EyeWorld India September 2017 Issue

by Ellen Stodola EyeWorld Senior Staff Writer September 2017 32 EWAP SECONDARY FEATURE Comparing glaucoma procedures AT A GLANCE r )ZQPUPOZ BOE CMFC SFMBUFE QSPCMFNT BSF QPUFOUJBM DPODFSOT XJUI TPNF PG UIFTF QSPDFEVSFT &BSMZ SFTVMUT XJUI UIF 9&/ IBWF TIPXO HPPE TBGFUZ BOE MPXFS SJTL PG TPNF DPNQMJDBUJPOT r (FOFSBMMZ VTJOH POF PG UIFTF QSPDFEVSFT EPFT OPU QSFDMVEF B TVSHFPO GSPN DIPPTJOH BOPUIFS PQUJPO JO UIF GVUVSF r "OUJàCSPUJD BHFOUT BSF JNQPSUBOU UP VTF XJUI USBCFDVMFDUPNZ BOE UIF 9&/ CVU BSF OPU HFOFSBMMZ VTFE XJUI UVCF TIVOUT Experts discuss use of trabeculectomy, tube shunts, and XEN Gel Stent A lthough trabeculectomy, tube shunts, and the XEN Gel Stent (Allergan, Dublin, Ireland) work by creating a pathway for aqueous humor to drain into the subcon- junctival space, these are all very different options for different types of patients. Patient factors such as disease severity and more can play into which procedure a glaucoma surgeon chooses. Kateki Vinod, MD , New York Eye and Ear Infirma- ry of Mount Sinai, New York, and Davinder Grover, MD , Glaucoma Associates of Texas, Dallas, dis- cussed aqueous drainage into the subconjunctival space and shared their thoughts on when to use each of these options and the advantages and disadvantages they offer. Aqueous drainage into the subconjunctival space The subconjunctival space is the site of aqueous drainage in tradi- tional filtering glaucoma surgery, including trabeculectomy and tube shunt surgery, Dr. Vinod said. “Procedures targeting the subcon- junctival space offer the advantage of achieving lower intraocular pressures than trabecular meshwork and Schlemm’s canal-based surger- ies can, as the latter are limited by downstream resistance to outflow and episcleral venous pressure,” she added. However, bleb-related problems, such as leaks and infections, may occur with operations that involve aqueous drainage to the subcon- junctival space. “Such complica- tions have become less common as a result of refinements in our trabeculectomy technique, includ- ing more diffuse application of antifibrotic-soaked sponges and, more recently, subconjunctival in- jection of antifibrotics,” Dr. Vinod said. “The risk of these and other complications associated with trabs and tubes has led to the develop- ment of MIGS procedures that seek to optimize safety.” The eye is like a faucet and drain, Dr. Grover said, in that it makes water and drains water. The majority of open-angle glaucoma is thought to be caused by drainage problems through the trabecular meshwork. Dr. Grover said his ap- proach is to tell patients that he will try to open their own drain, but if that’s not possible, a new drain will need to be created, which can be done with a tube shunt, trabeculec- tomy, or the XEN Gel Stent. The problem is that the aque- ous is not supposed to be in the subconjunctival space, so when it is, it creates an aggressive scarring response. To address this, Dr. Grover said that mitomycin-C (MMC) or a drainage implant can be used. All innovations with trabs and tubes are designed to trick the eye to not act as aggressively to aqueous in the subconjunctival space, he said. Dr. Grover thinks that the XEN could help create a more predictable outflow pathway. “It’s the best of both worlds between [trabeculec- tomy] and tube,” he said. Ideal patients for each option Dr. Grover said the ideal procedure often depends on the patient, and he noted that certain cases may be more clear-cut than others. In particular, he considers patients’ activity and where they live. For example, if the patient works in a dirty environment, a trabeculecto- my would not be ideal because this puts the patient at risk for infection. Tubes, he said, have the least risk of infection. Another example Dr. Grover gave was patients who scuba dive. In these patients, a tube shunt would be better. Dr. Grover added that in patients who are on blood thin- ners and can’t be taken off this medication, it’s risky to do a tube or trabeculectomy, and a XEN may be a better choice because of the lower risk of a sudden drop in pressure. The XEN creates a bleb, so this could put the patient at risk for bleb-related complications. But Dr. Grover noted that these problems have not been seen in Europe where the XEN has been approved for a longer period of time. Patients who are more prone to scar tissue formation tend to do better with glaucoma tubes, he added, and would not do well with a trabeculectomy or the XEN. If the patient has mild/moder- ate glaucoma to early advanced glaucoma, Dr. Grover noted that his general approach is to try to open up their own drain, but if that doesn’t work, then he tells patients he has to create a new drain. Right now, the safest, most predictable, and least invasive way of creating a new drain is the XEN, he said. According to Dr. Vinod, pa- tients who are ideal candidates for subconjunctival filtering procedures tend to be those with moderate to advanced glaucoma whose in- traocular pressures are uncontrolled with medical therapy and/or have demonstrated progression or are likely to progress. “Patients must not have extensive conjunctival scarring that would limit the ‘real estate’ available for a subconjuncti- val procedure whose success relies on formation of a bleb,” she said, referring to trabeculectomy and the XEN Gel Stent. Dr. Vinod prefers trabeculec- tomy as her “go-to” surgery for patients requiring low target IOPs, Patient factors such as disease severity and more can play into which procedure a glaucoma surgeon chooses.