MIGS is so hot right now! Any company with a connection to glaucoma has conjured devices to address the demand from doctors and patients to fill the niche, and as a result we are spoiled for choice when it comes to our interventional toolkit. This stuff excites me, but it’s given us some new problems — one, which MIGS do I choose? And two, how do we keep up with the pace of innovation? These are good problems to have, but I’m going to share my thoughts on how to approach them in a way that I believe gives us the best chance of success.
Step 1: Define Success
When exploring the world of MIGS, we need to become versed in setting realistic expectations. These are not one-size-fits-all, one-and-done surgeries. In fact, some doctors remain skeptical about the efficacy of MIGS, especially when compared with traditional filtering surgery. I welcome that skepticism and use it to refine my approach. MIGS weathered a scathing barrage of scrutiny recently with proposed Local Coverage Determination (LCD) changes — this became a call to action for glaucoma specialists, and we rebutted the sweeping proposals to gut MIGS reimbursement.1 It was also a wake-up call for us to do a better job of sharing our results. I’ll offer some tips for success that will help produce better results, and thus more convincing data for those who rightly ask the question, “Does MIGS work?”
Different procedures have different levels of potency, longevity, invasiveness, and risk. The fact that so many different options exist also means that none of these options are perfect. Where traditional studies have focused on numbers “mmHg of IOP lowering, etc.,” modern approaches include metrics that focus on patients’ quality of life as well — how many glaucoma drops do patients need? Can they come off drops altogether? How has the ocular surface improved? Is there diminished redness or discomfort? All these factors play into the MIGS we choose and why we continue to offer MIGS.
Step 2: We Don’t Know Everything … Yet
A Monte Carlo simulation is a model used to predict the probability of a variety of outcomes when the potential for random variables is present. The method works by estimating potential outcomes by simulating numerous random scenarios based on key variables, allowing us to understand the range and likelihood of different results in complex situations. These simulations are increasingly used in conjunction with artificial intelligence which may become more useful to us when we are trying to predict which MIGS surgery will work best. Unfortunately for us, we seldom have the sample sizes to put these types of statistical methods into practice, and even if we do, we seldom have the resources to collect and analyze the data formally.
With MIGS, there are a wide variety of starting points, interventions and outcomes. The data are messy! This is why we start describing glaucoma as an “art.” I do feel there is an art to it, and it’s one of the reasons I love glaucoma. At its core, the art of glaucoma is learned from multiple iterations of different surgeries that we perform on different patients with varying outcomes. We even go through training analogous to apprenticeship, and eventually progress to mastery. Although I think very few would claim to have “mastered” the art of glaucoma treatment, we should all strive for that goal through trial and error and, ultimately, accept some randomness.
Step 3: Try New Things
I would encourage you to try multiple devices and technologies. A few will become your favorites, and they will be the ones that suit your surgical style and your patient population. The existence of so many MIGS options has daunted some into thinking we always have some specific rationale for choosing one device over the other. However, it often comes down to surgeon preference, and that’s okay. The best surgeon’s I’ve known have also made a conscious effort to try new things. There is the risk of becoming set in one’s ways if we don’t venture outside of our comfort zone, and I think it’s worthwhile to keep a diverse skill set. The MIGS landscape will keep changing and we need to be ready to accept new technologies or risk stagnation.
Step 4: Be Methodical
The last concept I will leave you with is the most important: make it make sense. Glaucoma is full of unknowns and, yes, randomness. When patients ask me what causes glaucoma, the most honest answer I can think of is “a combination of genes and bad luck.”
For each patient, however, the goal is to simplify their clinical picture to be able to determine their best treatment pathway. Gather as much information as you can in the clinic. Start with a methodical approach. Is it an open-angle or closed-angle mechanism? Does the patient have thick corneal pachymetry? Is there pigment dispersion or pseudoexfoliation? What is the staging based on the visual field? How many types of drops is the patient taking? What was their maximum pressure? What is their tolerance for drops and their tolerance of surgical interventions? Is there neovascularization at play where you would avoid MIGS altogether? Is there vitreous in the anterior chamber causing iris chafe and IOP spikes? (This might make a vitrectomy more appropriate than MIGS.) What is your target pressure? I know these are the basics, but so many people say they don’t have time to do the basics like gonioscopy and pachymetry. However, it only takes a few minutes, and it’s billable. The more you do it, the quicker it becomes. With SLT being so prominent in our treatment paradigm since the LiGHT trial, gonioscopy remains a crucial component of the exam.2
As a spoiler, there are unfortunately few studies like the LiGHT trial that guide us which specific MIGS to use in each situation. I tend to separate them into broad categories: trabecular bypass MIGS, ciliary body ablation, canaloplasty, goniotomy, subconjunctival filtering MIGS, intracameral drug-eluting MIGS, and even suprachoroidal MIGS that are making a comeback. Each has their strengths in certain situations. Many angle-based MIGS can now be performed as standalone procedures, further adding to the variety of use cases. Leverage the strengths of each MIGS to help your specific patient: consider ECP of the ciliary processes combined with cataract surgery when there is a plateau mechanism. Careful use of viscoelastic can be used to break mild synechiae, canaloplasty can limit reflux bleeding from subsequent goniotomy. Stenting can be less likely to cause hyphema in those patients on blood thinners. Subconjunctival stents can be an option for those less prone to aggressive scaring and who need low pressures off drops. When a new MIGS device is released, ask which category it fits within, and add it to your repertoire.
Conclusion
We don’t always have the full picture, the entire mechanism, or all the answers. But use the information that you have to formulate a hypothesis for a mechanism as best you can, and use the MIGS that fits as many criteria for success as you can. Again, I can’t emphasize the concept of surgeon preference enough — often you can achieve great results in a wide variety of scenarios with a well-executed trabecular bypass MIGS that works very well in your hands. Trying new types of MIGS will always keep us open to the MIGS device that might become our new favorite. Don’t be afraid to try new technologies, and don’t be afraid to try the technologies you already know in new scenarios. Take this logical, thorough, methodical approach, and you will be rewarded with happier patients — that’s how MIGS and MIGS surgeons will maintain the great reputation they deserve. OM
References
1. US Centers for Medicare and Medicaid Services. Tracking sheet: microinvasive glaucoma surgery. Accessed September 23, 2024. https://localcoverage.cms.gov/mcd_archive/view/lcd.aspx?lcdInfo=39619:3&bc=0
2. Gazzard G, Konstantakopoulou E, Garway-Heath D, Barton K, Wormald R, Morris S, Hunter R, Rubin G, Buszewicz M, Ambler G, Bunce C; LiGHT Trial Study Group. Laser in Glaucoma and Ocular Hypertension (LiGHT) trial. A multicentre, randomised controlled trial: design and methodology. Br J Ophthalmol. 2018 May;102(5):593-598. Epub 2017 Sep 13. Erratum in: Br J Ophthalmol. 2021 Feb;105(2):e1.
