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MIGS procedures a game changer in glaucoma treatment
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Five years ago, attaching the words minimally invasive or microinvasive to any glaucoma procedure would have been considered by most ophthalmic surgeons to be an oxymoron.
While trabeculectomy and tube shunts were capable of generating significant drops in IOP, as shown in numerous series, including the more recent Tube vs. Trabeculectomy Study, the complication rate was daunting. This led most ophthalmologists to be very aggressive with medical therapy, adding second and third topical medications, or even the higher-risk systemic carbonic anhydrase inhibitors, to primary therapy before even considering the complication- and failure-prone incisional glaucoma surgical procedures.
Many experienced ophthalmic surgeons, including myself, stopped performing trabeculectomy and tube shunts, preferring to refer these patients to fellowship-trained glaucoma specialists because the intraoperative and postoperative skill required to generate a good outcome was hard to develop without a high-volume practice, and the time and effort required represented a poor value proposition compared with alternative procedures such as cataract surgery. Fortunately for us and our patients, cataract surgery in the modern form, with phacoemulsification and placement of a posterior chamber lens, turned out to be an outstanding glaucoma procedure itself, resulting in significant reductions in IOP in the patient with high preoperative pressure. A well-done cataract operation saved many thousands of patients from facing the risks of a trabeculectomy or tube shunt while allowing no reduction in success if these procedures were needed at a later date. Still, most patients after cataract surgery remained dependent on medical therapy, and some responded with pressure spikes that necessitated urgent intervention with trabeculectomy or tube shunts.
Now, after more than 10 years of research and development, we have our first U.S. Food and Drug Administration- approved glaucoma procedure that all agree is minimally or microinvasive glaucoma surgery (MIGS) and capable of being performed by any skilled ophthalmic microsurgeon: the Glaukos iStent. And even more exciting, in development by Glaukos, Transcend Medical, AqueSys, Ivantis, InnFocus and others is an extremely promising group of follow-on products that appear in early clinical trials capable of advancing the management of glaucoma in even the most complex cases, using a surgical procedure with a much more favorable risk-benefit ratio than the classic trabeculectomy and tube shunt.
In our practice at Minnesota Eye Consultants, both Tom Samuelson, a fellowship-trained glaucoma specialist, and I, with a practice more dominated by corneal disease, cataract and refractive surgery, have adopted the iStent. I have limited its use to implantation of a single stent in patients with glaucoma damage requiring medical therapy who need cataract surgery for the usual indications. Tom has found success in patients with cataract and glaucoma, and with select patients with other off-label indications, including phakic eyes; in some patients, he has implanted more than one stent, which in several non-FDA studies has generated enhanced efficacy when compared with single-stent implantation.
We have both been impressed by the elegance, safety, efficacy and high patient satisfaction generated by the procedure. In my small series, all patients have achieved a reduction in IOP and medication burden, and 80% have achieved an IOP of less than 18 mm Hg off medication. I have one patient who had a transient microhyphema that resolved spontaneously. For Tom, a highly skilled and experienced glaucoma surgeon who participated in the Glaukos clinical trials in the U.S. and Armenia, there was no learning curve. For me, the Glaukos training and on-site support allowed a rapid development of comfort with the procedure.
Our early experience at Minnesota Eye Consultants suggests to me that MIGS will not only be an important surgical procedure for the glaucoma specialist but also generate renewed interest in the surgical treatment of glaucoma by the comprehensive ophthalmologist whose most common surgery is for cataract. At least 10% of patients who undergo cataract surgery in the U.S. also have glaucoma, and if we include glaucoma suspects and ocular hypertension, the number approaches 20%. In the FDA study of the iStent, the complication rate in the control cataract surgery-only patients was higher than in those randomized to cataract surgery plus iStent. While there is no such thing as no-risk surgery, the additional risk to the patient of combining MIGS with cataract surgery appears to be very low.
If confirmed with increasing global experience, at least 300,000 patients per year undergoing cataract surgery in the U.S. alone might benefit from a combined procedure, and the global number is more than 2 million annually. This would represent a larger volume than the combined number of trabeculectomy and tube shunt procedures currently performed per year, and promises to make glaucoma surgery a comfortable part of every cataract surgeon’s practice.
While there is much more to learn, through the magic of the innovation cycle and competition, I expect great advances in MIGS over the next decade. This is a form of glaucoma surgery that, in my opinion, will be embraced by patients and performed by glaucoma specialists and comprehensive ophthalmologists/cataract surgeons in rapidly increasing numbers. It is possible for me to imagine the day when glaucoma treatment evolves from a disease dominated by medical therapy to one in which early surgery with a MIGS procedure combined with adjunctive medical therapy when needed is preferred by most ophthalmologists and patients. I see this possible — no, even probable — transition as a win for patients, ophthalmic surgeons and society as the economic and social burden of glaucoma is progressively reduced.