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Second-generation glaucoma stent combined with cataract surgery helps reduce IOP
The procedure offers patients the ability to reduce or eliminate their need for glaucoma medications.
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Unlike glaucoma surgery, cataract surgery offers quick visual and anatomic recovery. But the two procedures often have to be performed in a single eye, a situation that is likely to become more frequent as baby boomers age.
“Cataract procedures don’t mix well with traditional glaucoma surgeries,” according to Carlos Buznego, MD, who spoke at the American Society of Cataract and Refractive Surgery meeting in Chicago. Whereas the goal of refractive cataract surgery is to be rid of glasses, patients with glaucoma who need cataract surgery may prefer to be rid of their daily eye drops, Dr. Buznego told Ocular Surgery News.
Dr. Buznego presented results of two clinical trials investigating the use of the model GTS400 Glaukos iStent trabecular micro-bypass stent implanted in patients with open-angle glaucoma undergoing cataract surgery.
Carlos Buznego
The iStent is a second-generation ab interno implant that creates a minimally invasive bypass through the trabecular meshwork to Schlemm’s canal. It is inserted during cataract surgery through the corneal incision.
The inserter is preloaded with two stents, and the trocar is inserted into the trabecular meshwork and Schlemm’s canal. A trigger activates a spring-loaded injector that advances the stent into the proper position in Schlemm’s canal. The surgeon aims the inserter at the first target, presses a button to deliver the first stent, and then moves 2 clock hours over the meshwork to deliver the second stent.
Study details
Two prospective, randomized, multicenter U.S. Food and Drug Administration trials examined the safety and efficacy of the GTS400 over a period of 2 years. Patients were randomized to cataract surgery with or without the glaucoma stent procedure.
The primary endpoint was IOP of 18 mm Hg or less without medication in 44 eyes for one trial and 21 mm Hg or less without medication in 83 eyes for the other trial. In both trials, an IOP decrease of more than 20% without medication was a secondary outcome measure.
The safety data that were tracked consisted of the rate of ocular adverse events such as IOP elevation of 10 mm Hg or more, a loss of best corrected visual acuity of more than one line at 3 months postop or later, and a need for secondary surgical interventions.
Key inclusion criteria included mild to moderate open-angle glaucoma, glaucomatous visual field defect or optic nerve abnormalities, and no severe defects or other glaucoma. All study participants had IOP of less than 24 mm Hg on one to three medications, stable for at least 2 months.
Cataract surgery eligibility was determined by best corrected visual acuity with medium glare source worse than 20/40. Patients with prior glaucoma surgery other than iridectomy were excluded.
After a washout period, IOP was required to be between 22 mm Hg and 36 mm Hg in one trial and between 24 mm Hg and 36 mm Hg in the other trial.
Results
In 42 eyes in the first trial with data through 24 months, 72% of eyes treated with the iStent and 24% of control eyes achieved IOP of 18 mm Hg or less without medication at 12 months (P = .004). At 24 months, 68% of treated eyes and 35% of control eyes maintained IOP of 18 mm Hg or less; although the finding was not statistically significant, there was a trend for statistical significance.
IOP reduction of at least 20% without medication was achieved at 12 months in 72% of treated eyes and 18% of control eyes (P = .0018) and at 24 months in 68% of treated eyes and 29% of control eyes (P = .0265).
Dr. Buznego explained that the FDA protocols changed slightly, necessitating the second trial. If the study population had been larger, statistical significance may have been achieved at 24 months.
Thirty-nine eyes in the second trial have reached 12 months of follow-up. In this study, 79% of the treatment group and 33% of the control group achieved IOP of 21 mm Hg or less without medications (P = .0423). An IOP reduction of at least 20% without medications was achieved in 76% of treated eyes and 33% of control eyes; although the finding was not statistically significant, there was a trend for statistical significance.
Overall, complications and recovery time were similar between patients who received the stent and the control group.
Future demand
“The number of patients with coexistent cataracts and glaucoma will be increasing dramatically with the trends toward a more elderly population. How will we handle this important trend? If we can offer them a straightforward, low-risk procedure to rehabilitate their vision and reduce or eliminate their need for medications, that would make sense,” Dr. Buznego said.
Traditional glaucoma procedures are often avoided by many cataract surgeons. Because the trabecular micro-bypass stent procedure can readily be performed by cataract surgeons, more ophthalmologists will be able to perform the procedure.
“The good news is the technique is not outside the boundaries of the skill set of a cataract surgeon,” Dr. Buznego said. “If you can do cataract surgery, this trabecular meshwork bypass stent is definitely within your comfort zone. I’m trained in the anterior segment. I didn’t do a glaucoma fellowship. I didn’t do angle surgery as a resident. So this is something I learned de novo, and it’s not something that’s difficult or tricky.”
FDA trials for the iStent have been approved for cataract patients with glaucoma. However, once approved, it may not be long before physicians use the device in patients as a standalone procedure to control IOP without medications, Dr. Buznego said. – by Ryan DuBosar