Response to Letter to the Editor: Short-Term Efficacy and Safety of Open Conjunctiva Ab Externo XEN45 Gel Stent Implantation in Glaucoma Patients

We appreciate the insightful comments from Dr Arora and colleagues regarding our recently published manuscript in the Journal of Glaucoma. We are happy to reply to their comments as follows. We would like to start by stating that our retrospective study was not meant to compare the XEN45 implant to the trabeculectomy but rather to report the safety and efficacy of a relatively new glaucoma device with a novel surgical approach. Just as trabeculectomy has been studied for the last several decades, we must investigate the XEN45 in new environments and with different techniques to determine the optimal efficacy and niche for the implant. Regarding the comments on the use of the XEN45 for cases with previously failed filtering surgeries, we agree that management of these cases is particularly challenging and even more so in resource-limited settings. Furthermore, previous filtering surgery is often considered an exclusion criterion for many XEN45 studies.1 In our study, 60.0% of cases with previous filtering surgery achieved complete success without medications. A similar study by Grover et al2 evaluated the use of the ab interno XEN45 after previous filtering or cilioablative procedures and found that an impressive 75.4% of patients had a ≥20% intraocular pressure reduction from baseline on equal or fewer medications. In addition, we feel it is common for the results of clinical studies to deviate from the perceptions and practice patterns of different surgeons. For example, in 1 of the cited studies by Rajendrababu et al,3 there was a relatively low level of complete success (5.4%) and a high level of qualified success (75.7%) for repeat trabeculectomies, perhaps suggesting a lower threshold for restarting medications during the postoperative period compared with our study. We agree that an additional single-surgeon study comparing the ab externo XEN45 to trabeculectomy for refractory cases would be a welcomed addition to the literature. We agree that any filtration surgery takes up precious conjunctival space; however, the amount of conjunctiva affected by the XEN45 implant appears smaller compared with an average trabeculectomy. In fact, our group has used the XEN45 implant in patients with failed trabeculectomies or other filtering surgeries by sliding the XEN45 implant between other surgical areas. We share the perspective that trabeculectomy is considered the gold standard for glaucoma surgical intervention as it consistently demonstrates high levels of success. We would like to add that in our practice, however, we have found the XEN45 stent to be a relatively noninvasive option with a good safety profile compared with trabeculectomy. One study by Cappelli et al4 found that trabeculectomy had superior intraocular pressure-lowering efficacy but higher rates of flat anterior chambers and bleb leakage compared with ab interno XEN45 stents. Although they studied the ab interno and not ab externo approach, we also stress the importance of safety in addition to intraocular pressure lowering when choosing a surgical intervention. The final inquiry was regarding the 1 patient in our study who received a XEN45 stent for angle closure glaucoma. This patient had not undergone any previous glaucoma surgery and presented with grade zero angles on the gonioscopy examination. The patient was unfortunately considered a failure based on our study criteria at 12 months with an intraocular pressure of 20 mmHg on medications. To the best of our knowledge, the open conjunctiva ab externo approach has not been extensively studied for use in primary angle closure glaucoma. Wanichwecharungruang et al5 did, however, compare the ab interno approach to XEN45 implantation and identified similar levels of success between then XEN45 and traditional trabeculectomies in primary angle-closure glaucoma. Further investigation into the ab externo approach for this patient population is warranted. Once again, we would again like to thank Dr Arora and colleagues for their interest in our article and their commitment to providing high-quality glaucoma care.

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