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Minimally invasive glaucoma surgery (MIGS) is the latest development in the treatment of glaucoma. With two MIGS devices already approved in the United States, there are a variety of novel devices that have the potential to transform the treatment of glaucoma.
Minimally invasive glaucoma surgery (MIGS) is the latest development in the treatment of glaucoma. Two MIGS devices have already been approved for the U.S. market and more are in development. So are a variety of other novel devices that have the potential to transform the treatment of glaucoma.
Seven companies presented their latest devices in development or marketing during a “New Horizons in Glaucoma Devices” session as part of the New Horizons Forum at the 2017 Glaucoma 360 meeting. Malik Y. Kahook, MD, Slater Family Endowed Chair of Ophthalmology, University of Colorado, Denver, and Thomas W. Samuelson, MD, founding partner, Minnesota Eye Consultants, Minneapolis, were the sessions moderators.
The CyPass Micro-Stent was the second MIGS device to win FDA approval after the iStent (Glaukos). Both devices are indicated for the reduction of intraocular pressure (IOP) in adult patients with mild-to-moderate primary, open-angle glaucoma (POAG) in conjunction with cataract surgery.
“This is the first device in the United States designed to vent into the supraciliary space,” said Steven D. Vold, MD, president, Vold Vision, Bentonville, AR, and consultant to Alcon Laboratories. “This is something that can very easily be implemented into practice by comprehensive ophthalmologists. It may lower IOP more than a trabecular bypass. It has superior IOP-lowering efficacy than cataract surgery alone and the safety profile is comparable to cataract surgery alone.”
Complication rates are identical for CyPass plus cataract as in cataract alone, Dr. Vold continued. More than 70% of eyes achieved an unmedicated IOP reduction of at least 20% and many have maintained the reduction for as long as 7.5 years. Of patients who respond, 93% are off all medications at 24 months.
The XEN gel stent also was cleared for marketing in the United States in 2016 and launched in 2017. The 6-mm stent is implanted through the trabeculum into the subconjunctival space via a small incision in the cornea.
The highly flexible stent was approved for refractory POAG in patients who are unresponsive to maximum-tolerated medical therapy. More than 11,000 XEN stents have been placed globally and there were no operative adverse events reported in the trials used for FDA approval.
“These were patients with refractory glaucoma, medicated baselines were 25 mm Hg, mean meds 3.5, visual field deviation -15,” said Michael R. Robinson, MD, vice president, Therapeutic Area Head, Anterior Segment and Consumer Eye Care. “At month 12, mean meds were 1.7, 39% were drug free with a mean IOP of 13.5 mm Hg. This can be very successful in patients who have refractory glaucoma.”
Adverse events are minimal and minor, Dr. Robinson continued. About a quarter of patients required needling. Hypotension was transient and generally disappeared within seven days.
Equinox has a unique approach to glaucoma. Most devices treat glaucoma as a disease of elevated IOP. Equinox treats glaucoma as a disease of two pressuresÂ–intraocular pressure (IOP) and intracranial pressure (ICP). It is the pressure gradient between IOP and ICP at the optic nerve that destroys vision, not simply ocular hypertension.
“Patients who have glaucoma have a lower ICP than matched controls and those with normotensive glaucoma have even lower ICP,” said John Berdahl, MD, founder and CEO. “Patients with ocular hypertension but no glaucoma had higher, protective ICP. If IOP is higher, the head of the optic nerve bows out (glaucoma). If ICP is higher, the head of the optic nerve bows in (papilledema), which affects about 50% of the astronauts on the International Space Station.”
Berdahl’s solution is goggles that reduce the exterior pressure on the eye, effectively lowering IOP relative to ICP. The goggles can be worn at night and are compatible with IOP-lowering medications.
Because the goggles can also increase exterior pressure on the eye, raising IOP, they may be useful to combat papilledema on the International Space Station and during projected space flights to Mars. NASA is supporting research to develop the goggles.
Glaukos is one of the few device makers focused on glaucoma. It also developed the first MIGS device cleared for the U.S. market, the iStent, which restores physiologic outflow.
“We are not just iStent,” said Jeff Wells, PharmD, vice president of clinical, regulatory and quality. “Our portfolio consists of three other investigational flow and drug delivery devices.”
iStent Inject is an injector with two preloaded stents. The two devices are implanted into the Schlemm’s canal a couple of clock hours apart to increase outflow, Wells explained. The 2-year endpoint on the pivotal clinical trial comes up later in 2017 and Glaukos expects to file for premarketing approval by the end of 2017.
iStent Supra drains into the suprachoroidal space. Enrollment for a 2-year pivotal trial is in the final stages.
iDose is a travoprost depot that is injected into the sclera to elute drug into the anterior chamber. The device is in phase II with results expected by the end of 2017.
The MicroShunt is the first minimally invasive device for the treatment of mild, moderate, and severe POAG that promises to sustain IOP below 15 mm Hg and eliminate eye drop medications for most patients. It is also the only device in a randomized, controlled trial versus trabeculectomy.
“What we see in studies outside the United States is that the acute hypotony rate is a fraction of what you see with trabeculectomy, and chronic hypotony just isn’t there,” said Russ Trenary, president and CEO. “For the glaucoma surgeon, having an alternative to trabeculectomy is going to be wonderful, not just in the operating room, but postoperatively.”
The device is made of SIBS, used in more than a million cardiac patients over 15 years and as an investigational ophthalmic product for more than eight years.
A pooled analysis of over 300 patients with baseline IOP of 23 mm Hg and 3 medications showed an IOP of less than 15 mm Hg and 60% of patients are completely off glaucoma medications. The device can be used with or without cataract surgery and is expected to last the lifetime of the patient.
The Hydrus Microstent is the only device that dilates and reconstructs Schlemm’s canal. About 3,000 of the devices have been implanted and results of a pivotal U.S. trial are due later in 2017.
“We have tremendous confidence,” said Brett Trauthen, chief scientific officer. “In a smaller version of this pivotal trial published in 2015, 80% of patients showed at least a 20% drop in diurnal IOP after 2 years. That is the highest absolute response rate ever reported in a MIGS study.”
The device is introduced using a metal cannula that incises the trabecular meshwork (TM) and advances into the canal. Surgeons report placement is easy to verify and there have been no reports of device migration or loss.
The next step is a 24-hour IOP monitor attached to the stent. Working prototypes report through an iPhone and are in active development.
The device is also a potential platform for drug delivery. Ivantis is developing an ophthalmic-eluting stent using the same coating used on drug-eluting coronary stents.
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Surgeons who want to remove the TM have a new device, the Kahook Dual Blade. Because it is an ab interno micro-incisional instrument, not an implant, it is covered under existing reimbursement codes.
“We might call this a trabeculectomy ab interno, or we might call it an ab interno goniotomy,” said Nathan M. Radcliffe, MD, assistant professor of ophthalmology, director of Glaucoma Service, New York Eye Surgery Center, New York University Langone Medical Center. “In the surgical world, we sometimes struggle with reimbursement, but the goniotomy code has been around for years.”
The blade has a pointed tip that penetrates the TM and a ramp that elevates the tissue under pressure. Two blades free the tissue strip from the rest of the meshwork.
Blood reflux is common the first day, Radcliffe added, but clears in almost all patients within a week. Surgeons can expect about a 5 mm Hg reduction in pressure when used in conjunction with cataract surgery and 80% of patients are able to eliminate at least one medication.