GLAUCOMA IN THE ASC

MIGS Category Expands with CyPass

Recently approved suprachoroidal device shown to reduce IOP and medication use

By Desireé Ifft, Contributing Editor

The CyPass Micro-Stent (Alcon) recently became the second micro-invasive glaucoma surgery (MIGS) device available in the United States, but its FDA approval came with a couple of notable firsts. To date, the COMPASS trial that led to the approval of CyPass is the largest pivotal trial to evaluate a MIGS device. Also, CyPass is the first FDA-approved MIGS device to target the uveoscleral pathway/suprachoroidal space to increase aqueous humor outflow and decrease IOP. It’s approved for treating patients with mild to moderate primary open-angle glaucoma (POAG) in conjunction with cataract surgery.

Although physician and ASC payment for utilizing CyPass have yet to be determined, two surgeons who participated in COMPASS are eager to begin using the device. Expecting to achieve the type of positive results obtained in the clinical trial, Farrell Tyson, MD, FACS, says CyPass is a welcome addition for treating glaucoma. “Prior to this, our surgical options were tube shunt or trabeculectomy, which are more invasive and complication-prone, or a trans-trabecular MIGS device,” says Dr. Tyson. “With CyPass, we’re going into a virgin space, an area unaffected by glaucoma, and getting good pressure reduction and reduced topical medication use via a very elegant procedure.” E. Randy Craven, MD, agrees, noting, “The simplicity of CyPass placement is a huge benefit.”

The COMPASS Pivotal Trial

The 505 patients enrolled in the COMPASS multicenter randomized clinical trial¹ had POAG with mean diurnal unmedicated IOP of 21-33 mmHg and were undergoing cataract surgery. Patients were randomized to two groups; 374 patients received a CyPass Micro-Stent with cataract surgery, and 131 underwent cataract surgery alone. Of the patients randomized to the stent, 73% achieved a decrease of 20% or more in diurnal unmedicated IOP vs. baseline (the primary effectiveness endpoint) at 24 months compared with 58% of patients who had cataract surgery alone.

Two secondary effectiveness endpoints were also met: proportion of patients maintaining IOP between 6 and 18 mmHg (inclusive) without medication at 24 months and mean unmedicated IOP change at 24 months. For maintaining IOP between 6 and 18 mmHg without medication at 24 months, the proportions of patients were 62% in the stent group and 43% in the cataract surgery alone group.

For mean unmedicated IOP change at 24 months, IOP was reduced from baseline in the stent and cataract surgery alone groups by a mean of 7.4±4.4 mmHg (30% reduction) and 5.4±3.9 mmHg (21% reduction) respectively. The differences between the two groups on both the primary and secondary endpoints were statistically significant.

Regarding the exploratory endpoint of number of IOP-lowering topical medications needed to maintain target IOP at 24 months vs. baseline, from baseline to 24 months in the stent group, mean medication use decreased from 1.4±0.9 to 0.2±0.6 drugs compared with a decrease from 1.3±1.0 to 0.6±0.8 drugs in the cataract surgery alone group. COMPASS also indicated that stenting with CyPass has safety comparable to cataract surgery alone.

“The data show CyPass to be significantly better for lowering IOP and reducing medication use than cataract surgery alone,” says Dr. Craven.

Dr. Tyson says COMPASS is notable also for what it didn’t do, which was enroll patients with extremely high IOP. “It was a very well-orchestrated trial that took a solid look at how the device compares to cataract surgery alone,” he says. “It’s easy to show a pressure reduction from 40 mmHg to 32 mmHg, for example, which is a 30% reduction, but that doesn’t take care of the patient’s IOP problem. In contrast, what was achieved in COMPASS — low and sustained pressures — was challenging, and the CyPass did well.”

Both Drs. Tyson and Craven consider the patient population in COMPASS comparable to the glaucoma patient population in most general ophthalmology practices — patients who need cataract surgery and have mild to moderate glaucoma that is controlled with one or more medications. Favorable results also have been achieved with CyPass in other studies, including one similar to COMPASS² and another that evaluated the stent in patients with POAG failing topical therapy and candidates for conventional glaucoma surgery.³

Targeting Uveoscleral Outflow

The CyPass System consists of the stent that is pre-loaded into a stent delivery tool (CyPass Applier) that includes a guidewire. The stent is inserted under gonioscopic view at the time of cataract surgery through the phaco incision into the supraciliary space. Once in place, it connects the anterior chamber to the suprachoroidal space to increase uveoscleral outflow and lower IOP. The ab interno insertion spares conjunctival and scleral tissue.

Using the uveoscleral pathway/suprachoroidal space, rather than the subconjunctival space or trabecular meshwork, as an aqueous drainage route has been of interest for more than a century.⁴ Differences in hydrostatic pressure between the anterior chamber and suprachoroidal space enable the flow of aqueous through the face of the ciliary body and iris root to the interstitium of the ciliary muscle and into the suprachoroidal space.⁴ From there, via episcleral tissue, choroidal and scleral vessels carry aqueous to the orbit, and it enters the systemic circulation through lymphatic vessels.⁴ It’s been estimated that up to 50% of aqueous leaves the eye via this pathway, particularly in the eyes of younger people.⁵

Dr. Tyson elaborates, saying, “This pathway is a large area over which aqueous drainage can occur. It’s close to very vascularized tissue, so fluid deposited there can be absorbed rapidly. Think of it as similar to drainage being more effective with trabeculectomy or tube shunt when the bleb or plate is larger.” Adds Dr. Craven, “The uveoscleral pathway is also the part of the eye’s outflow system where the prostaglandins, our most effective topical medications, do their work.”

The tip of the CyPass Micro-Stent in the anterior chamber.

CyPass Patient Selection and Implantation

According to FDA, the CyPass Micro-Stent shouldn’t be used if patients have a type of glaucoma other than POAG or if eye anatomy or condition is unusual. For example, a patient with a very shallow anterior chamber, corneal opacity or significant corneal edema, a scarred angle, or adhesion may not be a good candidate. “Visibility of the angle is what’s needed for implantation,” Dr. Tyson says. “Are you able to see the iris root and where you want to place the stent? Surgeons can perform gonioscopy prior to surgery to ensure they’ll have good visibility of the angle intraoperatively. They can also practice using gonioscopy intraoperatively on patients who are undergoing only cataract surgery.”

Patients who have mild to moderate glaucoma, i.e., some visual field or optic nerve changes consistent with glaucoma, are often using one or more topical medications and are ideal CyPass candidates, Dr. Craven says. “These are patients who need something more than phaco for IOP reduction,” he adds.

CyPass is placed between the sclera and the ciliary body in just a few steps. After phaco and IOL insertion, fill the anterior chamber with viscoelastic and under direct gonioscopic visualization, introduce the CyPass Applier through the phaco incision, transversing the anterior chamber toward the iris root. Disinsert the iris to a very small degree and slide the Applier along the sclera until only the proximal collar of the stent (approximately 0.5 mm) remains in the anterior chamber. If too much of the stent is sticking out into the anterior chamber, it can be tapped into place. Once the stent is deployed, remove the CyPass Applier from the eye and use I/A to remove viscoelastic. In the COMPASS trial, the stent was implanted after IOL insertion, as described here, to take advantage of the added anterior chamber space, but it may be implanted prior to cataract surgery. Having implanted CyPass outside of the U.S., Dr. Craven has performed the procedure both ways and doesn’t prefer one way versus the other.

Useful Addition to the Glaucoma Toolkit

Surgeons need not expect too steep a learning curve as they begin to use CyPass, say Drs. Tyson and Craven. Having trained surgeons around the world how to implant the stent, Dr. Craven reports that even those who had never done a gonioscopic procedure “picked it up with no problems. Many have patients up to 5 years out who are doing very well.” Dr. Tyson offers this tip: “If you push the stent against the scleral spur, you’ll get resistance. You can ‘walk’ your way down, or left or right if you’re operating temporally, until it begins to slide in easily. You’ll know you’re in the right spot.” Dr. Craven sums up his thoughts on the new stent by saying that, especially for surgeons who have used another MIGS device, using CyPass should be a “slam dunk.” ■

References

	Farrell “Toby” Tyson, MD, FACS, is medical director and CEO of Cape Coral Eye Center and Tyson Eye in Fort Myers, Fla.
	E. Randy Craven, MD, of Johns Hopkins Wilmer Eye Institute, Baltimore, specializes in glaucoma and is chief of glaucoma for King Khaled Eye Specialist Hospital in Riyadh, Saudi Arabia.