gms | German Medical Science

Objective: To develop and establish surgical methods for safe implantation and explantation of wireless intraocular retina implant systems. To test the in vivo-function of active retina implants and to evaluate the tissue compatibility of epiretinal electrical stimulation.

Methods: Phacoemulsification and vitrectomy was performed at the right eye in 16 Goettinger minipigs under general anaesthesia. The implant consisting of an HF receiver coil and an electrode array was inserted through a scleral incision. The receiver coil was placed behind the iris and the electrode array was fixed onto the central retina with a retinal tack. Wireless electrical epiretinal stimulation experiments were performed in 12 minipigs using short biphasic charge-balanced charges of 0,9 mC/cm² or 2 mC/cm², respectively. Following successful start-up of the implant stimulation charges were applied for one hour. Animals were observed for a period of 14 days. After sacrificing, the eyes were enucleated and processed for histological evaluation. In separate explantation experiments the retinal tack was retained and the implant removed through a scleral incision.

Results: The implantation and explantation procedures could be well established and were safely performed. Intraoperatively a minor reversible punctiform bleeding of the retina occurred in one case and an iris bleeding in a second case. Stimulation artifacts were measured with subconjunctival needle electrodes in 11 eyes. Continuous in vivo-function of the implant was proved for a period of 24 months postoperatively. Electrical stimulation of the retina caused no tissue alterations at neither of the charges applied.

Conclusions: The performed surgical procedures are safe and effective. A long-term successful in vivo-function of the retina implants could be documented and charges of up to 2 mC/cm² are safely applicable to retinal tissue in a time range of 1 hour.

This lecture is available as video recording (Attachment 1 [Attach. 1]).