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CyPass migration uncommon, says glaucoma surgeon
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With proper anatomic placement of the CyPass Micro-Stent, postimplantation migration of a supraciliary device is not common, according to Shakeel Shareef, MD, professor at the University of Rochester School of Medicine and surgeon at the Flaum Eye Institute.
Shareef will report the findings from his retrospective review of his procedures involving the Cypass (which Alcon recalled in August 2018) at the American Society of Cataract and Refractive Surgery annual meeting in May.
In his retrospective review, 79 patients were implanted with the CyPass Micro-Stent and underwent postoperative baseline digital photography. The microstent’s final alignment of proximal collar on trabecular meshwork was confirmed, according to the study abstract.
“To determine anterior migration, by focusing on the trabecular meshwork, the segment of the microstent simultaneously in sharp view was estimated to be that portion displaced anteriorly,” according to the abstract.
Shareef also assessed progressive migration in a subset of 21 patients, and the number of rings present at baseline were recorded.
Baseline photos showed anterior migration in 33%. Shareef found displacement occurred to: the posterior aspect of the proximal collar in 10%, first ring in 70%, second ring in 10% and third ring in 10%.
In the subset group, 29% migrated. Of those who initially showed no migration (15 patients), 33% did so up to the first ring.
In the remaining six patients with the first ring on the trabecular meshwork, one microstent migrated to the second ring (17%). Twenty-eight patients, or 46%, had rings. In nine patients, or 32%, Shareef found no associated anterior migration. He reported that the presence of rings does not necessarily correlate with migration of the device.
More accurate endothelial cell loss can be made using trabecular meshwork as a reference to estimated anterior migration, he explained.
Shareef spoke with Primary Care Optometry News about the benefits of the CyPass device and the intricacies behind the microstent.
PCON: How long did you implant the Alcon CyPass prior to its recall, and approximately how many devices have you implanted?
Shareef: I implanted seventy-nine CyPass devices between June 7, 2017, and August 22, 2018 (15 months).
PCON: Overall, have you found the device surgeon-friendly and efficacious?
Shareef: I have found the device to be user-friendly, enabling, for the first time, access to the uveoscleral outflow pathway. Following proper hand and head positioning, identification of angle anatomy and appropriate selection of an intraoperative goniolens to provide counter traction, the actual implantation of the microstent takes less than 1 minute to perform. In patients with conjunctival immobility and scarring, this pathway provided another avenue to direct aqueous out of the eye to lower IOP in glaucoma patients who otherwise would not have been candidates for either the subconjunctival or trabecular bypass routes.
The device was the most efficacious of all available microstents at the time it was approved. In my hands, the average percentage drop in IOP with the iStent (Glaukos) first-generation is equivalent to a beta-blocker (ie, timolol). With ab interno canaloplasty and Kahook Dual Blade Goniotomy, the IOP lowering is close to a topical carbonic anhydrase inhibitor. With the CyPass, I have seen a significant drop, on average, equivalent to the potency of a prostaglandin (ie, latanoprost).
PCON: Do you think Alcon’s voluntary withdrawal was prudent?
Shareef: One of the hallmarks of minimally invasive glaucoma surgery is its excellent patient safety profile.
After FDA approval based on the outcomes of the original 2-year COMPASS trial, a 3-year extension called the COMPASS-XT trial was conducted. At the 60-month postsurgical time point, compared to patients undergoing cataract surgery alone, a significantly greater percentage of patients in the CyPass group were experiencing central endothelial cell loss (ECL) greater than 30%. This was not seen in the first 2 years of approval. Once this information became available, Alcon immediately enforced a voluntarily withdrawal out of concern for patient safety and the potential for progressive ECL long-term.
PCON: In your prospective follow-up of CyPass patients, have you found device migration to be an issue?
Shareef: All 79 patients underwent successful surgical implantation of the CyPass Micro-Stent aligning the proximal collar of the device with the trabecular meshwork (TM) as recommended. They were then evaluated postoperatively in the office with gonioscopy. A subset (n=61, 77%) underwent digital goniophotography (1 day to 10 months postop). Compared to the original anatomic placement of the device, the majority (70%) did not show anterior migration.
PCON: Much has been said about correlating CyPass ring exposure with ECL. Do you believe there is a correlation, or is there a better marker?
Shareef: The Alcon COMPASS-XT trial correlated the percentage of ECL per year based upon the number of retention rings present in the angle:
- 0 rings: 1.39% ECL/year;
- one ring: 2.74% ECL/year;
- two rings: 6.02% ECL/year; and
- three rings: 9.96% ECL/year.
The number of rings present served as a surrogate for assessing anterior migration of the microstent. However, analysis of those patients who underwent goniophotography showed 32% of subjects who presented with one to two rings had a properly aligned proximal collar with the TM with no evidence of anterior migration or corneal contact. A more accurate ECL risk can, therefore, be determined using the TM as a reference to estimate anterior migration and not the mere presence of rings.
In the study, of those subjects who exhibited migration, the majority (80%) did so to the first ring aligned with the TM with an ECL risk of 2.74%, slightly double that of age-matched controls (1.39%). The risk of ECL beyond one ring increases exponentially and was rare. These findings indicate that proper intraoperative anatomic implantation of the CyPass Micro-Stent can mitigate postop ECL. –by Abigail Sutton
- References:
- Alcon. A study to assess long-term safety of the CyPass Micro-Stent in patients completing the COMPASS Trial (COMPASS-XT) https://clinicaltrials.gov/ct2/show/NCT02700984. Posted March 7, 2016. Updated May 9, 2018.
- Vold S, et al. Ophthalmology. 2016;doi.org/10.1016/j.ophtha.2016.06.032.
- For more information:
- Shakeel Shareef, MD, can be reached at: shklshrf@gmail.com.
Disclosure: Shareef reports no relevant financial disclosures.