Glaucoma remains a leading cause of irreversible blindness worldwide, as the global population ages, and is destined to become an even more substantial clinical burden. At present, approximately 95 million people worldwide are affected by glaucoma; this number is expected to rise to 111.8 million cases by 2040.1
Although medical therapy and laser treatment remain first-line approaches, many patients ultimately require surgical intervention to achieve adequate intraocular pressure (IOP) control and prevent progressive optic nerve damage.2
Traditional glaucoma surgeries such as trabeculectomy and glaucoma drainage device implantation, are effective in lowering IOP, but have substantial intra- and post-operative risks and require intensive post-operative management.2
The evolving role of MIGS in glaucoma management
Minimally invasive glaucoma surgery (MIGS) emerged to bridge the gap between conservative management and conventional filtration surgery.2 Prior to the development of MIGS, glaucoma surgery was dominated by trabeculectomy, glaucoma drainage devices, cycloablative procedures as well as nonpenetrating surgeries.
The introduction of Trabectome in 2004 and FDA approval of the iStent in 2012 further advanced the field by establishing Schlemm’s canal-based micro-bypass surgery as a viable adjunct to cataract extraction in patients with mild to moderate open-angle glaucoma.
Current MIGS procedures encompass several mechanistic categories, including trabecular meshwork bypass, trabecular ablation, suprachoroidal shunting, and subconjunctival filtration.2
Enter canal-based procedures
Canal-based MIGS procedures were developed to improve physiologic aqueous humor outflow by targeting resistance within the conventional trabeculocanalicular pathway. After surgeons recognized that viscodilation of Schlemm’s canal could improve distal outflow resistance, canaloplasty emerged.
More recently, combined procedures that address both proximal and distal resistance within the aqueous outflow pathway, such as trabeculotomy with viscodilation, entered the glaucoma space.3,4
Because they target multiple sites of aqueous outflow resistance rather than bypassing only the trabecular meshwork, canal-based and combination MIGS procedures may offer advantages over stent-based approaches. Also noteworthy, these procedures avoid permanent implants, preserve the conjunctiva, and minimize tissue disruption, while potentially providing more sustained pressure lowering.3,4
We spoke with glaucoma specialist Mona Kaleem, MD, an associate professor of ophthalmology and the Glaucoma Fellowship Program Director at the Wilmer Eye Institute, Johns Hopkins Medicine to establish the ease and efficacy of combination MIGS.
There’s sometimes a perception that canal-based and stent-based MIGS compete with each other—how do you view their roles as complementary rather than redundant in clinical practice?
Dr. Kaleem: “In my practice I use both canal-based and stent-based procedures, so I don't consider them to be in competition with one another. I see canaloplasty fitting into my practice in a different way than what the stents provide. So the stents are actually like a conduit through the trabecular meshwork, whereas the canal-based procedures are opening up the canal and also opening up the distal collector channels.
The ability to open collector channels is something unique and different that the canaloplasty can provide. Another thing I like about the canaloplasty is that with Sight Sciences' OMNI device, I can also perform a goniotomy procedure—so with one device I can do two things.”
In your practice, how often are you doing a combination of stent-based and canal-based?
Dr. Kaleem: “I practice in an area where I am able to do both canal-based procedures and stents; I'm very fortunate in that way. I mostly perform a combination of both canal and stent-based. I'd say that’s how I do about 75% of my MIGS procedures.”
Why do you choose the combination approach for most patients?
Dr. Kaleem: “I find it easier to do a stent-based procedure with a canaloplasty. I generally find that when you're putting a stent in, depending on which one it is, it's easier to insert it when there's an opening already in the canal. It actually makes it significantly easier.
I don't want to waste a stent if I can’t lodge it into the canal properly; I don't like when a stent just doesn't go—or go in smoothly—because of the angulation. So, the canal-based procedure, which allows the viscoelastic to go through the canal making for a smoother entry for the stent, is my preference.
Also, stents are generally approved to be done in conjunction with cataract surgery, so I want to give patients the biggest bang for their buck. And I want to give them the greatest ‘wow’ and the best outcome possible while I’m in that space. So that's why I do both.”
How do canal-based procedures restore the eye’s natural outflow system, and why may that be important when treating mild-to-moderate glaucoma?
Dr. Kaleem: “You know glaucoma is a chronic condition. I tell most patients that this medicine or procedure will be good for you right now; however, you might need something in the future.
I think with glaucoma, we're trying to hit people pretty hard with everything that we have. But we also save things for later on. So in my practice, I like to start with more minimal treatments at first and then go to the more advanced surgeries if needed.”
What is your initial approach for a patient with moderate glaucoma?
Dr. Kaleem: “It depends on the patient's goal. So, the very first thing that I talk to them about is their function and how they feel about their function. I establish their lifestyle needs: Are they driving? Are they working? Are they taking care of small children? Do they garden? Do they read? What is it that they do? I also ask people what their goals are. Do they want to be medication free? Or do they just want to reduce their medications? What is their plan?
I also try to set a target eye pressure for them. I'll look at their previous eye pressures, sets of testing they've done—and not just once, but at the trends over time. That's how I come up with a target pressure for them. And we're working towards achieving that target.”
What does the current evidence show regarding IOP reduction and medication burden with canaloplasty, with or without trabeculotomy, and how does that compare to your experience with stent-based procedures?
Dr. Kaleem: “I tell patients the success rate—meaning the chance that they will be able to come off medications and not progress—is around 80% for all of these procedures, whether it's a stent-based procedure, canaloplasty, or goniotomy. When you look at the literature, it always fluctuates between 70 to 80%.
There are MIGS landmark trials, but then there are other retrospective reviews that have come out and I think we should show some value to those also. So I tell people again like there's about a 70 to 80% chance of success.”
How do you feel canal-based procedures compare in regard to tissue preservation and future surgical options?
Dr. Kaleem: “I think one of the nice things about the canal-based procedure is that it does spare tissue for, you know, X, Y, and Z. And it also leaves the patient eligible for a laser procedure as well as some of the traditional glaucoma surgeries.”
Are there any other situations where you feel canal-based procedures are preferable?
Dr. Kaleem: “I do work with a pediatric glaucoma specialist and, for some time, I was also doing some pediatric glaucoma cases. I like canaloplasty because it can be done for the younger patient population.”
What is the value and ease of implementing this into the OR workflow of an already existing practice?
Dr. Kaleem: “To me, it's just common sense that it's easier to put in something that doesn't have a stent. Because again, stents can be malpositioned. They can cause problems. They have to be extracted if they're not in the right place. With canal-based procedures, you can actually see something go through the canal.
So, I'm watching it as it's going. That way, if it's going in the wrong place, I can remove it. Even if you go in part of the way and don't get in for 180° or 360°, you're still accomplishing something; you're still opening some collector channels.”
Do you have any final pearls you’d like to share with the readers?
Dr. Kaleem: “I tell the fellows and residents that if you're trying to go in with some type of a catheter or like a canal-based procedure and it's not going through, then your stent is probably not going to go through either.”
In closing, can you elaborate on the advantages to using the OMNI device?
Dr. Kaleem: It is disposable, single-use, and allows me to see the Prolene suture. Also, I can do it myself; I don't need someone on the outside, like an assistant clicking for me. I am controlling the procedure. Additionally, I like the fact that it can just be done for as many clock hours as I want. And that I can perform a goniotomy or a canaloplasty with it. And, I feel it is less bulky and less costly.
Another thing I learned from my rep is that 13 clicks around is 180° for an OMNI device. And sometimes I'm not comfortable doing a full 180°; I just want to do 90° because someone is a very high myope or has some anatomical feature that puts them at a greater risk for the catheter diving into the wrong place. So, I can just do about 90°, which is seven to eight clicks of the device.
Overview of OMNI Surgical System
As noted by Dr. Kaleem, she utilizes the OMNI Surgical System. Introduced by Sight Sciences in 2018, this comprehensive platform that combines the power of microcatheterization with the precision of transluminal viscodilation.4
Building on the original OMNI platform, the OMNI Edge Surgical System incorporates TruSync technology to provide synchronized viscoelastic delivery and increase fluid capacity during treatment. It be used either as a standalone glaucoma procedure or in combination with cataract surgery.5,6
Notably, the device addresses all three major areas of aqueous outflow resistance: trabecular meshwork, schlemm’s canal, and collector channels.
A look at relevant research
OMNI procedures have demonstrated favorable results across multiple short- and long-term clinical studies:5,7,8
- Clinical studies of the OMNI Surgical System demonstrated significant IOP and medication reductions, including average IOP reductions of about 41% in pseudophakic patients.7
- The ROMEO study demonstrated sustained IOP reduction and meaningful reductions in glaucoma medication use through 12 months post-operatively.7
- In ROMEO, patients with baseline IOP >18mmHg undergoing OMNI combined with cataract surgery achieved a 28.2% mean IOP reduction at 6 months.7
- In the same ROMEO subgroup, 81.8% of patients achieved surgical success, defined as at least a 20% IOP reduction from baseline or IOP ≤18mmHg.7
- A retrospective study by Bleeker et al. demonstrated a 29% mean IOP reduction at 6 months after OMNI surgery, with 69.8% of patients achieving surgical success without increased glaucoma medication use.8
In conclusion
As the MIGS landscape continues to evolve, canal-based procedures are playing an increasingly important role in glaucoma management. Dr. Kaleem’s experience highlights how combination approaches can complement existing MIGS techniques.
