Eyeworld

MAY 2012

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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28 EW GLAUCOMA February 2011 Device focus May 2012 Newer surgical options changing glaucoma treatments by Michelle Dalton EyeWorld Contributing Editor Trabeculectomy may remain the standard surgical choice, but others may be safer T he pros and cons of trabeculectomy have not rad- ically changed over the decades—the technique involves moving the aqueous away from the anterior chamber to the subconjunctival space. "No other procedure will get a patient out of [intraocular pressure (IOP)] trouble as quickly as a trab," said Thomas W. Samuelson, M.D., Minnesota Eye Consultants, Min- neapolis. "This rapid and often dra- matic IOP reduction is worth the risk in far advanced patients but less so in early disease. There's always been a void for the early-to-moder- ate visual field loss patients." The influx of several different The iStent Source: Glaukos The Hydrus on a quarter Source: Ivantis types of devices (most of which are not commercially available in the U.S.) has allowed surgeons to start tailoring surgical treatment options at earlier phases in the disease. With almost 60 million people worldwide affected by glaucoma, these kinds of individualized treatments will be- come more commonplace, experts said. With patient non-compliance a significant factor in treatment, the newer surgical devices may allow glaucoma specialists to bypass that issue altogether. The latest devices can be categorized into ab interno, ab externo, or bleb forming, said Iqbal "Ike" K. Ahmed, M.D., assis- tant professor of ophthalmology, University of Toronto, and most are micro-incisional glaucoma surgery (MIGS). Dr. Samuelson said he prefers The Trabectome handpiece tip Source: NeoMedix "micro-incisional" to describe proce- dures that utilize enhanced micro- surgical techniques and "minimally invasive" to describe procedures that are both micro-invasive and have lower risk. Very few procedures are both micro-incisional and mini- mally invasive. For example, proce- dures such as canaloplasty (iScience Interventional, Menlo Park, Calif.) might be considered lower risk, but certainly are not micro-incisional. Conversely, the EX-PRESS Glaucoma Filtration Device (Alcon, Fort Worth, Texas), which uses a short tube under the scleral flap to help make trab more successful, is micro-inci- sional, but "anything that might subject the eye to hypotony carries risk, so I would not qualify it as minimally invasive." Dr. Ahmed added BAGS—or ble- bless ab externo glaucoma surgery— to the growing list of acronyms to better incorporate the SOLX Gold Shunt (SOLX, Waltham, Mass.) and canaloplasty. The benefit of either BAGS or MIGS is an improved safety profile compared with trabeculec- tomy, he said. "To me, as soon as we do a scleral dissection, we're no longer discussing MIGS," he said. To quickly differentiate, he said MIGS IOP targets are typically a little higher, with more mild-to-moderate patients; BAGS are reserved for a bit more aggressive surgery where IOP reduction is greater but the risks are higher as well; and finally, tradi- tional bleb-forming surgery is "the ultimate in efficacy" but exposes patients to higher risks. "All these new procedures must be trying to challenge the standard of trabeculectomy," said Norbert Pfeiffer, M.D., professor of ophthal- mology, University Medical Center, Mainz, Germany. "Trabeculectomy is far from ideal; we are looking for op- tions that should at least be similar if not superior [to] the outcomes we've achieved with trabeculec- tomies in the past." Whether any of these devices can eventually replace trabeculec- tomy will depend on the outcomes of clinical studies currently under- way or those that have yet to be un- dertaken. "It requires favorable results before we can declare MIGS the new standard," Dr. Pfeiffer said. With "over $500 million in- vested in the space," an increased in- terest from industry, and improved instrumentation, innovation will continue, Dr. Ahmed said. Incorporating a new surgical technique Patient selection is a major factor in how successful the newer devices might be. "Not every device will work well The SOLX Gold Shunt after implantation Source: Ike K. Ahmed, M.D. The CyPass MIGS device Source: Transcend Medical for every patient, and understanding that is incredibly important," Dr. Ahmed said. The technical side of performing these newer procedures differs from trab, and surgeons need to plan for a slight learning curve, Dr. Samuelson said. "You're performing anterior chamber angle surgery," Dr. Pfeiffer said, referring to the Hydrus Intra- canalicular Implant (Ivantis, Irvine, Calif.), a canalicular scaffold that in- creases outflow facility by bypassing the trabecular meshwork and dilat- ing Schlemm's canal to increase cir- cumferential flow. "We're working in a part of the eye that's not easily visible. Surgeons need to be comfort- able with the anatomy and know where Schlemm's canal is before using these devices." Additionally, he noted the newer devices mandate a bimanual surgical approach with a gonioscope in one hand that is more technically challenging. Ab interno procedures Fortunately, MIGS procedures "are very forgiving," Dr. Ahmed said. "There's not a lot of downside to these procedures." With MIGS, there are a lot of options. Subtle differences exist be- tween the devices, and experts agree additional studies will vet out long- term risks associated with the de- vices. The iStent (Glaukos, Laguna Hills, Calif.) works by placing the device directly into Schlemm's canal; second- and third-generation devices are also being developed for implantation into Schlemm's via the trabecular meshwork (iStent inject) or into the suprachoroidal space (iStent supra). "The iStent is a bit more mini- malist than other devices," Dr. Samuelson said. "At 1 mm long, the potential for disrupting the anatomy is small, and it can be titrated if nec- essary." At 8 mm, "the Hydrus is recruiting more collector channels, and there's a better chance of in- creased IOP reduction, when com- pared to a single iStent," he said. Studies by Dr. Ahmed and others have shown that mean IOPs of 15 mm Hg or less can also be attained by implanting two iStent devices. At 6 months, Dr. Pfeiffer's group reported "the majority of patients were medication free in the [Hydrus Intracanalicular Implant] eye," he said, with a mean IOP drop of about seven points from baseline in one study and almost nine points in an-

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