August 15, 2017
7 min read

MIGS changing the landscape of glaucoma treatment

Cathleen M. McCabe, MD, and Inder Paul Singh, MD, explain why they choose certain procedures for certain patients.

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Welcome to another edition of CEDARS/ASPENS Debates. CEDARS/ASPENS is a joint society of cornea, cataract and refractive surgery specialists, here to discuss some of the latest hot topics in ophthalmology.

A group of new surgical devices and procedures has received significant attention recently: minimally invasive glaucoma surgery devices. There are now multiple new devices and techniques available to allow earlier and safer intervention for our glaucoma patients. Being that there are so many options, this may be overwhelming to the surgeon. This month, Cathleen M. McCabe, MD, and Inder Paul Singh, MD, discuss their unique viewpoints on how to approach the use of these devices. We hope you enjoy the discussion.

Kenneth A. Beckman, MD, FACS

Cathleen M. McCabe

Options open up for cataract surgeons to treat glaucoma

As an anterior segment and busy refractive cataract surgeon, I am excited that we now have surgical options to offer patients undergoing cataract surgery who also have glaucoma. Minimally invasive glaucoma surgical procedures have enabled me to provide an additional service to my glaucoma patients that is safe, efficient and effective in lowering IOP. As modern surgery has evolved, it is rewarding to be able to expand the benefits of cataract surgery, which now include a more complete approach to the refractive needs of the patient including astigmatism and presbyopia correction as well as correcting the spherical equivalent. Similarly, the evaluation of the cataract patient currently includes analysis of the quality of the ocular surface, and emphasis on effective long-term maintenance of a healthy ocular surface allows for significantly improved refractive outcomes.

Fortunately, many tools for analysis and treatment of the ocular surface are now available and continue to be developed. For our glaucoma patients, analysis of optic nerve health with additional sophisticated technology and treatment with innovative MIGS devices have resulted in advancement in their care. Just as I would not consider an evaluation of a cataract surgery candidate to be complete without analysis of the ocular surface and precise measurements and treatment of astigmatism, I no longer consider evaluation and treatment of glaucoma patients with cataracts to be complete without considering the use of a MIGS device.

Available MIGS devices that I currently incorporate into my practice include trabecular meshwork bypass stents (iStent, Glaukos), endocyclophotocoagulation (ECP, Endo Optiks), trabeculotomy devices (Kahook Dual Blade, New World Medical) and supraciliary stents (CyPass, Alcon) for mild to moderate open-angle glaucoma. A shared critical feature of these devices is their excellent safety profile and postoperative course that does not significantly deviate from cataract surgery alone. Once I became comfortable with holding the gonioprism during surgery and visualizing the angle, it became relatively efficient to perform these procedures with little disruption to the flow of a busy surgical day.


At this point, I believe that every mild to moderate primary open-angle glaucoma patient deserves consideration and a discussion regarding the use of a MIGS device during cataract surgery. My choice of device currently is determined by the severity of glaucoma, the number of medications the patient is on, insurance coverage, and whether or not the patient has an increased bleeding risk. For mild glaucoma that is controlled on one or two medications, my go-to procedure is an iStent. I place the device after the capsulorrhexis when visualization is good and no additional viscoelastic is needed. If there is more optic nerve damage or if I feel the patient has a need for a greater pressure-lowering effect, I pair the iStent with ECP in order to increase outflow and decrease production of fluid. Alternatively, I will place a CyPass for a greater pressure-lowering effect. I am more cautious placing a CyPass or using a Kahook Dual Blade in patients on blood thinners, especially if they cannot be temporarily discontinued, or those who may be less cooperative during surgery because these procedures can have greater risk of bleeding. I also place the CyPass after the IOL is implanted at the end of the surgery because of the increased possibility of bleeding. A unique CPT code is now available for CyPass (0474T) as of July 1, which should improve billing and reimbursement issues.

New treatments are also available for more advanced glaucoma disease in which a greater pressure-lowering effect is desired. The most recently approved is the Xen gel stent (Allergan), which is inserted via an ab interno approach to create a conjunctival bleb in the treatment of refractory glaucoma. Because these cases involve more complicated postoperative care (management of the bleb with possible needling) and have more advanced disease, I refer these patients to my glaucoma colleague to manage.

There are many more MIGS devices on the horizon, a benefit to our patients and to the practitioners who will have many more “tools in their toolbelts” when choosing the best way to manage these patients. Choosing which tool is best in each unique case will continue to be the exciting challenge going forward.

Disclosure: McCabe reports she is a consultant for Bausch + Lomb and Omeros and is a consultant and does research for Alcon, Glaukos, Ivantis, Shire, Sun Ophthalmics and RVO.

Inder Paul Singh

Individualized treatments available for glaucoma patients

Since the approval of the iStent (Glaukos) in 2012, the MIGS space has seen an incredible proliferation of technology. In the U.S., we now have more than nine products and procedures approved that fit the definition of minimally/micro invasive glaucoma surgery, working on different outflow pathways. So, we went from literally only a of couple surgical options (filtering surgery and tube surgery), which carried a significant intra- and postoperative adverse event profile, to now multiple options with high safety profiles. The question then becomes, “What do I do now?”

For me, the key characteristic of MIGS is safety. Having a safe surgical option allows us to feel comfortable intervening a lot earlier in the disease and avoids the life sentence of drops for many of our patients. Although all the MIGS procedures have good adverse event profiles, there are some differences among them all. The decision of which procedure to perform involves balancing efficacy on one end with adverse event profile, ease of use and postop management on the other end.

Natural outflow procedures

Procedures that target the natural outflow/inflow tend to have the highest safety profile. These surgeries include iStent (trabecular meshwork bypass), goniotomy using Kahook Dual Blade (New World Medical) or Trabectome (NeoMedix), viscodilation of Schlemm’s canal/distal channels using the iTrack microcatheter (Ellex) or Visco360 device (Sight Sciences), and trabeculotomy via the GATT approach or Trab360 device (Sight Sciences), as well as laser cyclodestruction (ECP). Because there is no bleb formation and the focus is in the natural outflow system with its natural episcleral venous pressure, there is a low risk for intraoperative adverse events, including post op hypotony, and the postoperative course is often similar to a cataract procedure.

Unfortunately, with some of these natural outflow MIGS procedures, we may see variability in responders and amount of IOP reduction or reduction in medications. This variability may be due to the fact we do not have a great understanding of where the resistance to outflow is preoperatively, although I have used selective laser trabeculoplasty to help provide some information on where the resistance might be. For instance, resistance to flow may be located at the juxtacanalicular tissue (may have a good response to SLT), but in some it might be more in the canal of Schlemm or even distal to that (may have a poor response to SLT). Therefore, in some patients, a specific MIGS procedure, depending on where its main mechanism of action is, could have more or less of an impact than expected. So for many of my patients who have mild to moderate glaucoma on one or two medications, I try to use one of these natural outflow MIGS procedures, mainly because of the high safety profile and ability to still perform traditional glaucoma surgery in the future if needed. Although these procedures are absolutely indicated for those patients on three or four medications, I find we sometimes still need to place patients on one or two postop medications to maintain a low enough target IOP.


The labeling indication for a MIGS procedure is another factor in deciding on which MIGS device to perform. For instance, the iStent in the U.S. is approved for use in combination with cataract surgery. So if you have a pseudophakic patient, unless you perform it off label, you need to consider another option, such as goniotomy or one of the canal procedures.

Supraciliary procedures

If someone is on three or four medications and has more moderate disease, or if there is a concern about the angle, I will often consider the CyPass device (Alcon). This device bypasses the natural outflow system by placing a stent into the supraciliary space, with a negative pressure gradient. Therefore, the site of resistance in the natural outflow pathway does not affect the efficacy. This space has been shown to be effective, and the cleft created has been shown to be fairly stable over time. It does exhibit a good safety profile, although there is a small risk for hypotony. This procedure is also approved only during cataract surgery, so if I have a pseudophakic patient, I often consider one of the natural outflow procedures or a subconjunctival MIGS device.

Subconjunctival procedures

The Xen gel stent (Allergan) was cleared in the U.S. in 2016. It involves placing a 6-mm flexible stent from the anterior chamber into the subconjunctival space via an ab interno approach. There is no conjunctival wound and therefore no immediate postoperative bleb leak or foreign body sensation to worry about. This procedure has been shown to be highly effective and safe but does create a postoperative bleb (although a much different bleb than a trabeculectomy bleb), and therefore one needs to feel comfortable managing possible fibrosis (bleb needling). This procedure has largely replaced my trabeculectomy/express shunts and has allowed me to perform subconjunctival surgery much earlier in the disease process due to the higher safety profile than traditional subconjunctival surgery. If a patient is more advanced, phakic or pseudophakic (it can be done as a stand-alone procedure), I will often consider Xen.


The bottom line: We are finally able to “tailor” our treatment options to the patient. Just like the cataract world, there is no one size fits all. If surgeons want to offer MIGS in their practice, there is a change in mindset that needs to happen. Offering MIGS devices earlier in the disease allows us to reduce compliance as a significant risk factor for progression but also helps us better achieve a “20/happy” patient. I suggest, at first, gaining experience with all the available options, not limiting yourself to one or two procedures. This way, you can judge the efficacy, safety, ease of implantation and postop course for yourself.

Disclosure: Singh reports he is a speaker and/or consultant for Glaukos, Alcon, Allergan, Ivantis, Ellex and New World Medical.