Ultrastructural analysis of explanted CyPass microstents and correlation with clinical findings

Abstract

Purpose The purpose of this study was to obtain insight into cellular processes after CyPass microstent implantation into the supraciliary space. With this knowledge, we expected to find some reason for surgical failure. Methods Nine CyPass microstents of 8 patients with primary open-angle glaucoma (n = 1), pseudoexfoliation glaucoma (n = 5), uveitic glaucoma (n = 1), and posttraumatic open-angle glaucoma (n = 1) were explanted due to recurrence of IOP elevation, corneal decompensation, or persistent hypotony. The explants were processed for light and transmission electron microscopy. Results Fibrotic material, consisting of collagen fibrils, microfibrils, pseudoexfoliation fibrils produced by activated fibroblasts, was detected in the stent lumen of 4/5 pseudoexfoliation glaucoma patients and also in posttraumatic open-angle glaucoma. Fibrotic material was also present on the outer surface and within fenestrations of the majority of stents. Complete absence of fibrotic reaction was noticed in 3 of 9 microstents. Conclusion Although MIGS is known to be less invasive than conventional surgery, implants placed in the suprachoroidal space may be adversely affected by a fibrotic tissue reaction resulting in implant failure. Understanding mechanisms and risk factors leading to fibrotic scarring following antiglaucomatous surgery may help to develop novel strategies that improve surgical outcome.

Non-Viral Gene Therapy in Trabecular Meshwork Cells to Prevent Fibrosis in Minimally Invasive Glaucoma Surgery

“…Similar to trabeculectomy, fibrosis is the main cause of surgical failure in MIGS. Scarring and fibrotic membranes are observed around failed CyPass, iStent inject, Hydrus implants as well as in failed Kahook Dual Blade surgery [6,7].…”

“…Minimally invasive glaucoma surgery (MIGS), such as iStent, Hydrus, and Kahook Dual Blade, represent a group of glaucoma drainage devices and procedures that have recently been developed to provide a safer technique of reducing IOP [5]. Despite a microinvasive approach and minimally induced tissue trauma, the main cause of failure in MIGS is fibrosis around implants in the trabecular meshwork (TM) [6,7] (Figure 1A). Mitomycin-C (MMC) and 5-fluorouracil (5-FU) are too toxic to be used inside the eye and no anti-fibrotic drugs are available to be used intraocularly to prevent fibrosis in TM tissues.…”

“…MIGS is fibrosis around implants in the trabecular meshwork (TM) [6,7] (Figure 1A). Mitomycin-C (MMC) and 5-fluorouracil (5-FU) are too toxic to be used inside the eye and no anti-fibrotic drugs are available to be used intraocularly to prevent fibrosis in TM tissues.…”

„Minimally invasive glaucoma surgery“ – Kammerwinkelbasierte Verfahren im Vergleich

“…Die vorliegenden Ergebnisse stammen aus den Zulassungsstudien und zeigen eine durchschnittliche Senkung des Augeninnendruckes von 39 % über 2 Jahre bei einer gleichzeitigen Medikamentenreduktion von 2,4 auf 1,4 nach 24 Monaten [66, Zusammenfassend muss jedoch festgestellt werden, dass auch nach mehr als einem Jahrzehnt der MIGS die Evidenz hinsichtlich der Senkung des Augeninnendruckes und/oder der Reduktion der Medikamentenlast der Patienten bei vielen Verfahren noch gering ist und es daher weiterer qualitativ hochwertiger Studien bedarf, um klare Richtlinien für den Einsatz der einzelnen Verfahren abzuleiten. Es wird auch zu klären sein, ob durch eine gezielte Fibrosehemmung im Trabekelmaschenwerk [69] oder im suprachoroidalen Raum [70] die Langzeiterfolge nach unterschiedlichen MIGS-Verfahren verbessert werden können.…”