Eyeworld

I MIGS UPDATE N FOCUS 34 | EYEWORLD | JULY 2019 and avoids entanglement in Tenon's capsule, a major cause of XEN failure. Dr. Grover added a nuance to these advan- tages, noting that the injector isn't designed for the ab externo approach so this approach can sometimes be cumbersome to use; nevertheless, he added that it can readily be adapted with practice. Dr. Do, Dr. Kim, and Dr. Panarelli now insert the XEN 45 using an ab externo ap- proach almost exclusively. "I haven't done any ab interno XEN cases since September 2018," Dr. Kim said. "I'm not sure if this approach has a role for me anymore." Dr. Grover, however, still prefers the ab interno approach in patients with a prominent brow or sunken eyes, or in combination with cataract surgery when the eye has already been opened up. "I think it is essential to know how to comfortably perform the ab externo and ab interno techniques as sometimes, if the ab ex- terno technique does not provide the ideal po- sitioning for the XEN, I occasionally convert to an ab interno approach. Rarely, when using the ab externo approach, the XEN can be implant- ed too posteriorly and close to the iris. I then retrieve the device via an ab interno approach and reimplant via an ab interno approach." He therefore recommends that surgeons still learn the traditional ab interno approach first before "playing around" with ab externo techniques. Dr. Do and Dr. Panarelli avoid this prob- lem by having an open peritomy and direct visualization of the external tip of the XEN 45, allowing them to make micro-adjustments, pulling the stent out and pushing it into the anterior chamber to ensure that the stent is properly positioned in the intrascleral and sub-Tenon's space. Ensuring ideal positioning of the distal end of the microstent beneath the Tenon's layer and conjunctiva has resulted in surgical outcomes being more predictable, they said. Moreover, the blebs are more diffuse and posteriorly directed, and this improved bleb Meanwhile, though Dr. Kim uses XEN- ex in the majority of his cases, he said: "For cases at high risk for failure (young, deeply pigmented, inflamed conjunctiva patients), I will do 'open XEN' cases utilizing a fornix-based conjunctival peritomy combined with a gener- ous tenonectomy and ab externo XEN implan- tation." Dr. Kim weighs the advantages against disadvantages such as the risk of erosion in each patient. In addition, to minimize the risk with the open XEN tenonectomy technique, he sutures the XEN to the sclera with a 9-0 vicryl suture to make it flat. Dr. Grover, on the other hand, doesn't make a peritomy at all. "I usually tent the [con- junctiva] over and move the conjunctiva and drag it into place so that the buttonhole through the conjunctiva is nowhere near where the XEN will actually be; this minimizes the risk of erosion and exposure," he said. "Some people tunnel through the subconjunctival space; I pinch the conjunctiva and move it into place." One trick Dr. Grover does, which he credits to Oluwatosin Smith, MD, is putting ink on the tip of the XEN implant injector needle to allow him to know exactly where his conjuncti- val insertion site is located, whether it is Seidel positive and to confirm it is well away from the XEN implant. Performing under topical anesthesia, Dr. Grover uses a traction suture to control the eye and uses preservative-free dexamethasone on a 30-gauge needle to reform the eye. Rather than making a paracentesis, he will insert the 30-gauge needle through the cornea and inject this solution into the anterior chamber any time he needs to pressurize the eye. This modifica- tion again streamlines the surgery and avoids using a 15-degree blade and a viscoelastic. He also uses MMC after injecting the im- plant through a sub-Tenon's injection. In/ex "Extremely fast, extremely simple, and intui- tive," Dr. Kim said that the ab externo approach requires no incisions in the cornea, no visco- elastic, no balanced salt solution irrigation, and can be performed through a usually self-sealing 27-gauge needle tract in the conjunctiva and al- lows almost immediate visual recovery. The ap- proach also allows superotemporal implantation continued from page 32 About the doctors Anna Do, MD Resident New York Eye and Ear Infirmary of Mount Sinai Icahn School of Medicine New York Davinder S. Grover, MD Attending surgeon and clinician Glaucoma Associates of Texas Dallas Won Kim, MD Walter Reed National Military Medical Center Bethesda, Maryland Joseph Panarelli, MD Associate professor of ophthalmology Chief, Division of Glaucoma Services New York University Langone Eye Center New York Financial interests Do: None Grover: Allergan, Glaukos, New World Medical Kim: None Panarelli: Aerie Pharmaceuticals, Allergan, Glaukos, New World Medical, Santen Pharmaceutical

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