Glaucoma: Hot topics in ophthalmology
December 2022

by Ellen Stodola
Editorial Co-Director

Combining MIGS procedures is something James Murphy, MD, considers if he wants to get the most IOP-lowering effect balanced with a minimal surgical risk profile. “I routinely combine MIGS procedures that target different contributors to the conventional inflow/outflow system of the eye,” he said.

As an example, he described combining a canaloplasty with a MicroPulse TLT (Iridex) laser treatment or canaloplasty with goniotomy and a trabecular microbypass stent. “I sometimes combine subconjunctival MIGS with MicroPulse TLT as well,” he said. “Typically, I am targeting patients with mild to moderate open-angle glaucoma, patients with additional risk factors for complications from shunts or blebs, and patients for whom having one of the traditional glaucoma procedures may not fit well with their lifestyle. Sometimes patients present with an already well-informed impression of what types of glaucoma surgeries fit with their lifestyle and risk tolerance.” Dr. Murphy added that there are patients who have already had a tube shunt or trabeculectomy in the fellow eye, had a bad experience, and are therefore resistant to having the same or a similar procedure in the second eye, even if that procedure may be the most likely to achieve target IOP. “As a glaucoma surgeon, I use the preoperative counseling session as my opportunity to gauge what the patient’s acceptance of partial success or tolerance for failure would be. I want to avoid a patient who fails a MIGS procedure and is unwilling to follow through with an escalation in surgical care if the need arises.”

Reza Razeghinejad, MD, said that he would be more inclined to combine MIGS procedures in those patients with higher IOPs when it is preferable to avoid filtering procedures or in those needing lower target IOPs. 

Generally, MIGS is used in mild and moderate glaucoma patients, he said, but it may be used in severe glaucoma patients requiring a decrease of a few points of IOP, especially those patients with unfavorable outcomes with filtering surgery in the contralateral eye. 

“When we plan to combine MIGS, we are looking for more IOP reduction due to higher baseline IOP, more optic nerve damage requiring lower target IOP, or discontinuing of some of the medications,” Dr. Razeghinejad said. “We do not have any evidence-based data on combined MIGS efficacy and safety; currently physicians are combining MIGS based on their personal experience and the current literature on standalone MIGS.”

Dr. Murphy said there are cases in which it would be acceptable to perform MIGS if the patient is properly counseled that while MIGS offers an attractive risk profile, they are less likely to achieve target IOP, and the chances are higher that additional, more invasive glaucoma surgery will be required in the future. “I tend to take the team approach (surgeon and patient) when it comes to decision making, as many patients are reasonably well informed even before our surgical consultation, have often seen several other glaucoma surgeons, and I’m the second, third, or fourth opinion,” he said. “If one performs a MIGS procedure and it fails, the option to go more invasive is available, whereas if one proceeds with more invasive surgery right away, there is no role for most MIGS procedures at that point.”

The main reason Dr. Murphy chooses to combine MIGS is additional IOP-lowering power, targeting aqueous production and resistance to conventional outflow simultaneously, for example. “We as glaucoma surgeons know that sometimes a MIGS procedure fails, but if you perform two or three MIGS, it is theoretically less likely for all of them to fail simultaneously,” he said. 

In terms of which procedures might work best together, Dr. Murphy prefers to combine MIGS procedures that target different aspects of aqueous production and outflow. Reducing resistance to outflow at the level of the trabecular meshwork can be performed in several ways, including canaloplasty, goniotomy, and stenting procedures. “Often I will implant a stent in the nasal quadrant and perform a goniotomy in an adjacent quadrant, as well as perform a 360-degree canaloplasty,” he said. “You’re throwing multiple strategies at the conventional outflow pathway to try to jumpstart the system as much as you can.”

Dr. Razeghinejad said with the CyPass (Alcon), which was voluntarily recalled in 2018, it was easy to combine two different mechanisms of MIGS: conventional and uveoscleral pathway. “Currently, we do not have any FDA-approved supraciliary MIGS devices, and procedures aimed at the conventional pathway may be used together or with cyclodestructive procedures,” he said. 

For example, he said the OMNI Surgical System (Sight Sciences) may be combined with goniotomy to bypass the trabecular meshwork and dilate the distal outflow. Other trabecular meshwork bypassing procedures could also be combined, such as the Hydrus (Ivantis) and the iStent (Glaukos) or goniotomy. These could be done on different parts of the angle, as the collector channels and aqueous veins may not be functioning well in four quadrants. Performing two MIGS procedures on different parts of the conventional pathway may increase the chance of successfully lowering IOP, Dr. Razeghinejad said. Cyclodestructive procedures could also be combined with any of the conventional pathway MIGS, he added.

In order to partially mitigate the risk of entering the eye for surgery, Dr. Murphy will perform ab interno MIGS procedures simultaneously. If one is performing a non-incisional procedure or an ab externo procedure, those are very different risk profiles, he said. “But if I’m going to take on the risk of creating an incision and entering the anterior chamber with instrumentation, I am compelled to take as many surgical steps as possible to lower IOP for that patient.

“In my mind, the main drawback is the additional cost to the healthcare system because these devices are expensive, and if you use more than one, there’s no discount. There is negligible change to surgical risk, and if anything, OR time utilization is more efficient when combining MIGS,” he continued. “I tend to prefer non-implant MIGS over implant MIGS because while there is good data to support safety and efficacy of implants, they do come with a unique set of risks, and frankly, some patients have an aversion to the word ‘implant,’ especially if they’ve had a bad experience with an unrelated implant in the past. When one is discussing surgery to save a patient’s vision, I find that they are much less concerned with what the surgery costs and very interested in a spare-no-expense approach.” 

Each MIGS procedure has its own set of risks, Dr. Murphy added. Many of these procedures’ risk profiles overlap, though not entirely. “You can think of it like a Venn diagram; there may be two or three overlapping circles, but there are always additional risks or an increased risk of one particular adverse event when combining procedures. But in my experience, the additive risk is minimal.”

If one is performing canaloplasty, for example, there is a fairly low risk of bleeding and hyphema; however, if you add goniotomy to this, as many MIGS devices do, there is a higher risk of bleeding and hyphema, he said. If you perform a stent and goniotomy, there may be a higher risk of implant movement, at the time of surgery or later. If one is using a laser, there are risks associated with additional anesthesia required. While MIGS procedures have a lower risk profile compared to their more invasive counterparts, in Dr. Murphy’s opinion, combining MIGS does marginally increase risk compared to standalone. In his experience, the added benefits outweigh the risk.  

Dr. Razeghinejad said to decrease the chance of complications and the cost, combining the MIGS procedures in one session seems to be a reasonable approach. “Because of the possibility of MIGS failure and the progressive nature of glaucoma and to avoid taking the patient back to the operating room for a filtering surgery, MIGS procedures may be combined in one session,” he said. 

A combined procedure may increase the chance of hyphema, which in most patients is temporary. Combining MIGS procedures that involve device implantations may hypothetically have some impact on the corneal endothelium, but we need more data, Dr. Razeghinejad said.

Dr. Razeghinejad said it’s important that patients know that there is no evidence-based data on the safety and efficacy of combined MIGS, and insurance may not cover the combined MIGS. 

Dr. Razeghinejad added that combining MIGS does not seem to increase the chance for endophthalmitis, as the rate of endophthalmitis following MIGS has been similar to phacoemulsification. Combining MIGS with cyclodestructive procedures increases the risk of postoperative inflammation and cystoid macular edema, which could be managed with topical steroid therapy and NSAIDs in most patients, he said. 

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Editors’ note

This article has been updated to refer to MicroPulse TLT, not MicroPulse CPC. 

About the physicians 

James Murphy, MD
Adjunct Clinical Instructor
Yale New Haven Hospital
New Haven, Connecticut 

Reza Razeghinejad 
Director
Glaucoma Fellowship Program
Wills Eye Hospital
Philadelphia, Pennsylvania

Relevant disclosures  

Murphy: Nova Eye Medical, Sight Sciences 
Razeghinejad: None 

Contact 

Murphy: jamestmurphyiiimd@gmail.com
Razeghinejad: reza@willseye.org