Experts discuss the growing market of MIGS, as well as their benefits and possible concerns, while examining alternative non-invasive intervention methods.
Interest in new microinvasive glaucoma surgical (MIGS) procedures remained high in 2013.
Throughout the year, there was growing market adoption of the trabecular microbypass stent (iStent, Glaukos) as surgeons continued to wait for approval of two investigational MIGS devices: the Schlemm’s canal scaffold (Hydrus, Ivantis) and the supraciliary micro-stent (CyPass Micro-Stent, Transcend Medical).
Ophthalmology Times editorial advisors, Robert D. Fechtner, MD, Malik Kahook, MD, and Joel S. Schuman, MD, provided updates and insights on the status of glaucoma surgery.
The level of surgeon interest in performing trabecular microbypass stent implantation at the time of cataract surgery is noteworthy, Dr. Fechtner said, considering that in clinical trials, the proportion of patients achieving target IOP was only modestly higher among those who underwent the combined procedure compared with cataract surgery alone.
According to recent literature, implanting more than one trabecular microbypass stent affords greater benefit, and Dr. Fechtner said he is looking forward to learning more about this approach from surgeons outside the United States.
“One of the business realities of device approval in the United States is that we are unlikely to see additional large scale studies that could provide greater insight about the indications and limitations of new modalities,” said Dr. Fechtner, professor, Institute of Ophthalmology and Visual Science, and director, glaucoma division, Rutgers-New Jersey Medical School.
Dr. Kahook observed that currently, any patient who undergoes iStent implantation with two devices would need to pay out-of-pocket for the second device, which is significantly costly. Thus, there is interest in determining variables for predicting which patients might benefit most from the single implantation and in identifying ways to maximize the IOP-lowering effect achieved with a single device.
Image-guided placement is one possibility, and Dr. Kahook mentioned the work being done by Dr. Schuman and colleagues in this area.
“We know that the stent ideally should be implanted next to the collector channels, but currently there are no techniques to confirm proper localization,” said Dr. Kahook, The Slater Family Endowed Chair in Ophthalmology and professor of ophthalmology, University of Colorado. “Software for anterior segment OCT under development by Dr. Schuman and colleagues shows promise for imaging the collector channels preoperatively in order to guide a ‘smart’ implantation.”
According to Dr. Kahook, one of the most exciting developments in the realm of MIGS is the undertaking by Ivantis of a head-to-head-trial comparing its Hydrus device against dual iStent implantation.
“This kind of evidence-based research will give us an idea about the relative efficacy of these new options and perhaps start us on a path to tailored surgical therapy by potentially providing information that will help guide patient selection,” said Dr. Kahook. “Whereas not that long ago, our choices for surgical intervention were trabeculectomy or a drainage device, the options are expanding, and in the future we may be able to optimize care by individualizing our surgical decisions.”
However, there seem to be mixed reports on outcomes from surgeons who have been performing ab interno trabeculectomy using the Trabectome device (NeoMedix), noted Dr. Schuman, Eye and Ear Foundation professor and chairman of ophthalmology, University of Pittsburgh School of Medicine (UPMC), and director, UPMC Eye Center.
The conflicting results may be more technique-related than representing some limitation intrinsic to the procedure itself, and glaucoma surgeons should be watching for more information on this story, he said.
Novel, non-invasive intervention
As an alternative to compete with the Trabectome procedure and laser trabeculoplasty approaches, Dr. Kahook and colleagues have created Deep Wave Trabeculoplasty (DWT, Ocutherix), which is designed to enhance aqueous outflow through the trabecular meshwork without causing tissue damage.
The noninvasive procedure is now being developed by Ocutherix, which obtained rights to the technology from the University of Colorado.
DWT involves external application of mechanical energy to cause focal stretching and relaxation of the trabecular meshwork that induces an IOP-reducing stress response in the trabecular meshwork cells modulated by a change in the local protein environment. The changes are not associated with heat or tissue damage.
“Several years ago, Dr, Schuman reported laboratory evidence that the mechanism by which cataract surgery reduces IOP involves ultrasound activation of an ELAM-1/IL-1/NF-κB response in trabecular meshwork cells,” Dr. Kahook said. “Deep wave trabeculoplasty was developed to work using similar principles.”
The efficacy of DWT was first demonstrated in preclinical testing and showed ~30% IOP lowering. Results of an initial human trial in 30 patients found DWT treatment resulted in a 26% decrease in IOP with no complications. A second clinical trial that is randomized with comparison to selective laser trabeculoplasty is now underway in the Philippines with data expected to be reported in the next 6 months.
The second human trial is also exploring efficacy of repeated treatments.
“Our goal is to make DWT available as a more cost effective option compared to use of topical drops,” Dr. Kahook said. “We also believe this approach will negate any concerns regarding adherence to topical therapy, which is currently very poor in glaucoma patients.”
Alternative methods expanded
Discussion about cataract surgery for lowering IOP also continued throughout this past year.
Dr. Kahook commented that he still considers this approach appropriate only for patients with visually significant cataract.
“More discussion and more data is needed before clear lens removal should enter the mainstream of surgical glaucoma management,” Dr. Kahook said.
With its benefits for overcoming the drawbacks of medical therapy for glaucoma—including cost, adherence, and ocular surface issues—SLT continues to gain acceptance as a first-line treatment for open angle glaucoma.
Since SLT was first approved by the FDA in 2001, lasers for performing the procedure were available from only a single manufacturer—Lumenis—as a patent prevented other manufacturers from selling their SLT equipment in the United States. Competition came to the US marketplace in 2013 with introduction of SLT lasers by Ellex and Quantel.
Ellex first commercialized SLT technology for Coherent (now Lumenis) in 2001, and its proprietary SLT technology has been sold outside of the United States for almost 10 years.
Quantel has been providing SLT technology outside the US since 2007.
Facing the new frontier
Looking ahead, Dr. Schuman noted that the sweeping changes in medicine being brought on by the Affordable Care Act will cause practitioners to make difficult choices in patient management, recognizing that the quality of their care delivery is being judged in part by its cost.
“When glaucoma surgeons choose to use new devices, they will need to consider the cost versus the benefit compared with trabeculectomy or some other procedure,” Dr. Schuman said. “Now is the time to decide how we can prepare for these changes.”
Also commenting on the changing healthcare marketplace, Dr. Fechtner noted that only time will tell how ophthalmology fits into the accountable care organizations or what the implications of the newly insured population will be in terms of demand on ophthalmology services and resources.
However, it seems certain that practitioners can expect to face another cycle of adaptation.
“It is reasonable to expect there will be continued downward pressure on reimbursement, and I believe this will continue to stimulate interest in some of the components of our care that fall outside of strict insurance payment limits,” Dr. Fechtner said. “Therefore, the ‘cataract plus’ procedures are going to continue to be of interest for our otherwise healthy glaucoma patients.”
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