Forecasting the Future for Suprachoroidal Shunts

One surgeon tells why they will be a niche procedure for select surgeons and patients. Cheryl Guttman Krader reports from the 39th Congress of the ESCRS in Amsterdam. Increasing aqueous outflow through the suprachoroidal pathway is a potentially powerful method for lowering IOP. However, available evidence from studies with ab-interno suprachoroidal implants indicates they have limitations in terms of both safety and efficacy, according to Luís Abegão Pinto MD, PhD. Addressing the question of whether suprachoroidal shunts will survive long-term, Dr Pinto suggested a segment of glaucoma surgeons will likely adopt these devices. A wider uptake might be limited by multiple issues, including efficacy dependent on baseline IOP, non-negligible adverse events, and the technically challenging nature of the surgery itself. EVIDENCE ON EFFICACY Outcomes data for ab-interno suprachoroidal shunt surgery are limited. Results from clinical trials following patients for six months to two years after implantation with the MINIject (iStar Medical) show there is less than a 50% chance patients will be drop-free and achieve an IOP in the low teens. Data from two years of follow-up in the randomised COMPASS trial showed the percentage of patients who were medication-free with an IOP <18 mmHg was significantly higher in the group that had combined CyPass Micro-Stent (Alcon) and cataract surgery versus cataract surgery alone. Dr Pinto noted the mean baseline IOP for this study’s subjects was relatively high (>21 mmHg) because the protocol involved preoperative glaucoma medication washout. Data from a real-world study show lower IOP-lowering efficacy among eyes with a baseline IOP <21 mmHg, he said. “The main reasons to perform surgery in patients with low baseline IOP is to reduce IOP to the low teens or give a better quality of life by making patients drop-free. The question is whether these devices can meet those goals. Perhaps they are useful for patients with a very high IOP,” Dr Pinto speculated. SAFETY AND SURGERY OBSTACLES Suprachoroidal shunt surgery is challenging. Available data show the device is misplaced in almost 10% of eyes, even when experienced surgeons conduct the procedure. Data from the three-year safety extension of the CyPass randomised trial showed poor placement increases the risk for significant endothelial cell loss. “Surgeons have to be really good with the implantation to get the efficacy desired without compromising safety,” Dr Pinto said. As another consideration—the cleft is not silent. Fibrosis in the suprachoroidal space can lead to occlusion of the device or surrounding iatrogenic cleft, resulting in severe IOP spikes in a significant number of patients. “Unlike with a bleb, surgeons cannot monitor what is happening with fibrosis in the suprachoroidal space,” Dr Pinto said. TARGET POPULATIONS Considering current suprachoroidal shunt surgery knowledge, Dr Pinto suggested this technology would likely be adopted by surgeons who: have skill with intraoperative gonioscopy, are comfortable handling the potential anterior chamber complications, and accept the need for long-term, frequent patient monitoring. He proposed that the best candidates for a suprachoroidal shunt include patients with mild to moderate glaucoma not requiring surgery that will eliminate topical treatment, as well as individuals for whom a bleb-less procedure is indicated because of the state of the conjunctival tissue. Alcon announced a global voluntary recall of the CyPass Micro-Stent in August 2018 over concerns about long-term endothelial cell loss. The MINIject (iStar Medical) recently received an investigational device exemption (IDE) from the US FDA that allows it to begin a clinical trial. Luís Abegão Pinto MD, PhD is an assistant professor of pharmacology and ophthalmology, Lisbon University, Portugal. abegaopinto@gmail.com