Microstent promising in open-angle glaucoma

Liz Meszaros

The use of a trabecular microbypass stent in combination with cataract surgery in patients with mild-to-moderate open-angle glaucoma is safe and results in clinically safe and statistically significant reductions in IOP with fewer medications when compared with cataract surgery alone.

"The [trabecular micro-bypass stent] is a safe adjunct to cataract surgery in the management of early-to-moderate glaucoma," said Dr. Samuelson, attending surgeon, Minnesota Eye Consultants, Minneapolis, and adjunct associate professor at the University of Minnesota. "Patients receiving the [stent] were more likely to remain medication-free or have reduced medication burden postoperatively, as compared with cataract surgery alone."

Dr. Samuelson and co-authors, along with the United States iStent Study Group, conducted a prospective, multicenter FDA IDE/PMA trial.

For this prospective, randomized, open-label, controlled, multicenter trial, a total of 240 eyes with mild-to-moderate OAG with IOP =24 mm Hg controlled with one to three medications were studied. Patients underwent either cataract surgery with trabecular micro-bypass stent implantation or cataract surgery only. Under protocol expansion, 50 additional patients were enrolled to undergo cataract surgery with trabecular micro-bypass stent implantation. The data are based on the first 240 eyes enrolled.

Primary efficacy measure was unmedicated IOP ≤21 mm Hg at 1 year. A secondary measure was unmedicated IOP reduction ≥20% at 1 year.

Safety measures included best-corrected visual acuity, slit-lamp observations, complications, and adverse events.

The majority of eyes that underwent cataract surgery with trabecular micro-bypass stent implantation achieved unmedicated IOP ≤21 mm Hg at 1 year (72%), compared with only 50% of control eyes (p < 0.001).

IOP in both treatment groups was statistically significantly lower than baseline at 1 year postoperatively, and 66% of eyes undergoing trabecular micro-bypass stent implantation achieved an IOP reduction ≥20% without medication, compared with 48% of control eyes (p = 0.003). The overall incidence of adverse events was similar between the two groups.

"This is an important study in that it demonstrates the safety and efficacy of the [trabecular micro-bypass stent] for early-to-moderate glaucoma," Dr. Samuelson said. "In addition, it may [provide] the cleanest, most scientifically valid data to date that cataract extraction lowers IOP in patients with mild-to-moderate glaucoma.

"Both groups, treatment and control, achieved significant IOP reduction," he added. "The [trabecular micro-bypass stent] group required less medication than the cataract-alone group."

Since participating in this study, Dr. Samuelson has changed his approach.

"I do fewer combined cataract and trabeculectomy procedures. Rather, I prefer to remove the cataract and reassess the IOP postoperatively," he said.

These data offer promising results for future cataract management, Dr. Samuelson continued.

"That we may soon have a procedure that can reduce medications without compromising safety is an important advance," he said. "One might argue that we already have such procedures in the form of trabectomy, canaloplasty, or [endocyclophotocoagulation].

"However, there has not been a prospective randomized study of this sort to help discern how much additional benefit these procedures add over cataract extraction alone," he added.