CyPass: An Emerging Option for MIGS

Now in FDA trial, European results have shown lower IOP and medication burden.

By Magda Rau, MD

A combination of factors have raised interest in alternative approaches for increasing aqueous outflow in open-angle glaucoma. The limitations of medical management have been well documented. Studies have shown as many as one third of patients do not use their eyedrops as directed, and even good compliance on maximal medications may not achieve target IOP in all patients.

Surgical interventions for glaucoma have been directed almost exclusively at increasing aqueous outflow, often by creating an alternate or improved pathway to Schlemm’s canal, or by directing aqueous outflow externally to the subtenon or subconjunctival space. These latter methods, along with shunts that direct aqueous outflow via drainage sites outside of the interior of the eye, have been associated with complications such as hypotony, infection, bleb fibrosis and erosion.

One emerging alternative in micro-invasive glaucoma surgery (MIGS) is the CyPass Micro-Stent (Transcend Medical, Menlo Park, Calif.), which increases aqueous outflow through the suprachoroidal portion of the uveoscleral outflow system when implanted ab interno into the supraciliary space. The device is available in the United States only through the COMPASS clinical trial.¹ I first implanted CyPass Micro-Stent under the Multicenter European Clinical trials.^2,3

The CyPass Micro-Stent consists of a custom-designed inserter for transcorneal placement and a miniature polyimide stent approximately 6.2 mm in length with a 0.3-mm lumen. Fenestrations allow the aqueous to egress throughout its length. The surgeon places the device into the iridocorneal angle with its distal portion resting in the supraciliary space (Figure 1).

Early Study Results

The first studies included patients not subjected to the strict inclusion criteria later studies used. More recently, the multicenter CyPass Clinical Experience (CyCLE) study included 462 eyes with primary and secondary OAG. Subjects were divided in two groups: CyPass Micro-Stent implantation as a stand-alone procedure (222 eyes); and implantation after phacoemulsification as a combined procedure (238 eyes).⁴ I will focus on the first group because phacoemulsification did not influence IOP in them.

The CyPass-only group included 134 eyes with uncontrolled IOP (21 mm Hg or greater) despite medical therapy. The second group included 88 eyes with IOP controlled on medication (21 mm Hg or less). The average age of patients in the CyPass-only group was 69.2 years, 51.6% of whom were women; 83.8% had primary OAG. Mean baseline IOP was 22.6 mm Hg for all patients; 27.4 mm Hg in group 1 and 17.9 mm Hg in group 2. Mean medication use for all subjects was 2.4; 2.4 for group 1 and 2.3 for group 2. Half (50.2% of eyes) had a previous glaucoma intervention, and thus had more severe disease; 27.2% had trabeculectomy or tube placement.

Figure 1. The CyPass micro-stent is placed in the supraciliary space allowing outflow to the choroidal space.

None of the patients suffered maculopathy, suprachorodial hemorrhage, retinal detachment or other retinal complications, iris atrophy or endophthalmitis. In 0.4% the device was explanted. A similar number underwent device repositioning. Other adverse events included transient iritis (1.8%), transient hypotony less than 6 mm Hg (1.3%), postoperative IOP increase (7.6%), transient hyphema (2.7%), need for additional surgery (10.8%), anterior chamber shallowing (1.8%), endothelial touch (1.8%), obstruction (3.6%) and BCVA loss (0.4%).

IOP-Lowering Effects

In the CyPass-only group, mean baseline IOP was 27.4 mm Hg and 18.9 mm Hg 12 months postoperatively. Similarly, the number of IOP-lowering medications this group was taking declined from a mean of 2.4 at baseline to 1.6 at 12 months. We concluded that after 12 months, the achieved reduction was 26% of the previous IOP and 33 % reduction of medication.

The second group — the patients who achieved adequate IOP control with medication and had the CyPass Micro-Stent implanted — showed similar outcomes. Mean IOP at baseline was 17.7 mm Hg and, at 12 months, 16.2 mm Hg. Medication burden followed a similar trend: a mean of 2.3 at baseline and 1.4 at 12 months. Even this group achieved further IOP reduction and, in 39%, reduction in medications. This was more significant in demonstrating the efficacy of the device.

I offer the CyPass Micro-Stent to patients with OAG who meet the following criteria: IOP between 21 mm Hg and 35 mm Hg despite maximal medical therapy; a visual field defect on glaucoma hemifield test outside normal limits or a pattern standard deviation of more than p<5%; a vertical cup-to-disc ratio of 0.7 or greater; and OCT-demonstrated nerve fiber layer thinness with RNFL curve and half the fibers in pathologic area.

Visual recovery after the stand-alone procedure is very fast. On the first postoperative day visual acuity in most patients is the same or, at worse, only 1 or 2 lines below baseline. Vision improves rapidly.

In most cases, IOP reduction is noticeable on the first postoperative day, which allows, despite the use of postoperative antibiotic and steroid drops, reduction of medications in the first weeks. To make a final determination of when to reduce or even discontinue IOP-lowering eyedrops, we wait until the steroid drops are discontinued to assess the achieved reduction.

The Surgical Procedure

If the patient has lens opacities, even in the early stage, I perform the cataract operation and CyPass Micro-Stent implantation in one procedure. I perform the coaxial micro-phacoemulsification through 2.2 mm clear cornea incision. After I implant the IOL and remove the OVD, I inject acetylcholine in the anterior chamber to achieve a miosis. I then inject the viscoelastic to deepen the anterior chamber, especially near the angle where I plan to implant the CyPass Micro-Stent. I use the gonio lens to carefully visualize the angle and choose the implant site.

I place the inserter with the CyPass Micro-Stent loaded through the clear cornea incision, into the anterior chamber and lead it to the opposite side toward the angle. A small guidewire positions the device and gently separates the iris from the scleral spur to facilitate insertion (Figure 2). At first I establish contact of the tip with the scleral spur. After I feel resistance, I place the tip under the scleral spur and slowly advance the micro-stent into the small cleft the guidewire creates, and release it at the desired depth, leaving only the proximal collar of the device in the anterior chamber.

Figure 2. CyPass Micro-Stent on the delivery guidewire just before separation of the iris from the scleral spur.

The gonio lens helps confirm the position of the CyPass Micro-Stent. If the device is too anterior, I gently push it deeper with the inserter. The same can be done with the spatula through the paracentesis. My recommendation is to not implant the micro-stent too posteriorly because this position is more difficult, sometimes impossible, to correct.

Based on my longer experience with the CyPass Micro-Stent, I now implant it more anteriorly so the collar and 1-ring are visible. I remove the OVD and, if necessary, the acetylcholine injection after implantation, and close the clear cornea wound with hydration.

In the stand-alone procedure, I implant the CyPass Micro-Stent through 2.2 mm temporal clear corneal incision. The paracentesis also helps fine-tune its positioning.

Complications

Patients with high blood pressure or conjunctival hyperemia may be subjected to intraoperative bleeding around the CyPass Micro-Stent. In these cases, I have controlled the bleeding by continuing irrigation or aspiration, or by applying OVD. In some cases, I’ve observed hyphema on the first day postoperatively, and in one case diffuse slight anterior chamber bleeding. Usually the hyphema persisted for only three to seven days and was accompanied with a rise of IOP. Any hyphema or anterior chamber bleeding resorbed after IOP reduction. In one case, the CyPass Micro-Stent was dislocated anteriorly due to trauma on the third postoperative day. In this case, I repositioned the CyPass Micro-Stent by pushing it deeper in the suprachoroidal space.

In one case after three months, we observed with the gonio lens adherence of the CyPass Micro-Stent to the iris, which increased with the time and nearly caused obstruction of the micro-stent opening. In one case I performed a high-intensity YAG laser treatment of the iris near the CyPass Micro-Stent. The treatment caused atrophy of the iris in the treated area, laying bare the micro-stent.

Anecdotally, after three years of follow-up, we still observe the reduction of IOP and medication burden after CyPass Micro-Stent implantation. In some patients, we have even observed the improvement of the RNFL curve on OCT, and fibers in the border area have shown some sign of recovery. I believe this is due to pressure stabilization not only in the daytime but also during the night.

In our clinic, the CyPass Micro-Stent has in most cases replaced the trabeculectomy because it is faster and less invasive, and carries fewer risks. OM

REFERENCES

1. COMPASS Clinical Study. Available at: www.compassclinicalstudy.com. Accessed January 18, 2012.

2. Ianchulev T, Ahmed IK, Hoeh HR, Rau M. Minimally invasive ab interno suprachoroidal device (CyPass) for IOP control in open-angle glaucoma. Poster presented at: AAO Annual Meeting; October 18-19, 2010; Chicago, IL.

3. Erb C, Höh H, Rau M, Peters S, Nardi M, Ianchulev T. European clinical experience with the CyPass supraciliary micro-stent for IOP lowering. Poster presented at ESCRS Annual Meeting; September 17-22, 2011; Vienna, Austria.

4. ClinicalTrials.gov. CyPass Clinical Experience Study (CyCLE), Available at: http://clinicaltrials.gov/ct2/show/NCT01097174. Accessed January 18, 2012.

Magda Rau, MD, is head of the Augenklinik Cham and Refractive Privatklinik-Dr. Rau in Cham, Germany, and Eye Centre Prag in Prague, Czech Republic.