A task force convened by the American Society of Cataract and Refractive Surgery, consisting of glaucoma and cornea specialists, was created to analyze the cause of significant endothelial cell loss associated with the CyPass Micro-Stent (Alcon) at 5 years after implantation. The task force has reached a preliminary conclusion that a relationship existed between implant depth and endothelial cell loss (ECL). They found that some stents with excessive anterior-chamber exposure may have greater ECL at 5 years. Early migration of the implant has been observed. While most implants were found not to migrate over time, the potential for migration remains an important variable to be considered for long-term diagnostic monitoring. Alcon voluntarily withdrew the CyPass from the market on August 29, citing the endothelial loss occurring between year 2 and year 5 of the follow-up study.

“At 2 years post-surgery, there was little difference in endothelial cell loss between the CyPass Micro-Stent and cataract surgery-only groups, and results were consistent with peer-review literature benchmarks of cataract-related endothelial cell loss,” Alcon said in an August 29 news release.

“The COMPASS-XT study was designed to collect safety data on the subjects who participated in the COMPASS study for an additional 3 years, with analysis of the completed data set at 5 years post surgery. At 5 years, the CyPass Micro-Stent group experienced statistically significant endothelial cell loss compared to the group who underwent cataract surgery alone,” the news release concluded.

The task force reported that at 5 years following implant, there was more ECL in the group that had cataract extraction with CyPass compared to cataract extraction alone (control). Baseline endothelial cell counts were 2,432 for CyPass and 2,434 for control, falling at 48 months to 1,992 in cataract extraction with CyPass (n=116) vs 2,303 in control (n=33) and at 60 months to 1,931 in cataract extraction with CyPass (n=163) vs 2,189 in the control group (n=40). This represented an 18.4% reduction in ECL in cataract extraction with CyPass vs 7.5% ECL in the control group at month 48, and to a 60-month cataract extraction with CyPass ECL of 20.5% compared to 10.1% in the control group. 

The task force recommended that physicians who have implanted CyPass devices should refer to their hospitals, ASCs, or practice policies regarding patient notification for medical implants that have been voluntarily withdrawn from the market. Patients who have received CyPass devices should continue to be followed by their eye care provider(s) at appropriate intervals. 

The task force said gonioscopy should be performed on patients with an indwelling CyPass device, with attention to device position, the presence or absence of contact between the corneal endothelium and the CyPass device, the position of the device lumen anterior to Schwalbe’s line, and to the number of retention rings visible in the anterior chamber.

Intervention, likely in the form of a CyPass trimming, described in the CyPass instructions for use, would be reserved for cases with greater anterior chamber device exposure and clinically relevant corneal decompensation.

“The takeaway point here is that we are watching the FDA and industry execute a conservative regulatory process that is functioning appropriately,” said Nathan M. Radcliffe, MD, who served as a member of the task force. “A data monitoring plan was set in place, a safety signal was detected at 5 years, and the conservative move of withdrawing the product was set in place. I think surgeons should not be overly aggressive in trimming these stents, because most patients with a CyPass that has been appropriately placed will do well, and we know which patients we need to watch more carefully.”