FEATURE EWAP MARCH 2023 19 help if you’re thinking about combining different procedures. You want to combine procedures that are from a different category. For instance, you might not want to do two trabecular bypass stents. That’s not going to be as helpful as combining a trabecular bypass with something that reduces aqueous humor production or opens up the canal 360 degrees.” Dr. Noecker said that the variability in eye anatomy influencing MIGS efficacy makes understanding the different categories important. It also highlights the need to have experience across the different categories. Both Dr. Noecker and Dr. Francis said insurance coverage can play a role in why a surgeon might want to have experience in different MIGS categories as well. “It’s about having backup options. Some patients don’t want to have a device put in their eye. It’s nice to have another option,” Dr. Noecker said. “I like to hedge my bets, so I do a lot of combining of these procedures and understanding what makes sense to combine, what complements each other vs. doing the same thing.” In terms of choosing an option within each category, Dr. Noecker said to go with what you’re good at. “Figure out which one works best in your hands and go with it,” he said. Dr. Francis said without head-to-head data showing which MIGS is better, it boils down to what you’re comfortable with. “Within the same category, generally, they are similar in terms of their mechanism of action and efficacy. I don’t think it matters that much which you choose,” he said. Dr. Francis said trabecular bypass stents are the first step for most cataract surgeons. As a second step, he advised a goniotomy/trabeculotomy or combined canaloplasty- goniotomy/trabeculotomy procedure. “The reason those are nice is you can do them without cataract surgery,” he said. “The other category you might want to consider is an aqueous humor reduction procedure. Those can be combined with any procedure along the way.” Dr. Noecker said that each of these spaces has evolved and gotten better, but there is still room for improvement. “The techniques got better. The instrumentation got more elegant. It’s all with the goal of decreasing side effects, which in this case is primarily bleeding. I think all of the technologies have improved, but they all A natomical classifications of MIGS allows us to anticipate the efficacy and complications of these surgeries and to target them at the appropriate patient profile. Trabecular bypass procedures should encompass the stenting procedures with devices, the cutting procedures, and the dilation procedures. In Asia, the choice of trabecular bypass procedure often depends on the costs involved and ease of access to the device. The reimbursement environment and the socioeconomic status of patients are important factors in making this decision. Cutting procedures can be performed with low cost (e.g. bent ab interno needle goniotomy [BANG]) while the stenting procedures with devices are more expensive. In Singapore, stenting procedures with the Hydrus Microstent or the iStent Inject are preferred trabecular bypass procedures, as they are associated with less bleeding and tissue destruction compared with cutting procedures. Dilation procedures are not widely performed in Asia, and it remains to be seen whether they have an advantage over the other trabecular bypass procedures. Newer devices such as the i-Track, excimer laser trabeculostomy and the TrabEx Pro will struggle to find a place in an increasingly crowded trabecular bypass market. Hence, efforts in innovation and research should be directed towards suprachoroidal and subconjunctival MIGS. Both outflow pathways can potentially achieve lower intraocular pressure compared with the conventional aqueous outflow pathways, but more work is required to fully harness the potential of suprachoroidal and subconjunctival drainage. Scarring in the suprachoroidal space limits the efficacy of suprachoroidal MIGS devices, and cannot be modulated with antimetabolites unlike the subconjunctival space. Indeed, the COMPASS Trial results suggested that the efficacy of the CyPass Micro-Stent was similar to trabecular bypass devices, with increased risk of complications including early hypotony and endothelial cell loss. Similarly, the use of subconjunctival MIGS devices is not widespread in Asia, largely because of the significant postoperative bleb management required and the high needling rates. Hopefully, new suprachoroidal and subconjunctival MIGS devices in the horizon will be able to achieve better outcomes with lower intraocular pressures and less postoperative management, so that they can benefit patients with more advanced glaucoma who are not good candidates for trabecular bypass procedures. Editors’ note: Dr. Sng is a consultant for Alcon, Santen, Abbvie/Allergan, Zeiss, and Nidek. Chelvin Sng, MD Medical Director, Adjunct Associate Professor Chelvin Sng Eye Centre, National University of Singapore chelvin@gmail.com ASIA-PACIFIC PERSPECTIVES
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