Abstract
Purpose: :
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: :
Wireless epiretinal implants consisting of an HF receiver coil for power supply and an electrode array connected via a flexible cable were implanted into the right eye of 16 Göttinger minipigs under general anaesthesia. Fourteen of the implants were active, 2 were inactive. After phacoemulsification, complete three port pars plana vitrectomy was performed, and the implant 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. Electrical epiretinal stimulation was performed in 7 minipigs for 1 hour using short biphasic charge-balanced charges of 0,9 mC/cm2 or 2 mC/cm2, respectively. Animals were observed for a period of 14 days. After sacrificing, the eyes were enucleated and processed for histological evaluation. For explantation the retinal tack was retained and the implant removed through a scleral incision.
Results: :
The implantation and explantation procedures could be well established and are safely performed with the current design of the retina implant. 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 10 of 14 eyes up to a maximum period of 8 months postoperatively, proving successful in vivo-function of the implants. 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.
Keywords: degenerations/dystrophies • retinal degenerations: hereditary • vitreoretinal surgery