EyeWorld India September 2017 Issue

September 2017 EWAP SECONDARY FEATURE 33 such as those with normal tension glaucoma, as well as for patients without prior intraocular surgery and phakic patients with chronic angle closure whose anterior chambers are too shallow to ac- commodate a tube. Trabeculectomy remains the only available glau- coma procedure that allows titra- tion of aqueous flow after surgery to produce a desired degree of IOP lowering, she added. She said that she will perform tube shunt surgery in patients with prior failed trabeculectomy or in pa- tients who are likely to fail primary trabeculectomy surgery (such as those with neovascular glaucoma or uveitic glaucoma), as well as in pa- tients with extensive conjunctival scarring from previous surgery or trauma. “Of course, these are basic guidelines for patient selection in my practice, and one must always consider specific patient factors in order to choose the optimal surgery for a given individual,” she said. Dr. Vinod said that the XEN Gel Stent is one of the newer subconjunctival procedures, FDA approved last year, and offers the distinct advantage over trabs and tubes of being performed via an ab interno approach. “It is a gelati- nous tube with a fixed length (6 mm) and inner lumen diameter (45 microns) designed to re- strict aqueous outflow and limit hypotony, which is among the more frequent complications we encounter with trabs and tubes,” she said. “The XEN may be particularly helpful in patients with cataract and glaucoma who require a combined procedure, with potentially lower risks than those associated with combining cataract with either a trab or a tube.” Dr. Vinod finds the XEN to be a reasonable primary proce- dure in many of the patients who are candidates for traditional incisional surgery, and she added that the absence of a conjunctival flap and superonasal placement would not preclude future inci- sional surgery if needed. “Like trabeculectomy, the XEN Gel Stent may require more in-office postoperative inter- ventions, such as needling and antifibrotic injections, than a tube shunt and would therefore not be my procedure of choice in patients who cannot come in for frequent follow-up,” Dr. Vinod said. When asked about using an adjunctive antifibrotic agent with each of these procedures, Dr. Vinod said that antifibrotic agents are routinely required with trabeculec- tomy and the XEN Gel Stent, but she does not use antifibrotics with tube shunts. Dr. Grover also uses antifibrot- ics with the XEN and trabeculec- tomy, but not with tubes. “I think you have to use MMC with a XEN,” he said, “or it will fail.” Potential complications Dr. Vinod said that one compli- cation with trabeculectomy and tubes is hypotony. Complications of hypotony can include shallow anterior chamber and choroidal effusion, more often as a result of overfiltration, but occasionally due to wound leaks. “Hypotony is usually transient and amenable to medical management but can sometimes be visually significant,” she said. “Infectious complications resulting from wound leaks or tube erosion are less common but can be devastating.” Early studies of the XEN Gel Stent suggest that it is a fairly safe procedure with transient hypo- tony occurring in less than 10% of patients, Dr. Vinod said. “However, the initial XEN studies did not use antifibrotics, and long-term data regarding late complications relating to mitomycin-C use, bleb scarring and failure, and effects on endothelial cell counts are unavail- able for this relatively novel device,” she said. A tube is a foreign body in the eye, and it does put the eye at risk of erosion and double vision, Dr. Grover said. The tough part with a trabeculectomy is it’s a relatively in- vasive procedure, and there can be bleb-related problems, he said. Tra- beculectomy is also not as predict- able as a tube because it depends on a number of factors, including the size of the flap, how you close the conjunctiva, and how it heals. With the XEN, there is a lower rate of erosion, and it does not put patients at risk for double vision. But it also has the predictability of a tube because it’s a controlled outflow. “The other beauty of it is it does not require a conjunctiva dissection,” Dr. Grover said. The XEN is placed ab interno, so you’re not taking the conjunctiva down, he said, and it doesn’t preclude you from doing a tube or trab later. Slit lamp picture demonstrating the XEN Gel Stent. The black arrow shows the implant in the subconjunctival space. There is a classic low diffuse bleb. Implantation of the XEN Gel Stent; side photo demonstrates the external hand positioning during the implantation. Source (all): Davinder Grover, MD continued on page 34