EyeWorld Asia-Pacific September 2019 Issue

26 EWAP SEPTEMBER 2019 SECONDARY FEATURE Variations The parallel evolution of the ab externo approach among surgeons has led to variations in the exact technique individual surgeons use. At their practice, Dr. Do >˜` À° *>˜>Àiˆ «ÀiviÀ wÀÃÌ injecting MMC at 60–80 mcg 10 mm posterior to the limbus, then making a 3–4 clock hour peritomy. “The XEN is then inserted via an ab externo approach into the anterior chamber and the peritomy is closed with the stent safely tucked beneath the Tenon’s layer,” they said. “Performing a limited tenonectomy may decrease the risk of stent obstruction/early failure; however, this may potentially lead to a higher risk of erosion through the conjunctiva.” Meanwhile, though Dr. Kim uses XEN-ex in the majority of his cases, he said: “For cases at high risk for failure (young, `ii«Þ «ˆ}“i˜Ìi`] ˆ˜y>“i` conjunctiva patients), I will do ‘open XEN’ cases utilizing a fornix-based conjunctival peritomy combined with a generous tenonectomy and ab externo XEN implantation.” 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 ˆÌ y>Ì° Dr. Grover, on the other hand, doesn’t make a peritomy at all. “I usually tent the [conjunctiva] 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 conjunctival insertion site is located, whether it is Seidel positive and to Vœ˜wÀ“ ˆÌ ˆÃ Üi >Ü>Þ vÀœ“ ̅i 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 ̅i iÞi° /…ˆÃ “œ`ˆwV>̈œ˜ >}>ˆ˜ streamlines the surgery and avoids using a 15-degree blade and a viscoelastic. He also uses MMC after injecting the implant through a sub-Tenon’s injection. In/ex “Extremely fast, extremely simple, and intuitive,” Dr. Kim said that the ab externo approach requires no incisions in the cornea, no viscoelastic, no balanced salt solution irrigation, and can be performed through a usually self-sealing 27-gauge needle tract in the conjunctiva and allows almost immediate visual recovery. The approach also allows superotemporal implantation and avoids entanglement in Tenon’s capsule, a major cause of XEN failure. Dr. Grover added a nuance to these advantages, 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 approach 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 With an open conjunctival peritomy, the XEN gel stent position can be easily adjusted 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 (all): Joseph Panarelli, MD