Eyeworld

EW GLAUCOMA 78 January 2018 by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer MIGS and glaucoma: Deciding which space to target Not all MIGS options are suitable for patients in different stages of disease. Specialist suggests opting for devices that avoid the area of the pathology Presentation spotlight C hoosing the right MIGS device may not be as difficult a choice as many think. Although the ever-increasing number of FDA-approved MIGS options may seem blurring, the choice comes down to which space to aim for and which to avoid. MIGS devices that engage apparently viable segments of the trabecular meshwork and Schlemm's canal may be tapping into the wrong part of the drainage system. "With all of the MIGS options out there, it can be overwhelming for eye doctors to choose which one will work best in the individual patient," said Douglas Rhee, MD, professor and chair, Department of Ophthalmology and Visual Sciences, University Hospitals Eye Institute, Case Western Reserve University School of Medicine, Cleveland, who spoke at the 2017 ASCRS•ASOA Symposium & Congress. "The trabecular meshwork is the site of pathology and is the part of the system that should be bypassed, as the pathology in glaucoma is not a downstream issue. Trabecular mesh- work bypass procedures are safer but maybe not as effective with the current procedures/devices." IOP regulation The trabecular meshwork is a filter-like tissue whose primary func- tion is the regulation of aqueous flow and establishing IOP. The juxta- canalicular tissue (JCT) or cribriform region, adjacent to Schlemm's canal, responds to changes in pressure by launching a homeostatic re- sponse, allowing greater aqueous flow through the JCT. The JCT can be subdivided into inner and outer zones based on the presence of ex- tracellular matrix (ECM) molecules, which is critical in preserving open outflow channels. Researchers have proposed that the ECM engages in continuous maintenance remodel- ing of the trabecular meshwork by releasing trapped debris from the outflow pathways and acting like a barrier to functionally isolate the aqueous outflow channels from aberrant modification. The con- tinuous turnover process is what maintains open flow through the trabecular meshwork and rigorous IOP control. 1 According to Dr. Rhee, these processes seem to counteract MIGS applied in the trabecular mesh- work and Schlemm's canal, causing IOP to resurge after initial MIGS IOP-lowering effects. In his research on matricellular proteins in the trabecular meshwork, he explained that ECM molecules in non-ocular tissues generally increase fibrosis and may therefore play a significant role in IOP dysregulation. Some of these matricellular proteins (SPARC, thrombospondin-1 and -2, tena- scin-C and -X) have been identified in the trabecular meshwork and are thought to play a pivotal role in IOP regulation/dysregulation and in the pathophysiology of glaucoma. 2 Research on tenascin-C, a substance also found in the JCT, further sug- gests a continuous remodeling of the trabecular meshwork, with or without IOP increase. 3 Circumvent the pathology Knowing where the trouble is brewing should be enough to keep out of the trabecular meshwork and avail oneself of those MIGS options that circumvent the pathology. "The JCT is not a static structure. It is constantly undergoing remodeling," Dr. Rhee said. "We have known that the trabecular meshwork is the site of pathology since 1958 and thanks to some very influential papers. 4,5,6 The issue with the limited success observed with the iStent [Glaukos, San Clemente, California] and Trabectome [NeoMedix, Tustin, California] is not that the resistance to aqueous outflow is elsewhere, it is because they are being placed into the site of the pathology: the trabecular meshwork and Schlemm's canal." He explained that although procedures such as the Trabectome, iStent, Kahook Dual Blade (New World Medical, Rancho Cucamonga, California), GATT, iStent G2, and the Hydrus (Ivantis, Irvine, Califor- nia) all have excellent safety pro- files, their pressure-lowering effects are limited by the fact that their efficacy relies on placement within the trabecular meshwork. continued on page 82 © 2017 Novartis 9/17 US-ORA-17-E-2539 ORA SYSTEM ® PATIENT IMPORTANT PRODUCT INFORMATION CAUTION: Federal (USA) law restricts this device to sale by, or on the order of, a physician. INTENDED USE: The ORA SYSTEM ® uses wavefront aberrometry data in the measurement and analysis of the refractive power of the eye (i.e. sphere, cylinder, and axis measurements) to support cataract surgical procedures. CONTRAINDICATIONS: There are no known contraindications for this device. WARNINGS AND PRECAUTIONS: The following conditions may make it difficult for your doctor to obtain accurate readings using the ORA SYSTEM ® : Patients having progressive retinal pathology such as diabetic retinopathy, macular degeneration, or any other pathology that the physician deems would interfere with patient fixation; Patients having corneal pathology such as Fuchs', EBMD, keratoconus, advanced pterygium impairing the cornea, or any other pathology that the physician deems would interfere with the measurement process; Patients for which the preoperative regimen includes residual viscous substances left on the corneal surface such as lidocaine gel or viscoelastics; Visually significant media opacity, such as prominent floaters or asteroid hyalosis, will either limit or prohibit the measurement process; or Patients having received retro or peribulbar block or any other treatment that impairs their ability to visualize the fixation light. Use of iris hooks during an ORA SYSTEM ® image capture will yield inaccurate measurements. In addition: Significant central corneal irregularities resulting in higher order aberrations might yield inaccurate refractive measurements. Post refractive keratectomy eyes might yield inaccurate refractive measurement. The safety and effectiveness of using the data from the ORA SYSTEM ® have not been established for determining treatments involving higher order aberrations of the eye such as coma and spherical aberrations. The ORA SYSTEM ® is intended for use by qualified health personnel only. Improper use of this device may result in exposure to dangerous voltage or hazardous laser-like radiation exposure. The ORA SYSTEM ® should not be operated in the presence of flammable anesthetics or volatile solvents such as alcohol or benzene, or in locations that present an explosion hazard. ATTENTION: Ask your doctor for more information about the ORA SYSTEM ® and its use in your cataract procedure. SYSTEM® with Verif Eye ® + 100236 US-ORA-17-E-2539_PI EW.indd 1 12/8/17 12:20 PM

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