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Zhu Y, Liu X, Ma J, Wang Z, Jiang H, Sun C, Jeong DY, Guan H, Chu B. Wireless and Opto-Stimulated Flexible Implants: Artificial Retina Constructed by Ferroelectric BiFeO 3-BaTiO 3/P(VDF-TrFE) Composites. ACS APPLIED MATERIALS & INTERFACES 2024; 16:48395-48405. [PMID: 39223074 DOI: 10.1021/acsami.4c12460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
The degeneration of retinal photoreceptors is one of the primary causes of blindness, and the implantation of retinal prostheses offers hope for vision restoration in individuals who are completely blind. Flexible bioelectronic devices present a promising avenue for the next generation of retinal prostheses owing to their soft mechanical properties and tissue friendliness. In this study, we developed flexible composite films of ferroelectric BiFeO3-BaTiO3 (BFO-BTO) particles synthesized by the hydrothermal method and ferroelectric poly(vinyldene difluoride-trifluoroethylene) (P(VDF-TrFE)) polymer and investigated their applications in artificial retinas. Owing to the coupling of the photothermal effect of BFO-BTO particles and the pyroelectric effect of the P(VDF-TrFE) polymer, the composite films demonstrate a strong photoelectric response (a maximum peak-to-peak photovoltage > 80 V under blue light of 100 mW/cm2) in a wide wavelength range of light (from visible to infrared) with the inherent flexibility and ease of preparation, making it an attractive candidate for artificial retinal applications. Experimental results showed that blind rats implanted with artificial retinas of the composites display light-responsive behavior, showcasing the effectiveness of vision restoration. This study demonstrates a novel approach for employing ferroelectric materials in vision restoration and offers insights into future artificial retina design.
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Affiliation(s)
- Yuhong Zhu
- CAS Key Laboratory of Materials for Energy Conversion and Department of Materials Science and Engineering, Key Laboratory of Precision and Intelligent Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Xi Liu
- Eye Institute, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong University, Nantong 226001, China
| | - Jinyu Ma
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-Innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong 226001, China
| | - Zhaopeng Wang
- CAS Key Laboratory of Materials for Energy Conversion and Department of Materials Science and Engineering, Key Laboratory of Precision and Intelligent Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Haitao Jiang
- CAS Key Laboratory of Materials for Energy Conversion and Department of Materials Science and Engineering, Key Laboratory of Precision and Intelligent Chemistry, University of Science and Technology of China, Hefei 230026, China
| | - Cheng Sun
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-Innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong 226001, China
| | - Dae-Yong Jeong
- Department of Materials Science & Engineering, Inha University, Incheon 22212, Korea
| | - Huaijin Guan
- Eye Institute, Affiliated Hospital of Nantong University, Medical School of Nantong University, Nantong University, Nantong 226001, China
| | - Baojin Chu
- CAS Key Laboratory of Materials for Energy Conversion and Department of Materials Science and Engineering, Key Laboratory of Precision and Intelligent Chemistry, University of Science and Technology of China, Hefei 230026, China
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2
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Duvan FT, Cunquero M, Masvidal-Codina E, Walston ST, Marsal M, de la Cruz JM, Viana D, Nguyen D, Degardin J, Illa X, Zhang JM, Del Pilar Bernícola M, Macias-Montero JG, Puigdengoles C, Castro-Olvera G, Del Corro E, Dokos S, Chmeissani M, Loza-Alvarez P, Picaud S, Garrido JA. Graphene-based microelectrodes with bidirectional functionality for next-generation retinal electronic interfaces. NANOSCALE HORIZONS 2024. [PMID: 39229772 DOI: 10.1039/d4nh00282b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2024]
Abstract
Neuroelectronic prostheses are being developed for restoring vision at the retinal level in patients who have lost their sight due to photoreceptor loss. The core component of these devices is the electrode array, which enables interfacing with retinal neurons. Generating the perception of meaningful images requires high-density microelectrode arrays (MEAs) capable of precisely activating targeted retinal neurons. Achieving this precision necessitates the downscaling of electrodes to micrometer dimensions. However, miniaturization increases electrode impedance, which poses challenges by limiting the amount of current that can be delivered, thereby impairing the electrode's capability for effective neural modulation. Additionally, it elevates noise levels, reducing the signal quality of the recorded neural activity. This report focuses on evaluating reduced graphene oxide (rGO) based devices for interfacing with the retina, showcasing their potential in vision restoration. Our findings reveal low impedance and high charge injection limit for microscale rGO electrodes, confirming their suitability for developing next-generation high-density retinal devices. We successfully demonstrated bidirectional interfacing with cell cultures and explanted retinal tissue, enabling the identification and modulation of multiple cells' activity. Additionally, calcium imaging allowed real-time monitoring of retinal cell dynamics, demonstrating a significant reduction in activated areas with small-sized electrodes. Overall, this study lays the groundwork for developing advanced rGO-based MEAs for high-acuity visual prostheses.
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Affiliation(s)
- Fikret Taygun Duvan
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Spain.
| | - Marina Cunquero
- Institut de Ciències Fotòniques (ICFO), The Barcelona Institute of Science and Technology, Castelldefels, Spain
| | - Eduard Masvidal-Codina
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Spain.
| | - Steven T Walston
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Spain.
| | - Maria Marsal
- Institut de Ciències Fotòniques (ICFO), The Barcelona Institute of Science and Technology, Castelldefels, Spain
| | - Jose Manuel de la Cruz
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Spain.
| | - Damia Viana
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Spain.
| | - Diep Nguyen
- Institut de la Vision, Sorbonne Université, INSERM, CNRS, Paris, France
| | - Julie Degardin
- Institut de la Vision, Sorbonne Université, INSERM, CNRS, Paris, France
| | - Xavi Illa
- Institut de Microelectrònica de Barcelona, IMB-CNM (CSIC), Campus UAB, Bellaterra, Spain
- Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, Bellaterra, Spain
| | - Julie M Zhang
- Institut de la Vision, Sorbonne Université, INSERM, CNRS, Paris, France
| | - Maria Del Pilar Bernícola
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Spain.
| | | | - Carles Puigdengoles
- Institut de Física d'Altes Energies (IFAE), BIST, Campus UAB, Bellaterra, Spain
| | - Gustavo Castro-Olvera
- Institut de Ciències Fotòniques (ICFO), The Barcelona Institute of Science and Technology, Castelldefels, Spain
| | - Elena Del Corro
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Spain.
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, The University of New South Wales Sydney, Sydney, NSW, Australia
| | - Mokhtar Chmeissani
- Institut de Física d'Altes Energies (IFAE), BIST, Campus UAB, Bellaterra, Spain
| | - Pablo Loza-Alvarez
- Institut de Ciències Fotòniques (ICFO), The Barcelona Institute of Science and Technology, Castelldefels, Spain
| | - Serge Picaud
- Institut de la Vision, Sorbonne Université, INSERM, CNRS, Paris, France
| | - Jose A Garrido
- Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, Spain.
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
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3
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Yang R, Zhao P, Wang L, Feng C, Peng C, Wang Z, Zhang Y, Shen M, Shi K, Weng S, Dong C, Zeng F, Zhang T, Chen X, Wang S, Wang Y, Luo Y, Chen Q, Chen Y, Jiang C, Jia S, Yu Z, Liu J, Wang F, Jiang S, Xu W, Li L, Wang G, Mo X, Zheng G, Chen A, Zhou X, Jiang C, Yuan Y, Yan B, Zhang J. Assessment of visual function in blind mice and monkeys with subretinally implanted nanowire arrays as artificial photoreceptors. Nat Biomed Eng 2024; 8:1018-1039. [PMID: 37996614 DOI: 10.1038/s41551-023-01137-8] [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: 01/15/2022] [Accepted: 10/17/2023] [Indexed: 11/25/2023]
Abstract
Retinal prostheses could restore image-forming vision in conditions of photoreceptor degeneration. However, contrast sensitivity and visual acuity are often insufficient. Here we report the performance, in mice and monkeys with induced photoreceptor degeneration, of subretinally implanted gold-nanoparticle-coated titania nanowire arrays providing a spatial resolution of 77.5 μm and a temporal resolution of 3.92 Hz in ex vivo retinas (as determined by patch-clamp recording of retinal ganglion cells). In blind mice, the arrays allowed for the detection of drifting gratings and flashing objects at light-intensity thresholds of 15.70-18.09 μW mm-2, and offered visual acuities of 0.3-0.4 cycles per degree, as determined by recordings of visually evoked potentials and optomotor-response tests. In monkeys, the arrays were stable for 54 weeks, allowed for the detection of a 10-μW mm-2 beam of light (0.5° in beam angle) in visually guided saccade experiments, and induced plastic changes in the primary visual cortex, as indicated by long-term in vivo calcium imaging. Nanomaterials as artificial photoreceptors may ameliorate visual deficits in patients with photoreceptor degeneration.
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Affiliation(s)
- Ruyi Yang
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Peng Zhao
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Liyang Wang
- Department of Ophthalmology, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Chenli Feng
- Department of Ophthalmology, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Chen Peng
- Laboratory of Advanced Materials, Department of Chemistry, Fudan University, Shanghai, P. R. China
| | - Zhexuan Wang
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Yingying Zhang
- Key Laboratory of Brain Functional Genomics (Ministry of Education), East China Normal University, Shanghai, P. R. China
| | - Minqian Shen
- Department of Ophthalmology, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Kaiwen Shi
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Shijun Weng
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Chunqiong Dong
- Department of Ophthalmology, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Fu Zeng
- Key Laboratory of Brain Functional Genomics (Ministry of Education), East China Normal University, Shanghai, P. R. China
| | - Tianyun Zhang
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Xingdong Chen
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Shuiyuan Wang
- Shanghai Key Lab for Future Computing Hardware and System, School of Microelectronics, Fudan University, Shanghai, P. R. China
| | - Yiheng Wang
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Yuanyuan Luo
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Qingyuan Chen
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Yuqing Chen
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Chengyong Jiang
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Shanshan Jia
- School of Computer Science, Institute for Artificial Intelligence, Peking University, Beijing, P.R. China
| | - Zhaofei Yu
- School of Computer Science, Institute for Artificial Intelligence, Peking University, Beijing, P.R. China
| | - Jian Liu
- School of Computer Science, University of Birmingham, Birmingham, UK
| | - Fei Wang
- Department of Hand Surgery, the National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, P. R. China
| | - Su Jiang
- Department of Hand Surgery, the National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, P. R. China
| | - Wendong Xu
- Department of Hand Surgery, the National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, P. R. China
- Department of Hand and Upper Extremity Surgery, Jing'an District Central Hospital, Fudan University, Shanghai, P.R. China
| | - Liang Li
- Center of Brain Sciences, Beijing Institute of Basic Medical Sciences, Beijing, P. R. China
| | - Gang Wang
- Center of Brain Sciences, Beijing Institute of Basic Medical Sciences, Beijing, P. R. China
| | - Xiaofen Mo
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Gengfeng Zheng
- Laboratory of Advanced Materials, Department of Chemistry, Fudan University, Shanghai, P. R. China
| | - Aihua Chen
- Key Laboratory of Brain Functional Genomics (Ministry of Education), East China Normal University, Shanghai, P. R. China
| | - Xingtao Zhou
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China
| | - Chunhui Jiang
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China.
| | - Yuanzhi Yuan
- Department of Ophthalmology, Zhongshan Hospital, Fudan University, Shanghai, P. R. China.
- Zhongshan Hospital (Xiamen), Fudan University, Xiamen, P.R. China.
| | - Biao Yan
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China.
| | - Jiayi Zhang
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institutes of Brain Science, Institute for Medical and Engineering Innovation, Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, P. R. China.
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4
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Holiel HA, Fawzi SA, Al-Atabany W. Pre-processing visual scenes for retinal prosthesis systems: A comprehensive review. Artif Organs 2024. [PMID: 39023279 DOI: 10.1111/aor.14824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 05/13/2024] [Accepted: 06/21/2024] [Indexed: 07/20/2024]
Abstract
BACKGROUND Retinal prostheses offer hope for individuals with degenerative retinal diseases by stimulating the remaining retinal cells to partially restore their vision. This review delves into the current advancements in retinal prosthesis technology, with a special emphasis on the pivotal role that image processing and machine learning techniques play in this evolution. METHODS We provide a comprehensive analysis of the existing implantable devices and optogenetic strategies, delineating their advantages, limitations, and challenges in addressing complex visual tasks. The review extends to various image processing algorithms and deep learning architectures that have been implemented to enhance the functionality of retinal prosthetic devices. We also illustrate the testing results by demonstrating the clinical trials or using Simulated Prosthetic Vision (SPV) through phosphene simulations, which is a critical aspect of simulating visual perception for retinal prosthesis users. RESULTS Our review highlights the significant progress in retinal prosthesis technology, particularly its capacity to augment visual perception among the visually impaired. It discusses the integration between image processing and deep learning, illustrating their impact on individual interactions and navigations within the environment through applying clinical trials and also illustrating the limitations of some techniques to be used with current devices, as some approaches only use simulation even on sighted-normal individuals or rely on qualitative analysis, where some consider realistic perception models and others do not. CONCLUSION This interdisciplinary field holds promise for the future of retinal prostheses, with the potential to significantly enhance the quality of life for individuals with retinal prostheses. Future research directions should pivot towards optimizing phosphene simulations for SPV approaches, considering the distorted and confusing nature of phosphene perception, thereby enriching the visual perception provided by these prosthetic devices. This endeavor will not only improve navigational independence but also facilitate a more immersive interaction with the environment.
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Affiliation(s)
- Heidi Ahmed Holiel
- Medical Imaging and Image Processing Research Group, Center for Informatics Science, Nile University, Sheikh Zayed City, Egypt
| | - Sahar Ali Fawzi
- Medical Imaging and Image Processing Research Group, Center for Informatics Science, Nile University, Sheikh Zayed City, Egypt
- Systems and Biomedical Engineering Department, Cairo University, Giza, Egypt
| | - Walid Al-Atabany
- Medical Imaging and Image Processing Research Group, Center for Informatics Science, Nile University, Sheikh Zayed City, Egypt
- Biomedical Engineering Department, Helwan University, Helwan, Egypt
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Zhang B, Zhang R, Zhao J, Yang J, Xu S. The mechanism of human color vision and potential implanted devices for artificial color vision. Front Neurosci 2024; 18:1408087. [PMID: 38962178 PMCID: PMC11221215 DOI: 10.3389/fnins.2024.1408087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Accepted: 05/31/2024] [Indexed: 07/05/2024] Open
Abstract
Vision plays a major role in perceiving external stimuli and information in our daily lives. The neural mechanism of color vision is complicated, involving the co-ordinated functions of a variety of cells, such as retinal cells and lateral geniculate nucleus cells, as well as multiple levels of the visual cortex. In this work, we reviewed the history of experimental and theoretical studies on this issue, from the fundamental functions of the individual cells of the visual system to the coding in the transmission of neural signals and sophisticated brain processes at different levels. We discuss various hypotheses, models, and theories related to the color vision mechanism and present some suggestions for developing novel implanted devices that may help restore color vision in visually impaired people or introduce artificial color vision to those who need it.
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Affiliation(s)
- Bingao Zhang
- Key Laboratory for the Physics and Chemistry of Nanodevices, Institute of Physical Electronics, Department of Electronics, Peking University, Beijing, China
| | - Rong Zhang
- Key Laboratory for the Physics and Chemistry of Nanodevices, Institute of Physical Electronics, Department of Electronics, Peking University, Beijing, China
| | - Jingjin Zhao
- Key Laboratory for the Physics and Chemistry of Nanodevices, Institute of Physical Electronics, Department of Electronics, Peking University, Beijing, China
| | - Jiarui Yang
- Beijing Key Laboratory of Restoration of Damaged Ocular Nerve, Department of Ophthalmology, Peking University Third Hospital, Beijing, China
| | - Shengyong Xu
- Key Laboratory for the Physics and Chemistry of Nanodevices, Institute of Physical Electronics, Department of Electronics, Peking University, Beijing, China
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Santiago-Alvarado A, Granados-Agustín FS, López-Raymundo BR, Hernández-Mendez A, Huerta-Carranza O. Development of a bio-inspired optical system that mimics accommodation and lighting regulation like the human eye. APPLIED OPTICS 2024; 63:193-203. [PMID: 38175021 DOI: 10.1364/ao.506986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 12/02/2023] [Indexed: 01/05/2024]
Abstract
Bio-inspired optical systems have recently been developed using polarizers and liquid or rigid lenses. In this work, we propose a bio-inspired opto-mechatronic system that imitates the accommodation and regulation of light intensity as the human eye does. The system uses a polymeric lens as a cornea, an adjustable diaphragm as an iris, a tunable solid elastic lens as a crystalline lens, and a commercial sensor as a retina. We also present the development of the electronic control system to accommodate and regulate the amount of light that enters the system, for which two stepper motors, an Arduino control system, and light and movement sensors are used. The characterization of the system is presented together with the results obtained, where it can be seen that the system works in an acceptable range as the human eye does.
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Son Y, Chen ZC, Roh H, Lee BC, Im M. Effects on Retinal Stimulation of the Geometry and the Insertion Location of Penetrating Electrodes. IEEE Trans Neural Syst Rehabil Eng 2023; 31:3803-3812. [PMID: 37729573 DOI: 10.1109/tnsre.2023.3317496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
Retinal implants have been developed and implanted to restore vision from outer retinal degeneration, but their performance is still limited due to the poor spatial resolution. To improve the localization of stimulation, microelectrodes in various three-dimensional (3D) shapes have been investigated. In particular, computational simulation is crucial for optimizing the performance of a novel microelectrode design before actual fabrication. However, most previous studies have assumed a uniform conductivity for the entire retina without testing the effect of electrodes placement in different layers. In this study, we used the finite element method to simulate electric fields created by 3D microelectrodes of three different designs in a retina model with a stratified conductivity profile. The three electrode designs included two conventional shapes - a conical electrode (CE) and a pillar electrode (PE); we also proposed a novel structure of pillar electrode with an insulating wall (PEIW). A quantitative comparison of these designs shows the PEIW generates a stronger and more confined electric field with the same current injection, which is preferred for high-resolution retinal prostheses. Moreover, our results demonstrate both the magnitude and the shape of potential distribution generated by a penetrating electrode depend not only on the geometry, but also substantially on the insertion depth of the electrode. Although epiretinal insertions are mainly discussed, we also compared results for subretinal insertions. The results provide valuable insights for improving the spatial resolution of retinal implants using 3D penetrating microelectrodes and highlight the importance of considering the heterogeneity of conductivities in the retina.
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8
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Karadima V, Pezaris EA, Pezaris JS. Attitudes of potential recipients toward emerging visual prosthesis technologies. Sci Rep 2023; 13:10963. [PMID: 37414798 PMCID: PMC10325978 DOI: 10.1038/s41598-023-36913-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Accepted: 06/12/2023] [Indexed: 07/08/2023] Open
Abstract
With the advent of multiple visual prosthesis devices to treat blindness, the question of how potential patients view such interventions becomes important in order to understand the levels of expectation and acceptance, and the perceived risk-reward balance across the different device approaches. Building on previous work on single device approaches done with blind individuals in Chicago and Detroit, USA, Melbourne, Australia, and Bejing, China, we investigated attitudes in blind individuals in Athens, Greece with coverage expanded to three of the contemporary approaches, Retinal, Thalamic, and Cortical. We presented an informational lecture on the approaches, had potential participants fill out a preliminary Questionnaire 1, then organized selected subjects into focus groups for guided discussion on visual prostheses, and finally had these subjects fill out a more detailed Questionnaire 2. We report here the first quantitative data that compares multiple prosthesis approaches. Our primary findings are that for these potential patients, perceived risk continues to outweigh perceived benefits, with the Retinal approach having the least negative overall impression and the Cortical approach the most negative. Concerns about the quality of restored vision were primary. Factors that drove the choice of hypothetical participation in a clinical trial were age and years of blindness. Secondary factors focused on positive clinical outcomes. The focus groups served to swing the impressions of each approach from neutrality toward the extremes of a Likert scale, and shifted the overall willingness to participate in a clinical trial from neutral to negative. These results, coupled with informal assessment of audience questions after the informational lecture, suggest that a substantial improvement in performance over currently available devices will be necessary before visual prostheses gain wide acceptance.
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Affiliation(s)
- Vicky Karadima
- Multisensory and Temporal Processing Lab (MultiTimeLab), Department of Psychology, Panteion University of Social and Political Sciences, Athens, Greece
| | | | - John S Pezaris
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, USA.
- Department of Neurosurgery, Harvard Medical School, Boston, MA, USA.
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9
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Xu A, Beyeler M. Retinal ganglion cells undergo cell type-specific functional changes in a computational model of cone-mediated retinal degeneration. Front Neurosci 2023; 17:1147729. [PMID: 37274203 PMCID: PMC10233015 DOI: 10.3389/fnins.2023.1147729] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 05/02/2023] [Indexed: 06/06/2023] Open
Abstract
Introduction Understanding the retina in health and disease is a key issue for neuroscience and neuroengineering applications such as retinal prostheses. During degeneration, the retinal network undergoes complex and multi-stage neuroanatomical alterations, which drastically impact the retinal ganglion cell (RGC) response and are of clinical importance. Here we present a biophysically detailed in silico model of the cone pathway in the retina that simulates the network-level response to both light and electrical stimulation. Methods The model included 11, 138 cells belonging to nine different cell types (cone photoreceptors, horizontal cells, ON/OFF bipolar cells, ON/OFF amacrine cells, and ON/OFF ganglion cells) confined to a 300 × 300 × 210μm patch of the parafoveal retina. After verifying that the model reproduced seminal findings about the light response of retinal ganglion cells (RGCs), we systematically introduced anatomical and neurophysiological changes (e.g., reduced light sensitivity of photoreceptor, cell death, cell migration) to the network and studied their effect on network activity. Results The model was not only able to reproduce common findings about RGC activity in the degenerated retina, such as hyperactivity and increased electrical thresholds, but also offers testable predictions about the underlying neuroanatomical mechanisms. Discussion Overall, our findings demonstrate how biophysical changes typified by cone-mediated retinal degeneration may impact retinal responses to light and electrical stimulation. These insights may further our understanding of retinal processing and inform the design of retinal prostheses.
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Affiliation(s)
- Aiwen Xu
- Department of Computer Science, University of California, California, Santa Barbara, CA, United States
| | - Michael Beyeler
- Department of Computer Science, University of California, California, Santa Barbara, CA, United States
- Department of Psychological & Brain Sciences, University of California, California, Santa Barbara, CA, United States
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10
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Won SM, Cai L, Gutruf P, Rogers JA. Wireless and battery-free technologies for neuroengineering. Nat Biomed Eng 2023; 7:405-423. [PMID: 33686282 PMCID: PMC8423863 DOI: 10.1038/s41551-021-00683-3] [Citation(s) in RCA: 101] [Impact Index Per Article: 101.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 12/28/2020] [Indexed: 12/16/2022]
Abstract
Tethered and battery-powered devices that interface with neural tissues can restrict natural motions and prevent social interactions in animal models, thereby limiting the utility of these devices in behavioural neuroscience research. In this Review Article, we discuss recent progress in the development of miniaturized and ultralightweight devices as neuroengineering platforms that are wireless, battery-free and fully implantable, with capabilities that match or exceed those of wired or battery-powered alternatives. Such classes of advanced neural interfaces with optical, electrical or fluidic functionality can also combine recording and stimulation modalities for closed-loop applications in basic studies or in the practical treatment of abnormal physiological processes.
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Affiliation(s)
- Sang Min Won
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, South Korea
| | - Le Cai
- Biomedical Engineering, College of Engineering, The University of Arizona, Tucson, AZ, USA
| | - Philipp Gutruf
- Biomedical Engineering, College of Engineering, The University of Arizona, Tucson, AZ, USA.
- Bio5 Institute and Neuroscience GIDP, University of Arizona, Tucson, AZ, USA.
- Department of Electrical and Computer Engineering, University of Arizona, Tucson, AZ, USA.
| | - John A Rogers
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA.
- Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, USA.
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA.
- Center for Advanced Molecular Imaging, Northwestern University, Evanston, IL, USA.
- Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA.
- Department of Chemistry, Northwestern University, Evanston, IL, USA.
- Department of Neurological Surgery, Northwestern University, Evanston, IL, USA.
- Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL, USA.
- Simpson Querrey Institute for BioNanotechnology, Northwestern University, Evanston, IL, USA.
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11
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Xu A, Beyeler M. Retinal ganglion cells undergo cell typeâ€"specific functional changes in a biophysically detailed model of retinal degeneration. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.13.523982. [PMID: 36711897 PMCID: PMC9882163 DOI: 10.1101/2023.01.13.523982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Understanding the retina in health and disease is a key issue for neuroscience and neuroengineering applications such as retinal prostheses. During degeneration, the retinal network undergoes complex and multi-stage neuroanatomical alterations, which drastically impact the retinal ganglion cell (RGC) response and are of clinical importance. Here we present a biophysically detailed in silico model of retinal degeneration that simulates the network-level response to both light and electrical stimulation as a function of disease progression. The model is not only able to reproduce common findings about RGC activity in the degenerated retina, such as hyperactivity and increased electrical thresholds, but also offers testable predictions about the underlying neuroanatomical mechanisms. Overall, our findings demonstrate how biophysical changes associated with retinal degeneration affect retinal responses to both light and electrical stimulation, which may further our understanding of visual processing in the retina as well as inform the design and application of retinal prostheses.
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12
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Li N, Wang Q, He C, Li J, Li X, Shen C, Huang B, Tang J, Yu H, Wang S, Du L, Yang W, Yang R, Shi D, Zhang G. 2D Semiconductor Based Flexible Photoresponsive Ring Oscillators for Artificial Vision Pixels. ACS NANO 2023; 17:991-999. [PMID: 36607196 DOI: 10.1021/acsnano.2c06921] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Artificial retina implantation provides an effective and feasible attempt for vision recovery in addition to retinal transplantation. The most advanced artificial retinas ever developed based on silicon technology are rigid and thus less compatible with the biosystem. Here we demonstrate flexible photoresponsive ring oscillators (PROs) based on the 2D semiconductor MoS2 for artificial retinas. Under natural light illuminations, arrayed PROs on flexible substrates serving as vision pixels can efficiently output light-intensity-dependent electrical pulses that are processable and transmittable in the human visual nerve system. Such PROs can work under low supply voltages below 1 V with a record-low power consumption, e.g. only 12.4 nW at a light intensity of 10 mW/cm2, decreased by ∼500 times compared with that of the state-of-the-art silicon devices. Such flexible artificial retinas with a simple device structure, high light-to-signal conversion efficiency, ultralow power consumption, and high tunability provide an alternative prosthesis for further clinical trials.
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Affiliation(s)
- Na Li
- Songshan Lake Materials Laboratory, Dongguan 523808, People's Republic of China
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Qinqin Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Congli He
- Institute of Advanced Materials, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Jiawei Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Xiuzhen Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Cheng Shen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Biying Huang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Jian Tang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Hua Yu
- Songshan Lake Materials Laboratory, Dongguan 523808, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Shuopei Wang
- Songshan Lake Materials Laboratory, Dongguan 523808, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Luojun Du
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Wei Yang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Rong Yang
- Songshan Lake Materials Laboratory, Dongguan 523808, People's Republic of China
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Dongxia Shi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Guangyu Zhang
- Songshan Lake Materials Laboratory, Dongguan 523808, People's Republic of China
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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13
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Oh Y, Hong J, Kim J. Integrated Low-Voltage Compliance and Wide-Dynamic Stimulator Design for Neural Implantable Devices. SENSORS (BASEL, SWITZERLAND) 2023; 23:492. [PMID: 36617100 PMCID: PMC9823420 DOI: 10.3390/s23010492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 12/29/2022] [Accepted: 12/30/2022] [Indexed: 06/17/2023]
Abstract
In this study, a pulse frequency modulation (PFM)-based stimulator is proposed for use in biomedical implantable devices. Conventionally, functional electrical stimulation (FES) techniques have been used to reinforce damaged nerves, such as retina tissue and brain tissue, by injecting a certain amount of charge into tissues. Although several design methods are present for implementing FES devices, an FES stimulator for retinal implants is difficult to realize because of the chip area, which needs to be inserted in a fovea, sized 5 mm x 5 mm, and power limitations to prevent the heat generation that causes tissue damage. In this work, we propose a novel stimulation structure to reduce the compliance voltage during stimulation, which can result in high-speed and low-voltage operation. A new stimulator that is composed of a modified high-speed PFM, a 4-bit counter, a serializer, a digital controller, and a current driver is designed and verified using a DB HiTek standard 0.18 μm process. This proposed stimulator can generate a charge up to 130 nC, consumes an average power of 375 µW during a stimulation period, and occupies a total area of 700 µm × 68 µm.
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Affiliation(s)
- Yeonji Oh
- Department of Medical Science, Korea University, Seoul 02841, Republic of Korea
| | - Jonggi Hong
- Department of Health Sciences & Technology, Gachon Advanced Institute for Health Sciences & Technology, Gachon University, Incheon 21999, Republic of Korea
| | - Jungsuk Kim
- Department of Biomedical Engineering, Gachon University, Incheon 21936, Republic of Korea
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14
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Chang AY. Challenges of Treatment Methodologies and the Future of Gene Therapy and Stem Cell Therapy to Treat Retinitis Pigmentosa. Methods Mol Biol 2022; 2560:363-374. [PMID: 36481911 DOI: 10.1007/978-1-0716-2651-1_33] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Retinitis pigmentosa (RP) is a heterogeneous group of hereditary retinal degenerations for which there is currently no cure. Studies investigating the use of gene therapy, gene editing, and stem cells as potential treatment strategies have shown promising results in animal models and some early clinical trials. Even still, major barriers still exist, including the ability to develop therapies that can target the wide range of mutational etiologies and phenotypic presentations that encompass RP. Additionally, effective screening and early diagnosis are crucial for maximum therapeutic potential, especially because many therapeutic agents require a baseline level photoreceptor function.
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Affiliation(s)
- Angela Y Chang
- Edward S. Harkness Eye Institute, Department of Ophthalmology, Columbia University Medical Center, New York, NY, USA.
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15
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Choi GJ, Yoo HJ, Cho Y, Shim S, Yun S, Sung J, Lim Y, Jun SB, Kim SJ. Development of a miniaturized, reconnectable, and implantable multichannel connector. J Neural Eng 2022; 19. [PMID: 36228595 DOI: 10.1088/1741-2552/ac99ff] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 10/13/2022] [Indexed: 12/24/2022]
Abstract
Objective. Connectors for implantable neural prosthetic systems provide several advantages such as simplification of surgery, safe replacement of implanted devices, and modular design of the implant systems. With the rapid advancement of technologies for neural implants, miniaturized multichannel implantable connectors are also required. In this study, we propose a reconnectable and area-efficient multichannel implantable connector.Approach. A female-to-female adapter was fabricated using the thermal-press bonding of micropatterned liquid crystal polymer films. A bump inside the adapter enabled a reliable electrical connection by increasing the contact pressure between the contact pads of the adapter and the inserted cable. After connection, the adapter is enclosed in a metal case sealed with silicone elastomer packing. With different sizes of the packings, leakage current tests were performed under accelerated conditions to determine the optimal design for long-term reliability. Repeated connection tests were performed to verify the durability and reconnectability of the fabricated connector. The connector was implanted in rats, and the leakage currents were monitored to evaluate the stability of the connectorin vivo. Main results. The fabricated four- and eight-channel implantable connectors, assembled with the metal cases, had a diameter and length of 6 and 17 mm, respectively. Further, the contact resistances of the four- and eight-channel connectors were 53.2 and 75.2 mΩ, respectively. The electrical contact remained stable during repeated connection tests (50 times). The fabricated connectors with packings having 125%, 137%, and 150% volume ratios to the internal space of the metal case failed after 14, 88, and 14 d, respectively, in a 75 °C saline environment. In animal tests with rats, the connector maintained low leakage current levels for up to 92 d.Significance. An implantable and reconnectable multichannel connector was developed and evaluated. The feasibility of the proposed connector was evaluated in terms of electrical and mechanical characteristics as well as sealing performance. The proposed connector is expected to have potential applications in implantable neural prosthetic systems.
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Affiliation(s)
- Gwang Jin Choi
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Hyun Ji Yoo
- Department of Electronic and Electrical Engineering, Ewha Womans University, Seoul, Republic of Korea
| | - YoonKyung Cho
- Department of Electronic and Electrical Engineering, Ewha Womans University, Seoul, Republic of Korea
| | - Shinyong Shim
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Seunghyeon Yun
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Jaehoon Sung
- Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, United States of America (On a leave of absence)
| | - Yoonseob Lim
- Center for Intelligent and Interactive Robotics, Korea Institute of Science and Technology, Seoul, Republic of Korea.,Department of HY-KIST Bio-convergence, Hanyang University, Seoul, Republic of Korea
| | - Sang Beom Jun
- Department of Electronic and Electrical Engineering, Ewha Womans University, Seoul, Republic of Korea.,Graduate Program in Smart Factory, Ewha Womans University, Seoul, Republic of Korea.,Division of Brain and Cognitive Sciences, Ewha Womans University, Seoul, Republic of Korea
| | - Sung June Kim
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
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16
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Liang I, Spencer B, Scheller M, Proulx MJ, Petrini K. Assessing people with visual impairments’ access to information, awareness and satisfaction with high-tech assistive technology. BRITISH JOURNAL OF VISUAL IMPAIRMENT 2022. [DOI: 10.1177/02646196221131746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Assistive technology (AT) devices are designed to help people with visual impairments (PVIs) perform activities that would otherwise be difficult or impossible. Devices specifically designed to assist PVIs by attempting to restore sight or substitute it for another sense have a very low uptake rate. This study, conducted in England, aimed to investigate why this is the case by assessing accessibility to knowledge, awareness, and satisfaction with AT in general and with sensory restoration and substitution devices in particular. From a sample of 25 PVIs, ranging from 21 to 68 years old, results showed that participants knew where to find AT information; however, health care providers were not the main source of this information. Participants reported good awareness of different ATs, and of technologies they would not use, but reported poor awareness of specific sensory substitution and restoration devices. Only three participants reported using AT, each with different devices and varying levels of satisfaction. The results from this study suggest a possible breakdown in communication between health care providers and PVIs, and dissociation between reported AT awareness and reported access to AT information. Moreover, awareness of sensory restoration and substitution devices is poor, which may explain the limited use of such technology.
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17
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Muqit MMK, Mer YL, Holz FG, Sahel JA. Long-term observations of macular thickness after subretinal implantation of a photovoltaic prosthesis in patients with atrophic age-related macular degeneration. J Neural Eng 2022; 19:10.1088/1741-2552/ac9645. [PMID: 36174540 PMCID: PMC9684097 DOI: 10.1088/1741-2552/ac9645] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 09/29/2022] [Indexed: 11/12/2022]
Abstract
Objective. Subretinal prostheses electrically stimulate the residual inner retinal neurons to partially restore vision. We investigated the changes in neurosensory macular structures and it is thickness associated with subretinal implantation in geographic atrophy (GA) secondary to age-related macular degeneration (AMD).Approach. Using optical coherence tomography, changes in distance between electrodes and retinal inner nuclear layer (INL) as well as alterations in thickness of retinal layers were measured over time above and near the subretinal chip implanted within the atrophic area. Retinal thickness (RT) was quantified across the implant surface and edges as well as outside the implant zone to compare with the natural macular changes following subretinal surgery, and the natural course of dry AMD.Main results. GA was defined based on complete retinal pigment epithelium and outer retinal atrophy (cRORA). Based on the analysis of three patients with subretinal implantation, we found that the distance between the implant and the target cells was stable over the long-term follow-up. Total RT above the implant decreased on average, by 39 ± 12µm during 3 months post-implantation, but no significant changes were observed after that, up to 36 months of the follow-up. RT also changed near the temporal entry point areas outside the implantation zone following the surgical trauma of retinal detachment. There was no change in the macula cRORA nasal to the implanted zone, where there was no surgical trauma or manipulation.Significance. The surgical delivery of the photovoltaic subretinal implant causes minor RT changes that settle after 3 months, and then remain stable over long-term with no adverse structural or functional effects. Distance between the implant and the INL remains stable up to 36 months of the follow-up.
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Affiliation(s)
- Mahiul M K Muqit
- Vitreoretinal Service, Moorfields Eye Hospital, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Yannick Le Mer
- Department of Ophthalmology, Fondation Ophtalmologique A. de Rothschild, Paris, France
| | - Frank G Holz
- University of Bonn, Department of Ophthalmology, Bonn, Germany
| | - José A Sahel
- Department of Ophthalmology, Fondation Ophtalmologique A. de Rothschild, Paris, France
- Clinical Investigation Center INSERM-DGOS 1423, Quinze-Vingts National Eye Hospital, Paris, France
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States of America
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18
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Vu QA, Seo HW, Choi KE, Kim N, Kang YN, Lee J, Park SH, Kim JT, Kim S, Kim SW. Structural changes in the retina after implantation of subretinal three-dimensional implants in mini pigs. Front Neurosci 2022; 16:1010445. [PMID: 36248640 PMCID: PMC9561346 DOI: 10.3389/fnins.2022.1010445] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 09/16/2022] [Indexed: 11/30/2022] Open
Abstract
The retinal structural changes after subretinal implantation of three-dimensional (3D) microelectrodes were investigated in a mini pig. Three types of electrode were implanted into the subretinal spaces of nine mini pigs: 75-μm-high 3D electrodes on a 200-μm-thick right-angled polydimethylsiloxane (PDMS) substrate (group 1); a 140-μm-thick sloped PDMS substrate without electrodes (group 2); and a 140-μm-thick sloped PDMS substrate with 20-μm-high 3D electrodes (group 3). One mini pig was used as a control. Spectral domain–optical coherence tomography (SD–OCT) images were obtained at baseline and 2, 6, and 12 weeks post-surgery. Retinal specimens were immunostained using a tissue-clearing method 3 months post-implantation. The 75-μm-high 3D electrodes progressively penetrated the inner nuclear layer (INL) and touched the inner plexiform layer (IPL) 2 weeks post-surgery. At 6 weeks post-operatively, the electrodes were in contact with the nerve-fiber layer, accompanied by a severe fibrous reaction. In the other groups, the implants remained in place without subretinal migration. Immunostaining showed that retinal ganglion and bipolar cells were preserved without fibrosis over the retinal implants in groups 2 and 3 during the 12-week implantation period. In summary, SD–OCT and immunohistology results showed differences in the extent of reactions, such as fibrosis over the implants and penetration of the electrodes into the inner retinal layer depending on different types of electrodes. A sloped substrate performed better than a right-angled substrate in terms of retinal preservation over the implanted electrodes. The 20-μm-high electrodes showed better structural compatibility than the 75-μm-high 3D electrodes. There was no significant difference between the results of sloped implants without electrodes and 20-μm-high 3D electrodes, indicating that the latter had no adverse effects on retinal tissue.
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Affiliation(s)
- Que Anh Vu
- Department of Ophthalmology, Korea University School of Medicine, Seoul, South Korea
- Department of Ophthalmology, Hanoi Medical University, Hanoi, Vietnam
| | - Hee Won Seo
- Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
| | - Kwang-Eon Choi
- Department of Ophthalmology, Korea University School of Medicine, Seoul, South Korea
| | - Namju Kim
- Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
| | - Yoo Na Kang
- Department of Medical Assistant Robot, Korea Institute of Machinery and Materials (KIMM), Daegu, South Korea
| | - Jaemeun Lee
- R&D Center for Advanced Pharmaceuticals and Evaluation, Korea Institute of Toxicology, Daejeon, South Korea
| | - Sun-Hyun Park
- R&D Center for Advanced Pharmaceuticals and Evaluation, Korea Institute of Toxicology, Daejeon, South Korea
| | - Jee Taek Kim
- Department of Ophthalmology, Chung-Ang University College of Medicine, Seoul, South Korea
| | - Sohee Kim
- Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
- *Correspondence: Sohee Kim,
| | - Seong-Woo Kim
- Department of Ophthalmology, Korea University School of Medicine, Seoul, South Korea
- Seong-Woo Kim,
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Nadvar N, Stiles N, Choupan J, Patel V, Ameri H, Shi Y, Liu Z, Jonides J, Weiland J. Sight restoration reverses blindness-induced cross-modal functional connectivity changes between the visual and somatosensory cortex at rest. Front Neurosci 2022; 16:902866. [PMID: 36213743 PMCID: PMC9539921 DOI: 10.3389/fnins.2022.902866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 08/29/2022] [Indexed: 11/28/2022] Open
Abstract
Resting-state functional connectivity (rsFC) has been used to assess the effect of vision loss on brain plasticity. With the emergence of vision restoration therapies, rsFC analysis provides a means to assess the functional changes following sight restoration. Our study demonstrates a partial reversal of blindness-induced rsFC changes in Argus II retinal prosthesis patients compared to those with severe retinitis pigmentosa (RP). For 10 healthy control (HC), 10 RP, and 7 Argus II subjects, four runs of resting-state functional magnetic resonance imaging (fMRI) per subject were included in our study. rsFC maps were created with the primary visual cortex (V1) as the seed. The rsFC group contrast maps for RP > HC, Argus II > RP, and Argus II > HC revealed regions in the post-central gyrus (PostCG) with significant reduction, significant enhancement, and no significant changes in rsFC to V1 for the three contrasts, respectively. These findings were also confirmed by the respective V1-PostCG ROI-ROI analyses between test groups. Finally, the extent of significant rsFC to V1 in the PostCG region was 5,961 in HC, 0 in RP, and 842 mm3 in Argus II groups. Our results showed a reduction of visual-somatosensory rsFC following blindness, consistent with previous findings. This connectivity was enhanced following sight recovery with Argus II, representing a reversal of changes in cross-modal functional plasticity as manifested during rest, despite the rudimentary vision obtained by Argus II patients. Future investigation with a larger number of test subjects into this rare condition can further unveil the profound ability of our brain to reorganize in response to vision restoration.
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Affiliation(s)
- Negin Nadvar
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
| | - Noelle Stiles
- Laboratory of Neuro Imaging, USC Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, United States
| | - Jeiran Choupan
- Laboratory of Neuro Imaging, USC Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, United States
| | - Vivek Patel
- Irvine School of Medicine, The University of California, Irvine, Irvine, CA, United States
| | - Hossein Ameri
- Laboratory of Neuro Imaging, USC Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, United States
| | - Yonggang Shi
- Laboratory of Neuro Imaging, USC Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, United States
| | - Zhongming Liu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, United States
| | - John Jonides
- Department of Psychology, University of Michigan, Ann Arbor, MI, United States
| | - James Weiland
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI, United States
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20
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Haq W, Basavaraju S, Speck A, Zrenner E. Nature-inspired saccadic-like electrical stimulation paradigm promotes sustained retinal ganglion cell responses by spatiotemporally alternating activation of contiguous multi-electrode patterns. J Neural Eng 2022; 19. [PMID: 36066085 DOI: 10.1088/1741-2552/ac8ad0] [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: 03/25/2022] [Accepted: 08/18/2022] [Indexed: 11/12/2022]
Abstract
Objective. Retinal electrical stimulation using multi-electrode arrays (MEAs) aims to restore visual object perception in blind patients. However, the rate and duration of the artificial visual sensations are limited due to the rapid response decay of the stimulated neurons. Hence, we investigated a novel nature-inspired saccadic-like stimulation paradigm (biomimetic) to evoke sustained retinal responses. For implementation, the macroelectrode was replaced by several contiguous microelectrodes and activated non-simultaneously but alternating topologically.Approach.MEAs with hexagonally arranged electrodes were utilized to simulate and record mouse retinal ganglion cells (RGCs). Two shapes were presented electrically using MEAs: a 6e-hexagon (six hexagonally arranged 10µm electrodes; 6e-hexagon diameter: 80µm) and a double-bar (180µm spaced, 320µm in length). Electrodes of each shape were activated in three different modes (simultaneous, circular, and biomimetic ('zig-zag')), stimulating at different frequencies (1-20 Hz).Main results.The biomimetic stimulation generated enhanced RGC responses increasing the activity rate by 87.78%. In the spatiotemporal context, the electrical representation of the 6e-hexagon produced sustained and local RGC responses (∼130µm corresponding to ∼2.5° of the human visual angle) for up to 90 s at 10 Hz stimulation and resolved the electrically presented double-bar. In contrast, during conventional simultaneous stimulation, the responses were poor and declined within seconds. Similarly, the applicability of the biomimetic mode for retinal implants (7 × 8 pixels) was successfully demonstrated. An object shape impersonating a smile was presented electrically, and the recorded data were used to emulate the implant's performance. The spatiotemporal pixel mapping of the activity produced a complete retinal image of the smile.Significance.The application of electrical stimulation in the biomimetic mode produced locally enhanced RGC responses with significantly reduced fading effects and yielded advanced spatiotemporal performance reflecting the presented electrode shapes in the mapped activity imprint. Therefore, it is likely that the RGC responses persist long enough to evoke visual perception and generate a seamless image, taking advantage of the flicker fusion. Hence, replacing the implant's macroelectrodes with microelectrodes and their activation in a topologically alternating biomimetic fashion may overcome the patient's perceptual image fading, thereby enhancing the spatiotemporal characteristics of artificial vision.
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Affiliation(s)
- Wadood Haq
- Neuroretinal Electrophysiology and Imaging, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 5-7, D-72076 Tübingen, Germany
| | - Sunetra Basavaraju
- Neuroretinal Electrophysiology and Imaging, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 5-7, D-72076 Tübingen, Germany
| | - Achim Speck
- Neuroretinal Electrophysiology and Imaging, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 5-7, D-72076 Tübingen, Germany
| | - Eberhart Zrenner
- Neuroretinal Electrophysiology and Imaging, Centre for Ophthalmology, Institute for Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Str. 5-7, D-72076 Tübingen, Germany
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Wang J, Zhao R, Li P, Fang Z, Li Q, Han Y, Zhou R, Zhang Y. Clinical Progress and Optimization of Information Processing in Artificial Visual Prostheses. SENSORS (BASEL, SWITZERLAND) 2022; 22:6544. [PMID: 36081002 PMCID: PMC9460383 DOI: 10.3390/s22176544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 08/22/2022] [Accepted: 08/26/2022] [Indexed: 06/15/2023]
Abstract
Visual prostheses, used to assist in restoring functional vision to the visually impaired, convert captured external images into corresponding electrical stimulation patterns that are stimulated by implanted microelectrodes to induce phosphenes and eventually visual perception. Detecting and providing useful visual information to the prosthesis wearer under limited artificial vision has been an important concern in the field of visual prosthesis. Along with the development of prosthetic device design and stimulus encoding methods, researchers have explored the possibility of the application of computer vision by simulating visual perception under prosthetic vision. Effective image processing in computer vision is performed to optimize artificial visual information and improve the ability to restore various important visual functions in implant recipients, allowing them to better achieve their daily demands. This paper first reviews the recent clinical implantation of different types of visual prostheses, summarizes the artificial visual perception of implant recipients, and especially focuses on its irregularities, such as dropout and distorted phosphenes. Then, the important aspects of computer vision in the optimization of visual information processing are reviewed, and the possibilities and shortcomings of these solutions are discussed. Ultimately, the development direction and emphasis issues for improving the performance of visual prosthesis devices are summarized.
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Affiliation(s)
- Jing Wang
- School of Information, Shanghai Ocean University, Shanghai 201306, China
- Key Laboratory of Fishery Information, Ministry of Agriculture, Shanghai 200335, China
| | - Rongfeng Zhao
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Peitong Li
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Zhiqiang Fang
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Qianqian Li
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Yanling Han
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Ruyan Zhou
- School of Information, Shanghai Ocean University, Shanghai 201306, China
| | - Yun Zhang
- School of Information, Shanghai Ocean University, Shanghai 201306, China
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22
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Li W, Haji Ghaffari D, Misra R, Weiland JD. Retinal ganglion cell desensitization is mitigated by varying parameter constant excitation pulse trains. Front Cell Neurosci 2022; 16:897146. [PMID: 36035262 PMCID: PMC9407683 DOI: 10.3389/fncel.2022.897146] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 07/15/2022] [Indexed: 11/20/2022] Open
Abstract
Retinal prostheses partially restore vision in patients blinded by retinitis pigmentosa (RP) and age-related macular degeneration (AMD). One issue that limits the effectiveness of retinal stimulation is the desensitization of the retina response to repeated pulses. Rapid fading of percepts is reported in clinical studies. We studied the retinal output evoked by fixed pulse trains vs. pulse trains that have variable parameters pulse-to-pulse. We used the current clamp to record RGC spiking in the isolated mouse retina. Trains of biphasic current pulses at different frequencies and amplitudes were applied. The main results we report are: (1) RGC desensitization was induced by increasing stimulus frequency, but was unrelated to stimulus amplitude. Desensitization persisted when the 20 Hz stimulation pulses were applied to the retinal ganglion cells at 65 μA, 85 μA, and 105 μA. Subsequent pulses in the train evoked fewer spikes. There was no obvious desensitization when 2 Hz stimulation pulse trains were applied. (2) Blocking inhibitory GABAA receptor increased spontaneous activity but did not reduce desensitization. (3) Pulse trains with constant charge or excitation (based on strength-duration curves) but varying pulse width, amplitude, and shape increased the number of evoked spikes/pulse throughout the pulse train. This suggests that retinal desensitization can be partially overcome by introducing variability into each pulse.
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Affiliation(s)
- Wennan Li
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
| | - Dorsa Haji Ghaffari
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
| | - Rohit Misra
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
| | - James D. Weiland
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI, United States
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States
- *Correspondence: James D. Weiland
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23
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Kim S, Roh H, Im M. Artificial Visual Information Produced by Retinal Prostheses. Front Cell Neurosci 2022; 16:911754. [PMID: 35734216 PMCID: PMC9208577 DOI: 10.3389/fncel.2022.911754] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Accepted: 05/18/2022] [Indexed: 11/18/2022] Open
Abstract
Numerous retinal prosthetic systems have demonstrated somewhat useful vision can be restored to individuals who had lost their sight due to outer retinal degenerative diseases. Earlier prosthetic studies have mostly focused on the confinement of electrical stimulation for improved spatial resolution and/or the biased stimulation of specific retinal ganglion cell (RGC) types for selective activation of retinal ON/OFF pathway for enhanced visual percepts. To better replicate normal vision, it would be also crucial to consider information transmission by spiking activities arising in the RGC population since an incredible amount of visual information is transferred from the eye to the brain. In previous studies, however, it has not been well explored how much artificial visual information is created in response to electrical stimuli delivered by microelectrodes. In the present work, we discuss the importance of the neural information for high-quality artificial vision. First, we summarize the previous literatures which have computed information transmission rates from spiking activities of RGCs in response to visual stimuli. Second, we exemplify a couple of studies which computed the neural information from electrically evoked responses. Third, we briefly introduce how information rates can be computed in the representative two ways - direct method and reconstruction method. Fourth, we introduce in silico approaches modeling artificial retinal neural networks to explore the relationship between amount of information and the spiking patterns. Lastly, we conclude our review with clinical implications to emphasize the necessity of considering visual information transmission for further improvement of retinal prosthetics.
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Affiliation(s)
- Sein Kim
- Brain Science Institute, Korea Institute of Science and Technology, Seoul, South Korea
| | - Hyeonhee Roh
- Brain Science Institute, Korea Institute of Science and Technology, Seoul, South Korea
- School of Electrical Engineering, College of Engineering, Korea University, Seoul, South Korea
| | - Maesoon Im
- Brain Science Institute, Korea Institute of Science and Technology, Seoul, South Korea
- Division of Bio-Medical Science & Technology, KIST School, University of Science and Technology, Seoul, South Korea
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24
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Christie B, Sadeghi R, Kartha A, Caspi A, Tenore FV, Klatzky RL, Dagnelie G, Billings S. Sequential epiretinal stimulation improves discrimination in simple shape discrimination tasks only. J Neural Eng 2022; 19. [PMID: 35613043 DOI: 10.1088/1741-2552/ac7326] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 05/24/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Electrical stimulation of the retina can elicit flashes of light called phosphenes, which can be used to restore rudimentary vision for people with blindness. Functional sight requires stimulation of multiple electrodes to create patterned vision, but phosphenes tend to merge together in an uninterpretable way. Sequentially stimulating electrodes in human visual cortex has recently demonstrated that shapes could be "drawn" with better perceptual resolution relative to simultaneous stimulation. The goal of this study was to evaluate if sequential stimulation would also form clearer shapes when the retina is the neural target. APPROACH Two human participants with retinitis pigmentosa who had Argus® II retinal prostheses participated in this study. We evaluated different temporal parameters for sequential stimulation in phosphene shape mapping and forced-choice discrimination tasks. For the discrimination tasks, performance was compared between stimulating electrodes simultaneously versus sequentially. MAIN RESULTS Phosphenes elicited by different electrodes were reported as vastly different shapes. Sequential electrode stimulation outperformed simultaneous stimulation in simple discrimination tasks, in which shapes were created by stimulating 3-4 electrodes, but not in more complex discrimination tasks involving 5+ electrodes. For sequential stimulation, the optimal pulse train duration was 200 ms when stimulating at 20 Hz and the optimal gap interval was tied between 0 and 50 ms. Efficacy of sequential stimulation also depended strongly on selecting electrodes that elicited phosphenes with similar shapes and sizes. SIGNIFICANCE An epiretinal prosthesis can produce coherent simple shapes with a sequential stimulation paradigm, which can be used as rudimentary visual feedback. However, success in creating more complex shapes, such as letters of the alphabet, is still limited. Sequential stimulation may be most beneficial for epiretinal prostheses in simple tasks, such as basic navigation, rather than complex tasks such as object identification.
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Affiliation(s)
- Breanne Christie
- Research and Exploratory Development Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland, 20723, UNITED STATES
| | - Roksana Sadeghi
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, 733 N Broadway, Baltimore, Maryland, 21205, UNITED STATES
| | - Arathy Kartha
- Department of Ophthalmology, Johns Hopkins School of Medicine, 1800 Orleans St., Baltimore, Maryland, 21287, UNITED STATES
| | - Avi Caspi
- Jerusalem College of Technology, Ha-Va'ad ha-Le'umi St 21, Jerusalem, 91160, ISRAEL
| | - Francesco V Tenore
- Research and Exploratory Development Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland, 20723, UNITED STATES
| | - Roberta L Klatzky
- Department of Psychology, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, Pennsylvania, 15213-3815, UNITED STATES
| | - Gislin Dagnelie
- Department of Ophthalmology, Johns Hopkins School of Medicine, 1800 Orleans St., Baltimore, Maryland, 21287, UNITED STATES
| | - Seth Billings
- Research and Exploratory Development Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland, 20723-6005, UNITED STATES
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Ahn J, Cha S, Choi KE, Kim SW, Yoo Y, Goo YS. Correlated Activity in the Degenerate Retina Inhibits Focal Response to Electrical Stimulation. Front Cell Neurosci 2022; 16:889663. [PMID: 35602554 PMCID: PMC9114441 DOI: 10.3389/fncel.2022.889663] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 04/13/2022] [Indexed: 11/24/2022] Open
Abstract
Retinal prostheses have shown some clinical success in patients with retinitis pigmentosa and age-related macular degeneration. However, even after the implantation of a retinal prosthesis, the patient’s visual acuity is at best less than 20/420. Reduced visual acuity may be explained by a decrease in the signal-to-noise ratio due to the spontaneous hyperactivity of retinal ganglion cells (RGCs) found in degenerate retinas. Unfortunately, abnormal retinal rewiring, commonly observed in degenerate retinas, has rarely been considered for the development of retinal prostheses. The purpose of this study was to investigate the aberrant retinal network response to electrical stimulation in terms of the spatial distribution of the electrically evoked RGC population. An 8 × 8 multielectrode array was used to measure the spiking activity of the RGC population. RGC spikes were recorded in wild-type [C57BL/6J; P56 (postnatal day 56)], rd1 (P56), rd10 (P14 and P56) mice, and macaque [wild-type and drug-induced retinal degeneration (RD) model] retinas. First, we performed a spike correlation analysis between RGCs to determine RGC connectivity. No correlation was observed between RGCs in the control group, including wild-type mice, rd10 P14 mice, and wild-type macaque retinas. In contrast, for the RD group, including rd1, rd10 P56, and RD macaque retinas, RGCs, up to approximately 400–600 μm apart, were significantly correlated. Moreover, to investigate the RGC population response to electrical stimulation, the number of electrically evoked RGC spikes was measured as a function of the distance between the stimulation and recording electrodes. With an increase in the interelectrode distance, the number of electrically evoked RGC spikes decreased exponentially in the control group. In contrast, electrically evoked RGC spikes were observed throughout the retina in the RD group, regardless of the inter-electrode distance. Taken together, in the degenerate retina, a more strongly coupled retinal network resulted in the widespread distribution of electrically evoked RGC spikes. This finding could explain the low-resolution vision in prosthesis-implanted patients.
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Affiliation(s)
- Jungryul Ahn
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, South Korea
| | - Seongkwang Cha
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, South Korea
| | - Kwang-Eon Choi
- Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea
| | - Seong-Woo Kim
- Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea
- *Correspondence: Seong-Woo Kim,
| | - Yongseok Yoo
- Department of Electronics Engineering, Incheon National University, Incheon, South Korea
- Yongseok Yoo,
| | - Yong Sook Goo
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, South Korea
- Yong Sook Goo,
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26
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Su X, Zhou M, Di L, Chen J, Zhai Z, Liang J, Li L, Li H, Chai X. The Visual Cortical Responses to Sinusoidal Transcorneal Electrical Stimulation. Brain Res 2022; 1785:147875. [PMID: 35271821 DOI: 10.1016/j.brainres.2022.147875] [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: 11/08/2021] [Revised: 03/04/2022] [Accepted: 03/05/2022] [Indexed: 11/25/2022]
Abstract
Retinal stimulation has become a widely utilized approach to restore visual function for individuals with retinal degenerative diseases. Although the rectangular electrical pulse is the primary stimulus waveform used in retinal neuromodulation, it remains unclear whether alternate waveforms may be more effective. Here, we used the optical intrinsic signal imaging system to assess the responses of cats' visual cortex to sinusoidal electrical stimulation through contact lens electrode, analyzing the response to various stimulus parameters (frequency, intensity, pulse width). A comparison between sinusoidal and rectangular stimulus waveform was also investigated. The results indicated that the optimal stimulation frequency for sinusoidal electrical stimulation was approximately 20 Hz, supporting the hypothesis that low-frequency electrostimulation induces more responsiveness in retinal neurons than high-frequency electrostimulation in case of sinusoidal stimulation. We also demonstrated that for low-frequency retinal neuromodulation, sinusoidal pulses are more effective than rectangular ones. In addition, we found that compared to current intensity, the effect of the sinusoidal pulse width on cortical responses was more prominent. These results suggested that sinusoidal electrical stimulation may provide a promising strategy for improved retinal neuromodulation in clinical settings.
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Affiliation(s)
- Xiaofan Su
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Meixuan Zhou
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Liqing Di
- Department of Orthopedics, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China
| | - Jianpin Chen
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Zhenzhen Zhai
- The Network & Information Center, Shanghai Jiao Tong University, Shanghai, China
| | - Junling Liang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Liming Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Heng Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Xinyu Chai
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
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27
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Thorn JT, Chenais NAL, Hinrichs S, Chatelain M, Ghezzi D. Virtual reality validation of naturalistic modulation strategies to counteract fading in retinal stimulation. J Neural Eng 2022; 19. [PMID: 35240583 DOI: 10.1088/1741-2552/ac5a5c] [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: 11/10/2021] [Accepted: 03/03/2022] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Temporal resolution is a key challenge in artificial vision. Several prosthetic approaches are limited by the perceptual fading of evoked phosphenes upon repeated stimulation from the same electrode. Therefore, implanted patients are forced to perform active scanning, via head movements, to refresh the visual field viewed by the camera. However, active scanning is a draining task, and it is crucial to find compensatory strategies to reduce it. APPROACH To address this question, we implemented perceptual fading in simulated prosthetic vision using virtual reality. Then, we quantified the effect of fading on two indicators: the time to complete a reading task and the head rotation during the task. We also tested if stimulation strategies previously proposed to increase the persistence of responses in retinal ganglion cells to electrical stimulation could improve these indicators. MAIN RESULTS This study shows that stimulation strategies based on interrupted pulse trains and randomisation of the pulse duration allows significant reduction of both the time to complete the task and the head rotation during the task. SIGNIFICANCE The stimulation strategy used in retinal implants is crucial to counteract perceptual fading and to reduce active head scanning during prosthetic vision. In turn, less active scanning might improve the patient's comfort in artificial vision.
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Affiliation(s)
- Jacob Thomas Thorn
- Neuroengineering, EPFL STI, Chemin des Mines 9, Geneva, 1202, SWITZERLAND
| | | | - Sandrine Hinrichs
- École Polytechnique Fédérale de Lausanne, Chemin des Mines 9, Geneva, 1202, SWITZERLAND
| | - Marion Chatelain
- École Polytechnique Fédérale de Lausanne, Chemin des Mines 9, Geneva, 1202, SWITZERLAND
| | - Diego Ghezzi
- Medtronic Chair in Neuroengineering, Ecole Polytechnique Federale de Lausanne, EPFL STI IBI LNE, Lausanne, 1015, SWITZERLAND
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28
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Kasowski J, Beyeler M. Immersive Virtual Reality Simulations of Bionic Vision. AUGMENTED HUMANS 2022 2022; 2022:82-93. [PMID: 35856703 PMCID: PMC9289996 DOI: 10.1145/3519391.3522752] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Bionic vision uses neuroprostheses to restore useful vision to people living with incurable blindness. However, a major outstanding challenge is predicting what people "see" when they use their devices. The limited field of view of current devices necessitates head movements to scan the scene, which is difficult to simulate on a computer screen. In addition, many computational models of bionic vision lack biological realism. To address these challenges, we present VR-SPV, an open-source virtual reality toolbox for simulated prosthetic vision that uses a psychophysically validated computational model to allow sighted participants to "see through the eyes" of a bionic eye user. To demonstrate its utility, we systematically evaluated how clinically reported visual distortions affect performance in a letter recognition and an immersive obstacle avoidance task. Our results highlight the importance of using an appropriate phosphene model when predicting visual outcomes for bionic vision.
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29
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Cha S, Choi KE, Ahn J, Yoo M, Jeong Y, Kim SW, Goo YS. Electrical response of retinal ganglion cells in an N-methyl-N-nitrosourea-induced retinal degeneration porcine model. Sci Rep 2021; 11:24135. [PMID: 34921172 PMCID: PMC8683404 DOI: 10.1038/s41598-021-03439-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 12/02/2021] [Indexed: 12/28/2022] Open
Abstract
Retinal prosthesis is regarded as the treatment for vision restoration in the blind with retinal degeneration (RD) due to the loss of photoreceptors. A strategy for retinal prosthesis is to electrically activate surviving neurons. The retina’s response to electrical stimulation in a larger RD model has not been studied yet. Therefore, in this study, we investigated electrically evoked retinal responses in a previously validated N-methyl-N-nitrosourea (MNU)-induced porcine RD model. Electrically evoked responses were evaluated based on the number of retinal ganglion cell (RGC) spikes via multichannel recordings. Stimulation pulses were applied to degenerative and wild-type retinas with pulse modulation. Compared to wild-type retinas, degenerative retinas showed higher threshold values of pulse amplitude and pulse duration. The rate of increase in the number of RGC spikes relative to stimulus intensity was lower in degenerative retinas than in normal retinas. In severely degenerated retinas, few RGCs showed electrically evoked spikes. Our results suggest that the degenerative porcine retina requires a higher charge than the normal porcine retina. In the early stage of RD, it is easier to induce RGC spikes through electrical stimulation using retinal prosthesis; however, when the degeneration is severe, there may be difficulty recovering patient vision.
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Affiliation(s)
- Seongkwang Cha
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, 28644, Korea
| | - Kwang-Eon Choi
- Department of Ophthalmology, Korea University College of Medicine, Seoul, 08308, Korea
| | - Jungryul Ahn
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, 28644, Korea
| | - Minsu Yoo
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, 28644, Korea
| | - Yurim Jeong
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, 28644, Korea
| | - Seong-Woo Kim
- Department of Ophthalmology, Korea University College of Medicine, Seoul, 08308, Korea.
| | - Yong Sook Goo
- Department of Physiology, Chungbuk National University School of Medicine, Cheongju, 28644, Korea.
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30
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Otgondemberel Y, Roh H, Fried SI, Im M. Spiking Characteristics of Network-Mediated Responses Arising in Direction-Selective Ganglion Cells of Rabbit and Mouse Retinas to Electric Stimulation for Retinal Prostheses. IEEE Trans Neural Syst Rehabil Eng 2021; 29:2445-2455. [PMID: 34784280 PMCID: PMC8654582 DOI: 10.1109/tnsre.2021.3128878] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To restore the sight of individuals blinded by outer retinal degeneration, numerous retinal prostheses have been developed. However, the performance of those implants is still hampered by some factors including the lack of comprehensive understanding of the electrically-evoked responses arising in various retinal ganglion cell (RGC) types. In this study, we characterized the electrically-evoked network-mediated responses (hereafter referred to as electric responses) of ON-OFF direction-selective (DS) RGCs in rabbit and mouse retinas for the first time. Interestingly, both species in common demonstrated strong negative correlations between spike counts of electric responses and direction selective indices (DSIs), suggesting electric stimulation activates inhibitory presynaptic neurons that suppress null direction responses for high direction tuning in their light responses. The DS cells of the two species showed several differences including different numbers of bursts. Also, spiking patterns were more heterogeneous across DS RGCs of rabbits than those of mice. The electric response magnitudes of rabbit DS cells showed positive and negative correlations with ON and OFF light response magnitudes to preferred direction motion, respectively. But the mouse DS cells showed positive correlations in both comparisons. Our Fano Factor (FF) and spike time tiling coefficient (STTC) analyses revealed that spiking consistencies across repeats were reduced in late electric responses in both species. Moreover, the response consistencies of DS RGCs were lower than those of non-DS RGCs. Our results indicate the species-dependent retinal circuits may result in different electric response features and therefore suggest a proper animal model may be crucial in prosthetic researches.
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31
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Granley J, Beyeler M. A Computational Model of Phosphene Appearance for Epiretinal Prostheses. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:4477-4481. [PMID: 34892213 PMCID: PMC9255280 DOI: 10.1109/embc46164.2021.9629663] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Retinal neuroprostheses are the only FDA-approved treatment option for blinding degenerative diseases. A major outstanding challenge is to develop a computational model that can accurately predict the elicited visual percepts (phosphenes) across a wide range of electrical stimuli. Here we present a phenomenological model that predicts phosphene appearance as a function of stimulus amplitude, frequency, and pulse duration. The model uses a simulated map of nerve fiber bundles in the retina to produce phosphenes with accurate brightness, size, orientation, and elongation. We validate the model on psychophysical data from two independent studies, showing that it generalizes well to new data, even with different stimuli and on different electrodes. Whereas previous models focused on either spatial or temporal aspects of the elicited phosphenes in isolation, we describe a more comprehensive approach that is able to account for many reported visual effects. The model is designed to be flexible and extensible, and can be fit to data from a specific user. Overall this work is an important first step towards predicting visual outcomes in retinal prosthesis users across a wide range of stimuli.
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32
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Wang L, Marek N, Steffen J, Pollmann S. Perceptual Learning of Object Recognition in Simulated Retinal Implant Perception - The Effect of Video Training. Transl Vis Sci Technol 2021; 10:22. [PMID: 34661623 PMCID: PMC8525839 DOI: 10.1167/tvst.10.12.22] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Retinal implants (RIs) provide new vision for patients suffering from photoreceptor degeneration in the retina. The limited vision gained by RI, however, leaves room for improvement by training regimes. Methods Two groups of normal-sighted participants were respectively trained with videos or still images of daily objects in a labeling task. Object appearance was simulated to resemble RI perception. In Experiment 1, the training effect was measured as the change in performance during the training, and the same labeling task was conducted after 1 week to test the retention. In Experiment 2 with a different pool of participants, a reverse labeling task was included before (pre-test) and after the training (post-test) to show if the training effect could be generalized into a different task context. Results Both groups showed improved object recognition through training that was maintained for a week, and the video group showed better improvement (Experiment 1). Both groups showed improved object recognition in a different task that was maintained for a week, but the video group did not show better retention than the image group (Experiment 2). Conclusions Training with video materials leads to more improvement than training with still images in simulated RI perception, but this better improvement was specific to the trained task. Translational Relevance We recommend videos as better training materials than still images for patients with RIs to improve object recognition when the task-goal is highly specific. We also propose here that achieving highly specific training goals runs the risk of limiting the generalization of the training effects.
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Affiliation(s)
- Lihui Wang
- Institute of Psychology and Behavioral Science, Shanghai Jiao Tong University, Shanghai, China.,Shanghai Key Laboratory of Psychotic Disorder, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Department of Psychology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany.,Center for Behavioral Brain Sciences, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Nico Marek
- Department of Psychology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Johannes Steffen
- Department of Simulation and Graphics, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Stefan Pollmann
- Department of Psychology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany.,Center for Behavioral Brain Sciences, Otto-von-Guericke University Magdeburg, Magdeburg, Germany.,Beijing Key Laboratory of Learning and Cognition and School of Psychology, Capital Normal University, Beijing, China
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33
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Abstract
Visual retinal prostheses aim to restore vision for blind individuals who suffer from outer retinal degenerative diseases, such as retinitis pigmentosa and age-related macular degeneration. Perception through retinal prostheses is very limited, but it can be improved by applying object isolation. We used an object isolation algorithm based on integral imaging to isolate objects of interest according to their depth from the camera and applied image processing manipulation to the isolated-object images. Subsequently, we applied a spatial prosthetic vision simulation that converted the isolated-object images to phosphene images. We compared the phosphene images for two types of input images, the original image (before applying object isolation), and the isolated-object image to illustrate the effects of object isolation on simulated prosthetic vision without and with multiple spatial variations of phosphenes, such as size and shape variations, spatial shifts, and dropout rate. The results show an improvement in the perceived shape, contrast, and dynamic range (number of gray levels) of objects in the phosphene image.
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34
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Agarwal R, Tripathi A. Current Modalities for Low Vision Rehabilitation. Cureus 2021; 13:e16561. [PMID: 34466307 PMCID: PMC8396411 DOI: 10.7759/cureus.16561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2021] [Indexed: 11/16/2022] Open
Abstract
Visual rehabilitation is an effective method for increasing the quality of life among individuals with low vision or blindness due to untreatable causes. Low vision rehabilitation aims for patients to use their residual vision effectively and efficiently to enable them to live independent and productive lives. Low vision rehabilitation includes assessment of residual visual functions, prescription of rehabilitation aids, and training in the use of devices. A multidisciplinary approach and coordinated effort are necessary to take advantage of new scientific advances and achieve optimal results for the patient. This article aims to review the various aids and methods available for low vision rehabilitation and also discusses technology advances that can enhance the visual functioning of individuals who are visually impaired.
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Affiliation(s)
- Richa Agarwal
- Ophthalmology, All India Institute of Medical Sciences, Gorakhpur, IND
| | - Alka Tripathi
- Ophthalmology, All India Institute of Medical Sciences, Gorakhpur, IND
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35
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Hallum LE, Dakin SC. Retinal Implantation of Electronic Vision Prostheses to Treat Retinitis Pigmentosa: A Systematic Review. Transl Vis Sci Technol 2021; 10:8. [PMID: 34383874 PMCID: PMC8362638 DOI: 10.1167/tvst.10.10.8] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Purpose Retinitis pigmentosa (RP) is a hereditary disease causing photoreceptor degeneration and permanent vision loss. Retinal implantation of a stimulating electrode array is a new treatment for RP, but quantification of its efficacy is the subject of ongoing work. This review evaluates vision-related outcomes resulting from retinal implantation in participants with RP. Methods We searched MEDLINE and Embase for journal articles published since January 1, 2015. We selected articles describing studies of implanted participants that reported the postimplantation measurement of vision. We extracted study information including design, participants’ residual vision, comparators, and assessed outcomes. To assess the risk of bias, we used signaling questions and a target trial. Results Our search returned 425 abstracts. We reviewed the full text of 34 articles. We judged all studies to be at high risk of bias owing to the study design or experimental conduct. Regarding design, studies lacked the measures that typical clinical trials take to protect against bias (e.g., control groups and masking). Regarding experimental conduct, outcome measures were rarely comparable before and after implantation, and psychophysical methods were prone to bias (subjective, not forced choice, methods). The most common comparison found was between postimplantation visual function with the device powered off versus on. This comparison is at high risk of bias. Conclusions There is a need for high-quality evidence of efficacy of retinal implantation to treat RP. Translational Relevance For patients and clinicians to make informed choices about RP treatment, visual function restored by retinal implantation must be properly quantified and reported.
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Affiliation(s)
- Luke E Hallum
- Department of Mechanical Engineering, University of Auckland, Auckland, New Zealand
| | - Steven C Dakin
- School of Optometry and Vision Science, University of Auckland, Auckland, New Zealand
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36
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Petoe MA, Titchener SA, Kolic M, Kentler WG, Abbott CJ, Nayagam DAX, Baglin EK, Kvansakul J, Barnes N, Walker JG, Epp SB, Young KA, Ayton LN, Luu CD, Allen PJ. A Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis: Interim Clinical Trial Results. Transl Vis Sci Technol 2021; 10:12. [PMID: 34581770 PMCID: PMC8479573 DOI: 10.1167/tvst.10.10.12] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To report the initial safety and efficacy results of a second-generation (44-channel) suprachoroidal retinal prosthesis at 56 weeks after device activation. Methods Four subjects, with advanced retinitis pigmentosa and bare-light perception only, enrolled in a phase II trial (NCT03406416). A 44-channel electrode array was implanted in a suprachoroidal pocket. Device stability, efficacy, and adverse events were investigated at 12-week intervals. Results All four subjects were implanted successfully and there were no device-related serious adverse events. Color fundus photography indicated a mild postoperative subretinal hemorrhage in two recipients, which cleared spontaneously within 2 weeks. Optical coherence tomography confirmed device stability and position under the macula. Screen-based localization accuracy was significantly better for all subjects with device on versus device off. Two subjects were significantly better with the device on in a motion discrimination task at 7, 15, and 30°/s and in a spatial discrimination task at 0.033 cycles per degree. All subjects were more accurate with the device on than device off at walking toward a target on a modified door task, localizing and touching tabletop objects, and detecting obstacles in an obstacle avoidance task. A positive effect of the implant on subjects' daily lives was confirmed by an orientation and mobility assessor and subject self-report. Conclusions These interim study data demonstrate that the suprachoroidal prosthesis is safe and provides significant improvements in functional vision, activities of daily living, and observer-rated quality of life. Translational Relevance A suprachoroidal prosthesis can provide clinically useful artificial vision while maintaining a safe surgical profile.
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Affiliation(s)
- Matthew A Petoe
- Bionics Institute, East Melbourne, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Melbourne, Victoria, Australia
| | - Samuel A Titchener
- Bionics Institute, East Melbourne, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Melbourne, Victoria, Australia
| | - Maria Kolic
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - William G Kentler
- Department of Biomedical Engineering, University of Melbourne, Melbourne, Victoria, Australia
| | - Carla J Abbott
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
| | - David A X Nayagam
- Bionics Institute, East Melbourne, Victoria, Australia.,Department of Pathology, University of Melbourne, St. Vincent's Hospital, Victoria, Australia
| | - Elizabeth K Baglin
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - Jessica Kvansakul
- Bionics Institute, East Melbourne, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Melbourne, Victoria, Australia
| | - Nick Barnes
- Research School of Engineering, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Janine G Walker
- Research School of Engineering, Australian National University, Canberra, Australian Capital Territory, Australia.,Health & Biosecurity, CSIRO, Canberra, Australian Capital Territory, Australia
| | | | - Kiera A Young
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - Lauren N Ayton
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia.,Department of Optometry and Vision Sciences, University of Melbourne, Australia
| | - Chi D Luu
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
| | - Penelope J Allen
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
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Park Y, Park SY, Eom K. Current Review of Optical Neural Interfaces for Clinical Applications. MICROMACHINES 2021; 12:925. [PMID: 34442547 PMCID: PMC8400671 DOI: 10.3390/mi12080925] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 07/20/2021] [Accepted: 07/29/2021] [Indexed: 11/16/2022]
Abstract
Neural interfaces, which enable the recording and stimulation of living neurons, have emerged as valuable tools in understanding the brain in health and disease, as well as serving as neural prostheses. While neural interfaces are typically based on electrical transduction, alternative energy modalities have been explored to create safe and effective approaches. Among these approaches, optical methods of linking neurons to the outside world have gained attention because light offers high spatial selectivity and decreased invasiveness. Here, we review the current state-of-art of optical neural interfaces and their clinical applications. Optical neural interfaces can be categorized into optical control and optical readout, each of which can be divided into intrinsic and extrinsic approaches. We discuss the advantages and disadvantages of each of these methods and offer a comparison of relative performance. Future directions, including their clinical opportunities, are discussed with regard to the optical properties of biological tissue.
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Affiliation(s)
| | - Sung-Yun Park
- Department of Electronics Engineering, College of Engineering, Pusan National University, Busan 46241, Korea;
| | - Kyungsik Eom
- Department of Electronics Engineering, College of Engineering, Pusan National University, Busan 46241, Korea;
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38
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Xie H, Wang Y, Ye Z, Fang S, Xu Z, Wu T, Chan LLH. Monitoring Cortical Response and Electrode-Retina Impedance Under Epiretinal Stimulation in Rats. IEEE Trans Neural Syst Rehabil Eng 2021; 29:1178-1187. [PMID: 34152987 DOI: 10.1109/tnsre.2021.3090904] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Retinal prosthesis can restore partial vision in patients with retinal degenerative diseases such as retinitis pigmentosa and age-related macular degeneration. Epiretinal prosthesis is one of three therapeutic approaches, which received regulatory approval several years ago. The thresholds of an epiretinal stimulation is partly determined by the size of the physical gap between the electrode and the retina after implantation. Precise positioning of epiretinal stimulating electrode array is still a challenging task. In this study, we demonstrate an approach to positioning epiretinal prostheses for an optimal response at the cortical output by monitoring both the impedance at the electrode-retina interface and the evoked-potential at the cortical level. We implanted a single-channel electrode on the epiretinal surface in adult rats, acutely, guided by both the impedance at the electrode-retina interface and by electrically evoked potentials (EEPs) in the visual cortex during retinal stimulation. We observe that impedance monotonously increases with decreasing electrode-retina distance, but that the strongest cortical responses were achieved at intermediate impedance levels. When the electrode penetrates the retina, the impedance keeps increasing. The effect of stimulation on the retina changes from epiretinal paradigm to intra-retinal paradigm and a decrease in cortical activation is observed. It is found that high impedance is not always favorable to elicit best cortical responses. Histopathological results showed that the electrode was placed at the intra-retinal space at high impedance value. These results show that monitoring impedance at the electrode-retina interface is necessary but not sufficient in obtaining strong evoked-potentials at the cortical level. Monitoring the cortical EEPs together with the impedance can improve the safety of implantation as well as efficacy of stimulation in the next generation of retinal implants.
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39
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Yamashita K, Tanaka T, Matsuo T, Uchida T. Development and chemical properties of retinal prostheses using photoelectric dyes coupled to polyethylene films with various anions to achieve high durability. Polym J 2021. [DOI: 10.1038/s41428-021-00468-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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40
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Mailhot N, Cheriton R, Vyas K, Cook J, Prawer S, Hinzer K, Spinello D. Eighty-Five Percent of Improved Optical Power Delivery to Epiretinal Prostheses Using Rigid Body Compensation Algorithm. J Biomech Eng 2021; 143:061009. [PMID: 33537711 DOI: 10.1115/1.4050026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Indexed: 11/08/2022]
Abstract
Vision impairment caused by degenerative retinal pathologies such as age-related macular degeneration can be treated using retinal implants. Such devices receive power and data using cables passing through a permanent surgical incision in the eye wall (sclera), which increases the risk to patients and surgical costs. A recently developed retinal implant design eliminates the necessity of the implant cable using a photonic power converter (PPC), which receives optical power and data through the pupil and is directed by an ellipsoidal reflector and micro-electromechanical mirror. We present a misalignment compensation algorithm model that accounts for rigid-body motions of the reflector relative to the eye and applies the correction to the mirror coordinates in the presence of angular misalignment of the reflector. We demonstrate that up to 85% of the nominal optical power can be delivered to the implant with axial reflector misalignments up to 30 deg using the compensation algorithm.
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Affiliation(s)
- Nathaniel Mailhot
- Department of Mechanical Engineering, University of Ottawa, Ottawa, ON K1N 6M6, Canada
| | - Ross Cheriton
- National Research Council of Canada, Ottawa, ON K1N 6M6, Canada
| | - Kaustubh Vyas
- Electrical Engineering and Computer Science, University of Ottawa, Ottawa, ON K1N 6M6, Canada
| | - John Cook
- Electrical Engineering and Computer Science, University of Ottawa, Ottawa, ON K1N 6M6, Canada
| | - Steven Prawer
- Department of Physics, University of Melbourne, Melbourne VIC 3010, Australia
| | - Karin Hinzer
- Electrical Engineering and Computer Science, University of Ottawa, Ottawa, ON K1N 6M6, Canada
| | - Davide Spinello
- Department of Mechanical Engineering, University of Ottawa, Ottawa, ON K1N 6M6, Canada
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Full gaze contingency provides better reading performance than head steering alone in a simulation of prosthetic vision. Sci Rep 2021; 11:11121. [PMID: 34045485 PMCID: PMC8160142 DOI: 10.1038/s41598-021-86996-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 03/23/2021] [Indexed: 11/08/2022] Open
Abstract
The visual pathway is retinotopically organized and sensitive to gaze position, leading us to hypothesize that subjects using visual prostheses incorporating eye position would perform better on perceptual tasks than with devices that are merely head-steered. We had sighted subjects read sentences from the MNREAD corpus through a simulation of artificial vision under conditions of full gaze compensation, and head-steered viewing. With 2000 simulated phosphenes, subjects (n = 23) were immediately able to read under full gaze compensation and were assessed at an equivalent visual acuity of 1.0 logMAR, but were nearly unable to perform the task under head-steered viewing. At the largest font size tested, 1.4 logMAR, subjects read at 59 WPM (50% of normal speed) with 100% accuracy under the full-gaze condition, but at 0.7 WPM (under 1% of normal) with below 15% accuracy under head-steering. We conclude that gaze-compensated prostheses are likely to produce considerably better patient outcomes than those not incorporating eye movements.
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Yamashita K, Sundaram P, Uchida T, Matsuo T, Wong W. Modelling the visual response to an OUReP retinal prosthesis with photoelectric dye coupled to polyethylene film. J Neural Eng 2021; 18. [PMID: 33857924 DOI: 10.1088/1741-2552/abf892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 04/15/2021] [Indexed: 11/12/2022]
Abstract
Objective.Retinal prostheses have been developed to restore vision in blind patients suffering from diseases like retinitis pigmentosa.Approach.A new type of retinal prosthesis called the Okayama University-type retinal prosthesis (OUReP) was developed by chemically coupling photoelectric dyes to a polyethylene film surface. The prosthesis works by passively generating an electric potential when stimulated by light. However, the neurophysiological mechanism of how OUReP stimulates the degenerated retina is unknown.Main results.Here, we explore how the OUReP affects retinal tissues using a finite element model to solve for the potential inside the tissue and an active Hodgkin-Huxley model based on rat vision to predict the corresponding retinal bipolar response.Significance.We show that the OUReP is likely capable of eliciting responses in retinal bipolar cells necessary to generate vision under most ambient conditions.
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Affiliation(s)
- Koichiro Yamashita
- Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-Naka, Kita-ku, Okayama 700-8530, Japan
| | - Prathima Sundaram
- Department of Electrical and Computer Engineering, University of Toronto, 40 St. George Street, Toronto, ON M5S 2E4, Canada
| | - Tetsuya Uchida
- Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-Naka, Kita-ku, Okayama 700-8530, Japan
| | - Toshihiko Matsuo
- Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, 2-5-1 Shikata-cho, Kita-ku, Okayama 700-8558, Japan
| | - Willy Wong
- Department of Electrical and Computer Engineering, University of Toronto, 40 St. George Street, Toronto, ON M5S 2E4, Canada
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Moleirinho S, Whalen AJ, Fried SI, Pezaris JS. The impact of synchronous versus asynchronous electrical stimulation in artificial vision. J Neural Eng 2021; 18. [PMID: 33900206 DOI: 10.1088/1741-2552/abecf1] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Accepted: 03/09/2021] [Indexed: 11/12/2022]
Abstract
Visual prosthesis devices designed to restore sight to the blind have been under development in the laboratory for several decades. Clinical translation continues to be challenging, due in part to gaps in our understanding of critical parameters such as how phosphenes, the electrically-generated pixels of artificial vision, can be combined to form images. In this review we explore the effects that synchronous and asynchronous electrical stimulation across multiple electrodes have in evoking phosphenes. Understanding how electrical patterns influence phosphene generation to control object binding and perception of visual form is fundamental to creation of a clinically successful prosthesis.
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Affiliation(s)
- Susana Moleirinho
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, United States of America.,Department of Neurosurgery, Harvard Medical School, Boston, MA, United States of America
| | - Andrew J Whalen
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, United States of America.,Department of Neurosurgery, Harvard Medical School, Boston, MA, United States of America
| | - Shelley I Fried
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, United States of America.,Department of Neurosurgery, Harvard Medical School, Boston, MA, United States of America.,Boston VA Healthcare System, Boston, MA, United States of America
| | - John S Pezaris
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, United States of America.,Department of Neurosurgery, Harvard Medical School, Boston, MA, United States of America
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44
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Chenais NAL, Airaghi Leccardi MJI, Ghezzi D. Naturalistic spatiotemporal modulation of epiretinal stimulation increases the response persistence of retinal ganglion cell. J Neural Eng 2021; 18. [DOI: 10.1088/1741-2552/abcd6f] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 11/24/2020] [Indexed: 12/24/2022]
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45
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Yamashita K, Tanaka T, Matsuo T, Uchida T. Development of highly durable retinal prosthesis using photoelectric dyes coupled to polyethylene film and quantitative in vitro evaluation of its durability. Biomed Mater 2021; 16. [PMID: 33607636 DOI: 10.1088/1748-605x/abe809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 02/19/2021] [Indexed: 11/11/2022]
Abstract
Retinal prostheses have been developed to restore vision in blind patients suffering from such diseases as retinitis pigmentosa. In our previous studies, we developed a retinal prosthesis called dye-coupled film by chemical coupling of photoelectric dyes, which absorb light and then generate electrical potential, with a polyethylene film surface. The dye-coupled film is nontoxic, and we recovered the vision of a monkey with macular degeneration. The amount of dye on the dye-coupled film, however, decreased to one-third after five months in the monkey's eye. The photoelectric dye consists of a cation with photoresponsivity and a bromide ion (Br-). Therefore, an anion-exchange reaction could be applied to the dye-coupled film to improve its durability. In this study, the anion-exchange reaction was conducted using bis(trifluoromethanesulfonyl)imide ion (TFSI-), which has lower nucleophilicity than Br-. First, the long-term durability was examined without using animal subjects and in a short period. Subsequently, an elemental analysis was performed to confirm the exchange between Br-and TFSI-, and chemical properties, such as photoresponsivity and durability, before and after the anion exchange, were evaluated. It was quantitatively confirmed that the long-term durability of dye-coupled films can be evaluated in an in vitro environment and in a short period of one-thirtieth by utilizing a saline solution at 60°C, compared with an in vivo environment. In addition, the durability of the dye-coupled film with TFSI-was improved to 270%-320% compared with that of the dye-coupled film with Br-.
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Affiliation(s)
- Koichiro Yamashita
- Okayama University - Tsushima Campus, 3-1-1 Tsushimanaka, Kitaku, Okayama, Okayama, 700-8530, JAPAN
| | - Tenu Tanaka
- Okayama University Graduate School of Natural Science and Technology, 3-1-1 Tsushimanaka Kitaku, Okayama, Okayama, 700-8530, JAPAN
| | - Toshihiko Matsuo
- Okayama University, 2-5-1 Shikatacho,, Okayama, Okayama, 700-8558, JAPAN
| | - Tetsuya Uchida
- Okayama University Graduate School of Natural Science and Technology, 3-1-1 Tsushimanaka, Kitaku, Okayama, 700-8530, JAPAN
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What do blind people "see" with retinal prostheses? Observations and qualitative reports of epiretinal implant users. PLoS One 2021; 16:e0229189. [PMID: 33566851 PMCID: PMC7875418 DOI: 10.1371/journal.pone.0229189] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 11/30/2020] [Indexed: 01/13/2023] Open
Abstract
INTRODUCTION Retinal implants have now been approved and commercially available for certain clinical populations for over 5 years, with hundreds of individuals implanted, scores of them closely followed in research trials. Despite these numbers, however, few data are available that would help us answer basic questions regarding the nature and outcomes of artificial vision: what do recipients see when the device is turned on for the first time, and how does that change over time? METHODS Semi-structured interviews and observations were undertaken at two sites in France and the UK with 16 recipients who had received either the Argus II or IRIS II devices. Data were collected at various time points in the process that implant recipients went through in receiving and learning to use the device, including initial evaluation, implantation, initial activation and systems fitting, re-education and finally post-education. These data were supplemented with data from interviews conducted with vision rehabilitation specialists at the clinical sites and clinical researchers at the device manufacturers (Second Sight and Pixium Vision). Observational and interview data were transcribed, coded and analyzed using an approach guided by Interpretative Phenomenological Analysis (IPA). RESULTS Implant recipients described the perceptual experience produced by their epiretinal implants as fundamentally, qualitatively different than natural vision. All used terms that invoked electrical stimuli to describe the appearance of their percepts, yet the characteristics used to describe the percepts varied significantly between recipients. Artificial vision for these recipients was a highly specific, learned skill-set that combined particular bodily techniques, associative learning and deductive reasoning in order to build a "lexicon of flashes"-a distinct perceptual vocabulary that they then used to decompose, recompose and interpret their surroundings. The percept did not transform over time; rather, the recipient became better at interpreting the signals they received, using cognitive techniques. The process of using the device never ceased to be cognitively fatiguing, and did not come without risk or cost to the recipient. In exchange, recipients received hope and purpose through participation, as well as a new kind of sensory signal that may not have afforded practical or functional use in daily life but, for some, provided a kind of "contemplative perception" that recipients tailored to individualized activities. CONCLUSION Attending to the qualitative reports of implant recipients regarding the experience of artificial vision provides valuable information not captured by extant clinical outcome measures.
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Ptito M, Bleau M, Djerourou I, Paré S, Schneider FC, Chebat DR. Brain-Machine Interfaces to Assist the Blind. Front Hum Neurosci 2021; 15:638887. [PMID: 33633557 PMCID: PMC7901898 DOI: 10.3389/fnhum.2021.638887] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 01/19/2021] [Indexed: 12/31/2022] Open
Abstract
The loss or absence of vision is probably one of the most incapacitating events that can befall a human being. The importance of vision for humans is also reflected in brain anatomy as approximately one third of the human brain is devoted to vision. It is therefore unsurprising that throughout history many attempts have been undertaken to develop devices aiming at substituting for a missing visual capacity. In this review, we present two concepts that have been prevalent over the last two decades. The first concept is sensory substitution, which refers to the use of another sensory modality to perform a task that is normally primarily sub-served by the lost sense. The second concept is cross-modal plasticity, which occurs when loss of input in one sensory modality leads to reorganization in brain representation of other sensory modalities. Both phenomena are training-dependent. We also briefly describe the history of blindness from ancient times to modernity, and then proceed to address the means that have been used to help blind individuals, with an emphasis on modern technologies, invasive (various type of surgical implants) and non-invasive devices. With the advent of brain imaging, it has become possible to peer into the neural substrates of sensory substitution and highlight the magnitude of the plastic processes that lead to a rewired brain. Finally, we will address the important question of the value and practicality of the available technologies and future directions.
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Affiliation(s)
- Maurice Ptito
- École d’Optométrie, Université de Montréal, Montréal, QC, Canada
- Department of Nuclear Medicine, University of Southern Denmark, Odense, Denmark
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Maxime Bleau
- École d’Optométrie, Université de Montréal, Montréal, QC, Canada
| | - Ismaël Djerourou
- École d’Optométrie, Université de Montréal, Montréal, QC, Canada
| | - Samuel Paré
- École d’Optométrie, Université de Montréal, Montréal, QC, Canada
| | - Fabien C. Schneider
- TAPE EA7423 University of Lyon-Saint Etienne, Saint Etienne, France
- Neuroradiology Unit, University Hospital of Saint-Etienne, Saint-Etienne, France
| | - Daniel-Robert Chebat
- Visual and Cognitive Neuroscience Laboratory (VCN Lab), Department of Psychology, Faculty of Social Sciences and Humanities, Ariel University, Ariel, Israël
- Navigation and Accessibility Research Center of Ariel University (NARCA), Ariel, Israël
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48
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Bilteanu L, Geicu OI, Stanca L, Pisoschi AM, Serban F, Serban AI, Calu V. Human Eye Optics within a Non-Euclidian Geometrical Approach and Some Implications in Vision Prosthetics Design. Biomolecules 2021; 11:215. [PMID: 33557081 PMCID: PMC7913825 DOI: 10.3390/biom11020215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 01/29/2021] [Accepted: 02/01/2021] [Indexed: 11/25/2022] Open
Abstract
An analogy with our previously published theory on the ionospheric auroral gyroscope provides a new perspective in human eye optics. Based on cone cells' real distribution, we model the human eye macula as a pseudospherical surface. This allows the rigorous description of the photoreceptor cell densities in the parafoveal zones modeled further by an optimized paving method. The hexagonal photoreceptors' distribution has been optimally projected on the elliptical pseudosphere, thus designing a prosthetic array counting almost 7000 pixel points. Thanks to the high morphological similarities to a normal human retina, the visual prosthesis performance in camera-free systems might be significantly improved.
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Affiliation(s)
- Liviu Bilteanu
- Department of Preclinic Sciences, Faculty of Veterinary Medicine, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 105 Blvd. Splaiul Independentei, 050097 Bucharest, Romania; (L.B.); (O.I.G.); (L.S.); (A.M.P.); (F.S.)
- Molecular Nanotechnology Laboratory, National Institute for Research and Development in Microtechnologies, 126A, Erou Iancu Nicolae Street, 077190 Bucharest, Romania
| | - Ovidiu I. Geicu
- Department of Preclinic Sciences, Faculty of Veterinary Medicine, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 105 Blvd. Splaiul Independentei, 050097 Bucharest, Romania; (L.B.); (O.I.G.); (L.S.); (A.M.P.); (F.S.)
| | - Loredana Stanca
- Department of Preclinic Sciences, Faculty of Veterinary Medicine, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 105 Blvd. Splaiul Independentei, 050097 Bucharest, Romania; (L.B.); (O.I.G.); (L.S.); (A.M.P.); (F.S.)
| | - Aurelia M. Pisoschi
- Department of Preclinic Sciences, Faculty of Veterinary Medicine, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 105 Blvd. Splaiul Independentei, 050097 Bucharest, Romania; (L.B.); (O.I.G.); (L.S.); (A.M.P.); (F.S.)
| | - Florea Serban
- Department of Preclinic Sciences, Faculty of Veterinary Medicine, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 105 Blvd. Splaiul Independentei, 050097 Bucharest, Romania; (L.B.); (O.I.G.); (L.S.); (A.M.P.); (F.S.)
| | - Andreea I. Serban
- Department of Preclinic Sciences, Faculty of Veterinary Medicine, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 105 Blvd. Splaiul Independentei, 050097 Bucharest, Romania; (L.B.); (O.I.G.); (L.S.); (A.M.P.); (F.S.)
- Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Bucharest, 91-95 Blvd. Splaiul Independentei, 050095 Bucharest, Romania
| | - Valentin Calu
- Department of General Surgery, University of Medicine and Pharmacy “Carol Davila” Bucharest, 8 Blvd. Eroii Sanitari, 050474 Bucharest, Romania;
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Park JH, Tan JSY, Wu H, Dong Y, Yoo J. 1225-Channel Neuromorphic Retinal-Prosthesis SoC With Localized Temperature-Regulation. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2020; 14:1230-1240. [PMID: 33156793 DOI: 10.1109/tbcas.2020.3036091] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A 1225-Channel Neuromorphic Retinal Prosthesis (RP) SoC is presented. Existing RP SoCs directly convert light intensity to electrical stimulus, which limit the adoption of delicate stimulus patterns to increase visual acuity. Moreover, a conventional centralized image processor leads to the local hot spot that poses a risk to the nearby retinal cells. To solve these issues, the proposed SoC adopts a distributed Neuromorphic Image Processor (NMIP) located within each pixel that extracts the outline of the incoming image, which reduces current dispersion and stimulus power compared with light-intensity proportional stimulus pattern. A spike-based asynchronous digital operation results in the power consumption of 56.3 nW/Ch without local temperature hot spot. At every 5×5 pixels, the localized (49-point) temperature-regulation circuit limits the temperature increase of neighboring retinal cells to less than 1 °C, and the overall power consumption of the SoC to be less than that of the human eye. The 1225-channel SoC fabricated in 0.18 μm 1P6M CMOS occupies 15mm2 while consuming 2.7 mW, and is successfully verified with image reconstruction demonstration.
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Abstract
Visual prostheses aim to restore, at least to some extent, vision that leads to the type of perception available for sighted patients. Their effectiveness is almost always evaluated using clinical tests of vision. Clinical vision tests are designed to measure the limits of parameters of a functioning visual system. I argue here that these tests are rarely suited to determine the ability of prosthetic devices and other therapies to restore vision. This paper describes and explains many limitations of these evaluations. Prosthetic vision testing often makes use of multiple-alternative forced-choice (MAFC) procedures. Although these paradigms are suitable for many studies, they are frequently problematic in vision restoration evaluation. Two main types of problems are identified: (1) where nuisance variables provide spurious cues that can be learned in repeated training, which is common in prosthetic vision, and thus defeat the purpose of the test; and (2) even though a test is properly designed and performed, it may not actually measure what the researchers believe, and thus the interpretation of results is wrong. Examples for both types of problems are presented. Additional problems arise from confounding factors in the administration of tests are pointed as limitations of current device evaluation. For example, head tracing of magnified objects enlarged to compensate for the system's low resolution, in distinction from the scanning head (camera) movements with which users of prosthetic devices expand the limited field of view. Because of these problems, the ability to perform satisfactorily on the clinical tests is necessary but insufficient to prove vision restoration, therefore, additional tests are needed. I propose some directions to pursue in such testing. Translational Relevance Numerous prosthetic devices are being developed and introduced to the market. Proving the utility of these devices is crucial for regulatory and even for post market acceptance, which so far has largely failed, in my opinion. Potential reasons for the failures despite success in regulatory testing and directions for designing improved testing are provided. It is hoped that improved testing will guide improved designs of future prosthetic systems and other vision restoration approaches.
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Affiliation(s)
- Eli Peli
- Schepens Eye Research Institute of Mass Eye & Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
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