The Evolution of Combined Cataract-Glaucoma Procedures

FDA approval of the Glaukos iStent is another milestone for this class of surgeries.

By Bill Kekevian, Associate Editor

It was a busy morning for the relatively small team at Glaukos, an ophthalmic medical device company in Orange County, Calif. Although the young tech company employs fewer than three-dozen people, it had been working for this very moment for 11 years.

The cause of all the activity? Word had finally come down from the FDA that Glaukos' sole product, the trabecular micro-bypass stent, had been approved for use in the United States. Named the iStent, it's the first ab-interno micro-bypass implant available for lowering IOP.

The stent itself is less like a tube shunt and more like a half-pipe that sits in the trabecular meshwork. It's more than just the smallest stent created to bypass the trabecular meshwork. At less than 1 mm in length, Glaukos says it's the smallest medical device ever implanted in the human body.

The FDA's June decision made iStent just the latest in a diverse and growing collection of blebless glaucoma techniques developed by small and innovative companies seeking to link their specific procedures to the growing cataract surgery market. Here's what ophthalmologists say about how this emerging technology will impact combined cataract procedures.

Changing Times

“It's a very exciting time in glaucoma surgery,” says David Richardson, MD, of San Gabriel, Calif. Dr. Richardson is a consultant to iScience, creator of the blebless Canaloplasty surgery. “I'm very enthusiastic about this next round of procedures.”

COURTESY OF ALCON; BRIAN FRANCIS, MD; GLAUKOS

Newer options include (clockwise from upper left) the Express mini-shunt, canaloplasty, the iStent and the Trabectome.

The market is embracing a revolution in IOP-lowering devices and procedures that enable patients to recover faster and with fewer complications. A host of new techniques developed in the last decade have been designed to prevent the eventual need for trabeculectomy. Besides the Glaukos iStent, they include the Canaloplasty (iScience, Menlo Park, Calif.) and Trabectome (Neomedix, Tustin, Calif.).

The Trabectome ablates the obstructed segments of the trabecular meshwork using focused electrosurgical pulses to remove portions of the trabecular meshwork itself. It does not require implantation of a stent or shunt. That's the key distinction between the Trabectome and other devices.

Canaloplasty requires a scleral flap to expose Schlemm's canal. The surgeon then inserts a true lumen catheter with a fiber optic light on its tip through the canal, threading a suture 360 degrees around it. This holds the canal open to reduce pressure.

The iStent works by creating a channel between the anterior chamber and Schlemm's canal to restore aqueous outflow. The process requires an inserter and intraoperative gonioscopy. By all accounts, the procedure is most effective in patients in the early stages.

Placement of the iStent does not require creation of a scleral flap. That can leave options open for future operations, according to Glaukos. Data presented at ASCRS this year showed one iStent achieved target pressures between 15 mm Hg and 18 mm Hg while two produced target pressures below 15 mm Hg.¹

An Alternative to Trabeculectomy

Dr. Richardson foresees a day when trabeculectomy procedures will be phased out altogether. His chosen path to that day is Canaloplasty, a non-penetrating procedure by iScience. Canaloplasty, he says, is “truly the first glaucoma surgery that works better with cataract surgery than without.”

Dr. Richardson says he uses Canaloplasty because it's close to a true trabeculectomy replacement. Canaloplasty expands all 360 degrees of the canal. The procedure can treat patients in later stages of glaucoma with IOPs soaring above 30 mm Hg. When combined with phacoemulcsification, a Canaloplasty can decrease IOP by 35% or 40%, according to a 3-year study of 157 eyes by Richard Lewis, MD, of Sacramento, Calif.²

“The Canaloplasty's dissection, to me, is a little more complex,” says Brian Francis, MD, a glaucoma specialist at the Doheny Eye Institute in Los Angeles and a consultant to Neomedix.

Like the iStent and Trabectome, Dr. Francis says, Canaloplasty is a good option prior to trabeculectomy, but won't outright replace the need for it.

The Glaukos iStent in comparison to an IOL. Glaukos says the iStent is the smallest medical device ever implanted into the human body. It's the latest implant FDA approved for lowering IOP.

Market Factors

Glaukos has raised more than $125 million from venture capital firms. OrbiMed Healthcare Fund Management alone backed the company to the tune of $35 million. Why did these venture capitalists find Glaukos so attractive?

For starters, implanting an iStent can be completed in 5-10 minutes compared to Canaloplasty, which can take 30-45 minutes, or Trabectome, which can require 15 minutes. Obviously, this means surgeons can see more patients and focus more time and energy on the cataract surgery. However, the evolution of combined glaucoma procedures isn't contingent solely on the quickest technique. It's about what's most efficacious and most adaptable for clinical use.

“It's not all based on science. A lot of it is marketing, availability and economic factors,” Dr. Francis says.

“Trabectome is attractive because it's relatively fast and can be done with phaco surgery with little extra time or risk,” Dr. Richardson says. “But it requires a significant investment to purchase the equipment and the replaceable handpiece. Surgeons like it, but the surgery centers aren't sold.”

Dr. Francis notes the iStent and Canaloplasty present similar procedure and materials costs.

Although Glaukos isn't ready to reveal a fee structure for iStent, Louis “Skip” Nichamin, MD, a consultant to the company, says to “rest assured” that the Centers for Medicare and Medicaid Services “have seen fit to reimburse this product.”

Marching Forward

Trabectome, Canaloplasty and iStent each offer unique advantages to lowering IOP in the early stages of the disease, but all have a few features in common. They are all blebless outpatient procedures, and they are safer than traditional trabeculectomy, according to these surgeons. Yet all three may be vulnerable to even newer techniques as technology marches forward.

Dr. Nichamin explains that surgeons are a wily and innovative group. It's in their nature to customize procedures to meet their own needs. Maybe they'll even improve upon them.

“We're finding the niche for each of these new procedures. Surgeons will increasingly appreciate patient-specific procedures,” says Dr. Nichamin. So, the FDA trials should not be taken as the final word on these procedures.

“Once a device like [iStent] is approved, leave it to ingenious surgeons to find a better way to utilize it,” he says. “To the critics who pooh-pooh the FDA data, let's wait a year or two.”

Dr. Richardson expresses the same attitude, saying the criticism of Canaloplasty as a lengthy procedure is an issue only during the surgeon's learning curve and that an experienced surgeon could complete it in as little as 15 minutes.

The iStent up close.

There may be no superior procedure, but all three offer individual advantages. Most importantly, they all offer a successful way to make glaucoma surgery safer, with fewer instances of hypotony or other complications. This means more cataract surgeons can nip glaucoma in the bud earlier in the course of the disease and, perhaps, reduce the number of cases that progress to later stages.

“They'll all be around in some form,” Dr. Francis says. “All these procedures are going to evolve. Whether they evolve in a parallel fashion remains to be seen.” OM

References

1. Chang DF. Intraocular presure reduction following microinvasive glaucoma surgery to implant 2 trabecular micro-bypass stents in OAG. ASCRS 2012 (abstract).
2. Lewis RA, von Wolff K, Tetz M, et al. Canaloplasty: Three-year results of circumferential viscodilation and tensioning of Schlemm canal using microcatheter to treat open-angle galucoma. J Cataract Reform Surg. 2011; 37:682-690