MIGS developments continuing to transform glaucoma surgery

As MIGS continues to increase in popularity as a procedure, new products will enter the marketplace that will make surgery easier for physicians and patients alike.

Reviewed by Inder Paul Singh, MD

A redesigned injector for the ab interno gel stent (XEN Gel Stent, Allergan) features ergonomic enhancements that facilitate its usability and allow for improved surgeon control during stent placement, said Inder Paul Singh, MD.

“The current injector is ergonomic and straightforward to use, but the updated version is even more user-friendly and includes features that can be appreciated by new surgeons as well as those who have developed expertise,” said Dr. Singh, president, Eye Centers of Racine and Kenosha, WI.

Modifications to the new injector include a redesigned slider that is smaller and has a smoother surface than its predecessor. In addition, the start position of the slider was moved forward by 8 mm.

Surgeons will also feel slightly more resistance as they move the slider to deliver the stent and notice two subtle clicks, one at the midpoint when the needle starts to retract into the sleeve and the second near the end of its travel distance when the needle retraction is complete.

Dr. Singh noted that the smaller, smoother slider enables better grip and movement of the slider button. The reset start position makes the slider button easier to reach.

“Depending on hand size, some surgeons might have had difficulty accessing the slider with their thumb and may have found it necessary to use a second hand to use the injector or look away from the microscope to locate the slider button,” Dr. Singh said. “The smaller size and forward position of the slider button make it easier to engage without any additional maneuvers.”

The increase in slider resistance across its travel distance and the addition of the clicks, which are not mechanically disruptive, provide tactile feedback that allows for real-time confirmation and thus possibly more precise and predictable placement of the stent.

“Now surgeons can feel the progression of the stent’s delivery without having to look at the slider’s position, and the clicks are a nice add-on safety check for surgeons to know when the stent is fully deployed and the device can be withdrawn from eye,” Dr. Singh explained.

The MIGS era

The new injector for the ab interno gel stent is expected to be commercially available during the second quarter of 2019. Surgeons can look forward to other product releases in the MIGS space as it continues to transform the glaucoma management landscape.

“MIGS has created a new paradigm for glaucoma management in which surgery is being considered earlier as an approach that can decrease the need for topical drops and the compliance, cost, and safety concerns that accompany their use,” he said.

Dr. Singh added that given their proven safety advantages compared with conventional glaucoma surgeries, and with multiple data sets demonstrating good efficacy, surgeons today are less likely to wonder whether or not they should incorporate MIGS.

“With multiple MIGS procedures now available, surgeons are confronted with the question of which procedure to choose for which patient, and they need to become active participants as they aim to pick the right one for each patient,” he said.

Dr. Singh suggested surgeons consider several factors during their decision-making process, but noted it is important to understand where the available procedures work in the outflow pathway.

Explaining how he applies that information, Dr. Singh said that instead of categorizing disease severity based only on the condition of the optic nerve and visual field, he now also judges severity in terms of site or sites of outflow resistance.

Dr. Singh pointed out that conventional rating of glaucoma severity is still important for choosing the target IOP for a particular patient, which may also have implications for choosing a procedure. “A patient might have pre-perimetric disease and yet have an IOP of 25 mm Hg while on four medications,” he said.

“In that situation, I presume that the problem with resistance is not just in the trabecular meshwork but probably also in the Schlemm’s canal and the distal channels.

“Therefore, I would choose a procedure or combination of procedures that will address all of those sites of resistance,” Dr. Singh added. Although there are no preoperative diagnostic methods that allow surgeons to pinpoint the site of outflow resistance in a patient with glaucoma, such tools are in development and will likely be available in the future.

In the meantime, Dr. Singh said that based on published data and data he is collecting, the trabecular meshwork is likely not the only site of outflow resistance in patients who are refractory to selective laser trabeculoplasty (SLT). The type of response to SLT may provide an insight into the area of pathology in glaucoma patients.

Lens status is another factor that can influence the selection of a MIGS procedure. While some procedures are approved as standalone surgeries, others are indicated only for use in combination with cataract surgery. In addition, a procedure that does not violate trabecular meshwork may be preferred in a patient who is younger, still phakic, and has no sign of cataract.

“Avoiding a procedure that removes or “cuts” the trabecular meshwork in this situation allows for the opportunity to perform SLT later or place a trabecular bypass stent if the patient develops a cataract in the future,” Dr. Singh explained. Reimbursement can also be an issue, he noted.

“When all other factors are equal, surgeons are often forced to choose the procedure that is covered for the patient and may actually end up ruling out a procedure if it is not reimbursed at all and the patient cannot pay out-of-pocket,” Dr. Singh explained.

Becoming a MIGS surgeon

As glaucoma patient care has entered the MIGS era, Dr. Singh encouraged colleagues to become a comprehensive MIGS surgeon. Although it is not necessary to learn all of the available procedures, he recommended learning at least one within each category.

“If you handcuff yourself to one procedure, you limit your ability to help the spectrum of patients that you will encounter in practice,” he said. “Just as we have many pharmaceutical options, we now need to avail ourselves of the multiple surgical options.”

Comfort level with the required surgical technique and follow-up care (i.e., bleb management) are factors that can help surgeons choose the specific procedures they will adopt. As they build their toolbox and recognizing that patients may need to undergo multiple glaucoma procedures over time, MIGS surgeons also need to be prepared to spend time with patient counseling and expectation building.

“MIGS has increased the number of options we have in our therapeutic ladder, and so the breadth of our patient counseling conversations about the current options for glaucoma management and future needs has also increased,” Dr. Singh concluded. “We need to set the expectation that more than one surgery now or in the future may be necessary to halt the progression of the disease.”

Disclosures:

Inder Paul Singh, MD
E: inderspeak@gmail.com
Dr. Singh is a consultant to, does research for, and/or is a speaker for Allergan and other companies that market or are developing MIGS procedures.