Eyeworld

DECEMBER 2022 | EYEWORLD | 81 G About the physicians Brian Francis, MD Doheny Eye Institute UCLA David Geffen School of Medicine Los Angeles, California Robert Noecker, MD Ophthalmic Consultants of Connecticut Fairfield, Connecticut by Liz Hillman Editorial Co-Director W hen the term MIGS (microinva- sive glaucoma surgery) was first coined more than a decade ago, there were only a few options in the space, and they were often referred to by their brand name, not the mech- anism of action. Since then, however, the MIGS space has grown significantly with many options addressing the same outflow pathway. As such, it might be time to start talking about MIGS in terms of procedural categories. "The MIGS space has expanded throughout the years," said Brian Francis, MD. "There are some novel mechanisms that are being intro- duced, but there are also a lot of procedures in the same space. I think it makes sense to talk about the mechanism of action rather than the name of the procedure itself." As Robert Noecker, MD, put it, "we're at critical mass" with multiple entries available in each space, so "it only makes sense to talk about these in categories now." "It wasn't as important before because there were only a couple of things to think and talk about and everyone was on the same page. Now many companies offer multiple strategies and operate in different parts of the MIGS spectrum. It's important to do this to reduce confusion and help sort out the technologies," Dr. Noecker said. Dr. Noecker said MIGS has followed a similar trajectory to glaucoma medications 2 decades ago. "First all we had was [timolol], but now we also have prostaglandins, alpha ago- nists, rho-kinase inhibitors, CAIs, and others." There are multiple options, and classifying based on mechanism of action is a way to orga- nize things, he said, adding that when billing and coding a procedure, a brand is not speci- fied, so understanding the procedural category is helpful. MIGS procedural categories Here is a breakdown of the categories and the different brands available in each. Trabecular bypass: This category includes iStent (Glaukos), of which there are several generations now, and Hydrus (Alcon, formerly Ivantis). These devices provide a conduit through which aqueous can bypass a dysfunc- tional trabecular meshwork and flow into Schlemm's canal. Ab interno goniotomy/trabeculotomy: This category includes the Kahook Dual Blade/ KDB Glide (New World Medical), TrabEx and TrabEx+ (MicroSurgical Technologies), Tra- bectome (MicroSurgical Technologies), and the goniotomy-assisted transluminal trabeculotomy (GATT) procedure. Dr. Noecker also mentioned iAccess (Glaukos). According to Dr. Noeck- er, these procedures remove a section of the trabecular meshwork to increase outflow into Schlemm's canal. "The end result is the open- ing you leave behind, so that's why I think it's important to not specifically talk about devices you use but the end result," he said. According to Dr. Francis, there is a small distinction within the category of procedures that tear through the trabecular meshwork (GATT) and those that re- move trabecular meshwork tissue (the others). Canal dilation procedures: These include the iTrack Surgical System (Nova Eye Medical) and OMNI Surgical System (Sight Sciences). According to a paper by Riva et al., canaloplasty functions via viscodilation of Schlemm's canal "as it breaks adhesion inside the canal, stretches the trabecular plates by means of micro-per- forations into the inner wall of the trabecular meshwork and separates herniations of the inner wall of the trabecular meshwork into the outer wall collector channels." 1 Goniotomy/trabeculotomy-canaloplasty (hybrid procedures): The OMNI Surgical System performs both trabeculotomy and canaloplasty. The STREAMLINE Surgical System (New World Medical) performs goniotomies in the trabecular meshwork and delivers a small amount of OVD into Schlemm's canal. Suprachoroidal access devices: CyPass (Alcon), recalled in 2018 due to the potential for endothelial cell loss, was a device in this space. This device bypassed Schlemm's canal Procedural classifications of MIGS: How to understand, group the options continued on page 82

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