Long-Term in-vivo Operation of the Wireless Boston Retinal Neuroprosthesis

Abstract

Purpose: : This work is related to the efforts of the Boston Retinal Implant Project to develop a sub-retinal prosthesis to restore vision to the blind.

Methods: : Custom designed application-specific integrated, programmable stimulator chips having 16 output channels were mounted on flexible circuits together with discrete power supply components and secondary power and data receiving coils. These systems were mated with specially microfabricated, 15 µm-thick, 2.5 mm wide polyimide-based flexible electrode arrays. The arrays were inserted into the subretinal space of four Yucatan mini-pigs using an ab externo surgical technique in the superior nasal quadrant, and the electronic components aside from the electrode array were sutured in the superior nasal quadrant. In the photo, the gold secondary receiving coil of one embodiment of the prosthesis is shown as it is sutured around the minipig cornea.

Results: : These wirelessly driven micro-stimulators conformed to the shape of the eye orbit, were well tolerated, and have continued operation for seven months and more in an ongoing study. Periodic ocular examinations and stimulation trials verified continued implant performance. The devices could also be explanted successfully without harm to the animal. In some cases, exposure of portions of the prostheses through the conjunctiva was noted weeks to months post-operation. This was addressed in subsequent trials by re-positioning the device components.

Conclusions: : Our team has successfully developed a 16-channel wireless, programmable subretinal micro-stimulators that were implanted in 4 Yucatan mini-pig eyes in months-long trials. Our ongoing goals are to continue improving the biocompatibility and longevity of the device.

Keywords: retinal degenerations: hereditary • age-related macular degeneration • electrophysiology: non-clinical