EyeWorld India September 2017 Issue

September 2017 EWAP SECONDARY FEATURE 29 Dr. Palmberg explained that the dimensions of the XEN were calcu- lated to produce a pressure gradient from the anterior chamber to the subconjunctival space of 8 mmHg at normal aqueous flow, using the Hagen-Poiseuille equation. This greatly reduces the risk of persistent hypotony compared to trabeculec- tomy. He said that the XEN and the InnFocus MicroShunt (Santen, Osaka, Japan) are the only mini- mally invasive procedures that have produced low to normal average IOPs—11 mmHg for the InnFocus MicroShunt at 3 years 1 and 12.6 mmHg for the XEN at 2 years. 2 Dr. Palmberg cited a recent reevaluation of the Collaborative Initial Glaucoma Treatment Study that suggests achieving pressures in the low teens has an advantage for even modestly damaged POAG patients, based on an average 10% recovery of the visual field and the increased safety of surgical options. 3 The XEN and InnFo- cus MicroShunt potentially offer safer surgical options to reach such pressures, and the Micro-Shunt is currently being compared to MMC trabeculectomy in ongoing FDA and European trials. Dr. Panarelli thinks the best time to needle is when pressures first begin to creep up. “Early nee- dling to disrupt scar tissue forma- tion is easily accomplished as there is still flow through the device, and this can be done in the office,” he said, adding that he reserves more aggressive needling for the operat- ing room, especially when the stent becomes “capped,” resulting in a flat-appearing bleb. Another complication could be bleb leaks—though Dr. Panarelli called them uncommon—which should only result if there is perfora- tion of the conjunctiva. Though he has yet to encounter it, Dr. Panarelli said his biggest concern is erosion, which would more likely occur when the device fails and comes in close contact with the eyelid. He hasn’t had any cases of early or late onset hypotony, but Allergan does mention this as a possibility. The small luminal diameter of the stent provides sufficient resistance to mostly avoid these issues, he said. The XEN, like other MIGS proce- dures, leaves open the possibility of trabeculectomy and tube shunts, if needed, by the patient later. Because the XEN bleb tends to be more nasal, Dr. Radcliffe said a trabeculectomy could still be done at 12 o’clock, and as many tube shunts as needed could be performed. Dr. Panarelli said reimbursement has been a challenge thus far. While it’s likely to change in the future, he has found that prior authorization is required by many insurance plans, or the patient pays out of pocket. Dr. Radcliffe also said that while he’s found some insurance plans cover the XEN, it’s important to have a policy where patients under- stand they will pay out of pocket and be reimbursed by insurance, if covered. “I don’t hesitate to ask patients to pay out of pocket, re- minding them that if the insurance reimburses, they’ll be reimbursed. But this is the case where if patients pay several thousand dollars for a stent, they’re going to see excellent intraocular pressures, they’re going to have their glaucoma problems resolved, they’re going to be very thankful and happy that they made this investment in their vision,” Dr. Radcliffe said, adding that he’s optimistic about the future of XEN insurance reimbursement moving forward. Dr. Sheybani doesn’t implant the XEN without prior insurance approval, not wanting patients to pay out of pocket when there are other options covered by insurance. “These operations may replace trabeculectomy and tube-reservoir shunts in primary glaucoma surgery if the clinical trials show equal efficacy and greater safety. They will likely replace MIGS because of greater effectiveness and compa- rable safety, and will conceivably compete with medical therapy as initial treatment for glaucoma,” Dr. Palmberg said. EWAP References 1. Batlle JF, et al. Three-year follow-up of a novel aqueous humor microshunt. J Glaucoma. 2016;25:e58–65. 2. Ahmed IK, et al. Use of a 45 μm ab-in- terno subconjunctival gel-stent with ad- junctive mitomycin-C for the treatment of uncontrolled open angle glaucoma. 2015 AGS Annual Meeting. 3. Musch DC, et al. Visual field improve- ment in the collaborative initial glaucoma treatment study. Am J Ophthalmol. 2014;158:96–104. Editors’ note: Drs. Panarelli, Radcliffe, and Sheybani have financial inter- ests with Allergan. Dr. Palmberg has financial interests with Allergan and Santen. Contact information Palmberg: ppalmberg@med.miami.edu Panarelli: jpanarelli@NYEE.EDU Radcliffe: drradcliffe@gmail.com Sheybani: sheybaniar@wustl.edu “ It’s not that the technique is easy, but the procedure is reproducible and low risk compared to traditional glaucoma surgeries. ” –Arsham Sheybani, MD