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Title: In Vivo Feasibility of Epiretinal Stimulation Using Ultrananocrystalline Diamond 1 Electrodes
Authors: Shivdasani, Mohit
Evans, Mihailo
Burns, Owen
Yeoh, Jonathon
Allen, Penelope
Nayagam, David
Villalobos, Joel
Abbott, Carla
Luu, Chi
Opie, Nicholas
Sabu, Anu
Saunders, Alexia
McPhedran, Michelle
Cardamone, Lisa
McGowan, Ceara
Maxim, Vanessa
Williams, Richard
Fox, Kate
Cicione, Rosemary
Garrett, David
Ahnood, Arman
Ganesan, Kumaravelu
Meffin, Hamish
Burkitt, Anthony
Prawer, Steven
Williams, Chris
Shepherd, Robert
Keywords: Bionic eye
Electrical stimulation
Retinal implant
Retinitis pigmentosa
Visual cortex
Issue Date: Jul-2020
Publisher: IOP Publishing
Citation: Shivdasani, M. N., M. Evans, O. Burns, J. Yeoh, P. J. Allen, D. Nayagam, J. Villalobos, C. J. Abbott, C. D. Luu, N. L. Opie, A. Sabu, A. L. Saunders, M. McPhedran, L. Cardamone, C. McGowan, V. Maxim, R. A. Williams, K. Fox, R. Cicione, D. J. Garrett, A. Ahnood, K. Ganesan, H. Meffin, A. N. Burkitt, S. Prawer, C. E. Williams, and R. K. Shepherd. 2020. In vivo feasibility of epiretinal stimulation using ultrananocrystalline diamond electrodes. Journal of Neural Engineering: [epub ahead of print].
Abstract: PURPOSE: Due to their increased proximity to retinal ganglion cells (RGCs), epiretinal visual prostheses present the opportunity for eliciting phosphenes with low thresholds through direct RGC activation. This study characterised the in vivo performance of a novel prototype monolithic epiretinal prosthesis, containing Nitrogen incorporated ultrananocrystalline (N-UNCD) diamond electrodes. METHODS: A prototype implant containing up to twenty-five 120×120 µm N-UNCD electrodes was implanted into 16 anaesthetised cats and attached to the retina either using a single tack or via magnetic coupling with a suprachoroidally placed magnet. Multiunit responses to retinal stimulation using charge-balanced biphasic current pulses were recorded acutely in the visual cortex using a multichannel planar array. Several stimulus parameters were varied including; the stimulating electrode, stimulus polarity, phase duration, return configuration and the number of electrodes stimulated simultaneously. RESULTS: The rigid nature of the device and its form factor necessitated complex surgical procedures. Surgeries were considered successful in 10/16 animals and cortical responses to single electrode stimulation obtained in 8 animals. Clinical imaging and histological outcomes showed severe retinal trauma caused by the device in-situ in many instances. Cortical measures were found to significantly depend on the surgical outcomes of individual experiments, phase duration, return configuration and the number of electrodes stimulated simultaneously, but not stimulus polarity. Cortical thresholds were also found to increase over time within an experiment. CONCLUSIONS: The study successfully demonstrated that an epiretinal prosthesis containing diamond electrodes could produce cortical activity with high precision, albeit only in a small number of cases. Both surgical approaches were highly challenging in terms of reliable and consistent attachment to and stabilisation against the retina, and often resulted in severe retinal trauma. There are key challenges (device form factor and attachment technique) to be resolved for such a device to progress towards clinical application, as current surgical techniques are unable to address these issues.
URI: http://repository.bionicsinstitute.org:8080/handle/123456789/403
ISSN: 1741-2552
Appears in Collections:Bionic Vision Research Publications

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