, I would look at a suprachoroidal shunt or another approach.
I describe ABiC to my patients as essentially angioplasty for the eye. We take a drainage system that has been stopped up and we expand it, rejuvenating the natural outflow. Patients get that, because they all understand what angioplasty is.
—David D. Richardson, MD
Dr. Radcliffe: Dr. Khaimi, could you explain the phrase “trabecular herniation?” I just learned about this.
Dr. Khaimi: When pressures increase, we see trabecular meshwork herniating into Schlemm canal. Haiyan Gong, MD, PhD, in Boston has assembled a lot of beautiful pathology slides showing POAG compared to normal eyes. POAG eyes tend to have a lot more herniations, especially complete herniations.2 I tell my patients, “Your canal looks like this when it’s working normally. But if it has become clogged or collapsed, we need to balloon it open.” We need to alleviate the trabecular herniation.
I think that ABiC comprehensively treats outflow locations, which is why it is my first go-to MIGS procedure. I don’t have the diagnostic capability to know where the obstruction is located or what level of resistance exists, so I like to start off with a MIGS that addresses everything.
—Mahmoud A. Khaimi, MD
Dr. Gallardo: To add to Dr. Khaimi’s comments, Dr. Gong found that in postmortem POAG eyes fixed at 0 mm Hg, 95% of collector channels were obstructed by these TM herniations, while in non-POAG or normal eyes, only 15% of collector channels were obstructed despite being fixated at 10 mm Hg.1 The iTrack catheter itself lyses these herniations within the canal, in addition to viscodilating the distal system.
Robert Stegmann, MD, also showed that while viscodilating Schlemm canal using the iTrack catheter, microperforations within the inner wall of Schlemm canal are created.3 The microperforations help counter the reduction in the inter- and intracellular micropore population exhibited in glaucoma patients. Given the endothelial cells of Schlemm canal are connected by tight-junctions, it is thought that these micropores help facilitate aqueous outflow through the inner wall and into Schlemm canal.
Dr. Ahmed: We know the nondestructive nature of ABiC with iTrack. We’ve heard about the multiple mechanisms of action, plus its proximal system and distal system. We’ve been using it. What about our colleagues? What are the barriers to adoption? Are they technical or knowledge related? What barriers have you seen, and how do you approach them?
Dr. Gallardo: The most challenging portion of the procedure is the initial intubation of the canal. Once the catheter is in the canal, it’s very easy to thread the iTrack throughout the canal’s entirety.
Surgeons who are not MIGS trained at this point face the same barriers as any new surgeon to the angle. They need to learn to obtain a clear view of the nasal angle with a direct surgical gonioprism as well as to manipulate surgical tools within the angle. However, if a surgeon is MIGS trained, I think the barriers to ABiC are minimal. They will have a limited learning curve because they’re already in the angle, and it won’t be difficult for them to achieve success with this procedure.
Dr. Radcliffe: I was performing MIGS already, but I was probably the last of this group to adopt ABiC, and I think you’re right. Maybe it seemed a little bit intimidating, but actually not only was it fun to adopt, but it was enjoyable as well. I felt the thrill of actually doing surgery on the canal rather than just putting things in it in one simple shot.
What impressed me was the level of confidence I had during the procedure. I knew I was achieving the anatomical goal for the canal. I think surgeons commonly aren’t quite sure that they’re where they want to be in the canal, and this solves that problem 100 percent. Surprisingly for me, I think I felt more confident that I had achieved my surgical goal after my first ABiC procedure than I ever felt with a TM procedure. It was just so clear as the anatomy literally lit up, with the iTrack going around the circle, that I was certain it was right. It was fun, too. I said, “Why did I wait so long?”
My barriers to adoption were, first, some misconceptions. For example, I thought that I had to buy a big device that illuminates the iTrack microcatheter. I didn’t realize that it was easily obtainable with the first case without a capital investment. The other barrier is that it can be very difficult to change practice patterns. We have to find out who our rep is, make a phone call, and talk to a colleague who’s been doing it. If I operated in the same OR as an iTrack user, I would have adopted it a long time ago, but I had to start without any exposure. Once I got the ball rolling, it was easy. If there’s a lesson learned for me, it’s that there’s no need to wait.
Dr. Gong found that in postmortem POAG eyes fixed at 0 mm Hg, 95% of collector channels were obstructed by these TM herniations, while in non-POAG or normal eyes, only 15% of collector channels were obstructed despite being fixated at 10 mm Hg. The iTrack catheter itself lyses these herniations within the canal, in addition to viscodilating the distal system.
—Mark J. Gallardo, MD
Dr. Ahmed: How does ABiC with iTrack compare to the other MIGS out there, and where does it fit?
Dr. Khaimi: A lot of the other MIGS are stents that bypass the obstruction. For example, iStent bypasses a diseased TM. Cypass Micro-Stent (Alcon) is a suprachoroidal device. With ABiC, no device is implanted in the eye. We use the iTrack catheter to go around the canal, and as Dr. Radcliffe described, we can see exactly where we’re going. There’s no guessing game. That’s a big thing for me. I’m a belt-and-suspenders kind of guy, so if I think that the disease process is somewhere along the line from the TM to the distal region, it’s nice to be certain that I’m in the area I want to treat.
Dr. Richardson: In a comparison of trabeculectomy to all of the available alternative procedures, the only two that came close were glaucoma drainage devices and ab externo canaloplasty.4 The work that Dr. Gallardo and Dr. Khaimi have done has indicated that ABiC with iTrack produces results that are quite close to what we can expect from ab externo canaloplasty.5 So, while we don’t have a direct comparison among all of the players, the results certainly suggest that ABiC with iTrack may be a bit more effective than other MIGS options that we have, without a destructive ab externo procedure.
Dr. Ahmed: What does your the typical ABiC with iTrack patient look like?
Dr. Singh: I think the beauty of ABiC with iTrack is that a large population of patients can benefit from the procedure. It’s not just for a patient who is pseudophakic at the time of cataract surgery. Another nice feature is that it can be used for mild to moderate glaucoma as well as advanced disease. I’ve performed it on postoperative trabeculectomy and tube patients, in cases where there was good visualization and access to the TM. I find that the selection of patients is very broad, so when I want to manage the natural outflow system for any patient, this is a very universal choice.
In Dr. Khaimi and Dr. Gallardo’s respective data, ABiC worked very well used both as a standalone and in combination with cataract surgery, as well as in different types of patient populations.4 For those who had starting pressures that were high or in the middle to upper teens, you saw a significant reduction that was maintained. For those who had lower, more controlled IOPs, ABiC with iTrack kept the IOPs low but reduced the drop burden significantly. That responder rate is what excites me. We don’t know where the resistance to outflow is preoperatively. Is it the TM, Schlemm canal, or distal? While various MIGS procedures may work on specific sections of the outflow system, ABiC’s multiple mechanisms let us hedge our bets and, in my opinion, have a better chance of getting that reduction of pressure in the right type of patient population. As long as I have a good angle and can see it very well, I think the patient is a very good candidate for ABiC.
While various MIGS devices may work on specific sections of the outflow system, ABiC’s multiple mechanisms let us hedge our bets and, in my opinion, have a better chance of getting that reduction of pressure in the right type of patient population.
—Inder Paul Singh, MD
INTERVENTIONAL GLAUCOMA: SLT AND MIGS
A Roundtable Discussion Of Nondestructive Interventional Treatments For Open-angle Glaucoma
Cataract & Refractive Surgery Today
SUPPLEMENT | AUGUST 2018
Sponsored by Ellex Medical
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