The Standalone MIGS Decision Tree

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8 min read

Dr. Sheybani reviews workflows for treating patients with standalone minimally invasive glaucoma surgery (MIGS) procedures.

One of the biggest opportunities—and challenges—in glaucoma for ophthalmologists today is adopting standalone minimally invasive glaucoma surgery (MIGS) as an approach to lowering intraocular pressure (IOP).
Even though standalone MIGS can offer a safe and effective means to slow progression while reducing the drop burden, many surgeons still see taking the leap to the operating room as a hurdle.
An interventional mindset demands taking a more assertive stance and bridging the gap between diagnosis and progression in the most efficient manner available.

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What can standalone MIGS procedures offer patients?

Dr. Sheybani suggests one of the biggest reasons patients are not compliant with topical ophthalmic drops is due to the lack of truly effective drop therapy options, as many of them come with adverse effects to the ocular surface. The latest generation of MIGS can be the answer for many of these individuals.
In the past, when standalone glaucoma surgeries were relegated to tubes and trabeculectomies, the potential risks dictated that patients showed severe progression before warranting surgical intervention. However, the safety profile of many MIGS makes the case for earlier and earlier intervention.
One obstacle to adopting this approach is the lack of MIGS with standalone FDA approval. At the time of this interview, they were limited to goniotomies (e.g., goniotomy-assisted transluminal trabeculotomy [GATT], Kahook Dual Blade [KDB], Trabectome, endocyclophotocoagulation [ECP]) or subconjunctival filtration (e.g., Xen Gel Stent).

Xen as a standalone procedure

The two primary considerations when choosing any surgery are safety and effectiveness, which in the case of glaucoma means minimizing the risk of complications while adequately lowering IOP.
Of the approved MIGS, both surgeons agree that one of the most efficacious procedures with a favorable safety profile is the Xen Gel Stent, a first-of-its-kind ab interno bleb approved for the reduction of IOP in patients with primary open-angle glaucoma (POAG) as well as pseudoexfoliative or pigmentary glaucoma with open angles.
When performing a standalone procedure, the goal is to bring pressure down to a sustainable controlled number, not only to reduce drops but to also eliminate the need for a more aggressive future procedure. The safety profile of the Xen stent facilitates early intervention.

Study findings on the safety of the Xen Gel Stent

The Grover Study documented the safety of the ab interno gelatin stent and its potential to bring pressures down from 24mmHg to 16mmHg and reduce the drop burden from 3.5 to 1.5 topical medications.1 To this point, Dr. Radcliffe reported that, out of the hundreds of Xen Gel Stents he has implanted, zero cases required revision due to chronic hypotony.
In one rare case of a very frail, 90-year-old female with an IOP of 30mmHg who was on five classes of medication in conjunction with high-dose aspirin, he was required to perform choroidal fluid drainage. One year out from surgery, this patient registered an IOP pressure of 6mmHg. Dr. Sheybani also noted he has never had a case of chronic hypotony with Xen.

Note: Of the Xen procedures administered in his practice, Dr. Sheybani states that 75% of them were done as standalone procedures while the other 25% were done in combination with cataract surgery.

Patient selection for Xen

Upon his initial meeting with a glaucoma patient, Dr. Radcliffe outlines his objectives as such:
  • Our first priority is to preserve vision.
  • That being said, the overarching goal would be to avoid inserting a tube or performing a trabeculectomy if possible, and this is where a microinvasive glaucoma surgery comes in.
Within the glaucoma patient population, those for whom Xen Gel Stent is a viable option is fairly wide. As a reminder, this 6mm hydrophilic flexible stent is composed of a porcine collagen-derived gelatin crosslinked with glutaraldehyde.
Though he acknowledges this is a simplified algorithm, based on current data, Dr. Sheybani would consider the following two types of patients to be good candidates:
  • Individuals with controlled open-angle glaucoma (OAG) but drop intolerance, due to either noncompliance, ocular surface complications, or the sheer number of drops—three to four classes—they must instill daily to maintain IOP control.
  • Borderline patients who are nervous about the progression of their disease and therefore motivated to take early action to halt the advancement of their condition.
On the flipside, patients who are not good candidates from Dr. Sheybani’s standpoint are those with uveitic glaucoma and those with neovascular glaucoma whose angles have not been (re)opened prior.

Accentuate the positive

Both surgeons acknowledged It is common to focus on “failed” procedures wherein the results were less than optimal and complications occurred. One reason that negative results steal the spotlight is because patients with positive results are often discharged back to the referring doctor, whereas patients with complications return and remain on the radar.
However, the doctors urge colleagues to objectively weigh their surgical results and also look at the improvement over time from when the clinic first introduced the specific MIGS. Some criteria Dr. Sheybani takes into consideration are needling rates, reoperation rates, IOP, and drop reduction.
For example, at his clinic, he noted that needling rates went from 35 to 40% down to a consistent 25%. Similarly, reoperation rates leveled out to 10% or less, which he feels should be the standard at 1 year. Additionally and ideally, at 1 year post-procedure, the target IOP would be in the 14mmHg to 15mmHg range and medications could be reduced to 1 to 1.5 topical ophthalmic drops.
If these milestones are not being met, Dr. Sheybani suggests changing the surgical technique, as these results are possible with the Xen Gel Stent. Dr. Sheybani goes one step further by encouraging ophthalmologists to analyze the surgeries where they “hit a home run” to find those keys to success, including pre-operative patient selection, appropriate preparation, and treatment prior to the procedure, along with the technique used to place the device.

Put yourself in the patient’s shoes

When asked how they would prefer their own glaucoma be treated, a majority of members of the American Glaucoma Society (AGS) said they would choose a MIGS procedure over trabeculectomy due to the potential serious complications.2
When considering which treatment to administer, Dr. Sheybani and Dr. Radcliffe try to “put themselves on the other side of the slit lamp” and weigh out which procedure they would feel most confident having performed on their own eyes. This is another aspect of developing an interventional mindset.

Conclusion

Summing this up, Dr. Radcliffe stated, “Anytime there's a gap between how we would want ourselves treated and how we're treating our patients, then it's up to us to close it.”
  1. Grover DS, Flynn WJ, Bashford KP, et al. Performance and Safety of a New Ab Interno Gelatin Stent in Refractory Glaucoma at 12 Months. Am J Ophthalmol. 2017;183:25-36. doi: 10.1016/j.ajo.2017.07.023.
  2. Fellman RL, Mattox C, Singh K, et al. American Glaucoma Society Position Paper: Microinvasive Glaucoma Surgery. Ophthalmol Glaucoma. 2020;3(1):1-6. doi: 10.1016/j.ogla.2019.12.003. PMID: 32672638; PMCID: PMC7531041.
Arsham Sheybani, MD
About Arsham Sheybani, MD

Arsham Sheybani, MD is an associate professor of ophthalmology and visual sciences. His areas of specialty include glaucoma and surgical management of the anterior chamber.

Arsham Sheybani, MD
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