Ocular Biocompatibility of a Nitinol Capsular Tension Ring (CTR)

Abstract

Introduction: The biocompatibility of nitinol in the human body has extensively been demonstrated. Although nitinol is already being used for intraocular surgeries such as lens fragmentation and foreign body extraction, little is known about its intracapsular, long-term behavior. The purpose of this study is to evaluate the long-term uveal and capsular biocompatibility of a nitinol CTR placed in the capsular bag after cataract surgery in an animal model. Method: After approval of the study by the Institutional Animal Care and the Ethics Committee, bilateral phacoemulsification was performed in 6 rabbits; 1 eye received a nitinol CTR and the other a control polymethylmethacrylate (PMMA) open-ended ring. Ophthalmic evaluation for the presence of infections in all 12 eyes was performed after 7 days, 4 weeks, 3 months, and 6 months follow-up period. After a follow-up period of 6 months, the eyes were enucleated, and a histopathologic evaluation was performed. Results: Neither of the groups showed any clinical signs of posterior capsule opacification (PCO) or inflammation. The nitinol group showed slightly less inflammation during histopathologic examination compared to the PMMA group. No biocompatibility issues have been observed in this animal study. Conclusions: There were no histological differences between eyes implanted with nitinol and eyes implanted with PMMA rings. Nitinol has proven to show high biocompatibility when implanted in the capsular bag of the rabbit eye.