Stent combined with phaco effectively manages elevated IOP

Thomas W. Samuelson

A trabecular micro-bypass stent in combination with phacoemulsification may compare favorably with phaco alone in managing elevated IOP.

“We have a safer surgery for early to moderate glaucoma that does not achieve the same degree of pressure reduction as more traditional glaucoma operations but is synergistic with cataract surgery, can be done through the same clear corneal incision, and has none of the long-term bleb-related safety concerns inherent to traditional surgery,” Thomas W. Samuelson, MD, one of the study authors, said in an interview with Ocular Surgery News.

The prospective, randomized, open-label, controlled, multicenter study enrolled 240 eyes with mild to moderate open-angle glaucoma that had a medically controlled IOP of 24 mm Hg or less. Preoperative pressure was controlled with one to three medications.

The treatment group included patients who underwent cataract surgery and concomitant iStent (Glaukos) implantation, while patients in the control group underwent cataract surgery alone.

Generational differences

The study included the first-generation iStent, which is currently under U.S. Food and Drug Administration review; however, second- and third-generation iStents are also being evaluated internationally.

“Other studies are under way in Armenia, for example, utilizing all three generations of the Glaukos technology. The first two generations are Schlemm’s canal stents and then the third generation is a suprachoroidal device,” Dr. Samuelson said.

The comparative studies are assessing the use of one stent vs. two stents vs. three stents. Early results suggest that multiple stents may achieve greater pressure reduction, according to Dr. Samuelson.

“It may be that we can expand the indications for the iStent when we are able to place more than one device,” he said, hopeful that multiple stents may be used to treat more moderate or even moderately advanced glaucoma.

The G-1, or first-generation, iStent is L-shaped, resembling a snorkel or half-pipe. It is slightly more difficult to implant than later-generation stents but is also widely adoptable, Dr. Samuelson said.

The G-2 device is more conducive to implantation of multiple stents because it is preloaded with two stents that may be inserted through the same entryway and placed a few clock hours apart, he said. In contrast, multiple entries would be required to insert multiple G-1 stents.

The newest-generation iStent, the G-3, uses an ab interno approach to the suprachoroidal space. Transcend Medical offers a similar device, and Solx also offers an ab externo approach.

Study results

Dr. Samuelson and colleagues established the study’s primary efficacy measure as an unmedicated IOP of 21 mm Hg or less at 1 year postop. This outcome was achieved in 72% of treatment eyes and 50% of control eyes.

Moreover, 66% of treatment eyes and 48% of control eyes achieved at least a 20% pressure reduction without medication. While mean IOP lowering at final follow-up was similar for the two groups due to pressure management, substantially higher medication use was reported for the control group.

“The time to first medication use was statistically significantly longer in the iStent group, with subjects taking more medications in the control group at 1 week than subjects in the iStent group at 1 year,” the study authors wrote.

Adverse events were similar between the two groups overall, with no unanticipated side effects occurring due to iStent implantation.

The study authors said that the device spares a patient’s conjunctival tissue, thus preserving the option of future IOP-lowering treatments. Additionally, it prevents severe late-onset complications.

“In patients with advanced disease, we can justify the risks of trabeculectomy, but in patients with early to moderate disease, I have a hard time subjecting patients to the lifelong risks of bleb leaks and bleb infections,” Dr. Samuelson said.

Comparative head-to-head studies with other minimally invasive glaucoma surgeries have not been conducted, but Dr. Samuelson speculated that the iStent would compare favorably with Trabectome (NeoMedix) but would not lower pressure as effectively as canaloplasty (iScience Interventional), at least when only one stent is employed. However, the iStent offers reduced surgical time and less invasiveness, he said.

“Most surgeons will have an operation they do for early disease and then they will have a different operation they do for advanced disease, but not every surgeon is going to do all of the [minimally invasive procedures],” Dr. Samuelson said. “It is going to take time to sort out which procedures will prevail and which will fall by the wayside.” – by Michelle Pagnani

Reference:

• Samuelson TW, et al. Randomized evaluation of the trabecular micro-bypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology. 2011;118(3):459-467.

• Thomas W. Samuelson, MD, can be reached at Minnesota Eye Consultants, 701 E. 24th St., Suite 100, Minneapolis, MN 55404; 612-813-3628; fax: 612-813-3656; email: twsamuelson@mneye.com.
• Disclosure: Dr. Samuelson is a consultant for Glaukos, Alcon and Abbott Medical Optics. He has also been a consultant for iScience.

The iStent is a new breed of glaucoma device that is ultra safe, efficiently implanted at the time of cataract surgery and has demonstrated the potential for reasonable IOP lowering in mild to moderate disease. We see the use of a single iStent to be appropriate in certain cases and have found implantation of multiple stents to provide even greater reduction of IOP. Once available in the United States, the iStent will offer surgeons a titrable, non-pharmaceutical option for pressure reduction to treat the full range of open-angle glaucoma disease.

– Ike K. Ahmed, MD
OSN Glaucoma Board Member
Disclosure: Dr. Ahmed is a consultant for Glaukos.