Eyeworld

EW GLAUCOMA 72 June 2017 by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer A new option for tough cases, the InnFocus MicroShunt bypasses the primary collecting tubules, giving IOP relief to a wide spectrum of glaucoma patients M icroinvasive glauco- ma surgery (MIGS) devices are plentiful in number, diverse in construction, and indi- vidual in the way that they function to improve aqueous outflow. Most MIGS shunts aid in aqueous drain- age by connecting with viable seg- ments of Schlemm's canal, achieving moderate reductions in IOP that are beneficial mostly in mild glaucoma cases. The latest on the roster of glaucoma microshunts, the InnFo- cus MicroShunt (Santen/InnFocus, Miami), reduces IOP by approxi- mately 50% by directing aqueous fluid past Schlemm's canal and the tubules of the collector system. The InnFocus MicroShunt creates a drainage outlet from the anterior chamber by bypassing the defunct trabecular meshwork and Schlemm's canal and redirecting aqueous to the more voluminous subconjunctival area where fluid can wick through the conjunctiva into the tear film or be absorbed by the episcleral veins. It is effective in patients with moder- ate to severe glaucoma and is easy to implant. EyeWorld spoke with two InnFocus specialists, Isabelle Riss, MD, Pole Ophtalmologique de la Clinique Mutualiste, Pessac, Cedex, France, and Juan Batlle, MD, profes- sor and chairman of ophthalmology, Elias Santana Hospital/Centro Cris- tiano de Servicios Médicos, Santo Domingo, Dominican Republic, about patient results and what sets this device apart. Drastic IOP and medication reduction A 2-year study that involved the implantation of the InnFocus Mi- croShunt in phakic, pseudophakic, and combined MicroShunt/cataract surgery patients resulted in IOP reductions of 47% from baseline, 74% of patients off glaucoma drops entirely, and no notable difference between the patient groups in terms of IOP reduction or necessity for postoperative glaucoma medication, according to a presentation given by Dr. Riss at the 21st Winter Meeting of the European Society of Cataract and Refractive Surgeons (ESCRS), in Maastricht, Holland. The study included 79 glaucoma patients, of which 31 were phakic, 30 aphakic, and 18 who underwent combined cataract/shunt placement surgery. The patients had a mean age of 63 ± 13 years, mean IOP of 24.8 ± 6.1 mm Hg, and were taking 2.3 ± 1.2 medications each. Their visual field was –11.8 ± 10.8 (mean deviation) and visual acuity was 6.7 ± 3.3 (Monoyer). Forty-six of the patients were Caucasian and 33 were of mixed heritage. "InnFocus implantation is a simple procedure that gives immedi- ate and safe pressure reduction, and no sight-threatening long-term complications at 2 years' time," Dr. Riss said. "The change in IOP was dramatic immediately on day 1, with all three groups' IOPs under 10 mm Hg. IOP outcomes were not significantly different over time, when looking at results up to 2 years. The implantation is a straight- forward technique that comprehen- sive ophthalmologists will have no trouble learning. It can be combined with cataract surgery, and the IOP outcomes in patients with combined surgery are not any different from outcomes in patients receiving only the shunt, according to our out- comes." Straightforward insertion The InnFocus MicroShunt insertion procedure takes approximately 20 minutes, and is performed ab exter- no under topical anesthesia, with the patient looking downward. A 4 mm wide limbus cut is made and a flap dissected under the conjunctiva and Tenon's capsule. Mitomycin-C is placed in the flap for 3 minutes and then rinsed out. A shallow pocket is made in the sclera with a trian- gular-tipped knife through which a 25-gauge needle is inserted, forming a needle tract under the limbus to gain access to the anterior chamber. The InnFocus MicroShunt is thread- ed through the pocket and needle tract and a fin located halfway down Cutting IOP in half N o important eye operation has been more resistant to improvement than the trabe- culectomy. Antimetabolites and the EX-PRESS Glaucoma Filtration Device (Alcon, Fort Worth, Texas) have been enhancements, but neither was a dramatic reworking of the basic trabeculectomy technique. Finally, after more than 40 years of nearly static technique, there are two major filtering surgery innovations. The first is the XEN implant (Allergan), a tube delivered ab interno that creates a filtering conduit to a subconjunctival bleb. The second is the InnFocus MicroShunt (Santen/InnFocus), also a tube but one delivered into the anterior chamber ab externo beneath a conjunctival flap. Both the XEN and the InnFocus Microshunt promise to deliver the pressure-lowering of a trabeculectomy but with a much simpler and safer approach. The XEN stent received FDA approval in 2016 and is in the middle of a national roll-out. The InnFocus device has not yet received FDA approval, so the published data is from studies performed outside the U.S. But U.S. approval is expected in the next year. We are fortunate in this "Glaucoma editor's corner of the world" to have the expert insights of Isabelle Riss, MD, and Juan Battlle, MD, on the InnFocus MicroShunt. The InnFocus device is implanted after making a conjunctival incision at the limbus, creating a scleral pocket and applying mitomycin-C. This approach creates a bleb space in preparation for the fluid that will be directed from the anterior chamber through the InnFocus MicroShunt to the bleb. The XEN implant is different in that it is delivered from inside the an- terior chamber and does not create a bleb pocket. Instead, the XEN relies on the flow of fluid through tube to inflate the bleb and keep it elevated. Also, the mitomycin-C has to be injected into the subconjunctival space in the XEN procedure because there is no conjunctival incision. It is not known how the success rate of the InnFocus MicroShunt procedure will compare to the XEN surgery. The two operations are broadly similar, but the implants differ in size and material. Some also think that blebs develop better when a bleb space is created surgically— as we currently do with a trabeculectomy. But this surgical approach is a double-edged sword because it creates a risk for leaking wounds and more variable healing. The availability of these new glaucoma filtering procedures raises many questions. How much bleb management will be required? There are reports that needling of the bleb may be required in some patients. Will these implants be widely adopted by comprehensive cata- ract surgeons who traditionally have avoided trabeculectomies and tube shunts because of their higher complication rates? Will these procedures be done in combination with cataract surgery and perhaps in preference to the iStent (Glaukos, San Clemente, California) or CyPass (Alcon)? Only time can give us answers. Both the XEN and the InnFocus MicroShunt claim MIGS status but are outside the "classi- cal" MIGS definition because they create external drainage to a bleb. However, if they deliver on their promise of trabeculectomy-level IOP reduction with a MIGS-like safety profile, the MIGS label will probably stick. We are fortunate to have these new devices that give surgeons safer options for patients who need substantial pressure lowering. The best news is that we finally have competition in the filtering surgery space, and this will lead to further innovation. Reay Brown, MD, Glaucoma co-editor Glaucoma editor's corner of the world

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