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I morphology makes them comfortable injecting higher concentrations of MMC. Their needling rate is less than 5%, and they have not had any erosions with their approach. Expanding toolbox Even as XEN use evolves, surgeons are already expectantly awaiting the FDA approval of an- other microsurgical glaucoma drainage device: the PreserFlo (formerly the InnFocus Micro- shunt, Santen Pharmaceutical). While we can postulate, Dr. Grover said that we don't know yet how exactly these devices will fit together in the expanding glaucoma surgical toolbox. He was a primary investigator for the FDA trial on the InnFocus and speaks to the efficiency of this surgery as well. Moreover, what he does know is that the XEN has been a game chang- er; if and when the PreserFlo is approved, he thinks the device will be a game changer as well. "We'll have to play it by ear and determine which surgery is better for which patient, but I think the big theme is they both will be tremen- dous additions to our surgical armamentarium," he said, adding, "The data coming out of Can- ada and the Dominican Republic with regard to PreserFlo are extremely encouraging and make most U.S. glaucoma doctors excited to get their hands on the PreserFlo." Editors' note: The views expressed in this article attributed to Dr. Kim are his own and do not reflect the official policy of the Department of Army/Navy/ Air Force, Department of Defense, or U.S. Govern- ment. The identification of specific products or scientific instrumentation is considered an integral part of the scientific endeavor and does not constitute endorsement or implied endorsement on the part of Dr. Kim, DoD, or any component agency. The views expressed in Dr. Kim's interview are his own and do not reflect the official policy of the Department of Army/Navy/Air Force, Department of Defense, or U.S. Government. From left: In the open conjunctival approach, a peritomy is open and the XEN gel stent is inserted via an ab externo approach. With an open conjunctival peritomy, the XEN gel stent position can be easily ad- justed after it is injected to ensure proper positioning. Once the XEN gel stent is placed in the desired position, it is safely tucked under the conjunctiva and the conjunctival peritomy is closed. Source: Joseph Panarelli, MD Implanted via an ab externo technique similar to the way Dr. Do and Dr. Panarelli are currently implanting the XEN 45, they expect the PreserFlo will help surgeons "bridge the large gap between our trabecular bypass/ ablative procedures and traditional glaucoma surgeries," they said. "In a sense, it functions similarly to a trabeculectomy in that it creates a subconjunctival bleb, but the procedure is considerably less invasive and requires much less postoperative intervention." Dr. Kim posits how his practice might look with these new devices in his surgical toolbox. "I think for those patients for whom I am seeking profound IOP lowering that Schlemm's canal-based MIGS cannot deliver, and who have healthy and unscarred con- junctiva, open angles, no history of uveitis/ inflammation, and no history of NVG, I will likely use XEN-ex (ab externo transconjuncti- val XEN implantation) as the first line surgical treatment," he said. "If this fails and bleb needling for it fails, I will turn to the InnFocus Microshunt (if and when it gets FDA approved and becomes commercially available) placed in an adjacent superior quadrant. If this fails, I would then likely turn to glaucoma drain- age implants such as a Baerveldt Glaucoma Implant [Johnson & Johnson Vision]. XEN-ex has the advantage of being extremely vast, not requiring incisions, and offering immediate visual recovery. The InnFocus has the advan- tage of having a larger diameter lumen less likely to get clogged by pigment and debris but would have the disadvantage of requiring extensive conjunctival dissection and closure. PreserFlo: The device formerly known as the InnFocus Microshunt I think the InnFocus would replace my current open XEN with tenonectomy technique, so I would probably use it in place of XEN-ex in cases at higher risk for failure (young, deeply pigmented, inflamed conjunctiva, etc)." The devices differ in terms of material and size. "The InnFocus Microshunt is 8.5 mm in length with a luminal diameter of 70 micrometers and is composed of SIBS (styrene-block-isobutylene-block-styrene) material," Dr. Do and Dr. Panarelli said. "By contrast, the XEN gel stent is 6 mm in length with a 45-micrometer lumen and is made of porcine gelatin. These subtle differences may lead to slight differences in outcomes with each device, but a comparison among the two new microstents has not been performed yet." JULY 2019 | EYEWORLD | 35

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