The Hydrus Microstent from Ivantis has a unique trimodal mechanism of action that permanently reconstructs the patient’s natural outflow pathway and lowers intraocular pressure (IOP). First, it creates a large bypass opening through the trabecular meshwork, allowing outflow of aqueous humor. Secondly, it dilates and scaffolds Schlemm’s canal to augment outflow. Finally, it spans 90 degrees of the canal, providing expanded access to the eye’s fluid collector channels. The device is the first canal-based microinvasive glaucoma surgery (MIGS) microstent to dilate such a distance, says Brett Trauthen, MS, chief scientific officer of Ivantis.

“Because the stent is placed in the natural outflow system, it doesn’t change the eye’s structures significantly, which maximizes safety and minimizes trauma to targeted tissues,” says Inder Paul Singh, MD, president of The Eye Centers of Racine and Kenosha, in Racine and Kenosha, Wisconsin, who was a trial investigator for the device.

In August, the device received FDA approval for use in patients with mild to moderate primary open-angle glaucoma in combination with cataract surgery. “When you combine it with cataract surgery, you don’t have to make a separate incision to place the device,” says Steven Vold, MD, medical director, Vold Vision, Fayetteville, Arkansas, who participated in the early clinical validation of the device and was a trial investigator.

“From a practical standpoint, lower IOP reduces the need for medications,” Trauthen says. “Patients appreciate the comfort of knowing their IOP is in control without having to take medications.”

Using the Device

Similar to other MIGS devices, the Hydrus Microstent is delivered ab interno via a clear corneal incision with a gonioscope. The microstent is advanced from the injector by using a roller wheel advanced by the surgeon’s index finger, and is placed in the nasal quadrant of Schlemm’s canal.

“It’s a very intuitive, straightforward device,” Dr. Singh says. “After scoring the trabecular meshwork, it slides in beautifully with little hand manipulation. Some other procedures often require more steps and/or hand motions. The learning curve is fairly quick because the visualization technique is similar to other MIGS devices.”

In addition, surgeons can clearly visualize correct anatomic placement into the canal. “A surgeon can be confident that it’s placed correctly, because once in the canal, it follows the natural curvature and the surgeon can see the stent scaffolding the canal,” Dr. Singh continues. With other devices, proper positioning is not readily verifiable.

Roughly the size of an eyelash at 8 mm long, the Hydrus Microstent is made of a lightweight biocompatible alloy called nitinol comprised of nickel and titanium. Known for its flexibility and shape memory, nitinol is commonly used in medical devices and has been implanted in more than 1 million cases in different bodily areas, including blood vessels and bones. Its curved design matches the contour of Schlemm’s canal.

Promising Study Results

The Hydrus Microstent is one of the most rigorously researched and thoroughly studied of all MIGS devices, with more than 4,000 patients treated globally with a wide range of disease severities since 2010. Patients are monitored in the SPECTRUM registry, which is the largest real-world MIGS registry ever run.

FDA approval was based on the HORIZON pivotal study,¹ the largest prospective, randomized, controlled trial to date for a MIGS device. The study involved 556 glaucoma patients undergoing cataract surgery. The results at 2 years were “best in class” compared to other MIGS pivotal trials, with the greatest number of responders receiving a 20% IOP drop relative to the control group, as well as the greatest percentage of patients remaining medication free relative to the control group, Trauthen says.

More than three-quarters (77.2%) of patients in the Hydrus Microstent group achieved a statistically significant decrease (≥20% reduction in unmedicated IOP) at 24 months postoperatively, compared to 57.8% in the cataract surgery alone group, meeting the primary effectiveness endpoint. Additionally, more than 78% of Hydrus Microstent patients remained medication free compared to 48% in the control group, a 30% difference and the largest delta of any MIGS pivotal trial to date. GP

Reference

1. Samuelson TW, Chang DF, Marquis R, et al. A Schlemm’s canal microstent for intraocular pressure reduction in primary open angle glaucoma and cataract: the HORIZON trial. Ophthalmology. 2018 Jun 23. [Epub ahead of print]