Microbypass trabecular stent delivers significant, durable efficacy

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Follow-up to 3 years in a study of eyes undergoing combination cataract surgery with implantation of a single microbypass trabecular stent shows a 36% reduction from baseline mean medicated IOP and 84% reduction in daily medication use.

By Cheryl Guttman Krader; Reviewed by Tobias H. Neuhann, MD

Munich-Implantation of a single microbypass trabecular stent (iStent, Glaukos)-combined with small-incision cataract surgery-provides safe and sustained IOP-lowering, show data from follow-up through 3 years in a single-center study, according to Tobias H. Neuhann, MD.

Dr. Neuhann first began performing the microinvasive glaucoma surgery about 4 years ago, and has collected data from 62 eyes of 43 patients who underwent the combined procedure. Data from follow-up to 2 years were available for 45 eyes, and 41 eyes had reached the 3-year visit.

At 3 years, mean IOP was reduced 36% from its preoperative medicated level. The improvement was achieved with an 84% reduction in daily medication use and an excellent safety profile, said Dr. Neuhann, medical director, AaM Augenklinik am Marienplatz, Munich, Germany.

“Patients with glaucoma who undergo cataract surgery typically achieve some IOP-lowering benefit, but it usually only persists for 6 to 12 months,” he said. “Therefore, the magnitude and durability of the efficacy of this combined MIGS-cataract surgery is remarkable, and importantly, its benefit was achieved without any intraoperative complications or any of the more serious complications that occur with filtration surgery.”

The study cohort included 39 eyes with primary open-angle glaucoma, 11 eyes with pseudoexfoliation, 10 eyes with ocular hypertension, and 2 eyes with secondary glaucoma. Sixty percent of the eyes were surgically naïve, but 13% had prior trabeculectomy and others had undergone some laser procedure. Most of the eyes were being treated with 2 topical medications and 18 were using 3 or more medications.

Mean IOP was 24.1 mm Hg preoperatively on medication, was reduced to 14.2 mm Hg at 3 months and remained stable throughout follow-up, averaging 14.5 mm Hg at 24 months and 14.9 mm Hg at 36 months.

“We did not separate the eyes by diagnosis, but we observed it did take a little bit longer for the IOP to be fall after surgery in the pseudoexfoliation cases compared with the open-angle glaucoma patients,” Dr. Neuhann said.

Average medication use was reduced from 1.8 preoperatively to 0.3 at month 6, 0.2 at month 24, and 0.3 at month 36.

“At month 36, 79% of eyes had an IOP of 16 mm Hg or less and 74% were medication free,” Dr. Neuhann said. “And the results at 36 months are similar looking at a consistently seen cohort of 39 eyes.”

Best-corrected visual acuity (BCVA) was 20/40 or better in 44% of eyes preoperatively and in 93% of eyes at month 36.

“The BCVA was excellent as we expect when we do cataract surgery,” Dr. Neuhann said.

During the follow-up, two patients became intolerant to topical and systemic IOP-lowering therapy and underwent shunt surgery. One eye had photocoagulation.

Surgical pearls

The stent is placed into Schlemm’s canal through the same temporal, limbal incision used for the cataract procedure and after filling the anterior chamber with viscoelastic, Dr. Neuhann said.

Offering some surgical tips to facilitate visualization, he suggested performing the insertion from the temporal side with the help of a gonioscopic lens, tilting the microscope towards the surgeon and patient’s head away. To guide accurate placement of the stent, Dr. Neuhann said he messages the collector channels and veins until the channels fill with blood.

“When you see the blood, you know you are where you want to go,” he said.

Eyes may rarely develop hyphema postoperatively from bleeding through the channels, but in the absence of that event, postoperative bleeding is a positive sign, he added..

“Blood is the enemy of glaucoma surgery, but in this case it is your friend because it shows the stent is in the right position,” Dr. Neuhann explained.

Tobias H. Neuhann, MD

E: tneuhann@web.de

Dr. Neuhann has no relevant financial interest to disclose.