A prototype suprachoroidal retinal prosthesis: device reliability and patient safety report of a 2 year clinical study.

Abstract

Purpose: To determine whether implantation and electrical stimulation of a retinal prosthesis in the suprachoroidal space is surgically safe and efficacious. This study reports on the two-year stability and safety data of this novel device.

Methods: A retinal prosthesis was implanted in the suprachoroidal space in three patients with bare light perception due to retinitis pigmentosa (clinical trials.gov NCTO1603576). Stimulation was made via a percutaneous connector for a period of two years. Clinical assessments, retinal imaging and CT scans were performed regularly to assess the ocular health and the stability of the implant. At the end of the study, the external components were explanted in two patients, and the entire device removed in the third. Specimens were collected for microbiology and histopathology.

Results: The surgical implantation was uncomplicated in all three patients. All three developed limited suprachoroidal haemorrhage and in one case, vitreous haemorrhage, postoperatively, but this cleared spontaneously in all cases. Stimulation enabled reliable phosphenes to be generated for all three patients within safe charge limits throughout the study. The devices remained stable over the two years with no wire breakages or loss of electrode function. A fibrous capsule developed around all three devices, but stimulation remained within safe limits. During the trial no serious ocular adverse events occurred. The only device-related serious adverse events were infections around the percutaneous connector. Analysis of the explanted devices revealed no significant presence of organisms. Histology of scleral sections adjacent to the insertion wound revealed homogeneous fibrous encapsulation, but no evidence of active inflammatory response or micro-organisms in the eye tissue.

Conclusions: Implantation of a retinal prosthesis in the suprachoroidal space was surgically safe, and the device remained stable over a two-year period. Electrical stimulation resulted in reliable phosphenes within safe charge limits.No serious ocular complications developed in the three patients. Although some fibrous encapsulation of the intraocular arrays occurred, effective stimulation was able to continue until the conclusion of the study. Post-explant analysis of the arrays, and surrounding tissue, confirmed the encapsulation was fibrotic tissue and that there were no infective organisms present.