FEATURE 18 EWAP MARCH 2023 glaucoma medications 2 decades ago. “First all we had was [timolol], but now we also have prostaglandins, alpha agonists, rho-kinase inhibitors, CAIs, and others.” There are multiple options, and classifying based on mechanism of action is a way to organize things, he said, adding that when billing and coding a procedure, a brand is not specified, 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 dysfunctional 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), Trabectome (MicroSurgical Technologies), and the goniotomy-assisted transluminal trabeculotomy (GATT) procedure. Dr. Noecker also mentioned iAccess (Glaukos). According to Dr. Noecker, these procedures remove a section of the trabecular meshwork to increase outflow into Schlemm’s canal. “The end result is the opening 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 remove 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-perforations 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 and the traditional outflow pathway, facilitating outflow directly from the anterior chamber into the suprachoroidal space. Dr. Noecker said there is work being done to bring back a device that uses the suprachoroidal space. Dr. Francis also mentioned the MINIject (iSTAR Medical) and iStent Supra (Glaukos). Ciliary body procedures: These include endocyclophotocoagulation (ECP) and MicroPulse Laser Therapy (Iridex). These procedures, Dr. Noecker said, contribute to aqueous reduction and may increase uveo-scleral outflow. There is also some evidence that the latter may increase suprachoroidal or trabecular outflow, according to Dr. Francis. Bleb-forming “MIGS”: The PreserFlo MicroShunt (Santen, not FDA approved in U.S.) and the XEN Gel Stent (Allergan) fall into this category. Dr. Noecker said they’re not quite MIGS because they are a little more invasive with the formation of a bleb and use of mitomycin, but they are still “basically bypass procedures” that are less invasive than traditional filtering procedures. Why is categorizing helpful? Dr. Francis said that it’s good to know these general categories, as well as the subtle differences among the procedures within the categories. First, he said, it can help you decide the procedures you want to do on a regular basis. “You don’t have to become proficient in multiple procedures that are in the same category. It makes more sense to span two or three different categories within your armamentarium,” he said. Dr. Francis said it’s helpful to know the different categories and what they address to customize choices for patients based on their disease and anatomy. “That can sometimes give you an idea of what procedures might be more successful depending on how they work,” he said. “The categories also
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