Cortical activation following chronic passive implantation of a wide-field suprachoroidal retinal prosthesis

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dc.contributor.authorVillalobos, Joel
dc.contributor.authorFallon, James
dc.contributor.authorNayagam, David
dc.contributor.authorShivdasani, Mohit
dc.contributor.authorLuu, Chi
dc.contributor.authorAllen, Penelope
dc.contributor.authorShepherd, Robert
dc.contributor.authorWilliams, Chris
dc.date.accessioned2015-06-02T02:14:02Z
dc.date.available2015-06-02T02:14:02Z
dc.date.issued2014-06
dc.description.abstractOBJECTIVE: The research goal is to develop a wide-field retinal stimulating array for prosthetic vision. This study aimed at evaluating the efficacy of a suprachoroidal electrode array in evoking visual cortex activity after long term implantation. APPROACH: A planar silicone based electrode array (8 mm × 19 mm) was implanted into the suprachoroidal space in cats (ntotal = 10). It consisted of 20 platinum stimulating electrodes (600 μm diameter) and a trans-scleral cable terminated in a subcutaneous connector. Three months after implantation (nchronic = 6), or immediately after implantation (nacute = 4), an electrophysiological study was performed. Electrode total impedance was measured from voltage transients using 500 μs, 1 mA pulses. Electrically evoked potentials (EEPs) and multi-unit activity were recorded from the visual cortex in response to monopolar retinal stimulation. Dynamic range and cortical activation spread were calculated from the multi-unit recordings. MAIN RESULTS: The mean electrode total impedance in vivo following 3 months was 12.5 ± 0.3 kΩ. EEPs were recorded for 98% of the electrodes. The median evoked potential threshold was 150 nC (charge density 53 μC cm(-2)). The lowest stimulation thresholds were found proximal to the area centralis. Mean thresholds from multiunit activity were lower for chronic (181 ± 14 nC) compared to acute (322 ± 20 nC) electrodes (P < 0.001), but there was no difference in dynamic range or cortical activation spread. SIGNIFICANCE: Suprachoroidal stimulation threshold was lower in chronic than acute implantation and was within safe charge limits for platinum. Electrode-tissue impedance following chronic implantation was higher, indicating the need for sufficient compliance voltage (e.g. 12.8 V for mean impedance, threshold and dynamic range). The wide-field suprachoroidal array reliably activated the retina after chronic implantation.en_US
dc.description.sponsorshipFunding was provided by the Ian Potter Foundation and the Australian Research Council through its Special Research Initiative in Bionic Vision Science and Technology grant to Bionic Vision Australia (BVA). The Bionics Institute and the Centre for Eye Research Australia acknowledge the support they receive from the Victorian Government through its Operational Infrastructure Support Program.en_US
dc.identifier.citationVillalobos, J., J. B. Fallon, D. A. X. Nayagam, M. N. Shivdasani, C. D. Luu, P. J. Allen, R. K. Shepherd and C. E. Williams (2014). Cortical activation following chronic passive implantation of a wide-field suprachoroidal retinal prosthesis. Journal of Neural Engineering 11(4): 046017en_US
dc.identifier.urihttp://repository.bionicsinstitute.org:8080/handle/123456789/127
dc.language.isoenen_US
dc.publisherIOP Publishingen_US
dc.subjectblindnessen_US
dc.subjectretinal prosthesisen_US
dc.subjectsuprachoroidalen_US
dc.subjectelectrical stimulationen_US
dc.titleCortical activation following chronic passive implantation of a wide-field suprachoroidal retinal prosthesisen_US
dc.typeArticleen_US
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