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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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2
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Chung WG, Jang J, Cui G, Lee S, Jeong H, Kang H, Seo H, Kim S, Kim E, Lee J, Lee SG, Byeon SH, Park JU. Liquid-metal-based three-dimensional microelectrode arrays integrated with implantable ultrathin retinal prosthesis for vision restoration. NATURE NANOTECHNOLOGY 2024; 19:688-697. [PMID: 38225357 PMCID: PMC11106006 DOI: 10.1038/s41565-023-01587-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Accepted: 11/28/2023] [Indexed: 01/17/2024]
Abstract
Electronic retinal prostheses for stimulating retinal neurons are promising for vision restoration. However, the rigid electrodes of conventional retinal implants can inflict damage on the soft retina tissue. They also have limited selectivity due to their poor proximity to target cells in the degenerative retina. Here we present a soft artificial retina (thickness, 10 μm) where flexible ultrathin photosensitive transistors are integrated with three-dimensional stimulation electrodes of eutectic gallium-indium alloy. Platinum nanoclusters locally coated only on the tip of these three-dimensional liquid-metal electrodes show advantages in reducing the impedance of the stimulation electrodes. These microelectrodes can enhance the proximity to the target retinal ganglion cells and provide effective charge injections (72.84 mC cm-2) to elicit neural responses in the retina. Their low Young's modulus (234 kPa), owing to their liquid form, can minimize damage to the retina. Furthermore, we used an unsupervised machine learning approach to effectively identify the evoked spikes to grade neural activities within the retinal ganglion cells. Results from in vivo experiments on a retinal degeneration mouse model reveal that the spatiotemporal distribution of neural responses on their retina can be mapped under selective localized illumination areas of light, suggesting the restoration of their vision.
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Affiliation(s)
- Won Gi Chung
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Jiuk Jang
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Gang Cui
- Institute of Vision Research, Department of Ophthalmology, Severance Eye Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Sanghoon Lee
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Han Jeong
- Institute of Vision Research, Department of Ophthalmology, Severance Eye Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
- Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Haisu Kang
- School of Chemical Engineering, Pusan National University, Busan, Republic of Korea
| | - Hunkyu Seo
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Sumin Kim
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Enji Kim
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea
| | - Junwon Lee
- Institute of Vision Research, Department of Ophthalmology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Seung Geol Lee
- School of Chemical Engineering, Pusan National University, Busan, Republic of Korea.
- Department of Organic Material Science and Engineering, Pusan National University, Busan, Republic of Korea.
| | - Suk Ho Byeon
- Institute of Vision Research, Department of Ophthalmology, Severance Eye Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.
- Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea.
| | - Jang-Ung Park
- Department of Materials Science & Engineering, Yonsei University, Seoul, Republic of Korea.
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul, Republic of Korea.
- Graduate Program of Nano Biomedical Engineering (NanoBME), Advanced Science Institute, Yonsei University, Seoul, Republic of Korea.
- Department of Neurosurgery, Yonsei University College of Medicine, Seoul, Republic of Korea.
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3
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Hou Y, Nanduri D, Granley J, Weiland JD, Beyeler M. Axonal stimulation affects the linear summation of single-point perception in three Argus II users. J Neural Eng 2024; 21:026031. [PMID: 38457841 PMCID: PMC11003296 DOI: 10.1088/1741-2552/ad31c4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 02/20/2024] [Accepted: 03/08/2024] [Indexed: 03/10/2024]
Abstract
Objective.Retinal implants use electrical stimulation to elicit perceived flashes of light ('phosphenes'). Single-electrode phosphene shape has been shown to vary systematically with stimulus parameters and the retinal location of the stimulating electrode, due to incidental activation of passing nerve fiber bundles. However, this knowledge has yet to be extended to paired-electrode stimulation.Approach.We retrospectively analyzed 3548 phosphene drawings made by three blind participants implanted with an Argus II Retinal Prosthesis. Phosphene shape (characterized by area, perimeter, major and minor axis length) and number of perceived phosphenes were averaged across trials and correlated with the corresponding single-electrode parameters. In addition, the number of phosphenes was correlated with stimulus amplitude and neuroanatomical parameters: electrode-retina and electrode-fovea distance as well as the electrode-electrode distance to ('between-axon') and along axon bundles ('along-axon'). Statistical analyses were conducted using linear regression and partial correlation analysis.Main results.Simple regression revealed that each paired-electrode shape descriptor could be predicted by the sum of the two corresponding single-electrode shape descriptors (p < .001). Multiple regression revealed that paired-electrode phosphene shape was primarily predicted by stimulus amplitude and electrode-fovea distance (p < .05). Interestingly, the number of elicited phosphenes tended to increase with between-axon distance (p < .05), but not with along-axon distance, in two out of three participants.Significance.The shape of phosphenes elicited by paired-electrode stimulation was well predicted by the shape of their corresponding single-electrode phosphenes, suggesting that two-point perception can be expressed as the linear summation of single-point perception. The impact of the between-axon distance on the perceived number of phosphenes provides further evidence in support of the axon map model for epiretinal stimulation. These findings contribute to the growing literature on phosphene perception and have important implications for the design of future retinal prostheses.
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Affiliation(s)
- Yuchen Hou
- Department of Computer Science, University of California, Santa Barbara, CA, United States of America
- Department of Psychological & Brain Sciences, University of California, Santa Barbara, CA, United States of America
| | - Devyani Nanduri
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States of America
| | - Jacob Granley
- Department of Computer Science, University of California, Santa Barbara, CA, United States of America
| | - James D Weiland
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States of America
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
| | - Michael Beyeler
- Department of Computer Science, University of California, Santa Barbara, CA, United States of America
- Department of Psychological & Brain Sciences, University of California, Santa Barbara, CA, United States of America
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4
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Pogoncheff G, Hu Z, Rokem A, Beyeler M. Explainable machine learning predictions of perceptual sensitivity for retinal prostheses. J Neural Eng 2024; 21:10.1088/1741-2552/ad310f. [PMID: 38452381 PMCID: PMC11144548 DOI: 10.1088/1741-2552/ad310f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 03/07/2024] [Indexed: 03/09/2024]
Abstract
Objective.Retinal prostheses evoke visual precepts by electrically stimulating functioning cells in the retina. Despite high variance in perceptual thresholds across subjects, among electrodes within a subject, and over time, retinal prosthesis users must undergo 'system fitting', a process performed to calibrate stimulation parameters according to the subject's perceptual thresholds. Although previous work has identified electrode-retina distance and impedance as key factors affecting thresholds, an accurate predictive model is still lacking.Approach.To address these challenges, we (1) fitted machine learning models to a large longitudinal dataset with the goal of predicting individual electrode thresholds and deactivation as a function of stimulus, electrode, and clinical parameters ('predictors') and (2) leveraged explainable artificial intelligence (XAI) to reveal which of these predictors were most important.Main results.Our models accounted for up to 76% of the perceptual threshold response variance and enabled predictions of whether an electrode was deactivated in a given trial with F1 and area under the ROC curve scores of up to 0.732 and 0.911, respectively. Our models identified novel predictors of perceptual sensitivity, including subject age, time since blindness onset, and electrode-fovea distance.Significance.Our results demonstrate that routinely collected clinical measures and a single session of system fitting might be sufficient to inform an XAI-based threshold prediction strategy, which has the potential to transform clinical practice in predicting visual outcomes.
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Affiliation(s)
- Galen Pogoncheff
- Department of Computer Science, University of California, Santa Barbara, CA, United States of America
| | - Zuying Hu
- Department of Computer Science, University of California, Santa Barbara, CA, United States of America
| | - Ariel Rokem
- Department of Psychology, University of Washington, Seattle, WA, United States of America
- eScience Institute, University of Washington, Seattle, WA, United States of America
| | - Michael Beyeler
- Department of Computer Science, University of California, Santa Barbara, CA, United States of America
- Department of Psychological & Brain Sciences, University of California, Santa Barbara, CA, United States of America
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5
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Jolly JK, Grigg JR, McKendrick AM, Fujinami K, Cideciyan AV, Thompson DA, Matsumoto C, Asaoka R, Johnson C, Dul MW, Artes PH, Robson AG. ISCEV and IPS guideline for the full-field stimulus test (FST). Doc Ophthalmol 2024; 148:3-14. [PMID: 38238632 PMCID: PMC10879267 DOI: 10.1007/s10633-023-09962-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 12/15/2023] [Indexed: 02/21/2024]
Abstract
The full-field stimulus test (FST) is a psychophysical technique designed for the measurement of visual function in low vision. The method involves the use of a ganzfeld stimulator, as used in routine full-field electroretinography, to deliver full-field flashes of light. This guideline was developed jointly by the International Society for Clinical Electrophysiology of Vision (ISCEV) and Imaging and Perimetry Society (IPS) in order to provide technical information, promote consistency of testing and reporting, and encourage convergence of methods for FST. It is intended to aid practitioners and guide the formulation of FST protocols, with a view to future standardisation.
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Affiliation(s)
- J K Jolly
- Vision and Eye Research Institute, Anglia Ruskin University, Young Street, Cambridge, CB1 2LZ, UK.
| | - J R Grigg
- Save Sight Institute, Specialty of Clinical Ophthalmology and Eye Health, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
- Eye Genetics Research Unit, Sydney Children's Hospitals Network, Save Sight Institute, Children's Medical Research Institute, The University of Sydney, Sydney, NSW, Australia
| | - A M McKendrick
- Lions Eye Institute, University of Western Australia, Perth, Australia
- School of Allied Health, University of Western Australia, Crawley, Australia
| | - K Fujinami
- Laboratory of Visual Physiology, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
- Institute of Ophthalmology, University College London, London, UK
| | - A V Cideciyan
- Center for Hereditary Retinal Degenerations, Scheie Eye Institute, University of Pennsylvania, Philadelphia, USA
| | - D A Thompson
- The Tony Kriss Visual Electrophysiology Unit, Clinical and Academic, Department of Ophthalmology, Sight and Sound Centre, Great Ormond Street Hospital for Children NHS Trust, London, UK
- Great Ormond Street Institute of Child Health, University College London, London, UK
| | - C Matsumoto
- Department of Ophthalmology, Kindai University, Osakasayama, Japan
| | - R Asaoka
- Department of Ophthalmology, Seirei Hamamatsu General Hospital, Hamamatsu, Shizuoka, Japan
- Seirei Christopher University, Hamamatsu, Shizuoka, Japan
- Nanovision Research Division, Research Institute of Electronics, Shizuoka University, Shizuoka, Japan
- The Graduate School for the Creation of New Photonics Industries, Shizuoka, Japan
| | - C Johnson
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, USA
- School of Optometry, The Ohio State University, Columbus, IA, USA
| | - M W Dul
- Department of Biological and Vision Science, College of Optometry, State University of New York, New York, USA
| | - P H Artes
- Faculty of Health, University of Plymouth, Plymouth, UK
| | - A G Robson
- Institute of Ophthalmology, University College London, London, UK
- Department of Electrophysiology, Moorfields Eye Hospital, London, UK
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6
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Henze D, Majdi JA, Cohen ED. Effect of epiretinal electrical stimulation on the glial cells in a rabbit retinal eyecup model. Front Neurosci 2024; 18:1290829. [PMID: 38318467 PMCID: PMC10839094 DOI: 10.3389/fnins.2024.1290829] [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: 09/08/2023] [Accepted: 01/03/2024] [Indexed: 02/07/2024] Open
Abstract
Introduction We examined how pulse train electrical stimulation of the inner surface of the rabbit retina effected the resident glial cells. We used a rabbit retinal eyecup preparation model, transparent stimulus electrodes, and optical coherence tomography (OCT). The endfeet of Müller glia processes line the inner limiting membrane (ILM). Methods To examine how epiretinal electrode stimulation affected the Müller glia, we labeled them post stimulation using antibodies against soluble glutamine synthetase (GS). After 5 min 50 Hz pulse train stimulation 30 μm from the surface, the retina was fixed, immunostained for Müller glia, and examined using confocal microscopic reconstruction. Stimulus pulse charge densities between 133-749 μC/cm2/ph were examined. Results High charge density stimulation (442-749 μC/cm2/ph) caused significant losses in the GS immunofluorescence of the Müller glia endfeet under the electrode. This loss of immunofluorescence was correlated with stimuli causing ILM detachment when measured using OCT. Müller cells show potassium conductances at rest that are blocked by barium ions. Using 30 msec 20 μA stimulus current pulses across the eyecup, the change in transretinal resistance was examined by adding barium to the Ringer. Barium caused little change in the transretinal resistance, suggesting under low charge density stimulus pulse conditions, the Müller cell radial conductance pathway for these stimulus currents was small. To examine how epiretinal electrode stimulation affected the microglia, we used lectin staining 0-4 h post stimulation. After stimulation at high charge densities 749 μC/cm2/ph, the microglia under the electrode appeared rounded, while the local microglia outside the electrode responded to the stimulated retina by process orientation inwards in a ring by 30 min post stimulation. Discussion Our study of glial cells in a rabbit eyecup model using transparent electrode imaging suggests that epiretinal electrical stimulation at high pulse charge densities, can injure the Müller and microglia cells lining the inner retinal surface in addition to ganglion cells.
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Affiliation(s)
- Dean Henze
- University of San Diego, San Diego, CA, United States
| | - Joseph A. Majdi
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, MD, United States
| | - Ethan D. Cohen
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, MD, United States
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Shi LF, Hall AJ, Thompson DA. Full-field stimulus threshold testing: a scoping review of current practice. Eye (Lond) 2024; 38:33-53. [PMID: 37443335 PMCID: PMC10764876 DOI: 10.1038/s41433-023-02636-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 04/21/2023] [Accepted: 06/13/2023] [Indexed: 07/15/2023] Open
Abstract
The full-field stimulus threshold (FST) is a psychophysical measure of whole-field retinal light sensitivity. It can assess residual visual function in patients with severe retinal disease and is increasingly being adopted as an endpoint in clinical trials. FST applications in routine ophthalmology clinics are also growing, but as yet there is no formalised standard guidance for measuring FST. This scoping review explored current variability in FST conduct and reporting, with an aim to inform further evidence synthesis and consensus guidance. A comprehensive electronic search and review of the literature was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis Extension for Scoping Reviews (PRISMA-ScR) checklist. Key source, participant, methodology and outcomes data from 85 included sources were qualitatively and quantitatively compared and summarised. Data from 85 sources highlight how the variability and insufficient reporting of FST methodology, including parameters such as units of flash luminance, colour, duration, test strategy and dark adaptation, can hinder comparison and interpretation of clinical significance across centres. The review also highlights an unmet need for paediatric-specific considerations for test optimisation. Further evidence synthesis, empirical research or structured panel consultation may be required to establish coherent standardised guidance on FST methodology and context or condition dependent modifications. Consistent reporting of core elements, most crucially the flash luminance equivalence to 0 dB reference level is a first step. The development of criteria for quality assurance, calibration and age-appropriate reference data generation may further strengthen rigour of measurement.
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Affiliation(s)
- Linda F Shi
- Tony Kriss Visual Electrophysiology Unit, Clinical and Academic Department of Ophthalmology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
- College of Health and Life Sciences, Aston University, Birmingham, UK
| | - Amanda J Hall
- College of Health and Life Sciences, Aston University, Birmingham, UK
| | - Dorothy A Thompson
- Tony Kriss Visual Electrophysiology Unit, Clinical and Academic Department of Ophthalmology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK.
- UCL Great Ormond Street Institute for Child Health, University College London, London, UK.
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8
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Hou Y, Nanduri D, Granley J, Weiland JD, Beyeler M. Axonal stimulation affects the linear summation of single-point perception in three Argus II users. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.07.21.23292908. [PMID: 37546858 PMCID: PMC10402233 DOI: 10.1101/2023.07.21.23292908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Purpose Retinal implants use electrical stimulation to elicit perceived flashes of light ("phosphenes"). Single-electrode phosphene shape has been shown to vary systematically with stimulus parameters and the retinal location of the stimulating electrode, due to incidental activation of passing nerve fiber bundles. However, this knowledge has yet to be extended to paired-electrode stimulation. Methods We retrospectively analyzed 3548 phosphene drawings made by three blind participants implanted with an Argus II Retinal Prosthesis. Phosphene shape (characterized by area, perimeter, major and minor axis length) and number of perceived phosphenes were averaged across trials and correlated with the corresponding single-electrode parameters. In addition, the number of phosphenes was correlated with stimulus amplitude and neuroanatomical parameters: electrode-retina and electrode-fovea distance as well as the electrode-electrode distance to ("between-axon") and along axon bundles ("along-axon"). Statistical analyses were conducted using linear regression and partial correlation analysis. Results Simple regression revealed that each paired-electrode shape descriptor could be predicted by the sum of the two corresponding single-electrode shape descriptors (p < .001). Multiple regression revealed that paired-electrode phosphene shape was primarily predicted by stimulus amplitude and electrode-fovea distance (p < .05). Interestingly, the number of elicited phosphenes tended to increase with between-axon distance (p < .05), but not with along-axon distance, in two out of three participants. Conclusions The shape of phosphenes elicited by paired-electrode stimulation was well predicted by the shape of their corresponding single-electrode phosphenes, suggesting that two-point perception can be expressed as the linear summation of single-point perception. The notable impact of the between-axon distance on the perceived number of phosphenes provides further evidence in support of the axon map model for epiretinal stimulation. These findings contribute to the growing literature on phosphene perception and have important implications for the design of future retinal prostheses.
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Affiliation(s)
- Yuchen Hou
- Department of Computer Science, University of California, Santa Barbara, CA
- Department of Psychological & Brain Sciences, University of California, Santa Barbara, CA
| | - Devyani Nanduri
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI
| | - Jacob Granley
- Department of Computer Science, University of California, Santa Barbara, CA
| | - James D Weiland
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI
| | - Michael Beyeler
- Department of Computer Science, University of California, Santa Barbara, CA
- Department of Psychological & Brain Sciences, University of California, Santa Barbara, CA
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9
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Kish KE, Yuan A, Weiland JD. Patient-specific computational models of retinal prostheses. Sci Rep 2023; 13:22271. [PMID: 38097732 PMCID: PMC10721907 DOI: 10.1038/s41598-023-49580-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 12/09/2023] [Indexed: 12/17/2023] Open
Abstract
Retinal prostheses stimulate inner retinal neurons to create visual perception for blind patients. Implanted arrays have many small electrodes. Not all electrodes induce perception at the same stimulus amplitude, requiring clinicians to manually establish a visual perception threshold for each one. Phosphenes created by single-electrode stimuli can also vary in shape, size, and brightness. Computational models provide a tool to predict inter-electrode variability and automate device programming. In this study, we created statistical and patient-specific field-cable models to investigate inter-electrode variability across seven epiretinal prosthesis users. Our statistical analysis revealed that retinal thickness beneath the electrode correlated with perceptual threshold, with a significant fixed effect across participants. Electrode-retina distance and electrode impedance also correlated with perceptual threshold for some participants, but these effects varied by individual. We developed a novel method to construct patient-specific field-cable models from optical coherence tomography images. Predictions with these models significantly correlated with perceptual threshold for 80% of participants. Additionally, we demonstrated that patient-specific field-cable models could predict retinal activity and phosphene size. These computational models could be beneficial for determining optimal stimulation settings in silico, circumventing the trial-and-error testing of a large parameter space in clinic.
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Affiliation(s)
- Kathleen E Kish
- Biomedical Engineering, University of Michigan, Ann Arbor, 48105, USA
- BioInterfaces Institute, University of Michigan, Ann Arbor, 48105, USA
| | - Alex Yuan
- Ophthalmology and Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, 44195, USA
| | - James D Weiland
- Biomedical Engineering, University of Michigan, Ann Arbor, 48105, USA.
- BioInterfaces Institute, University of Michigan, Ann Arbor, 48105, USA.
- Ophthalmology and Visual Science, University of Michigan, Ann Arbor, 48105, USA.
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10
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Kish KE, Yuan A, Weiland JD. Patient-specific computational models of retinal prostheses. RESEARCH SQUARE 2023:rs.3.rs-3168193. [PMID: 37577674 PMCID: PMC10418526 DOI: 10.21203/rs.3.rs-3168193/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Retinal prostheses stimulate inner retinal neurons to create visual perception for blind patients. Implanted arrays have many small electrodes, which act as pixels. Not all electrodes induce perception at the same stimulus amplitude, requiring clinicians to manually establish a visual perception threshold for each one. Phosphenes created by single-electrode stimuli can also vary in shape, size, and brightness. Computational models provide a tool to predict inter-electrode variability and automate device programming. In this study, we created statistical and patient-specific field-cable models to investigate inter-electrode variability across seven epiretinal prosthesis users. Our statistical analysis revealed that retinal thickness beneath the electrode correlated with perceptual threshold, with a significant fixed effect across participants. Electrode-retina distance and electrode impedance also correlated with perceptual threshold for some participants, but these effects varied by individual. We developed a novel method to construct patient-specific field-cable models from optical coherence tomography images. Predictions with these models significantly correlated with perceptual threshold for 80% of participants. Additionally, we demonstrated that patient-specific field-cable models could predict retinal activity and phosphene size. These computational models could be beneficial for determining optimal stimulation settings in silico, circumventing the trial-and-error testing of a large parameter space in clinic.
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Affiliation(s)
| | - Alex Yuan
- Cole Eye Institute, Cleveland Clinic Foundation
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11
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Palanker D. Electronic Retinal Prostheses. Cold Spring Harb Perspect Med 2023; 13:a041525. [PMID: 36781222 PMCID: PMC10411866 DOI: 10.1101/cshperspect.a041525] [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] [Indexed: 02/15/2023]
Abstract
Retinal prostheses are a promising means for restoring sight to patients blinded by photoreceptor atrophy. They introduce visual information by electrical stimulation of the surviving inner retinal neurons. Subretinal implants target the graded-response secondary neurons, primarily the bipolar cells, which then transfer the information to the ganglion cells via the retinal neural network. Therefore, many features of natural retinal signal processing can be preserved in this approach if the inner retinal network is retained. Epiretinal implants stimulate primarily the ganglion cells, and hence should encode the visual information in spiking patterns, which, ideally, should match the target cell types. Currently, subretinal arrays are being developed primarily for restoration of central vision in patients impaired by age-related macular degeneration (AMD), while epiretinal implants-for patients blinded by retinitis pigmentosa, where the inner retina is less preserved. This review describes the concepts and technologies, preclinical characterization of prosthetic vision and clinical outcomes, and provides a glimpse into future developments.
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Affiliation(s)
- Daniel Palanker
- Department of Ophthalmology and Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305, USA
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12
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Calabrèse A, Fournet V, Dours S, Matonti F, Castet E, Kornprobst P. A New Vessel-Based Method to Estimate Automatically the Position of the Nonfunctional Fovea on Altered Retinography From Maculopathies. Transl Vis Sci Technol 2023; 12:9. [PMID: 37418249 PMCID: PMC10337789 DOI: 10.1167/tvst.12.7.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 06/01/2023] [Indexed: 07/08/2023] Open
Abstract
Purpose The purpose of this study was to validate a new automated method to locate the fovea on normal and pathological fundus images. Compared to the normative anatomic measures (NAMs), our vessel-based fovea localization (VBFL) approach relies on the retina's vessel structure to make predictions. Methods The spatial relationship between the fovea location and vessel characteristics is learnt from healthy fundus images and then used to predict fovea location in new images. We evaluate the VBFL method on three categories of fundus images: healthy images acquired with different head orientations and fixation locations, healthy images with simulated macular lesions, and pathological images from age-related macular degeneration (AMD). Results For healthy images taken with the head tilted to the side, the NAM estimation error is significantly multiplied by 4, whereas VBFL yields no significant increase, representing a 73% reduction in prediction error. With simulated lesions, VBFL performance decreases significantly as lesion size increases and remains better than NAM until lesion size reaches 200 degrees2. For pathological images, average prediction error was 2.8 degrees, with 64% of the images yielding an error of 2.5 degrees or less. VBFL was not robust for images showing darker regions and/or incomplete representation of the optic disk. Conclusions The vascular structure provides enough information to precisely locate the fovea in fundus images in a way that is robust to head tilt, eccentric fixation location, missing vessels, and actual macular lesions. Translational Relevance The VBFL method should allow researchers and clinicians to assess automatically the eccentricity of a newly developed area of fixation in fundus images with macular lesions.
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Affiliation(s)
- Aurélie Calabrèse
- Aix-Marseille Univ, CNRS, LPC, Marseille, France
- Université Côte d'Azur, Inria, France
| | | | | | - Frédéric Matonti
- Centre Monticelli Paradis d'Ophtalmologie, Marseille, France
- Aix-Marseille Univ, CNRS, INT, Marseille, France
- Groupe Almaviva Santé, Clinique Juge, Marseille, France
| | - Eric Castet
- Aix-Marseille Univ, CNRS, LPC, Marseille, France
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13
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Kish KE, Lempka SF, Weiland JD. Modeling extracellular stimulation of retinal ganglion cells: theoretical and practical aspects. J Neural Eng 2023; 20:026011. [PMID: 36848677 PMCID: PMC10010067 DOI: 10.1088/1741-2552/acbf79] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 02/15/2023] [Accepted: 02/27/2023] [Indexed: 03/01/2023]
Abstract
Objective.Retinal prostheses use electric current to activate inner retinal neurons, providing artificial vision for blind people. Epiretinal stimulation primarily targets retinal ganglion cells (RGCs), which can be modeled with cable equations. Computational models provide a tool to investigate the mechanisms of retinal activation, and improve stimulation paradigms. However, documentation of RGC model structure and parameters is limited, and model implementation can influence model predictions.Approach.We created a functional guide for building a mammalian RGC multi-compartment cable model and applying extracellular stimuli. Next, we investigated how the neuron's three-dimensional shape will influence model predictions. Finally, we tested several strategies to maximize computational efficiency.Main results.We conducted sensitivity analyses to examine how dendrite representation, axon trajectory, and axon diameter influence membrane dynamics and corresponding activation thresholds. We optimized the spatial and temporal discretization of our multi-compartment cable model. We also implemented several simplified threshold prediction theories based on activating function, but these did not match the prediction accuracy achieved by the cable equations.Significance.Through this work, we provide practical guidance for modeling the extracellular stimulation of RGCs to produce reliable and meaningful predictions. Robust computational models lay the groundwork for improving the performance of retinal prostheses.
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Affiliation(s)
- Kathleen E Kish
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
- BioInterfaces Institute, University of Michigan, Ann Arbor, MI, United States of America
| | - Scott F Lempka
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
- Department of Anesthesiology, University of Michigan, Ann Arbor, MI, United States of America
- BioInterfaces Institute, University of Michigan, Ann Arbor, MI, United States of America
| | - James D Weiland
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States of America
- Department of Ophthalmology and Visual Science, University of Michigan, Ann Arbor, MI, United States of America
- BioInterfaces Institute, University of Michigan, Ann Arbor, MI, United States of America
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14
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Ghani N, Bansal J, Naidu A, Chaudhary KM. Long term positional stability of the Argus II retinal prosthesis epiretinal implant. BMC Ophthalmol 2023; 23:70. [PMID: 36797684 PMCID: PMC9933348 DOI: 10.1186/s12886-022-02736-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 12/13/2022] [Indexed: 02/18/2023] Open
Abstract
BACKGROUND The Argus II Retinal Prosthesis System (Second Sight Medical Products, Sylmar, California) is an epiretinal prosthesis that serves to provide useful vision to people who are affected by retinal degenerative diseases such as retinitis pigmentosa (RP). The purpose of this study was to analyze postoperative movement of the electrode array. METHODS Five patients diagnosed with profound retinal dystrophy who have undergone implantation of retinal prosthesis at Stony Brook University Hospital. Fundoscopy was performed at postoperative month 1 (M1), month 3 (M3), month 6 (M6), month 12 (M12), and month 24 (M24) visits. Fundoscopy was extracted and analyzed via NIH ImageJ. Data analysis was completed using IBM SPSS. Various lengths and angles were measured each postoperative month using ImageJ. RESULTS There was no significant change in distance between the optic disc and the surgical handle (length AB) over the two-year span (F = 0.196, p = 0.705). There was a significant change in distance of length AB over time between patients between M3 and M6 (p = 0.025). A repeated measures ANOVA revealed that there was statistically significant change of the optic disc-tack-surgical handle angle (𝛾) (M1 to M24) (F = 3.527, p = 0.030). There was no significant change in angle 𝜟 (the angle to the horizontal of the image), angle 𝜶 (tack-optic disc-surgical handle), and angle 𝜷 (optic-disc-surgical handle-tack). CONCLUSION Our results demonstrate that there may be postoperative movement of the retinal prosthesis over time, as a statistically significant downward rotation is reported over the 2 years span. It is important, moving forward, to further study this movement and to take into consideration such movement when designing retinal implants. It is important to note that this study is limited by the small sample size, and therefore, the conclusions drawn are limited.
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Affiliation(s)
- Nimra Ghani
- Department of Ophthalmology, Stony Brook University Hospital, Stony Brook, NY, 11790, USA.
| | - Jahnvi Bansal
- grid.412695.d0000 0004 0437 5731Department of Ophthalmology, Stony Brook University Hospital, Stony Brook, NY 11790 USA
| | - Abhishek Naidu
- grid.412695.d0000 0004 0437 5731Department of Ophthalmology, Stony Brook University Hospital, Stony Brook, NY 11790 USA
| | - Khurram M. Chaudhary
- grid.412695.d0000 0004 0437 5731Department of Ophthalmology, Stony Brook University Hospital, Stony Brook, NY 11790 USA
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15
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Pogoncheff G, Hu Z, Rokem A, Beyeler M. Explainable Machine Learning Predictions of Perceptual Sensitivity for Retinal Prostheses. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.02.09.23285633. [PMID: 36798201 PMCID: PMC9934792 DOI: 10.1101/2023.02.09.23285633] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
To provide appropriate levels of stimulation, retinal prostheses must be calibrated to an individual's perceptual thresholds ('system fitting'), despite thresholds varying drastically across subjects, across electrodes within a subject, and over time. Although previous work has identified electrode-retina distance and impedance as key factors affecting thresholds, an accurate predictive model is still lacking. To address these challenges, we 1) fitted machine learning (ML) models to a large longitudinal dataset with the goal of predicting individual electrode thresholds and deactivation as a function of stimulus, electrode, and clinical parameters ('predictors') and 2) leveraged explainable artificial intelligence (XAI) to reveal which of these predictors were most important. Our models accounted for up to 77% of the perceptual threshold response variance and enabled predictions of whether an electrode was deactivated in a given trial with F1 and AUC scores of up to 0.740 and 0.913, respectively. Deactivation and threshold models identified novel predictors of perceptual sensitivity, including subject age, time since blindness onset, and electrode-fovea distance. Our results demonstrate that routinely collected clinical measures and a single session of system fitting might be sufficient to inform an XAI-based threshold prediction strategy, which may transform clinical practice in predicting visual outcomes.
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Affiliation(s)
- Galen Pogoncheff
- Department of Computer Science, University of California, Santa Barbara
| | - Zuying Hu
- Department of Computer Science, University of California, Santa Barbara
| | - Ariel Rokem
- Department of Psychology and the eScience Institute, University of Washington, WA
| | - Michael Beyeler
- Department of Computer Science, University of California, Santa Barbara; Department of Psychological & Brain Sciences, University of California, Santa Barbara
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16
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Carleton M, Oesch NW. Differences in the spatial fidelity of evoked and spontaneous signals in the degenerating retina. Front Cell Neurosci 2022; 16:1040090. [PMID: 36419935 PMCID: PMC9676928 DOI: 10.3389/fncel.2022.1040090] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 10/20/2022] [Indexed: 07/01/2024] Open
Abstract
Vision restoration strategies aim to reestablish vision by replacing the function of lost photoreceptors with optoelectronic hardware or through gene therapy. One complication to these approaches is that retinal circuitry undergoes remodeling after photoreceptor loss. Circuit remodeling following perturbation is ubiquitous in the nervous system and understanding these changes is crucial for treating neurodegeneration. Spontaneous oscillations that arise during retinal degeneration have been well-studied, however, other changes in the spatiotemporal processing of evoked and spontaneous activity have received less attention. Here we use subretinal electrical stimulation to measure the spatial and temporal spread of both spontaneous and evoked activity during retinal degeneration. We found that electrical stimulation synchronizes spontaneous oscillatory activity, over space and through time, thus leading to increased correlations in ganglion cell activity. Intriguingly, we found that spatial selectivity was maintained in rd10 retina for evoked responses, with spatial receptive fields comparable to wt retina. These findings indicate that different biophysical mechanisms are involved in mediating feed forward excitation, and the lateral spread of spontaneous activity in the rd10 retina, lending support toward the possibility of high-resolution vision restoration.
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Affiliation(s)
- Maya Carleton
- Department of Psychology, University of California, San Diego, La Jolla, CA, United States
| | - Nicholas W. Oesch
- Department of Psychology, University of California, San Diego, La Jolla, CA, United States
- Department of Ophthalmology, University of California, San Diego, La Jolla, CA, United States
- The Neurosciences Graduate Program, University of California, San Diego, La Jolla, CA, United States
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17
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Abbott CJ, Baglin EK, Kolic M, McGuinness MB, Titchener SA, Young KA, Yeoh J, Luu CD, Ayton LN, Petoe MA, Allen PJ. Interobserver Agreement of Electrode to Retina Distance Measurements in a Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis. Transl Vis Sci Technol 2022; 11:4. [PMID: 36066322 PMCID: PMC9463715 DOI: 10.1167/tvst.11.9.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The electrode to retina (ER) distance is an important contributory factor to the safety and efficacy of a suprachoroidal retinal prosthesis. Measuring ER distance may be performed by different observers during multisite studies. The aim of this study was to assess the interobserver agreement in measuring ER distance. Methods Three independent, trained observers measured ER distance from the center of each suprachoroidal electrode to the inner retinal pigment epithelium in spectral-domain optical coherence tomography (SD-OCT) B-scans. A total of 121 ER distance measurements from 77 B-scans collected over 5 months from one subject implanted with a second-generation 44-channel suprachoroidal retinal prosthesis (NCT03406416) were made by each observer. Results ER distance ranged from 208 to 509 µm. Pearson's correlation coefficient (ρ) showed agreement of 0.99 (95% confidence interval [CI] = 0.98–0.99) in measuring ER for each pairwise comparison. The mean difference in ER distance between observers ranged from 2.4 to 6.4 µm with pairwise limits of agreement (95% CI) of ±20 µm (5.5% of mean). Intraclass correlation coefficient (ICC) showed agreement of 0.98 (95% CI = 0.97–0.99) between observers. Conclusions There is high agreement in measuring ER distances for suprachoroidal retinal prostheses using our systematic approach between multiple, trained observers, supporting the use of a single observer for each image. Translational Relevance High interobserver agreement outcomes indicate that multiple, trained observers can be used to take ER measurements across different images in suprachoroidal retinal prosthesis studies. This improves multisite study efficiency and gives confidence in interpreting results relating to the safety and efficacy of suprachoroidal retinal prostheses.
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Affiliation(s)
- Carla J Abbott
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia.,Department of Surgery (Ophthalmology), University of Melbourne, Victoria, Australia
| | - Elizabeth K Baglin
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia
| | - Maria Kolic
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia
| | - Myra B McGuinness
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia.,Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Victoria, Australia
| | - Samuel A Titchener
- Bionics Institute of Australia, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Victoria, Australia
| | - Kiera A Young
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia
| | - Jonathan Yeoh
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia
| | - Chi D Luu
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia.,Department of Surgery (Ophthalmology), University of Melbourne, Victoria, Australia
| | - Lauren N Ayton
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia.,Department of Surgery (Ophthalmology), University of Melbourne, Victoria, Australia.,Department of Optometry and Vision Sciences, University of Melbourne, Australia
| | - Matthew A Petoe
- Bionics Institute of Australia, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Victoria, Australia
| | - Penelope J Allen
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Victoria, Australia.,Department of Surgery (Ophthalmology), University of Melbourne, Victoria, Australia
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18
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Yücel EI, Sadeghi R, Kartha A, Montezuma SR, Dagnelie G, Rokem A, Boynton GM, Fine I, Beyeler M. Factors affecting two-point discrimination in Argus II patients. Front Neurosci 2022; 16:901337. [PMID: 36090266 PMCID: PMC9448992 DOI: 10.3389/fnins.2022.901337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 07/11/2022] [Indexed: 11/13/2022] Open
Abstract
Two of the main obstacles to the development of epiretinal prosthesis technology are electrodes that require current amplitudes above safety limits to reliably elicit percepts, and a failure to consistently elicit pattern vision. Here, we explored the causes of high current amplitude thresholds and poor spatial resolution within the Argus II epiretinal implant. We measured current amplitude thresholds and two-point discrimination (the ability to determine whether one or two electrodes had been stimulated) in 3 blind participants implanted with Argus II devices. Our data and simulations show that axonal stimulation, lift and retinal damage all play a role in reducing performance in the Argus 2, by either limiting sensitivity and/or reducing spatial resolution. Understanding the relative role of these various factors will be critical for developing and surgically implanting devices that can successfully subserve pattern vision.
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Affiliation(s)
- Ezgi I. Yücel
- Department of Psychology, University of Washington, Seattle, WA, United States
| | - Roksana Sadeghi
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, United States
| | - Arathy Kartha
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, United States
| | - Sandra Rocio Montezuma
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, MN, United States
| | - Gislin Dagnelie
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, United States
| | - Ariel Rokem
- Department of Psychology, University of Washington, Seattle, WA, United States,eScience Institute, University of Washington, Seattle, WA, United States
| | - Geoffrey M. Boynton
- Department of Psychology, University of Washington, Seattle, WA, United States
| | - Ione Fine
- Department of Psychology, University of Washington, Seattle, WA, United States,*Correspondence: Ione Fine,
| | - Michael Beyeler
- Department of Computer Science, University of California, Santa Barbara, Santa Barbara, CA, United States,Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
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19
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Meikle SJ, Hagan MA, Price NSC, Wong YT. Intracortical current steering shifts the location of evoked neural activity. J Neural Eng 2022; 19. [PMID: 35688125 DOI: 10.1088/1741-2552/ac77bf] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 06/10/2022] [Indexed: 11/12/2022]
Abstract
Objective.Intracortical visual prostheses are being developed to restore sight in people who are blind. The resolution of artificial vision is dictated by the location, proximity and number of electrodes implanted in the brain. However, increasing electrode count and proximity is traded off against tissue damage. Hence, new stimulation methods are needed that can improve the resolution of artificial vision without increasing the number of electrodes. We investigated whether a technique known as current steering can improve the resolution of artificial vision provided by intracortical prostheses without increasing the number of physical electrodes in the brain.Approach.We explored how the locus of neuronal activation could be steered when low amplitude microstimulation was applied simultaneously to two intracortical electrodes. A 64-channel, four-shank electrode array was implanted into the visual cortex of rats (n= 7). The distribution of charge ranged from single-electrode stimulation (100%:0%) to an equal distribution between the two electrodes (50%:50%), thereby steering the current between the physical electrodes. The stimulating electrode separation varied between 300 and 500μm. The peak of the evoked activity was defined as the 'virtual electrode' location.Main results.Current steering systematically shifted the virtual electrode on average between the stimulating electrodes as the distribution of charge was moved from one stimulating electrode to another. This effect was unclear in single trials due to the limited sampling of neurons. A model that scales the cortical response to each physical electrode when stimulated in isolation predicts the evoked virtual electrode response. Virtual electrodes were found to elicit a neural response as effectively and predictably as physical electrodes within cortical tissue on average.Significance.Current steering could be used to increase the resolution of intracortical electrode arrays without altering the number of physical electrodes which will reduce neural tissue damage, power consumption and potential heat dispersion issues.
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Affiliation(s)
- Sabrina J Meikle
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic 3800, Australia.,ARC Centre of Excellence for Integrative Brain Function, Clayton, Vic, 3800, Australia.,Department of Electrical and Computer Systems Engineering, Monash University, Clayton, Vic, 3800, Australia.,Monash Vision Group, Monash University, Clayton, Vic 3800, Australia
| | - Maureen A Hagan
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic 3800, Australia.,ARC Centre of Excellence for Integrative Brain Function, Clayton, Vic, 3800, Australia
| | - Nicholas S C Price
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic 3800, Australia.,ARC Centre of Excellence for Integrative Brain Function, Clayton, Vic, 3800, Australia
| | - Yan T Wong
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic 3800, Australia.,ARC Centre of Excellence for Integrative Brain Function, Clayton, Vic, 3800, Australia.,Department of Electrical and Computer Systems Engineering, Monash University, Clayton, Vic, 3800, Australia.,Monash Vision Group, Monash University, Clayton, Vic 3800, Australia
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20
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Titchener SA, Nayagam DAX, Kvansakul J, Kolic M, Baglin EK, Abbott CJ, McGuinness MB, Ayton LN, Luu CD, Greenstein S, Kentler WG, Shivdasani MN, Allen PJ, Petoe MA. A Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis: Long-Term Observation of the Electrode-Tissue Interface. Transl Vis Sci Technol 2022; 11:12. [PMID: 35696133 PMCID: PMC9202334 DOI: 10.1167/tvst.11.6.12] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Purpose To report the long-term observations of the electrode–tissue interface and perceptual stability in humans after chronic stimulation with a 44-channel suprachoroidal retinal implant. Methods Four subjects (S1–4) with end-stage retinitis pigmentosa received the implant unilaterally (NCT03406416). Electrode impedances, electrode–retina distance (measured using optical coherence tomography imaging), and perceptual thresholds were monitored up to 181 weeks after implantation as the subjects used the prosthesis in the laboratory and in daily life. Stimulation charge density was limited to 32 µC/cm2 per phase. Results Electrode impedances were stable longitudinally. The electrode–retina distances increased after surgery and then stabilized, and were well-described by an asymptotic exponential model. The stabilization of electrode–retina distances was variable between subjects, stabilizing after 45 weeks for S1, 63 weeks for S2, and 24 weeks for S3 (linear regression; Pgradient > 0.05). For S4, a statistically significant increase in electrode–retina distance persisted (P < 0.05), but by the study end point the rate of increase was clinically insignificant (exponential model: 0.33 µm/wk). Perceptual electrical thresholds were stable in one subject, decreased over time in two subjects (linear model; P < 0.05), and increased slightly in one subject but remained within the predefined charge limits (P = 0.02). Conclusions Chronic stimulation with the suprachoroidal retinal prosthesis over 3 years resulted in stable impedances, small individual changes in perceptual electrical thresholds, and no clinically significant increase in electrode–retina distances after a period of settling after surgery. Translational Relevance Chronic stimulation with the 44-channel suprachoroidal retinal implant with a charge density of up to 32 µC/cm2 per phase is suitable for long-term use in humans.
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Affiliation(s)
- Samuel A Titchener
- Bionics Institute, East Melbourne, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Melbourne, Victoria, Australia
| | - David A X Nayagam
- Bionics Institute, East Melbourne, Victoria, Australia.,Department of Pathology, University of Melbourne, Victoria, Australia.,Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, Victoria, Australia
| | - Jessica Kvansakul
- 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 & Ear Hospital, Melbourne, Victoria, Australia
| | - Elizabeth K Baglin
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, Victoria, Australia
| | - Carla J Abbott
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
| | - Myra B McGuinness
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, Victoria, Australia.,Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia
| | - Lauren N Ayton
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia.,Department of Optometry and Vision Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Chi D Luu
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
| | - Steven Greenstein
- Bionics Institute, East Melbourne, Victoria, Australia.,Department of Biomedical Engineering, University of Melbourne, Melbourne, Victoria, Australia
| | - William G Kentler
- Department of Biomedical Engineering, University of Melbourne, Melbourne, Victoria, Australia
| | - Mohit N Shivdasani
- Bionics Institute, East Melbourne, Victoria, Australia.,Graduate School of Biomedical Engineering, University of New South Wales, Kensington, NSW, Australia
| | - Penelope J Allen
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
| | - Matthew A Petoe
- Bionics Institute, East Melbourne, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Melbourne, Victoria, Australia
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21
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Italiano ML, Guo T, Lovell NH, Tsai D. Improving the spatial resolution of artificial vision using midget retinal ganglion cell populations modelled at the human fovea. J Neural Eng 2022; 19. [PMID: 35609556 DOI: 10.1088/1741-2552/ac72c2] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 05/24/2022] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Retinal prostheses seek to create artificial vision by stimulating surviving retinal neurons of patients with profound vision impairment. Notwithstanding tremendous research efforts, the performance of all implants tested to date has remained rudimentary, incapable of overcoming the threshold for legal blindness. To maximize the perceptual efficacy of retinal prostheses, a device must be capable of controlling retinal neurons with greater spatiotemporal precision. Most studies of retinal stimulation were derived from either non-primate species or the peripheral primate retina. We investigated if artificial stimulation could leverage the high spatial resolution afforded by the neural substrates at the primate fovea and surrounding regions to achieve improved percept qualities. APPROACH We began by developing a new computational model capable of generating anatomically accurate retinal ganglion cell (RGC) populations within the human central retina. Next, multiple RGC populations across the central retina were stimulated in-silico to compare clinical and recently proposed neurostimulation configurations based on their ability to improve perceptual efficacy and reduce activation thresholds. MAIN RESULTS Our model uniquely upholds eccentricity-dependent characteristics such as RGC density and dendritic field diameter, whilst incorporating anatomically accurate features such as axon projection and three-dimensional RGC layering, features often forgone in favor of reduced computational complexity. Following epiretinal stimulation, the RGCs in our model produced response patterns in shapes akin to the complex percepts reported in clinical trials. Our results also demonstrated that even within the neuron-dense central retina, epiretinal stimulation using a multi-return hexapolar electrode arrangement could reliably achieve spatially focused RGC activation and could achieve single-cell excitation in 74% of all tested locations. SIGNIFICANCE This study establishes an anatomically accurate three-dimensional model of the human central retina and demonstrates the potential for an epiretinal hexapolar configuration to achieve consistent, spatially confined retinal responses, even within the neuron-dense foveal region. Our results promote the prospect and optimization of higher spatial resolution in future epiretinal implants.
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Affiliation(s)
- Michael Lewis Italiano
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
| | - David Tsai
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
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22
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Khan M, Branham K, Jayasundera KT, Khan NW. Adherence and satisfaction in Argus II prosthesis users: a self determination theory model. Ophthalmic Genet 2022; 43:462-469. [PMID: 35296218 DOI: 10.1080/13816810.2022.2050765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
BACKGROUND Self-determination theory (SDT) of human motivation was used to examine associations between different forms of motivation in Argus II retinal prosthesis users and their engagement and satisfaction with the Argus device. MATERIALS AND METHODS Nine subjects were administered: 1) a Situational Motivation Scale (SIMS) questionnaire to measure intrinsic motivation, identified regulation, external regulation, and amotivation, and 2) the Argus questionnaire (AQ) which was organized into 5 categories to measure 'Decision to get an Argus implant,' 'Self-perception as an Argus user', 'Utility of Argus,' 'Perceived competence,' and 'Family support.' Spearman correlations (rs) were used to find associations between measures from SIMS and AQ. RESULTS Nine subjects completed both questionnaires. Statistically significant associations were observed between identified regulation and AQ items from categories: Decision to get Argus, Self-perception, Utility of Argus, and Perceived competence; and between intrinsic motivation and AQ items from Self-perception and Utility. External regulation was negatively associated with Family support, and amotivation was associated with one item from Self-perception. Engagement with the device and satisfaction were associated to both identified regulation and intrinsic motivation. There was no significant relationship between external regulation and adherence to the device. CONCLUSIONS The SDT model can be used to investigate the types of motivation that influence uptake and engagement of the Argus device. Clinicians can use this knowledge to improve outcomes by supporting confidence in users and by encouraging them to maintain internalization and continued commitment to adherence.
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Affiliation(s)
- Mariam Khan
- Department of Ophthalmology and Visual Sciences, W.K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, USA
| | - Kari Branham
- Department of Ophthalmology and Visual Sciences, W.K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, USA
| | - Kanishka T Jayasundera
- Department of Ophthalmology and Visual Sciences, W.K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, USA
| | - Naheed W Khan
- Department of Ophthalmology and Visual Sciences, W.K. Kellogg Eye Center, University of Michigan, Ann Arbor, Michigan, USA
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23
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Song X, Qiu S, Shivdasani MN, Zhou F, Liu Z, Ma S, Chai X, Chen Y, Cai X, Guo T, Li L. An in-silico analysis of electrically-evoked responses of midget and parasol retinal ganglion cells in different retinal regions. J Neural Eng 2022; 19. [PMID: 35255486 DOI: 10.1088/1741-2552/ac5b18] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 03/07/2022] [Indexed: 11/12/2022]
Abstract
BACKGROUND Visual outcomes provided by present retinal prostheses that primarily target retinal ganglion cells (RGCs) through epiretinal stimulation remain rudimentary, partly due to the limited knowledge of retinal responses under electrical stimulation. Better understanding of how different retinal regions can be quantitatively controlled with high spatial accuracy, will be beneficial to the design of micro-electrode arrays (MEAs) and stimulation strategies for next-generation wide-view, high-resolution epiretinal implants. METHODS A computational model was developed to assess neural activity at different eccentricities (2 mm and 5 mm) within the human retina. This model included midget and parasol RGCs with anatomically accurate cell distribution and cell-specific morphological information. We then performed in silico investigations of region-specific RGC responses to epiretinal electrical stimulation using varied electrode sizes (5 µm - 210 µm diameter), emulating both commercialized retinal implants and recently-developed prototype devices. RESULTS Our model of epiretinal stimulation predicted RGC population excitation analogous to the complex percepts reported in human subjects. Following this, our simulations suggest that midget and parasol RGCs have characteristic regional differences in excitation under preferred electrode sizes. Relatively central (2 mm) regions demonstrated higher number of excited RGCs but lower overall activated receptive field (RF) areas under the same stimulus amplitudes (two-way ANOVA, p < 0.05). Furthermore, the activated RGC numbers per unit active RF area (number-RF ratio) were significantly higher in central than in peripheral regions, and higher in the midget than in the parasol population under all tested electrode sizes (two-way ANOVA, p < 0.05). Our simulations also suggested that smaller electrodes exhibit a higher range of controllable stimulation parameters to achieve pre-defined performance of RGC excitation. ..
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Affiliation(s)
- Xiaoyu Song
- , Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
| | - Shirong Qiu
- Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
| | - Mohit N Shivdasani
- Graduate School of Biomedical Engineering, University of New South Wales, Lower Ground, Samuels Building (F25), Kensington, New South Wales, 2052, AUSTRALIA
| | - Feng Zhou
- Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
| | - Zhengyang Liu
- Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
| | - Saidong Ma
- Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
| | - Xinyu Chai
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, Shanghai, 200240, CHINA
| | - Yao Chen
- Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200040, Shanghai, 200240, CHINA
| | - Xuan Cai
- Department of Ophthalmology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Shanghai, Shanghai, 200233, CHINA
| | - Tianruo Guo
- the University of New South Wales, Lower Ground, Samuels Building (F25), Sydney, 2052, AUSTRALIA
| | - Liming Li
- Shanghai Jiao Tong University, Dongchuan Road, Shanghai Minhang District No. 800, Shanghai, 200240, CHINA
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24
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Paknahad J, Humayun M, Lazzi G. Selective Activation of Retinal Ganglion Cell Subtypes Through Targeted Electrical Stimulation Parameters. IEEE Trans Neural Syst Rehabil Eng 2022; 30:350-359. [PMID: 35130164 PMCID: PMC8904155 DOI: 10.1109/tnsre.2022.3149967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
To restore vision to the low vision, epiretinal implants have been developed to electrically stimulate the healthy retinal ganglion cells (RGCs) in the degenerate retina. Given the diversity of retinal ganglion cells as well as the difference in their visual function, selective activation of RGCs subtypes can significantly improve the quality of the restored vision. Our recent results demonstrated that with the proper modulation of the current amplitude, small D1-bistratified cells with the contribution to blue/yellow color opponent pathway can be selectively activated at high frequency (200 Hz). The computational results correlated with the clinical findings revealing the blue sensation of 5/7 subjects with epiretinal implants at high frequency. Here we further explored the impacts of alterations in pulse duration and interphase gap on the response of RGCs at high frequency. We used the developed RGCs, A2-monostratified and D1-bistratified, and examined their response to a range of pulse durations (0.1−1.2 ms) and interphase gaps (0−1 ms). We found that the use of short pulse durations with no interphase gap at high frequency increases the differential response of RGCs, offering better opportunities for selective activation of D1 cells. The presence of the interphase gap has shown to reduce the overall differential response of RGCs. We also explored how the low density of calcium channels enhances the responsiveness of RGCs at high frequency.
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25
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Esquenazi RB, Meier K, Beyeler M, Boynton GM, Fine I. Learning to see again: Perceptual learning of simulated abnormal on- off-cell population responses in sighted individuals. J Vis 2021; 21:10. [PMID: 34935878 PMCID: PMC8727313 DOI: 10.1167/jov.21.13.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Many forms of artificial sight recovery, such as electronic implants and optogenetic proteins, generally cause simultaneous, rather than complementary firing of on- and off-center retinal cells. Here, using virtual patients—sighted individuals viewing distorted input—we examine whether plasticity might compensate for abnormal neuronal population responses. Five participants were dichoptically presented with a combination of original and contrast-reversed images. Each image (I) and its contrast-reverse (Iʹ) was filtered using a radial checkerboard (F) in Fourier space and its inverse (Fʹ). [I * F′] + [Iʹ * F] was presented to one eye, and [I * F] + [Iʹ * F′] was presented to the other, such that regions of the image that produced on-center responses in one eye produced off-center responses in the other eye, and vice versa. Participants continuously improved in a naturalistic object discrimination task over 20 one-hour sessions. Pre-training and post-training tests suggest that performance improvements were due to two learning processes: learning to recognize objects with reduced visual information and learning to suppress contrast-reversed image information in a non–eye-selective manner. These results suggest that, with training, it may be possible to adapt to the unnatural on- and off-cell population responses produced by electronic and optogenetic sight recovery technologies.
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Affiliation(s)
| | - Kimberly Meier
- Department of Psychology, University of Washington, USA.,
| | - Michael Beyeler
- Department of Computer Science, University of California, Santa Barbara, Santa Barbara, California, USA.,Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, California, USA.,
| | | | - Ione Fine
- Department of Psychology, University of Washington, USA.,
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26
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Villarreal DL, Jose Cabezas Zevallos E, Perea Del Angel AM, Krautschneider WH. A Treatise on Electrode Carrier Dislocation in Visual Prosthetic Devices. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:4277-4280. [PMID: 34892167 DOI: 10.1109/embc46164.2021.9629768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Visual implants electrically activate adjacent neurons to induce artificial perception for visual impairment patients to restore some sight. Proximity of electrode carrier to the ganglion cell has attracted careful consideration due to its implications on secure electrochemical and single-localized stimulation. In this study, we postulate a novel strategy to treat the proximity of electrode-cell. A simulation framework includes the carrier dislocation using the geometric parameters of Argus II® epiretinal electrode carrier design. Lastly, we present results on the offset angle of displacement.Clinical Relevance- This postulates a novel strategy to treat the dislocation of electrode carrier confined with a single tack.
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27
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Arevalo JF, Al Rashaed S, Alhamad TA, Al Kahtani E, Al-Dhibi HA. Argus II retinal prosthesis for retinitis pigmentosa in the Middle East: The 2015 Pan-American Association of Ophthalmology Gradle Lecture. Int J Retina Vitreous 2021; 7:65. [PMID: 34706764 PMCID: PMC8554988 DOI: 10.1186/s40942-021-00324-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 08/26/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND To describe the outcomes of patients with retinitis pigmentosa (RP) who received the Argus II Retinal Prosthesis System. METHODS This retrospective, interventional case series evaluated 10 consecutive patients who received the Argus II retinal implant and underwent visual function tests with the system on and system off. The main outcome measures were safety (the number, seriousness, and relatedness of adverse events), and visual function measured by computer-based objective tests, including square localization (SL) and direction of motion (DOM). Secondary measures included functional vision performance, including orientation and mobility (O&M) tasks. RESULTS There were no intraoperative complications and all prostheses remained implanted at the end of follow up. The mean patient age was 41.3 years; mean duration of the implant in vivo was 2.1 years. One patient had a suture exposure over the coil suture tab and over the inferior case suture tab at 2 years postoperatively, which was managed successfully. One patient developed mild vitreous hemorrhage that resolved spontaneously. One patient developed high intraocular pressure postoperatively due to a tight scleral band (SB) that was managed successfully. Patients performed significantly better with the Argus II system on than off on all tasks. CONCLUSION Patients who received the Argus II had a safety profile out to 4 years post-implantation that was markedly better than that observed in the pre-approval phase of the Argus II. In this population of RP patients, the Argus II retinal prosthesis provided useful visual function over several years that likely translates into improved quality of life. TRIAL REGISTRATION clinicaltrials.gov identifier, NCT00407602.
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Affiliation(s)
- J Fernando Arevalo
- Vitreoretinal Division, King Khaled Eye Specialist Hospital, P. O. Box 7191, Riyadh, 11462, Saudi Arabia.,Retina Division, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Saba Al Rashaed
- Vitreoretinal Division, King Khaled Eye Specialist Hospital, P. O. Box 7191, Riyadh, 11462, Saudi Arabia
| | - Tariq A Alhamad
- Vitreoretinal Division, King Khaled Eye Specialist Hospital, P. O. Box 7191, Riyadh, 11462, Saudi Arabia
| | - Eman Al Kahtani
- Vitreoretinal Division, King Khaled Eye Specialist Hospital, P. O. Box 7191, Riyadh, 11462, Saudi Arabia
| | - Hassan A Al-Dhibi
- Vitreoretinal Division, King Khaled Eye Specialist Hospital, P. O. Box 7191, Riyadh, 11462, Saudi Arabia.
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28
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Patelli F, Colombo L, Aly MOM, Rossetti L. ANATOMICAL CHANGES BETWEEN ARGUS II RETINAL PROSTHESIS AND INNER RETINAL LAYERS DETECTED BY SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY IN FIRST YEAR: A CASE REPORT. Retin Cases Brief Rep 2021; 15:457-461. [PMID: 30234794 PMCID: PMC8219081 DOI: 10.1097/icb.0000000000000816] [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] [Indexed: 11/25/2022]
Abstract
PURPOSE To report and describe the anatomical changes detected by spectral domain optical coherence tomography between an Argus II retinal prosthesis and the inner retinal layers during 1-year follow-up. METHODS AND RESULTS A patient presented with epiretinal fibrosis 12 months after implant of an Argus II epiretinal prosthesis. One month after uneventful surgery in March 2016, an evident hyporeflective space was detected between the epiretinal prosthesis and the inner retinal surface by spectral domain optical coherence tomography. An epiretinal hyperreflective band was noticed during follow-up and 1 year after surgery. Spectral domain optical coherence tomography showed close contact of the band with the array, which greatly increased the electrical threshold of stimulation for most of the electrodes. Some electrodes were no longer functioning. No changes in visual performance were detected. CONCLUSION Argus II epiretinal prosthesis implant may be complicated by the formation of a hyperreflective epiretinal band, detectable by spectral domain optical coherence tomography. The band may alter prosthesis function; to date, the patient did not scored any decrease in visual function.
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Affiliation(s)
- Fabio Patelli
- Department of Ophthalmology, San Paolo Hospital, University of Milan, Milan, Italy; and
| | - Leonardo Colombo
- Department of Ophthalmology, San Paolo Hospital, University of Milan, Milan, Italy; and
| | - Mohamed Omar M. Aly
- Department of Ophthalmology, San Paolo Hospital, University of Milan, Milan, Italy; and
- Department of Ophthalmology, Assiut University Hospital, Assiut, Egypt
| | - Luca Rossetti
- Department of Ophthalmology, San Paolo Hospital, University of Milan, Milan, Italy; and
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29
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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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30
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Kish KE, Graham RD, Wong KY, Weiland JD. The effect of axon trajectory on retinal ganglion cell activation with epiretinal stimulation. INTERNATIONAL IEEE/EMBS CONFERENCE ON NEURAL ENGINEERING : [PROCEEDINGS]. INTERNATIONAL IEEE EMBS CONFERENCE ON NEURAL ENGINEERING 2021; 2021:263-266. [PMID: 34646429 PMCID: PMC8510560 DOI: 10.1109/ner49283.2021.9441073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
For epiretinal prostheses, disc electrodes stimulate retinal ganglion cells (RGCs) with electric current to create visual percepts. Prior studies have determined that the sodium channel band (SOCB), located on the RGC axon (30-50 μm from the soma) is the most sensitive site to extracellular stimulation because of its high sodium channel density. Biophysical cable models used to study RGC activation in silico often rely on simplified axon trajectories, disregarding the non-uniform paths that axons follow to the optic disc. However, since axonal activation is a critical mechanism in epiretinal stimulation, it is important to investigate variable RGC axon trajectories. In this study, we use a computational model to perform a sensitivity analysis examining how the morphology of an RGC axon affects predictions of retinal activation. We determine that RGC cable models are sensitive to changes in the ascending axon trajectory between the soma and nerve fiber layer. On the other hand, RGC cable models are relatively robust to trajectory deviations in the plane parallel to the disc electrode's surface. Overall, our results suggest that incorporating natural variations of soma depth and nerve fiber layer entry angle could result in a more realistic model of the retina's response to epiretinal stimulation and a better understanding of elicited visual percepts.
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Affiliation(s)
- Kathleen E Kish
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and are associated with the Biointerfaces Institute
| | - Robert D Graham
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and are associated with the Biointerfaces Institute
| | | | - James D Weiland
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and are associated with the Biointerfaces Institute
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31
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Kosta P, Iseri E, Loizos K, Paknahad J, Pfeiffer RL, Sigulinsky CL, Anderson JR, Jones BW, Lazzi G. Model-based comparison of current flow in rod bipolar cells of healthy and early-stage degenerated retina. Exp Eye Res 2021; 207:108554. [PMID: 33794197 DOI: 10.1016/j.exer.2021.108554] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 03/04/2021] [Accepted: 03/23/2021] [Indexed: 12/27/2022]
Abstract
Retinal degenerative diseases, such as retinitis pigmentosa, are generally thought to initiate with the loss of photoreceptors, though recent work suggests that plasticity and remodeling occurs prior to photoreceptor cell loss. This degeneration subsequently leads to death of other retinal neurons, creating functional alterations and extensive remodeling of retinal networks. Retinal prosthetic devices stimulate the surviving retinal cells by applying external current using implanted electrodes. Although these devices restore partial vision, the quality of restored vision is limited. Further knowledge about the precise changes in degenerated retina as the disease progresses is essential to understand how current flows in retinas undergoing degenerative disease and to improve the performance of retinal prostheses. We developed computational models that describe current flow from rod photoreceptors to rod bipolar cells (RodBCs) in the healthy and early-stage degenerated retina. Morphologically accurate models of retinal cells with their synapses are constructed based on retinal connectome datasets, created using serial section transmission electron microscopy (TEM) images of 70 nm-thick slices of either healthy (RC1) or early-stage degenerated (RPC1) rabbit retina. The passive membrane and active ion currents of each cell are implemented using conductance-based models in the Neuron simulation environment. In response to photocurrent input at rod photoreceptors, the simulated membrane potential at RodBCs in early degenerate tissue is approximately 10-20 mV lower than that of RodBCs of that observed in wild type retina. Results presented here suggest that although RodBCs in RPC1 show early, altered morphology compared to RC1, the lower membrane potential is primarily a consequence of reduced rod photoreceptor input to RodBCs in the degenerated retina. Frequency response and step input analyses suggest that individual cell responses of RodBCs in either healthy or early-degenerated retina, prior to substantial photoreceptor cell loss, do not differ significantly.
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Affiliation(s)
- Pragya Kosta
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, USA.
| | - Ege Iseri
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Kyle Loizos
- Institute for Technology and Medical Systems Innovation (ITEMS), Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Javad Paknahad
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Rebecca L Pfeiffer
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | | | - James R Anderson
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA
| | - Bryan W Jones
- John Moran Eye Center at the University of Utah, Salt Lake City, UT, USA.
| | - Gianluca Lazzi
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA; Institute for Technology and Medical Systems Innovation (ITEMS), Keck School of Medicine, University of Southern California, Los Angeles, CA, USA; Department of Electrical Engineering, University of Southern California, Los Angeles, CA, USA; Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA.
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32
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Paknahad J, Loizos K, Yue L, Humayun MS, Lazzi G. Color and cellular selectivity of retinal ganglion cell subtypes through frequency modulation of electrical stimulation. Sci Rep 2021; 11:5177. [PMID: 33664347 PMCID: PMC7933163 DOI: 10.1038/s41598-021-84437-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 02/15/2021] [Indexed: 01/31/2023] Open
Abstract
Epiretinal prostheses aim at electrically stimulating the inner most surviving retinal cells-retinal ganglion cells (RGCs)-to restore partial sight to the blind. Recent tests in patients with epiretinal implants have revealed that electrical stimulation of the retina results in the percept of color of the elicited phosphenes, which depends on the frequency of stimulation. This paper presents computational results that are predictive of this finding and further support our understanding of the mechanisms of color encoding in electrical stimulation of retina, which could prove pivotal for the design of advanced retinal prosthetics that elicit both percept and color. This provides, for the first time, a directly applicable "amplitude-frequency" stimulation strategy to "encode color" in future retinal prosthetics through a predictive computational tool to selectively target small bistratified cells, which have been shown to contribute to "blue-yellow" color opponency in the retinal circuitry. The presented results are validated with experimental data reported in the literature and correlated with findings in blind patients with a retinal prosthetic implant collected by our group.
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Affiliation(s)
- Javad Paknahad
- grid.42505.360000 0001 2156 6853Department of Electrical Engineering, University of Southern California, Los Angeles, CA USA ,grid.42505.360000 0001 2156 6853The Institute for Technology and Medical Systems (ITEMS), Keck School of Medicine, University of Southern California, Los Angeles, CA USA
| | - Kyle Loizos
- grid.42505.360000 0001 2156 6853The Institute for Technology and Medical Systems (ITEMS), Keck School of Medicine, University of Southern California, Los Angeles, CA USA
| | - Lan Yue
- grid.42505.360000 0001 2156 6853Roski Eye Institute, University of Southern California, Los Angeles, CA USA
| | - Mark S. Humayun
- grid.42505.360000 0001 2156 6853Roski Eye Institute, University of Southern California, Los Angeles, CA USA ,grid.42505.360000 0001 2156 6853Departments of Ophthalmology and Biomedical Engineering, University of Southern California, Los Angeles, CA USA
| | - Gianluca Lazzi
- grid.42505.360000 0001 2156 6853Department of Electrical Engineering, University of Southern California, Los Angeles, CA USA ,grid.42505.360000 0001 2156 6853The Institute for Technology and Medical Systems (ITEMS), Keck School of Medicine, University of Southern California, Los Angeles, CA USA ,grid.42505.360000 0001 2156 6853Departments of Ophthalmology and Biomedical Engineering, University of Southern California, Los Angeles, CA USA
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33
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Yohannes AR, Jung CY, Shea KI, Wong WT, Beylin A, Cohen ED. The microglia response to electrical overstimulation of the retina imaged under a transparent stimulus electrode. J Neural Eng 2021; 18. [PMID: 33418555 DOI: 10.1088/1741-2552/abda0a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 01/08/2021] [Indexed: 11/12/2022]
Abstract
OBJECTIVE We investigated using the morphological response of retinal microglia as indicators of tissue damage from electrical overstimulation by imaging them through an optically transparent stimulus electrode. APPROACH To track the microglia, we used a transgenic mouse where the microglia expressed a water soluble green fluorescent protein (GFP). The clear stimulus electrode was placed epiretinally on the inner limiting membrane and the microglia layers were imaged using time-lapse confocal microscopy. We examined how the microglia responded both temporally and spatially to local overstimulation of the retinal tissue. Using confocal microscope vertical image stacks, the microglia under the electrode were imaged at 2.5min intervals. The retina was overstimulated for a 5 minute period using 1msec 749μC/cm2/ph biphasic current pulses and changes in the microglia morphology were followed for 1 hour post stimulation. After the imaging period, a label for cellular damage was applied to the retina. MAIN RESULTS The microglia response to overstimulation depended on their spatial location relative to the electrode lumen and could result in 3 different morphological responses. Some microglia were severely injured and became a series of immotile ball-like fluorescent processes. Other microglia survived, and reacted rapidly to the injury by extending filopodia oriented toward the damage zone. This response was seen in inner retinal microglia outside the stimulus electrode edge. A third effect, seen with the deeper outer microglia under the electrode, was a fading of their fluorescent image which appeared to be due to optical scatter caused by overstimulation-induced retinal edema. SIGNIFICANCE The microglial morphological responses to electrical overstimulation injury occur rapidly and can show both direct and indirect effects of the stimulus electrode injury. The microglia injury pattern closely follows models of the electric field distribution under thinly insulated disc electrodes.
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Affiliation(s)
- Alula R Yohannes
- Division of Biomedical Physics, Center for Dev. and Rad. Health, FDA, Bldg. 62 Rm 1204, Silver Spring, Maryland, MD 20993-0002, UNITED STATES
| | - Christopher Yi Jung
- University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland, MD 21250, UNITED STATES
| | - Katherine I Shea
- CDER/Division of Applied Regulatory Science, US Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, Maryland, MD 20993-0002, UNITED STATES
| | - Wai T Wong
- Section on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, 6 Center Drive, Bethesda, Maryland, MD 20814, UNITED STATES
| | - Alexander Beylin
- Office of Product Quality and Evaluation, Center for Dev. and Rad. Health, FDA, Silver Spring, Maryland, UNITED STATES
| | - Ethan D Cohen
- Division of Biomedical Physics, Center for Dev. and Rad. Health, FDA, Office of Science and Engineering Labs, Bld 62 White Oak Fed Res Ctr., 10903 New Hampshire Ave, Silver Spring, Maryland, 20993, UNITED STATES
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Yoon YH, Humayun MS, Kim YJ. One-Year Anatomical and Functional Outcomes of the Argus II Implantation in Korean Patients with Late-Stage Retinitis Pigmentosa: A Prospective Case Series Study. Ophthalmologica 2020; 244:291-300. [PMID: 33279905 DOI: 10.1159/000513585] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Accepted: 12/03/2020] [Indexed: 12/28/2022]
Abstract
PURPOSE To report the anatomical and functional outcomes of Argus II retinal prosthesis implantation in Korean patients. METHODS We included 5 consecutive patients with end-stage retinitis pigmentosa (RP) who underwent Argus II retinal prosthesis implantation and were followed for at least 12 months. The transcorneal electrical evoked response was utilized for patient selection. We used intraoperative optical coherence tomography (OCT) for optimal placement of the array and provided specialized vision rehabilitation training. A morphological evaluation using SD-OCT and a functional evaluation using computer-based visual function tests, a letter-reading ability test, and the Functional Low-Vision Observer Rated Assessment (FLORA) were conducted. RESULTS Postoperatively, the array was completely apposed to the retinal surface in all eyes, except for one eye which had a preexisting macular concavity. Fibrosis-like tissues of ≥50-μm thickness developed at the interface in 2 eyes. All of the patients showed improvement in computer-based visual function tests and could read ETDRS letters at a distance of 50 cm. Three patients could read Korean words. FLORA was improved in all patients, mainly in tasks of visual mobility, daily activities, and social interactions. CONCLUSIONS Along with good anatomical outcomes and specialized rehabilitation practices, recipients of the Argus II implant showed profound improvements in functional vision and mobility.
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Affiliation(s)
- Young Hee Yoon
- Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea,
| | - Mark S Humayun
- USC Roski Eye Institute, USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, California, USA
| | - Yoon Jeon Kim
- Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
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Gehlen J, Esser S, Schaffrath K, Johnen S, Walter P, Müller F. Blockade of Retinal Oscillations by Benzodiazepines Improves Efficiency of Electrical Stimulation in the Mouse Model of RP, rd10. Invest Ophthalmol Vis Sci 2020; 61:37. [PMID: 33252632 PMCID: PMC7705397 DOI: 10.1167/iovs.61.13.37] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Purpose In RP, photoreceptors degenerate. Retinal prostheses are considered a suitable strategy to restore vision. In animal models of RP, a pathologic rhythmic activity seems to compromise the efficiency of retinal ganglion cell stimulation by an electrical prosthesis. We, therefore, strove to eliminate this pathologic activity. Methods Electrophysiologic recordings of local field potentials and spike activity of retinal ganglion cells were obtained in vitro from retinae of wild-type and rd10 mice using multielectrode arrays. Retinae were stimulated electrically. Results The efficiency of electrical stimulation was lower in rd10 retina than in wild-type retina and this was highly correlated with the presence of oscillations in retinal activity. Glycine and GABA, as well as the benzodiazepines diazepam, lorazepam, and flunitrazepam, abolished retinal oscillations and, most important, increased the efficiency of electrical stimulation to values similar to those in wild-type retina. Conclusions Treatment of patients with these benzodiazepines may offer a way to improve the performance of retinal implants in cases with poor implant proficiency. This study may open the way to a therapy that supports electrical stimulation by prostheses with pharmacologic treatment.
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Affiliation(s)
- Jana Gehlen
- Institute of Biological Information Processing, Molecular and Cellular Physiology, IBI-1, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Stefan Esser
- Institute of Biological Information Processing, Molecular and Cellular Physiology, IBI-1, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Kim Schaffrath
- Department of Ophthalmology, RWTH Aachen University, Aachen, Germany
| | - Sandra Johnen
- Department of Ophthalmology, RWTH Aachen University, Aachen, Germany
| | - Peter Walter
- Department of Ophthalmology, RWTH Aachen University, Aachen, Germany
| | - Frank Müller
- Institute of Biological Information Processing, Molecular and Cellular Physiology, IBI-1, Forschungszentrum Jülich GmbH, Jülich, Germany
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Kartha A, Sadeghi R, Barry MP, Bradley C, Gibson P, Caspi A, Roy A, Dagnelie G. Prosthetic Visual Performance Using a Disparity-Based Distance-Filtering System. Transl Vis Sci Technol 2020; 9:27. [PMID: 33244447 PMCID: PMC7683856 DOI: 10.1167/tvst.9.12.27] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 10/06/2020] [Indexed: 01/31/2023] Open
Abstract
PURPOSE At present, Argus II is the only retinal prosthesis approved by the US Food and Drug Administration that induces visual percepts in people who are blind from end-stage outer retinal degenerations such as retinitis pigmentosa. It has been shown to work well in sparse, high-contrast settings, but in daily practice visual performance with the device is likely to be hampered by the cognitive load presented by a cluttered real-world environment. In this study, we investigated the effect of a stereo-disparity-based distance-filtering system on four experienced Argus II users for a range of tasks: object localization, depth discrimination, orientation and size discrimination, and people detection and direction of motion. METHODS Functional vision was assessed in a semicontrolled setup using unfiltered (normal camera) and distance-filtered (stereo camera) imagery. All tasks were forced choice designs and an extension of signal detection theory to latent (unobservable) variables was used to analyze the data, allowing estimation of person ability (person measures) and task difficulty (item measures) on the same axis. RESULTS All subjects performed better with the distance filter compared with the unfiltered image (P < 0.001 on all tasks except localization). CONCLUSIONS Our results show that depth filtering using a disparity-based algorithm has significant benefits for people with Argus II implants. TRANSLATIONAL RELEVANCE The improvement in functional vision with the distance filter found in this study may have an important impact on vision rehabilitation and quality of life for people with visual prostheses and ultra low vision.
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Affiliation(s)
- Arathy Kartha
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Roksana Sadeghi
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | | | - Chris Bradley
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Paul Gibson
- Advanced Medical Electronics Corporation, Maple Grove, MN, USA
| | - Avi Caspi
- Second Sight Medical Products, Sylmar, California, USA
- Jerusalem College of Technology, Jerusalem, Israel
| | - Arup Roy
- Second Sight Medical Products, Sylmar, California, USA
| | - Gislin Dagnelie
- Department of Ophthalmology, Johns Hopkins School of Medicine, Baltimore, MD, USA
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Naidu A, Ghani N, Yazdanie MS, Chaudhary K. Effect of the electrode array-retina gap distance on visual function in patients with the Argus II retinal prosthesis. BMC Ophthalmol 2020; 20:366. [PMID: 32943044 PMCID: PMC7495685 DOI: 10.1186/s12886-020-01631-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/31/2020] [Indexed: 11/10/2022] Open
Abstract
Background Post-implantation visual outcomes in patients with the Argus II Retinal Prosthesis is dependent on a multitude of factors including the positioning of the electrode array on the retina. The purpose of this study is to determine whether the average electrode array-retina gap distance correlates with objective visual function outcomes and sensitivity detection thresholds in patients implanted with the Argus II Retinal Prosthesis. Methods Five patients with implantation of the Argus II Retinal Prosthesis were enrolled in this single-institution retrospective study. Patient demographics were collected from medical records. Visual function data (Square Localization [SL] and Direction of Motion [DOM]) and Optical Coherence Tomography (Cirrus HD-OCT) images were extracted retrospectively from the Argus II Retinal Prosthesis Post-Approval study. Visual function tests were performed with the device OFF and ON at each study visit. Electrode array-retina gap distances were measured at each of the array’s 60 electrodes using the Cirrus HD-OCT software in both the nasotemporal and superoinferior planes. Data was obtained at baseline, and post-operative month 1, month 3, month 6, and year 1. Sensitivity detection thresholds were obtained at the initial programming visit and each reprogramming session. Results Three patients performed significantly better in SL visual function testing with the device ON. Patients that worsened in visual function testing with the device ON in both SL and DOM testing had a statistically significant decrease in performance. The electrode array-retina gap distance was found to effect performance in SL testing in a patient-dependent manner. No effect was found between the electrode-array gap distance and DOM testing or sensitivity detection threshold. Conclusion Our results demonstrate that the electrode array-retina gap distance may affect visual function outcomes in SL testing in certain patients with the Argus II Retinal Prosthesis, and the direction and magnitude of this effect is likely patient-dependent. Furthermore, complete apposition between the electrode array and retina may not always be necessary to achieve optimal visual outcomes.
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Affiliation(s)
- Abhishek Naidu
- Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA.
| | - Nimra Ghani
- Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA
| | | | - Khurram Chaudhary
- Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, 11794, USA
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Straňák Z, Kousal B, Ardan T, Veith M. Innovative strategies for treating retinal diseases. ACTA ACUST UNITED AC 2020; 75:287-295. [PMID: 32911944 DOI: 10.31348/2019/6/1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE The aim of this comprehensive paper is to acquaint the readers with innovative approaches in the treatment of retinal diseases, which could in the coming years to get into clinical practice. Retinal prostheses, retinal pigment epithelial (RPE) transplantation, gene therapy and optogenetics will be described in this paper. METHODOLOGY Describing the basic characteristics and mechanisms of different types of therapy and subsequently literary minireview clarifying the current state of knowledge in the area. RESULTS Retinal prostheses, RPE transplantation, gene therapy and optogenetics offer yet unexplored possibilities and are considered as the future of treatment of retinal diseases where classical pharmacotherapy or surgical treatment are no longer sufficient. However, all these methods challenge not only in the innovative technical implementation itself, but also for the ethical, administrative and economic demands. CONCLUSION There will be certainly interesting development in the treatment of retinal diseases, but it is not possible to fully estimate which modality of treatment will be dominant in the future.
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Meer AMVD, Berger T, Müller F, Foldenauer AC, Johnen S, Walter P. Establishment and Characterization of a Unilateral UV-Induced Photoreceptor Degeneration Model in the C57Bl/6J Mouse. Transl Vis Sci Technol 2020; 9:21. [PMID: 32879777 PMCID: PMC7443125 DOI: 10.1167/tvst.9.9.21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 11/01/2019] [Accepted: 11/21/2019] [Indexed: 01/10/2023] Open
Abstract
Purpose To investigate whether UV irradiation of the mouse eye can induce photoreceptor degeneration, producing a phenotype reminiscent of the rd10 mouse, left eyes of female C57Bl/6J mice were irradiated with a UV LED array (370 nm). A lens was placed between the cornea and LED, allowing illumination of about one-third of the retina. The short-term and long-term effects on the retina were evaluated. Methods First, a dose escalation study, in which corneal dosages between 2.8 and 9.3 J/cm2 were tested, was performed. A dosage of 7.5 J/cm2 was chosen for the following characterization study. Before and after irradiation slit-lamp examinations, full-field electroretinography, spectral domain optical coherence tomography and macroscopy were performed. After different time spans (5 days to 12 weeks) the animals were sacrificed and the retinae used for immunohistochemistry or multielectrode array testing. Right eyes served as untreated controls. Results In treated eyes, spectral domain optical coherence tomography revealed a decrease in retinal thickness to 53%. Full-field electroretinography responses decreased significantly from day 5 on in treated eyes. Multielectrode array recordings revealed oscillatory potentials with a mean frequency of 5.2 ± 0.6 Hz in the illuminated area. Structural changes in the retina were observed in immunohistochemical staining. Conclusions UV irradiation proved to be efficient in inducing photoreceptor degeneration in the mouse retina, while leaving the other retinal layers largely intact. The irradiated area of treated eyes can be identified easily in spectral domain optical coherence tomography and in explanted retinae. Translational Relevance This study provides information on anatomic and functional changes in UV-treated retina, enabling the use of this model for retinitis pigmentosa-like diseases in animals suited for experimental retinal surgery.
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Affiliation(s)
| | - Tanja Berger
- Department of Medical Statistics, RWTH Aachen University, Aachen, Germany
| | - Frank Müller
- Institute of Complex Systems, Cellular Biophysics, ICS-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Ann Christina Foldenauer
- Department of Medical Statistics, RWTH Aachen University, Aachen, Germany.,Department of Clinical Research Fraunhofer Institute for Molecular Biology and Applied Ecology (IME) Branch for Translational Medicine and Pharmacology (TMP), Frankfurt, Germany
| | - Sandra Johnen
- Department of Ophthalmology, University Hospital RWTH Aachen, Aachen, Germany
| | - Peter Walter
- Department of Ophthalmology, University Hospital RWTH Aachen, Aachen, Germany
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Shivdasani MN, Evans M, Burns O, Yeoh J, Allen PJ, Nayagam DAX, Villalobos J, Abbott CJ, Luu CD, Opie NL, Sabu A, Saunders AL, McPhedran M, Cardamone L, McGowan C, Maxim V, Williams RA, Fox KE, Cicione R, Garrett DJ, Ahnood A, Ganesan K, Meffin H, Burkitt AN, Prawer S, Williams CE, Shepherd RK. In vivo feasibility of epiretinal stimulation using ultrananocrystalline diamond electrodes. J Neural Eng 2020; 17:045014. [PMID: 32659750 DOI: 10.1088/1741-2552/aba560] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
OBJECTIVE Due to their increased proximity to retinal ganglion cells (RGCs), epiretinal visual prostheses present the opportunity for eliciting phosphenes with low thresholds through direct RGC activation. This study characterised the in vivo performance of a novel prototype monolithic epiretinal prosthesis, containing Nitrogen incorporated ultrananocrystalline (N-UNCD) diamond electrodes. APPROACH A prototype implant containing up to twenty-five 120 × 120 µm N-UNCD electrodes was implanted into 16 anaesthetised cats and attached to the retina either using a single tack or via magnetic coupling with a suprachoroidally placed magnet. Multiunit responses to retinal stimulation using charge-balanced biphasic current pulses were recorded acutely in the visual cortex using a multichannel planar array. Several stimulus parameters were varied including; the stimulating electrode, stimulus polarity, phase duration, return configuration and the number of electrodes stimulated simultaneously. MAIN RESULTS The rigid nature of the device and its form factor necessitated complex surgical procedures. Surgeries were considered successful in 10/16 animals and cortical responses to single electrode stimulation obtained in eight animals. Clinical imaging and histological outcomes showed severe retinal trauma caused by the device in situ in many instances. Cortical measures were found to significantly depend on the surgical outcomes of individual experiments, phase duration, return configuration and the number of electrodes stimulated simultaneously, but not stimulus polarity. Cortical thresholds were also found to increase over time within an experiment. SIGNIFICANCE The study successfully demonstrated that an epiretinal prosthesis containing diamond electrodes could produce cortical activity with high precision, albeit only in a small number of cases. Both surgical approaches were highly challenging in terms of reliable and consistent attachment to and stabilisation against the retina, and often resulted in severe retinal trauma. There are key challenges (device form factor and attachment technique) to be resolved for such a device to progress towards clinical application, as current surgical techniques are unable to address these issues.
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Affiliation(s)
- Mohit N Shivdasani
- Graduate School of Biomedical Engineering, University of New South Wales, Kensington, NSW 2033, Australia. The Bionics Institute of Australia, East Melbourne, VIC 3002, Australia
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Ayton LN, Rizzo JF, Bailey IL, Colenbrander A, Dagnelie G, Geruschat DR, Hessburg PC, McCarthy CD, Petoe MA, Rubin GS, Troyk PR. Harmonization of Outcomes and Vision Endpoints in Vision Restoration Trials: Recommendations from the International HOVER Taskforce. Transl Vis Sci Technol 2020; 9:25. [PMID: 32864194 PMCID: PMC7426586 DOI: 10.1167/tvst.9.8.25] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 12/08/2019] [Indexed: 01/05/2023] Open
Abstract
Translational research in vision prosthetics, gene therapy, optogenetics, stem cell and other forms of transplantation, and sensory substitution is creating new therapeutic options for patients with neural forms of blindness. The technical challenges faced by each of these disciplines differ considerably, but they all face the same challenge of how to assess vision in patients with ultra-low vision (ULV), who will be the earliest subjects to receive new therapies. Historically, there were few tests to assess vision in ULV patients. In the 1990s, the field of visual prosthetics expanded rapidly, and this activity led to a heightened need to develop better tests to quantify end points for clinical studies. Each group tended to develop novel tests, which made it difficult to compare outcomes across groups. The common lack of validation of the tests and the variable use of controls added to the challenge of interpreting the outcomes of these clinical studies. In 2014, at the bi-annual International "Eye and the Chip" meeting of experts in the field of visual prosthetics, a group of interested leaders agreed to work cooperatively to develop the International Harmonization of Outcomes and Vision Endpoints in Vision Restoration Trials (HOVER) Taskforce. Under this banner, more than 80 specialists across seven topic areas joined an effort to formulate guidelines for performing and reporting psychophysical tests in humans who participate in clinical trials for visual restoration. This document provides the complete version of the consensus opinions from the HOVER taskforce, which, together with its rules of governance, will be posted on the website of the Henry Ford Department of Ophthalmology (www.artificialvision.org). Research groups or companies that choose to follow these guidelines are encouraged to include a specific statement to that effect in their communications to the public. The Executive Committee of the HOVER Taskforce will maintain a list of all human psychophysical research in the relevant fields of research on the same website to provide an overview of methods and outcomes of all clinical work being performed in an attempt to restore vision to the blind. This website will also specify which scientific publications contain the statement of certification. The website will be updated every 2 years and continue to exist as a living document of worldwide efforts to restore vision to the blind. The HOVER consensus document has been written by over 80 of the world's experts in vision restoration and low vision and provides recommendations on the measurement and reporting of patient outcomes in vision restoration trials.
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Affiliation(s)
- Lauren N. Ayton
- Department of Optometry and Vision Sciences and Department of Surgery (Ophthalmology), The University of Melbourne, Parkville, Australia
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | - Joseph F. Rizzo
- Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA
| | - Ian L. Bailey
- School of Optometry, University of California-Berkeley, Berkeley, CA, USA
| | - August Colenbrander
- Smith-Kettlewell Eye Research Institute and California Pacific Medical Center, San Francisco, CA, USA
| | - Gislin Dagnelie
- Lions Vision Research and Rehabilitation Center, Johns Hopkins Wilmer Eye Institute, Baltimore, MD, USA
| | - Duane R. Geruschat
- Lions Vision Research and Rehabilitation Center, Johns Hopkins Wilmer Eye Institute, Baltimore, MD, USA
| | - Philip C. Hessburg
- Detroit Institute of Ophthalmology, Henry Ford Health System, Grosse Pointe Park, MI, USA
| | - Chris D. McCarthy
- Department of Computer Science & Software Engineering, Swinburne University of Technology, Melbourne, Australia
| | | | - Gary S. Rubin
- University College London Institute of Ophthalmology, London, UK
| | - Philip R. Troyk
- Armour College of Engineering, Illinois Institute of Technology, Chicago, IL, USA
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Kosta P, Loizos K, Lazzi G. Stimulus waveform design for decreasing charge and increasing stimulation selectivity in retinal prostheses. Healthc Technol Lett 2020; 7:66-71. [PMID: 32754340 PMCID: PMC7353818 DOI: 10.1049/htl.2019.0115] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 05/04/2020] [Accepted: 05/12/2020] [Indexed: 02/03/2023] Open
Abstract
Retinal degenerative diseases, such as retinitis pigmentosa, begin with damage to the photoreceptor layer of the retina. In the absence of presynaptic input from photoreceptors, networks of electrically coupled AII amacrine and cone bipolar cells have been observed to exhibit oscillatory behaviour and result in spontaneous firing of ganglion cells. This ganglion cell activity could interfere with external stimuli provided by retinal prosthetic devices and potentially degrade their performance. In this work, the authors computationally investigate stimulus waveform designs, which can improve the performance of retinal prostheses by suppressing undesired spontaneous firing of ganglion cells and generating precise temporal spiking patterns. They utilise a multi-scale computational model for electrical stimulation of degenerated retina based on the admittance method and NEURON simulation environments. They present a class of asymmetric biphasic pulses that can generate precise ganglion cell firing patterns with up to 55% lower current requirements compared to traditional symmetric biphasic pulses. This lower current results in activation of only proximal ganglion cells, provides more focused stimulation and lowers the risk of tissue damage.
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Affiliation(s)
- Pragya Kosta
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112, USA
| | - Kyle Loizos
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Gianluca Lazzi
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA 90089, USA.,Department of Ophthalmology, University of Southern California, Los Angeles, CA 90033, USA
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Retinal Drug Delivery: Rethinking Outcomes for the Efficient Replication of Retinal Behavior. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10124258] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The retina is a highly organized structure that is considered to be "an approachable part of the brain." It is attracting the interest of development scientists, as it provides a model neurovascular system. Over the last few years, we have been witnessing significant development in the knowledge of the mechanisms that induce the shape of the retinal vascular system, as well as knowledge of disease processes that lead to retina degeneration. Knowledge and understanding of how our vision works are crucial to creating a hardware-adaptive computational model that can replicate retinal behavior. The neuronal system is nonlinear and very intricate. It is thus instrumental to have a clear view of the neurophysiological and neuroanatomic processes and to take into account the underlying principles that govern the process of hardware transformation to produce an appropriate model that can be mapped to a physical device. The mechanistic and integrated computational models have enormous potential toward helping to understand disease mechanisms and to explain the associations identified in large model-free data sets. The approach used is modulated and based on different models of drug administration, including the geometry of the eye. This work aimed to review the recently used mathematical models to map a directed retinal network.
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Zhou M, Kang DH, Kim J, Weiland JD. Shape Morphable Hydrogel/Elastomer Bilayer for Implanted Retinal Electronics. MICROMACHINES 2020; 11:mi11040392. [PMID: 32283779 PMCID: PMC7231290 DOI: 10.3390/mi11040392] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 04/03/2020] [Accepted: 04/06/2020] [Indexed: 01/09/2023]
Abstract
Direct fabrication of a three-dimensional (3D) structure using soft materials has been challenging. The hybrid bilayer is a promising approach to address this challenge because of its programable shape-transformation ability when responding to various stimuli. The goals of this study are to experimentally and theoretically establish a rational design principle of a hydrogel/elastomer bilayer system and further optimize the programed 3D structures that can serve as substrates for multi-electrode arrays. The hydrogel/elastomer bilayer consists of a hygroscopic polyacrylamide (PAAm) layer cofacially laminated with a water-insensitive polydimethylsiloxane (PDMS) layer. The asymmetric volume change in the PAAm hydrogel can bend the bilayer into a curvature. We manipulate the initial monomer concentrations of the pre-gel solutions of PAAm to experimentally and theoretically investigate the effect of intrinsic mechanical properties of the hydrogel on the resulting curvature. By using the obtained results as a design guideline, we demonstrated stimuli-responsive transformation of a PAAm/PDMS flower-shaped bilayer from a flat bilayer film to a curved 3D structure that can serve as a substrate for a wide-field retinal electrode array.
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Affiliation(s)
- Muru Zhou
- Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA;
| | - Do Hyun Kang
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA;
| | - Jinsang Kim
- Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA;
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA;
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
- Correspondence: (J.K.); (J.D.W.); Tel.: +1-734-936-4681 (J.K.); +1-734-764-9793 (J.D.W.)
| | - James D. Weiland
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48109, USA
- Correspondence: (J.K.); (J.D.W.); Tel.: +1-734-936-4681 (J.K.); +1-734-764-9793 (J.D.W.)
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Photovoltaic Restoration of Central Vision in Atrophic Age-Related Macular Degeneration. Ophthalmology 2020; 127:1097-1104. [PMID: 32249038 DOI: 10.1016/j.ophtha.2020.02.024] [Citation(s) in RCA: 102] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 02/14/2020] [Accepted: 02/18/2020] [Indexed: 11/20/2022] Open
Abstract
PURPOSE Loss of photoreceptors in atrophic age-related macular degeneration results in severe visual impairment, although some peripheral vision is retained. To restore central vision without compromising the residual peripheral field, we developed a wireless photovoltaic retinal implant (PRIMA; Pixium Vision, Paris, France) in which pixels convert images projected from video glasses using near-infrared light into electric current to stimulate the nearby inner retinal neurons. DESIGN We carried out a first-in-human clinical trial to test the safety and efficacy of the prosthesis in patients with geographic atrophy (ClinicalTrials.gov identifier, NCT03333954). PARTICIPANTS Five patients with geographic atrophy zone of at least 3 optic disc diameters, no foveal light perception, and best-corrected visual acuity of 20/400 to 20/1000 in the worse-seeing study eye. METHODS The 2-mm wide, 30-μm thick chip, containing 378 pixels (each 100 μm in diameter), was implanted subretinally in the area of atrophy (absolute scotoma). MAIN OUTCOME MEASURES Anatomic outcomes were assessed with fundus photography and OCT for up to 12 months of follow-up. Prosthetic vision was assessed by mapping light perception, bar orientation, letter recognition, and Landolt C acuity. RESULTS In all patients, the prosthesis was implanted successfully under the macula, although in 2 patients, it was implanted in unintended locations: within the choroid and off center by 2 mm. All 5 patients could perceive white-yellow prosthetic visual patterns with adjustable brightness in the previous scotomata. The 3 with optimal placement of the implant demonstrated prosthetic acuity of 20/460 to 20/550, and the patient with the off-center implant demonstrated 20/800 acuity. Residual natural acuity did not decrease after implantation in any patient. CONCLUSIONS Implantation of the PRIMA did not decrease the residual natural acuity, and it restored visual sensitivity in the former scotoma in each of the 5 patients. In 3 patients with the proper placement of the chip, prosthetic visual acuity was only 10% to 30% less than the level expected from the pixel pitch (20/420). Therefore, the use of optical or electronic magnification in the glasses as well as smaller pixels in future implants may improve visual acuity even further.
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Influence of optic media of the human eye on the imaging of Argus® II retinal prosthesis with intraoperative spectral-domain optical coherence tomography. SPEKTRUM DER AUGENHEILKUNDE 2020. [DOI: 10.1007/s00717-019-0429-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Ophthalmologic Applications. Biomater Sci 2020. [DOI: 10.1016/b978-0-12-816137-1.00072-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Finn KE, Zander HJ, Graham RD, Lempka SF, Weiland JD. A Patient-Specific Computational Framework for the Argus II Implant. IEEE OPEN JOURNAL OF ENGINEERING IN MEDICINE AND BIOLOGY 2020; 1:190-196. [PMID: 33748766 PMCID: PMC7971167 DOI: 10.1109/ojemb.2020.3001563] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Goal Retinal prosthesis performance is limited by the variability of elicited phosphenes. The stimulating electrode's position with respect to retinal ganglion cells (RGCs) affects both perceptual threshold and phosphene shape. We created a modeling framework incorporating patient-specific anatomy and electrode location to investigate RGC activation and predict inter-electrode differences for one Argus II user. Methods We used ocular imaging to build a three-dimensional finite element model characterizing retinal morphology and implant placement. To predict the neural response to stimulation, we coupled electric fields with multi-compartment cable models of RGCs. We evaluated our model predictions by comparing them to patient-reported perceptual threshold measurements. Results Our model was validated by the ability to replicate clinical impedance and threshold values, along with known neurophysiological trends. Inter-electrode threshold differences in silico correlated with in vivo results. Conclusions We developed a patient-specific retinal stimulation framework to quantitatively predict RGC activation and better explain phosphene variations.
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Affiliation(s)
- Kathleen E Finn
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and are associated with the Biointerfaces Institute
| | - Hans J Zander
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and are associated with the Biointerfaces Institute
| | - Robert D Graham
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and are associated with the Biointerfaces Institute
| | - Scott F Lempka
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and are associated with the Biointerfaces Institute
| | - James D Weiland
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and are associated with the Biointerfaces Institute
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Abstract
In outer retinal degenerative diseases such as retinitis pigmentosa, choroideremia, and geographic atrophy, 30% of the ganglion cell layer in the macula remains intact. With subretinal and epiretinal prostheses, these inner retinal cells are stimulated with controlled electrical current by either a microphotodiode placed in the subretinal area or a microelectrode array tacked to the epiretinal region. As the patient learns to interpret the resulting phosphene patterns created in the brain through special rehabilitation exercises, their orientation, mobility, and quality of life increase. Implants that stimulate the lateral geniculate nucleus or visual cortex are currently being studied for diseases in which the ganglion cells and optic nerve are completely destroyed.
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Affiliation(s)
- Emin Özmert
- Ankara University Faculty of Medicine, Department of Ophthalmology, Divisions of Medical and Surgical-Retina-Bionic Eye and Artificial Vision, Ankara, Turkey
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An update on retinal prostheses. Clin Neurophysiol 2019; 131:1383-1398. [PMID: 31866339 DOI: 10.1016/j.clinph.2019.11.029] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 11/13/2019] [Accepted: 11/14/2019] [Indexed: 11/23/2022]
Abstract
Retinal prostheses are designed to restore a basic sense of sight to people with profound vision loss. They require a relatively intact posterior visual pathway (optic nerve, lateral geniculate nucleus and visual cortex). Retinal implants are options for people with severe stages of retinal degenerative disease such as retinitis pigmentosa and age-related macular degeneration. There have now been three regulatory-approved retinal prostheses. Over five hundred patients have been implanted globally over the past 15 years. Devices generally provide an improved ability to localize high-contrast objects, navigate, and perform basic orientation tasks. Adverse events have included conjunctival erosion, retinal detachment, loss of light perception, and the need for revision surgery, but are rare. There are also specific device risks, including overstimulation (which could cause damage to the retina) or delamination of implanted components, but these are very unlikely. Current challenges include how to improve visual acuity, enlarge the field-of-view, and reduce a complex visual scene to its most salient components through image processing. This review encompasses the work of over 40 individual research groups who have built devices, developed stimulation strategies, or investigated the basic physiology underpinning retinal prostheses. Current technologies are summarized, along with future challenges that face the field.
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