title: A CMOS retinal neurostimulator capable of focussed, simultaneous stimulation.
abstract: Restoring vision to the blind by way of medical device technology has been an objective of several research teams for a number of years. It is known that spots of light-phosphenes-can be elicited by way of electrical stimulation of surviving retinal neurons. Beyond this our understanding of prosthetic vision remains rudimentary. We have designed and manufactured an integrated circuit neurostimulator with substantial versatility, able to provide focussed, simultaneous stimulation using current sources and sinks, steering the current to the intended site of stimulation. The ASIC utilizes high-voltage CMOS transistors in key circuits, to manage voltage compliance issues (due to an unknown or changing electrode/tissue interface impedance) given the relatively high stimulation thresholds necessary to elicit physiological excitation of retinal neurons. In addition, a unique multiplexing system comprised of electrodes arranged in a hexagonal mosaic is used, wherein each electrode can be addressed to be a stimulating electrode and all adjacent electrodes serve as the return path. This allows for simultaneous stimulation to be delivered while appropriately managing cross-talk between the stimulating electrodes. Test results indicate highly linear current sources and sinks (differential nonlinearity error of 0.13 least significant bits -2.6 microA), with the ASIC clearly able to provide focussed stimulation using electrodes immersed in a saline solution.
authors.affiliation: Graduate School of Biomedical Engineering, University of New South Wales, Sydney NSW 2052, Australia.
authors.forename: N B
authors.initials: NB
authors.lastname: Dommel
authors.forename: Y T
authors.initials: YT
authors.lastname: Wong
authors.forename: T
authors.initials: T
authors.lastname: Lehmann
authors.forename: C W
authors.initials: CW
authors.lastname: Dodds
authors.forename: N H
authors.initials: NH
authors.lastname: Lovell
authors.forename: G J
authors.initials: GJ
authors.lastname: Suaning
mesh_terms: D001185:Artificial Intelligence; D001698:Biomedical Engineering / Q000295:instrumentation*; D001766:Blindness / Q000534:rehabilitation*; D004599:Electric Stimulation Therapy / Q000295:instrumentation* / Q000639:trends; D004567:Electrodes, Implanted; D006801:Humans; D019736:Prostheses and Implants; D011474:Prosthesis Design / Q000379:methods; D012666:Semiconductors