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Oh Y, Hong J, Kim J. Retinal prosthesis edge detection (RPED) algorithm: Low-power and improved visual acuity strategy for artificial retinal implants. PLoS One 2024; 19:e0305132. [PMID: 38889114 PMCID: PMC11185494 DOI: 10.1371/journal.pone.0305132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 05/23/2024] [Indexed: 06/20/2024] Open
Abstract
This paper proposes a retinal prosthesis edge detection (RPED) algorithm that can achieve high visual acuity and low power. Retinal prostheses have been used to stimulate retinal tissue by injecting charge via an electrode array, thereby artificially restoring the vision of visually impaired patients. The retinal prosthetic chip, which generates biphasic current pulses, should be located in the foveal area measuring 5 mm × 5 mm. When a high-density stimulation pixel array is realized in a limited area, the distance between the stimulation pixels narrows, resulting in current dispersion and high-power dissipation related to heat generation. Various edge detection methods have been proposed over the past decade to reduce these deleterious effects and achieve high-resolution pixels. However, conventional methods have the disadvantages of high-power consumption and long data processing times because many pixels are activated to detect edges. In this study, we propose a novel RPED algorithm that has a higher visual acuity and less power consumption despite using fewer active pixels than existing techniques. To verify the performance of the devised RPED algorithm, the peak signal-to-noise ratio and structural similarity index map, which evaluates the quantitative numerical value of the image are employed and compared with the Sobel, Canny, and past edge detection algorithms in MATLAB. Finally, we demonstrate the effectiveness of the proposed RPED algorithm using a 1600-pixel retinal stimulation chip fabricated using a 0.35 μm complementary metal-oxide-semiconductor process.
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Affiliation(s)
- Yeonji Oh
- Department of Medical Science, Korea University, Seoul, South Korea
| | - Jonggi Hong
- Department of Health Sciences & Technology, Gachon Advanced Institute for Health Sciences & Technology, Gachon University, Incheon, South Korea
| | - Jungsuk Kim
- Department of Biomedical Engineering, Gachon University, Sungnam, South Korea
- Cellico Research and Development Laboratory, Sungnam, South Korea
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2
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Shokri M, Gogliettino AR, Hottowy P, Sher A, Litke AM, Chichilnisky EJ, Pequito S, Muratore D. Spike sorting in the presence of stimulation artifacts: a dynamical control systems approach. J Neural Eng 2024; 21:016022. [PMID: 38271715 PMCID: PMC10853761 DOI: 10.1088/1741-2552/ad228f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 11/08/2023] [Accepted: 01/25/2024] [Indexed: 01/27/2024]
Abstract
Objective. Bi-directional electronic neural interfaces, capable of both electrical recording and stimulation, communicate with the nervous system to permit precise calibration of electrical inputs by capturing the evoked neural responses. However, one significant challenge is that stimulation artifacts often mask the actual neural signals. To address this issue, we introduce a novel approach that employs dynamical control systems to detect and decipher electrically evoked neural activity despite the presence of electrical artifacts.Approach. Our proposed method leverages the unique spatiotemporal patterns of neural activity and electrical artifacts to distinguish and identify individual neural spikes. We designed distinctive dynamical models for both the stimulation artifact and each neuron observed during spontaneous neural activity. We can estimate which neurons were active by analyzing the recorded voltage responses across multiple electrodes post-stimulation. This technique also allows us to exclude signals from electrodes heavily affected by stimulation artifacts, such as the stimulating electrode itself, yet still accurately differentiate between evoked spikes and electrical artifacts.Main results. We applied our method to high-density multi-electrode recordings from the primate retina in anex vivosetup, using a grid of 512 electrodes. Through repeated electrical stimulations at varying amplitudes, we were able to construct activation curves for each neuron. The curves obtained with our method closely resembled those derived from manual spike sorting. Additionally, the stimulation thresholds we estimated strongly agreed with those determined through manual analysis, demonstrating high reliability (R2=0.951for human 1 andR2=0.944for human 2).Significance. Our method can effectively separate evoked neural spikes from stimulation artifacts by exploiting the distinct spatiotemporal propagation patterns captured by a dense, large-scale multi-electrode array. This technique holds promise for future applications in real-time closed-loop stimulation systems and for managing multi-channel stimulation strategies.
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Affiliation(s)
- Mohammad Shokri
- Delft Center for Systems and Control, Delft University of Technology, Delft 2628 CN, The Netherlands
| | - Alex R Gogliettino
- Neurosciences PhD Program, Stanford University, Stanford, CA 94305, United States of America
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, United States of America
| | - Paweł Hottowy
- Faculty of Physics and Applied Computer Science, AGH University of Krakow, Krakow, Poland
| | - Alexander Sher
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA, United States of America
| | - Alan M Litke
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA, United States of America
| | - E J Chichilnisky
- Departments of Neurosurgery and Ophthalmology, Stanford University, Stanford, CA 94305, United States of America
| | - Sérgio Pequito
- Division of Systems and Control, Department of Information Technology, Uppsala University, 751 05 Uppsala, Sweden
| | - Dante Muratore
- Microelectronics Department, Delft University of Technology, Delft 2628 CN, The Netherlands
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Borda E, Gaillet V, Airaghi Leccardi MJI, Zollinger EG, Moreira RC, Ghezzi D. Three-dimensional multilayer concentric bipolar electrodes restrict spatial activation in optic nerve stimulation. J Neural Eng 2022; 19. [PMID: 35523152 DOI: 10.1088/1741-2552/ac6d7e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Accepted: 05/06/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Intraneural nerve interfaces often operate in a monopolar configuration with a common and distant ground electrode. This configuration leads to a wide spreading of the electric field. Therefore, this approach is suboptimal for intraneural nerve interfaces when selective stimulation is required. APPROACH We designed a multilayer electrode array embedding three-dimensional concentric bipolar electrodes. First, we validated the higher stimulation selectivity of this new electrode array compared to classical monopolar stimulation using simulations. Next, we compared them in-vivo by intraneural stimulation of the rabbit optic nerve and recording evoked potentials in the primary visual cortex. MAIN RESULTS Simulations showed that three-dimensional concentric bipolar electrodes provide a high localisation of the electric field in the tissue so that electrodes are electrically independent even for high electrode density. Experiments in-vivo highlighted that this configuration restricts spatial activation in the visual cortex due to the fewer fibres activated by the electric stimulus in the nerve. SIGNIFICANCE Highly focused electric stimulation is crucial to achieving high selectivity in fibre activation. The multilayer array embedding three-dimensional concentric bipolar electrodes improves selectivity in optic nerve stimulation. This approach is suitable for other neural applications, including bioelectronic medicine.
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Affiliation(s)
- Eleonora Borda
- Medtronic Chair in Neuroengineering, Ecole Polytechnique Federale de Lausanne, EPFL STI IBI LNE, Geneva, 1012, SWITZERLAND
| | - Vivien Gaillet
- Medtronic Chair in Neuroengineering, Ecole Polytechnique Federale de Lausanne, EPFL STI IBI LNE, Geneva, 1012, SWITZERLAND
| | | | - Elodie Geneviève Zollinger
- Medtronic Chair in Neuroengineering, Ecole Polytechnique Federale de Lausanne, EPFL STI IBI LNE, Geneva, 1012, SWITZERLAND
| | | | - Diego Ghezzi
- École Polytechnique Fédérale de Lausanne, Chemin des Mines 9, Geneva, 1202, SWITZERLAND
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Damle S, Carleton M, Kapogianis T, Arya S, Cavichini-Corderio M, Freeman WR, Lo YH, Oesch NW. Minimizing Iridium Oxide Electrodes for High Visual Acuity Subretinal Stimulation. eNeuro 2021; 8:ENEURO.0506-20.2021. [PMID: 34799411 PMCID: PMC8704424 DOI: 10.1523/eneuro.0506-20.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 10/28/2021] [Accepted: 11/15/2021] [Indexed: 11/21/2022] Open
Abstract
Vision loss from diseases of the outer retina, such as age-related macular degeneration, is among the leading causes of irreversible blindness in the world today. The goal of retinal prosthetics is to replace the photo-sensing function of photoreceptors lost in these diseases with optoelectronic hardware to electrically stimulate patterns of retinal activity corresponding to vision. To enable high-resolution retinal prosthetics, the scale of stimulating electrodes must be significantly decreased from current designs; however, this reduces the amount of stimulating current that can be delivered. The efficacy of subretinal stimulation at electrode sizes suitable for high visual acuity retinal prosthesis are not well understood, particularly within the safe charge injection limits of electrode materials. Here, we measure retinal ganglion cell (RGC) responses in a mouse model of blindness to evaluate the stimulation efficacy of 10, 20, and 30 μm diameter iridium oxide electrodes within the electrode charge injection limits, focusing on measures of charge threshold and dynamic range. Stimulation thresholds were lower for smaller electrodes, but larger electrodes could elicit a greater dynamic range of spikes and recruited more ganglion cells within charge injection limits. These findings suggest a practical lower limit for planar electrode size and indicate strategies for maximizing stimulation thresholds and dynamic range.
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Affiliation(s)
- Samir Damle
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093
| | - Maya Carleton
- Department of Psychology, University of California San Diego, La Jolla, CA 92093
| | - Theodoros Kapogianis
- Department of Psychology, University of California San Diego, La Jolla, CA 92093
| | - Shaurya Arya
- Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, CA 92161
| | - Melina Cavichini-Corderio
- Jacobs Retina Center at Shiley Eye Institute, Department of Ophthalmology, University of California San Diego, La Jolla, CA 92093
| | - William R Freeman
- Jacobs Retina Center at Shiley Eye Institute, Department of Ophthalmology, University of California San Diego, La Jolla, CA 92093
| | - Yu-Hwa Lo
- Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, CA 92161
| | - Nicholas W Oesch
- Department of Psychology, University of California San Diego, La Jolla, CA 92093
- Jacobs Retina Center at Shiley Eye Institute, Department of Ophthalmology, University of California San Diego, La Jolla, CA 92093
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On the DC Offset Current Generated during Biphasic Stimulation: Experimental Study. ELECTRONICS 2020. [DOI: 10.3390/electronics9081198] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This paper deals with the DC offset currents generated by a platinum electrode matrix during biphasic stimulation. A fully automated test bench evaluates the nanoampere range DC offset currents in a realistic and comprehensive scenario by using platinum electrodes in a saline solution as a load for the stimulator. Measurements are performed on different stimulation patterns for single or dual hexagonal stimulation sites operating simultaneously and alternately. The effectiveness of the return electrode presence in reducing the DC offset current is considered. Experimental results show how for a defined nominal injected charge, the generated DC offset currents differ depending on the stimulation patterns, frequency, current amplitude, and pulse width of a biphasic signal.
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Lyu Q, Lu Z, Li H, Qiu S, Guo J, Sui X, Sun P, Li L, Chai X, Lovell NH. A Three-Dimensional Microelectrode Array to Generate Virtual Electrodes for Epiretinal Prosthesis Based on a Modeling Study. Int J Neural Syst 2020; 30:2050006. [DOI: 10.1142/s0129065720500069] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Despite many advances in the development of retinal prostheses, clinical reports show that current retinal prosthesis subjects can only perceive prosthetic vision with poor visual acuity. A possible approach for improving visual acuity is to produce virtual electrodes (VEs) through electric field modulation. Generating controllable and localized VEs is a crucial factor in effectively improving the perceptive resolution of the retinal prostheses. In this paper, we aimed to design a microelectrode array (MEA) that can produce converged and controllable VEs by current steering stimulation strategies. Through computational modeling, we designed a three-dimensional concentric ring–disc MEA and evaluated its performance with different stimulation strategies. Our simulation results showed that electrode–retina distance (ERD) and inter-electrode distance (IED) can dramatically affect the distribution of electric field. Also the converged VEs could be produced when the parameters of the three-dimensional MEA were appropriately set. VE sites can be controlled by manipulating the proportion of current on each adjacent electrode in a current steering group (CSG). In addition, spatial localization of electrical stimulation can be greatly improved under quasi-monopolar (QMP) stimulation. This study may provide support for future application of VEs in epiretinal prosthesis for potentially increasing the visual acuity of prosthetic vision.
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Affiliation(s)
- Qing Lyu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Zhuofan Lu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Heng Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Shirong Qiu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Jiahui Guo
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Xiaohong Sui
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Pengcheng Sun
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Liming Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Xinyu Chai
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Nigel H. Lovell
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW 2052, Australia
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Kiele P, Braig D, Weis J, Baslan Y, Pasluosta C, Stieglitz T. Neural Implants Without Electronics: A Proof-of-Concept Study on a Human Skin Model. IEEE OPEN JOURNAL OF ENGINEERING IN MEDICINE AND BIOLOGY 2020; 1:91-97. [PMID: 35402961 PMCID: PMC8975271 DOI: 10.1109/ojemb.2020.2981254] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 01/16/2020] [Accepted: 03/10/2020] [Indexed: 11/25/2022] Open
Abstract
Objective: Chronic neural implants require energy and signal supply. The objective of this work was to evaluate a multichannel transcutaneous coupling approach in an ex vivo split-concept study, which minimizes the invasiveness of such an implant by externalizing the processing electronics. Methods: Herein, the experimental work focused on the transcutaneous energy and signal transmission. The performance was discussed with widely evaluated concepts of neural interfaces in the literature. Results: The performance of the transcutaneous coupling approach increased with higher channel count and higher electrode pitches. Electrical crosstalk among channels was present, but acceptable for the stimulation of peripheral nerves. Conclusions: Transcutaneous coupling with extracorporeal transmitting arrays and subcutaneous counterparts provide a promising alternative to the inductive concept particularly when a fully integration of the system in a prosthetic shaft is intended. The relocation of the electronics can potentially prevent pressure sores, improve accessibility for maintenance and increase lifetime of the implant.
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Affiliation(s)
- Patrick Kiele
- Laboratory of Biomedical MicrotechnologyDepartment of Microsystems Engineering-IMTEKUniversity of Freiburg 79110 Freiburg Germany
| | - David Braig
- Department of Plastic and Hand Surgery, Medical Center-University of FreiburgFaculty of MedicineUniversity of Freiburg 79106 Freiburg Germany
- Division of HandPlastic and Aesthetic SurgeryUniversity Hospital 80336 LMU Munich Germany
| | - Jakob Weis
- Division of HandPlastic and Aesthetic SurgeryUniversity Hospital 80336 LMU Munich Germany
| | - Yara Baslan
- Laboratory of Biomedical MicrotechnologyDepartment of Microsystems Engineering-IMTEKUniversity of Freiburg 79110 Freiburg Germany
| | - Cristian Pasluosta
- Laboratory of Biomedical MicrotechnologyDepartment of Microsystems Engineering-IMTEKUniversity of Freiburg 79110 Freiburg Germany
| | - Thomas Stieglitz
- Laboratory of Biomedical MicrotechnologyDepartment of Microsystems Engineering-IMTEKUniversity of Freiburg 79110 Freiburg Germany
- Bernstein Center FreiburgUniversity of Freiburg 79098 Freiburg Germany
- BrainLinks-BrainToolsUniversity of Freiburg 79110 Freiburg Germany
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8
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Bosse B, Damle S, Akinin A, Jing Y, Bartsch DU, Cheng L, Oesch N, Lo YH, Cauwenberghs G, Freeman WR. In Vivo Photovoltaic Performance of a Silicon Nanowire Photodiode-Based Retinal Prosthesis. Invest Ophthalmol Vis Sci 2019; 59:5885-5892. [PMID: 30550611 PMCID: PMC6295940 DOI: 10.1167/iovs.18-24554] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Purpose For more than 20 years, there has been an international, multidisciplinary effort to develop retinal prostheses to restore functional vision to patients blinded by retinal degeneration. We developed a novel subretinal prosthesis with 1512 optically addressed silicon nanowire photodiodes, which transduce incident light into an electrical stimulation of the remaining retinal circuitry. This study was conducted to evaluate the efficacy of optically driving the subretinal prosthesis to produce visual cortex activation via electrical stimulation of the retina. Methods We measured electrically evoked potential responses (EEPs) in rabbit visual cortex in response to illumination of the subretinal nanowire prosthesis with pulsed 852-nm infrared (IR) light. We compared the EEP responses to visually evoked potential responses (VEPs) to pulsed 532-nm visible light (positive control) and pulsed 852-nm IR light (negative control). Results Activating the devices with IR light produced EEP responses with a significantly higher trough-to-peak amplitude (54.17 ± 33.4 μV) than IR light alone (24.07 ± 22.1 μV) or background cortical activity (23.22 ± 17.2 μV). EEP latencies were significantly faster than focal VEP latencies. Focal VEPs produced significantly higher amplitudes (94.88 ± 43.3 μV) than EEPs. We also demonstrated how an electrode placed on the cornea can be used as a noninvasive method to monitor the function of the implant. Conclusions These results show that subretinal electrical stimulation with nanowire electrodes can elicit EEPs in the visual cortex, providing evidence for the viability of a subretinal nanowire prosthetic approach for vision restoration.
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Affiliation(s)
- Brandon Bosse
- Nanovision Biosciences, Inc., La Jolla, California, United States
| | - Samir Damle
- Department of Bioengineering, University of California, San Diego, California, United States
| | - Abraham Akinin
- Department of Bioengineering, University of California, San Diego, California, United States
| | - Yi Jing
- Nanovision Biosciences, Inc., La Jolla, California, United States
| | - Dirk-Uwe Bartsch
- Jacobs Retina Center at Shiley Eye Institute, Department of Ophthalmology, University of California, San Diego, California, United States
| | - Lingyun Cheng
- Jacobs Retina Center at Shiley Eye Institute, Department of Ophthalmology, University of California, San Diego, California, United States
| | - Nicholas Oesch
- Jacobs Retina Center at Shiley Eye Institute, Department of Ophthalmology, University of California, San Diego, California, United States.,Department of Psychology, University of California, San Diego, California, United States
| | - Yu-Hwa Lo
- Department of Electrical and Computer Engineering, University of California, San Diego, California, United States
| | - Gert Cauwenberghs
- Department of Bioengineering, University of California, San Diego, California, United States
| | - William R Freeman
- Jacobs Retina Center at Shiley Eye Institute, Department of Ophthalmology, University of California, San Diego, California, United States
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9
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Barriga-Rivera A, Guo T, Yang CY, Abed AA, Dokos S, Lovell NH, Morley JW, Suaning GJ. High-amplitude electrical stimulation can reduce elicited neuronal activity in visual prosthesis. Sci Rep 2017; 7:42682. [PMID: 28209965 PMCID: PMC5314337 DOI: 10.1038/srep42682] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 01/13/2017] [Indexed: 12/13/2022] Open
Abstract
Retinal electrostimulation is promising a successful therapy to restore functional vision. However, a narrow stimulating current range exists between retinal neuron excitation and inhibition which may lead to misperformance of visual prostheses. As the conveyance of representation of complex visual scenes may require neighbouring electrodes to be activated simultaneously, electric field summation may contribute to reach this inhibitory threshold. This study used three approaches to assess the implications of relatively high stimulating conditions in visual prostheses: (1) in vivo, using a suprachoroidal prosthesis implanted in a feline model, (2) in vitro through electrostimulation of murine retinal preparations, and (3) in silico by computing the response of a population of retinal ganglion cells. Inhibitory stimulating conditions led to diminished cortical activity in the cat. Stimulus-response relationships showed non-monotonic profiles to increasing stimulating current. This was observed in vitro and in silico as the combined response of groups of neurons (close to the stimulating electrode) being inhibited at certain stimulating amplitudes, whilst other groups (far from the stimulating electrode) being recruited. These findings may explain the halo-like phosphene shapes reported in clinical trials and suggest that simultaneous stimulation in retinal prostheses is limited by the inhibitory threshold of the retinal ganglion cells.
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Affiliation(s)
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia
| | - Chih-Yu Yang
- Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia
| | - Amr Al Abed
- Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia
| | - John W Morley
- School of Medicine, Western Sydney University, Sydney, 2753, Australia.,School of Medical Science, UNSW, Sydney, 2052, Australia
| | - Gregg J Suaning
- Graduate School of Biomedical Engineering, UNSW, Sydney, 2052, Australia.,Sydney Medical School, University of Sydney, 2000, Australia
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Synthetic 3D diamond-based electrodes for flexible retinal neuroprostheses: Model, production and in vivo biocompatibility. Biomaterials 2015. [PMID: 26210174 DOI: 10.1016/j.biomaterials.2015.07.018] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Two retinal implants have recently received the CE mark and one has obtained FDA approval for the restoration of useful vision in blind patients. Since the spatial resolution of current vision prostheses is not sufficient for most patients to detect faces or perform activities of daily living, more electrodes with less crosstalk are needed to transfer complex images to the retina. In this study, we modelled planar and three-dimensional (3D) implants with a distant ground or a ground grid, to demonstrate greater spatial resolution with 3D structures. Using such flexible 3D implant prototypes, we showed that the degenerated retina could mould itself to the inside of the wells, thereby isolating bipolar neurons for specific, independent stimulation. To investigate the in vivo biocompatibility of diamond as an electrode or an isolating material, we developed a procedure for depositing diamond onto flexible 3D retinal implants. Taking polyimide 3D implants as a reference, we compared the number of neurones integrating the 3D diamond structures and their ratio to the numbers of all cells, including glial cells. Bipolar neurones were increased whereas there was no increase even a decrease in the total cell number. SEM examinations of implants confirmed the stability of the diamond after its implantation in vivo. This study further demonstrates the potential of 3D designs for increasing the resolution of retinal implants and validates the safety of diamond materials for retinal implants and neuroprostheses in general.
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