Eyeworld

EW GLAUCOMA 82 January 2018 Dr. Rhee was part of a team of researchers that compared ab interno trabeculectomy with trabeculectomy plus mitomycin, demonstrating that the trabecular meshwork was strongly implicated in the resistance to aqueous outflow. The study included 115 open angle glaucoma patients, uncontrolled and on maximal tolerated medica- tions, who underwent ab interno trabeculectomy and demonstrated a lower success rate than 102 pa- tients who had trabeculectomy plus mitomycin. The success rate in the ab interno group, which was mea- sured as IOP <21 mm Hg and >20% reduction from baseline, was 46% at 1 year and 22% at 2 years, and 85% at 1 year and 76% at 2 years in the trabeculectomy group. A higher makes it difficult to create MIGS pas- sages in these regions of the eye. "All surgical therapies eventu- ally fall victim to wound healing and homeostatic compensation, meaning that the body will try to return itself to the state that it was in before you started cutting into it, even if it is not a productive state to be in, namely a high pressure state," Dr. Rhee said. "Wound healing is something that we are going to have to overcome. The biggest reason to bypass the trabecular meshwork is to bypass the site of pathology. It irks me to hear we don't know what causes glaucoma, because in fact, we have a good sense. We are not necessarily that far away from being able to avoid these seemingly challenging surgical procedures with limited success rates. We are getting closer, and I am optimistic about the new devices in development," Dr. Rhee said. EW References 1. Keller KE, et al. The juxtacanalicular region of the ocular trabecular meshwork: a tissue with a unique extracellular matrix and special- ized function. J Ocul Biol. 2013;1:3. 2. Rhee DJ, et al. Matricellular proteins in the trabecular meshwork. Exp Eye Res. 2009;88:694–703. 3. Keller KE, et al. The effects of tenascin C knockdown on trabecular meshwork outflow resistance. Invest Ophthalmol Vis Sci. 2013;54:5613–23. 4. Grant WM. Further studies on facility of flow through the trabecular meshwork. AMA Arch Ophthalmol. 1958;60:523–33. 5. Bill A, et al. Uveoscleral drainage of aqueous humor in human eyes. Exp Eye Res. 1971;12:275–81. 6. Maepea O, et al. Pressures in the juxta- canalicular tissue and Schlemm's canal in monkeys. Exp Eye Res. 1992;54:879–83. 7. Jea SY, et al. Ab interno trabeculectomy versus trabeculectomy for open-angle glauco- ma. Ophthalmology. 2012;119:36–42. 8. Samuelson TW, et al. Randomized evalu- ation of the trabecular micro-bypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology. 2011;118:459–67. Editors' note: Dr. Rhee has financial interests with some of the companies mentioned in his comments. Contact information Rhee: douglas.rhee@uhhospitals.org MIGS continued from page 78 number of additional glaucoma procedures were performed after ab interno trabeculectomy (43%) than after trabeculectomy (11%). 7 In another, unrelated investi- gation, researchers demonstrated limited success of a single iStent by comparing pressure reduc- tions achieved with the iStent or phacoemulsification in 240 patients with cataract and mild to moderate open angle glaucoma. The primary efficacy measure of unmedicated IOP <21 mm Hg at 1 year after surgery was met by 72% of the treatment eyes compared to 50% of the controls, who had phaco alone. Furthermore, 66% of the treat- ment eyes and 48% of the controls achieved >20% IOP reduction at 1 year without medications. 8 "Wound healing is the major factor negatively impacting out- comes with MIGS devices placed in the trabecular meshwork," Dr. Rhee said. "Initial success rates are excellent, exceeding 95% efficacy, but plummet due to wound heal- ing effects. The body is trying to readjust from ablation or removal of parts of the trabecular meshwork. At first there is a high success rate that quickly decreases due to wound healing." A further issue in trying to bypass the trabecular meshwork is that the drainage around the trabecular meshwork is not uniform for 360 degrees—it is segmental. This means that the outflow does not progress evenly in all areas and Trabecular meshwork SPARC and collagen IV Source: Douglas Rhee, MD

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