Advances in implantable bionic devices for blindness: a review

Abstract

Since the 1950s, vision researchers have been working towards the ambitious goal of restoring a functional level of vision to the blind via electrical stimulation of the visual pathways. Groups based in Australia, USA, Germany, France and Japan report progress in the translation of retinal visual prosthetics from the experimental to clinical domains, with two retinal visual prostheses having recently received regulatory approval for clinical use. Regulatory approval for cortical visual prostheses is yet to be obtained; however, several groups report plans to conduct clinical trials in the near future, building upon the seminal clinical studies of Brindley and Dobelle. In this review, we discuss the general principles of visual prostheses employing electrical stimulation of the visual pathways, focusing on the retina and visual cortex as the two most extensively studied stimulation sites. We also discuss the surgical and functional outcomes reported to date for retinal and cortical prostheses, concluding with a brief discussion of novel developments in this field and an outlook for the future.

Keywords: bionics; blindness; brain; prosthesis; retina; vision.

Figure 1

Top: Schematic representation of the human eye showing the surgical locations for epiretinal, subretinal, suprachoroidal and intrascleral electrodes. Reproduced from Ayton et al.,14 with permission under the terms of the Creative Commons Attribution License. Bottom: The prototype suprachoroidal implant used in the Bionic Vision Australia pilot study. The electrode array is composed of 33 platinum electrodes on a silicone substrate, of which 24 were able to be stimulated. The array was attached to a percutaneous connector via a helical lead wire, which was implanted behind the ear and allowed direct stimulation of the array. Image provided by Dr David Nayagam, Bionics Institute.

Figure 2

(a) A close‐up view of a single cortical visual prosthesis tile with 43 penetrating electrodes, as developed by the Monash Vision Group. (b) Scanning electron micrograph of the electrodes, showing an annular stimulating surface approximately 500 μm from the tips. (c) Artist's rendering of the headwear, showing the data and power transmitting/receiving coil overlying the recipient's occiput and the implanted tiles. (a and b) Reproduced from Lowery et al.,18 with permission (© 2015 IEEE). (c) Supplied courtesy of Monash Art, Design and Architecture and Monash Vision Group.