Delayed Corneal Endothelial Cell Loss Following CyPass Stent Insertion: A Case Report

We report a case of delayed corneal endothelial cell loss (CECL) following CyPass® stenting in a 71-year-old female with normal-tension glaucoma. CECL is a known complication of the CyPass® stent, which resulted in its withdrawal from the market in 2018; however, the mechanism for CECL is often attributed to mechanical endothelial disruption from poorly positioned stents. In this case, our patient suffered around a 40% CECL, which first started five years following stent implantation and responded well to ripasudil therapy. This occurred despite it being optimally positioned, prompting an alternate explanation for the mechanism of CECL following CyPass® stent insertion. We propose three areas for future research, which may explain the CECL: mechanical stress, such as from device-cornea touching; inflammation, from a chronic foreign body reaction; and direct cytotoxicity from degradation of irradiated polyimide material. Further research is needed to establish the biocompatibility of irradiated polyimide in the eye, as well as the role of ripasudil in stabilizing minimally invasive glaucoma surgery-related CECL.