Implantation of a Wirelessly Powered Retinal Prosthesis Using an ab externo Surgical Technique

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. The specific purpose of this effort is to perform ab externo implantation of wirelessly powered micro-stimulators in Yucatan minipig models.

Methods: : Our team has developed two generations of wirelessly powered retinal prostheses based on custom integrated circuit technology. These devices contain a circuitry module, secondary power and data receiving coils, and specially microfabricated, 15 µm-thick flexible electrode arrays. These arrays were implanted in the subretinal space of Yucatan mini-pigs along a 10 mm arc through an incision 9 mm below the limbus in the superior temporal quadrant using an ab externo technique. The electronic components apart from the electrode array were sutured in the extraocular space in the superior nasal quadrant, and the conjunctiva was re-closed over the implant.

Results: : The design of the serpentine electrode array evolved through a series of surgeries with dummy implants to develop a device that offered considerable flexibility in the relative placements of the electronics module and the electrode array. The extraocular components conform to the shape of the eye orbit, and after improvements to the form of the prosthesis components, the implants were well tolerated, and did not erode through the conjunctiva when the animals were followed for up to three months. The prosthesis could also be explanted successfully without harm to the animal or to the electrical functioning of the device.

Conclusions: : Our team has successfully developed a 16-channel wireless, programmable subretinal micro-stimulator for implantation in Yucatan minipigs. Our ongoing goals are to continue improving upon the longevity of the implantable electronics module and the electrode array, increase biocompatibility, and to raise the number of input and output channels.

Keywords: retina • retinal degenerations: hereditary • age-related macular degeneration