1
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He Y, Toft-Nielsen J, Legge G, Montezuma SR. Pattern-reversal visual evoked potentials in prosthetic vision and simulated visual reduction. BMJ Open Ophthalmol 2024; 9:e001705. [PMID: 39103235 PMCID: PMC11308878 DOI: 10.1136/bmjophth-2024-001705] [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: 03/10/2024] [Accepted: 07/12/2024] [Indexed: 08/07/2024] Open
Abstract
OBJECTIVE To quantitatively evaluate visual evoked potentials (VEPs) in prosthetic vision and simulated visual reduction. METHODS AND ANALYSIS Four blind patients implanted with the Argus II retinal prosthesis and seven sighted controls participated. VEPs were recorded with pattern-reversal stimuli (2 cycles of a horizontal square wave grating, 0.1 cycle/degree) at 1.07 reversals per second (rps) for Argus II subjects and 3.37 rps for controls. Argus II patients had both eyes patched, viewing the pattern solely through their implant. Controls viewed the pattern monocularly, either with their best-corrected vision or with simulated visual reduction (field restriction, added blur or reduced display contrast). RESULTS VEPs recorded in Argus II patients displayed a similar shape to normal VEPs when controls viewed the pattern without simulated visual reduction. In sighted controls, adding blur significantly delayed the P100 peak time by 8.7 ms, 95% CI (0.9, 16.6). Reducing stimulus contrast to 32% and 6% of full display contrast significantly decreased P100 amplitude to 55% (37%, 82%) and 20% (13%, 31%), respectively. Restriction on the field of view had no impact on either the amplitude or the peak latency of P100. CONCLUSION The early visual cortex in retinal prosthesis users remains responsive to retinal input, showing a similar response profile to that of sighted controls. Pattern-reversal VEP offers valuable insights for objectively evaluating artificial vision therapy systems (AVTSs) when selecting, fitting and training implant users, but the uncertainties in the exact timing and location of electrode stimulation must be considered when interpreting the results.
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Affiliation(s)
- Yingchen He
- Department of Psychology, North Carolina State University, Raleigh, North Carolina, USA
| | - Jonathon Toft-Nielsen
- Department of Biomedical Engineering, University of Miami, Coral Gables, Florida, USA
- Intelligent Hearing Systems, Miami, Florida, USA
| | - Gordon Legge
- Department of Psychology, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA
| | - Sandra R Montezuma
- Ophthalmology and Visual Neurosciences, University of Minnesota Twin Cities, Minneapolis, Minnesota, USA
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2
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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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3
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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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4
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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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5
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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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6
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Karadima V, Pezaris EA, Pezaris JS. Attitudes of potential recipients toward emerging visual prosthesis technologies. Sci Rep 2023; 13:10963. [PMID: 37414798 PMCID: PMC10325978 DOI: 10.1038/s41598-023-36913-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Accepted: 06/12/2023] [Indexed: 07/08/2023] Open
Abstract
With the advent of multiple visual prosthesis devices to treat blindness, the question of how potential patients view such interventions becomes important in order to understand the levels of expectation and acceptance, and the perceived risk-reward balance across the different device approaches. Building on previous work on single device approaches done with blind individuals in Chicago and Detroit, USA, Melbourne, Australia, and Bejing, China, we investigated attitudes in blind individuals in Athens, Greece with coverage expanded to three of the contemporary approaches, Retinal, Thalamic, and Cortical. We presented an informational lecture on the approaches, had potential participants fill out a preliminary Questionnaire 1, then organized selected subjects into focus groups for guided discussion on visual prostheses, and finally had these subjects fill out a more detailed Questionnaire 2. We report here the first quantitative data that compares multiple prosthesis approaches. Our primary findings are that for these potential patients, perceived risk continues to outweigh perceived benefits, with the Retinal approach having the least negative overall impression and the Cortical approach the most negative. Concerns about the quality of restored vision were primary. Factors that drove the choice of hypothetical participation in a clinical trial were age and years of blindness. Secondary factors focused on positive clinical outcomes. The focus groups served to swing the impressions of each approach from neutrality toward the extremes of a Likert scale, and shifted the overall willingness to participate in a clinical trial from neutral to negative. These results, coupled with informal assessment of audience questions after the informational lecture, suggest that a substantial improvement in performance over currently available devices will be necessary before visual prostheses gain wide acceptance.
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Affiliation(s)
- Vicky Karadima
- Multisensory and Temporal Processing Lab (MultiTimeLab), Department of Psychology, Panteion University of Social and Political Sciences, Athens, Greece
| | | | - John S Pezaris
- Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, USA.
- Department of Neurosurgery, Harvard Medical School, Boston, MA, USA.
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7
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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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8
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Titchener SA, Goossens J, Kvansakul J, Nayagam DAX, Kolic M, Baglin EK, Ayton LN, Abbott CJ, Luu CD, Barnes N, Kentler WG, Shivdasani MN, Allen PJ, Petoe MA. Estimating Phosphene Locations Using Eye Movements of Suprachoroidal Retinal Prosthesis Users. Transl Vis Sci Technol 2023; 12:20. [PMID: 36943168 PMCID: PMC10043502 DOI: 10.1167/tvst.12.3.20] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023] Open
Abstract
Purpose Accurate mapping of phosphene locations from visual prostheses is vital to encode spatial information. This process may involve the subject pointing to evoked phosphene locations with their finger. Here, we demonstrate phosphene mapping for a retinal implant using eye movements and compare it with retinotopic electrode positions and previous results using conventional finger-based mapping. Methods Three suprachoroidal retinal implant recipients (NCT03406416) indicated the spatial position of phosphenes. Electrodes were stimulated individually, and the subjects moved their finger (finger based) or their eyes (gaze based) to the perceived phosphene location. The distortion of the measured phosphene locations from the expected locations (retinotopic electrode locations) was characterized with Procrustes analysis. Results The finger-based phosphene locations were compressed spatially relative to the expected locations all three subjects, but preserved the general retinotopic arrangement (scale factors ranged from 0.37 to 0.83). In two subjects, the gaze-based phosphene locations were similar to the expected locations (scale factors of 0.72 and 0.99). For the third subject, there was no apparent relationship between gaze-based phosphene locations and electrode locations (scale factor of 0.07). Conclusions Gaze-based phosphene mapping was achievable in two of three tested retinal prosthesis subjects and their derived phosphene maps correlated well with the retinotopic electrode layout. A third subject could not produce a coherent gaze-based phosphene map, but this may have revealed that their phosphenes were indistinct spatially. Translational Relevance Gaze-based phosphene mapping is a viable alternative to conventional finger-based mapping, but may not be suitable for all subjects.
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Affiliation(s)
- Samuel A Titchener
- Bionics Institute, East Melbourne, VIC, Australia
- Medical Bionics Department, University of Melbourne, Melbourne, VIC, Australia
| | - Jeroen Goossens
- Donders Institute for Brain Cognition and Behaviour, Radboudumc, the Netherlands
| | - Jessica Kvansakul
- Bionics Institute, East Melbourne, VIC, Australia
- Medical Bionics Department, University of Melbourne, Melbourne, VIC, Australia
| | - David A X Nayagam
- Bionics Institute, East Melbourne, VIC, Australia
- Department of Pathology, University of Melbourne, Victoria, Australia
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, VIC, Australia
| | - Maria Kolic
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, VIC, Australia
| | - Elizabeth K Baglin
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, VIC, Australia
| | - Lauren N Ayton
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, VIC, Australia
- Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, VIC, Australia
- Department of Optometry and Vision Sciences, University of Melbourne, Melbourne, VIC, Australia
| | - Carla J Abbott
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, VIC, Australia
- Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, VIC, Australia
| | - Chi D Luu
- Centre for Eye Research Australia, Royal Victorian Eye & Ear Hospital, Melbourne, VIC, Australia
- Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, VIC, Australia
| | - Nick Barnes
- Data61, CSIRO, Canberra, ACT, Australia
- Research School of Engineering, Australian National University, ACT, Australia
| | - William G Kentler
- Department of Biomedical Engineering, University of Melbourne, Melbourne, VIC, Australia
| | - Mohit N Shivdasani
- 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, VIC, Australia
- Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, VIC, Australia
| | - Matthew A Petoe
- Bionics Institute, East Melbourne, VIC, Australia
- Medical Bionics Department, University of Melbourne, Melbourne, VIC, Australia
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9
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Ly K, Guo T, Tsai D, Muralidharan M, Shivdasani MN, Lovell NH, Dokos S. Simulating the impact of photoreceptor loss and inner retinal network changes on electrical activity of the retina. J Neural Eng 2022; 19. [PMID: 36368033 DOI: 10.1088/1741-2552/aca221] [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: 08/03/2022] [Accepted: 11/11/2022] [Indexed: 11/13/2022]
Abstract
Objective.A major reason for poor visual outcomes provided by existing retinal prostheses is the limited knowledge of the impact of photoreceptor loss on retinal remodelling and its subsequent impact on neural responses to electrical stimulation. Computational network models of the neural retina assist in the understanding of normal retinal function but can be also useful for investigating diseased retinal responses to electrical stimulation.Approach.We developed and validated a biophysically detailed discrete neuronal network model of the retina in the software package NEURON. The model includes rod and cone photoreceptors, ON and OFF bipolar cell pathways, amacrine and horizontal cells and finally, ON and OFF retinal ganglion cells with detailed network connectivity and neural intrinsic properties. By accurately controlling the network parameters, we simulated the impact of varying levels of degeneration on retinal electrical function.Main results.Our model was able to reproduce characteristic monophasic and biphasic oscillatory patterns seen in ON and OFF neurons during retinal degeneration (RD). Oscillatory activity occurred at 3 Hz with partial photoreceptor loss and at 6 Hz when all photoreceptor input to the retina was removed. Oscillations were found to gradually weaken, then disappear when synapses and gap junctions were destroyed in the inner retina. Without requiring any changes to intrinsic cellular properties of individual inner retinal neurons, our results suggest that changes in connectivity alone were sufficient to give rise to neural oscillations during photoreceptor degeneration, and significant network connectivity destruction in the inner retina terminated the oscillations.Significance.Our results provide a platform for further understanding physiological retinal changes with progressive photoreceptor and inner RD. Furthermore, our model can be used to guide future stimulation strategies for retinal prostheses to benefit patients at different stages of disease progression, particularly in the early and mid-stages of RD.
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Affiliation(s)
- Keith Ly
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia
| | - David Tsai
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia.,School of Electrical Engineering & Telecommunications, UNSW, Sydney, NSW 2052, Australia
| | | | - Mohit N Shivdasani
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia.,Tyree Institute of Health Engineering (IHealthE), UNSW, Sydney, NSW 2052, Australia
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, UNSW, Sydney, NSW, 2052, Australia
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10
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Rotov AY, Firsov ML. Optogenetic Prosthetization of Retinal Bipolar Cells. J EVOL BIOCHEM PHYS+ 2022. [DOI: 10.1134/s0022093022060011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Abstract
Although the experience of optogenetic retinal prosthetics
in animal models dates back to more than 16 years, the first results
obtained on humans have only been reported in the last year. Over this
period, the main challenges of prosthetics became clear and the
approaches to their solution were proposed. In this review, we aim
to present the achievements in the field of optogenetic prosthetization
of retinal bipolar cells with a focus mainly on relatively recent
publications. The review addresses the advantages and disadvantages
of bipolar cell prosthetics as compared to the alternative target,
retinal ganglion cells, and provides a comparative analysis of the
effectiveness of ionotropic light-sensitive proteins (channelrhodopsins)
or metabotropic receptors (rhodopsins) as prosthetic tools.
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11
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Roh H, Otgondemberel Y, Im M. Short pulses of epiretinal prostheses evoke network-mediated responses in retinal ganglion cells by stimulating presynaptic neurons. J Neural Eng 2022; 19. [PMID: 36055185 DOI: 10.1088/1741-2552/ac8ed7] [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: 04/07/2022] [Accepted: 09/02/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Microelectronic retinal implant aims to restore functional vision with electric stimulation. Short pulses are generally known to directly activate retinal ganglion cells (RGCs) with a notion of one or two spike(s) per pulse. In the present work, we systematically explore network-mediated responses that arise from various short pulses in both normal and degenerate retinas. APPROACH Cell-attached patch clamping was used to record spiking responses of RGCs in wild-type (C57BL/6J) and retinal degeneration (rd10) mice. Alpha RGCs of the mouse retinas were targeted by their large soma sizes and classified by their responses to spot flashes. Then, RGCs were electrically stimulated by various conditions such as duration (100-460 μs), count (1-10), amplitude (100-400 μA), and repeating frequency (10-40 Hz) of short pulses. Also, their responses were compared with each own response to a single 4-ms-long pulse which is known to evoke strong indirect responses. MAIN RESULTS Short pulses evoked strong network-mediated responses not only in both ON and OFF types of RGCs in the healthy retinas but also in RGCs of the severely degenerate retina. However, the spike timing consistency across repeats not decreased significantly in the rd10 RGCs compared to the healthy ON and OFF RGCs. Network-mediated responses of ON RGCs were highly dependent on the current amplitude of stimuli but much less on the pulse count and the repetition frequency. In contrast, responses of OFF RGCs were more influenced by the number of stimuli than the current amplitude. SIGNIFICANCE Our results demonstrate that short pulses also elicit indirect responses by activating presynaptic neurons. In the case of the commercial retinal prostheses using repeating short pulses, there is a possibility that the performance of clinical devices is highly related to the preserved retinal circuits. Therefore, examination of surviving retinal neurons in patients would be necessary to improve the efficacy of retinal prostheses.
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Affiliation(s)
- Hyeonhee Roh
- Korea Institute of Science and Technology (KIST), 5 Hwarang-ro 14-gil, Seongbuk-gu, Seoul, 02792, Korea (the Republic of)
| | - Yanjinsuren Otgondemberel
- Brain Science Institute, Korea Institute of Science and Technology (KIST), 5 Hwarang-ro 14-gil, Seongbuk-gu, Seoul, 02792, Korea (the Republic of)
| | - Maesoon Im
- Brain Science Institute, Center for BioMicrosystems, Korea Institute of Science and Technology, 5 Hwarang-ro 14-gil, Seongbuk-gu, L7325B, Seoul, Seoul, Seoul, 02792, Korea (the Republic of)
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12
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Avraham D, Yitzhaky Y. Simulating the perceptual effects of electrode-retina distance in prosthetic vision. J Neural Eng 2022; 19. [PMID: 35561665 DOI: 10.1088/1741-2552/ac6f82] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Accepted: 05/13/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Retinal prostheses aim to restore some vision in retinitis pigmentosa and age-related macular degeneration blind patients. Many spatial and temporal aspects have been found to affect prosthetic vision. Our objective is to study the impact of the space-variant distance between the stimulating electrodes and the surface of the retina on prosthetic vision and how to mitigate this impact. APPROACH A prosthetic vision simulation was built to demonstrate the perceptual effects of the electrode-retina distance (ERD) with different random spatial variations, such as size, brightness, shape, dropout, and spatial shifts. Three approaches for reducing the ERD effects are demonstrated: electrode grouping (quads), ERD-based input-image enhancement, and object scanning with and without phosphene persistence. A quantitative assessment for the first two approaches was done based on experiments with 20 subjects and three vision-based computational image similarity metrics. MAIN RESULTS The effects of various ERDs on phosphenes' size, brightness, and shape were simulated. Quads, chosen according to the ERDs, effectively elicit phosphenes without exceeding the safe charge density limit, whereas single electrodes with large ERD cannot do so. Input-image enhancement reduced the ERD effects effectively. These two approaches significantly improved ERD-affected prosthetic vision according to the experiment and image similarity metrics. A further reduction of the ERD effects was achieved by scanning an object while moving the head. SIGNIFICANCE ERD has multiple effects on perception with retinal prostheses. One of them is vision loss caused by the incapability of electrodes with large ERD to evoke phosphenes. The three approaches presented in this study can be used separately or together to mitigate the impact of ERD. A consideration of our approaches in reducing the perceptual effects of the ERD may help improve the perception with current prosthetic technology and influence the design of future prostheses.
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Affiliation(s)
- David Avraham
- Department of Electro-Optical Engineering, Ben-Gurion University of the Negev, 1 Ben-Gurion Blvd., Beer-Sheva, 84105, ISRAEL
| | - Yitzhak Yitzhaky
- Electro-Optical Engineering, School of Engineering, Ben-Gurion University of the Negev, 1 Ben-Gurion Blvd., Beer-Sheva, Southern, 84105, ISRAEL
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13
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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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Schneider N, Sundaresan Y, Gopalakrishnan P, Beryozkin A, Hanany M, Levanon EY, Banin E, Ben-Aroya S, Sharon D. Inherited retinal diseases: Linking genes, disease-causing variants, and relevant therapeutic modalities. Prog Retin Eye Res 2021; 89:101029. [PMID: 34839010 DOI: 10.1016/j.preteyeres.2021.101029] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 11/11/2021] [Accepted: 11/16/2021] [Indexed: 12/11/2022]
Abstract
Inherited retinal diseases (IRDs) are a clinically complex and heterogenous group of visual impairment phenotypes caused by pathogenic variants in at least 277 nuclear and mitochondrial genes, affecting different retinal regions, and depleting the vision of affected individuals. Genes that cause IRDs when mutated are unique by possessing differing genotype-phenotype correlations, varying inheritance patterns, hypomorphic alleles, and modifier genes thus complicating genetic interpretation. Next-generation sequencing has greatly advanced the identification of novel IRD-related genes and pathogenic variants in the last decade. For this review, we performed an in-depth literature search which allowed for compilation of the Global Retinal Inherited Disease (GRID) dataset containing 4,798 discrete variants and 17,299 alleles published in 31 papers, showing a wide range of frequencies and complexities among the 194 genes reported in GRID, with 65% of pathogenic variants being unique to a single individual. A better understanding of IRD-related gene distribution, gene complexity, and variant types allow for improved genetic testing and therapies. Current genetic therapeutic methods are also quite diverse and rely on variant identification, and range from whole gene replacement to single nucleotide editing at the DNA or RNA levels. IRDs and their suitable therapies thus require a range of effective disease modelling in human cells, granting insight into disease mechanisms and testing of possible treatments. This review summarizes genetic and therapeutic modalities of IRDs, provides new analyses of IRD-related genes (GRID and complexity scores), and provides information to match genetic-based therapies such as gene-specific and variant-specific therapies to the appropriate individuals.
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Affiliation(s)
- Nina Schneider
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, 91120, Israel
| | - Yogapriya Sundaresan
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, 91120, Israel
| | - Prakadeeswari Gopalakrishnan
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, 91120, Israel
| | - Avigail Beryozkin
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, 91120, Israel
| | - Mor Hanany
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, 91120, Israel
| | - Erez Y Levanon
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 5290002, Israel
| | - Eyal Banin
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, 91120, Israel
| | - Shay Ben-Aroya
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 5290002, Israel
| | - Dror Sharon
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, 91120, Israel.
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15
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Ezeokafor I, Upadhya A, Shetty S. Neurosensory Prosthetics: An Integral Neuromodulation Part of Bioelectronic Device. Front Neurosci 2021; 15:671767. [PMID: 34867141 PMCID: PMC8637173 DOI: 10.3389/fnins.2021.671767] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 10/07/2021] [Indexed: 12/28/2022] Open
Abstract
Bioelectronic medicines (BEMs) constitute a branch of bioelectronic devices (BEDs), which are a class of therapeutics that combine neuroscience with molecular biology, immunology, and engineering technologies. Thus, BEMs are the culmination of thought processes of scientists of varied fields and herald a new era in the treatment of chronic diseases. BEMs work on the principle of neuromodulation of nerve stimulation. Examples of BEMs based on neuromodulation are those that modify neural circuits through deep brain stimulation, vagal nerve stimulation, spinal nerve stimulation, and retinal and auditory implants. BEDs may also serve as diagnostic tools by mimicking human sensory systems. Two examples of in vitro BEDs used as diagnostic agents in biomedical applications based on in vivo neurosensory circuits are the bioelectronic nose and bioelectronic tongue. The review discusses the ever-growing application of BEDs to a wide variety of health conditions and practices to improve the quality of life.
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Affiliation(s)
| | - Archana Upadhya
- Shobhaben Pratapbhai Patel School of Pharmacy & Technology Management, Shri Vile Parle Kelavani Mandal (SVKM) Narsee Monjee Institute of Management Studies (NMiMS) (SVKM’S NMiMS), Mumbai, India
| | - Saritha Shetty
- Shobhaben Pratapbhai Patel School of Pharmacy & Technology Management, Shri Vile Parle Kelavani Mandal (SVKM) Narsee Monjee Institute of Management Studies (NMiMS) (SVKM’S NMiMS), Mumbai, India
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16
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Paknahad J, Kosta P, Iseri E, Farzad S, Bouteiller JMC, Humayun MS, Lazzi G. Modeling ON Cone Bipolar Cells for Electrical Stimulation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2021; 2021:6547-6550. [PMID: 34892609 PMCID: PMC8754156 DOI: 10.1109/embc46164.2021.9629884] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Retinal prosthetic systems have been developed to help blind patients suffering from retinal degenerative diseases gain some useful form of vision. Various experimental and computational studies have been performed to test electrical stimulation strategies that can improve the performance of these devices. Detailed computational models of retinal neurons, such as retinal ganglion cells (RGCs) and bipolar cells (BCs), allow us to explore the mechanisms underlying the response of cells to electrical stimulation. While electrophysiological studies have shown the presence of voltage-gated ionic channels in different regions of BCs, many of the existing cone BCs models are assumed to be passive or only contain calcium channels at the synaptic terminals. We have utilized our Admittance Method (AM)-NEURON computational platform to implement a more realistic model of ON-BCs. Our model closely replicates the recent patch-clamp experiments directly measuring the response of ON-BCs to epiretinal electrical stimulation and thereby predicts the regional distributions of the ionic channels. Our computational results further indicate that outward potassium current strongly contributes to the depolarizing voltage transient of ON-BCs in response to electrical stimulation.
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17
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Avraham D, Jung JH, Yitzhaky Y, Peli E. Retinal prosthetic vision simulation: temporal aspects. J Neural Eng 2021; 18. [PMID: 34359062 DOI: 10.1088/1741-2552/ac1b6c] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 08/06/2021] [Indexed: 11/11/2022]
Abstract
Objective. The perception of individuals fitted with retinal prostheses is not fully understood, although several retinal implants have been tested and commercialized. Realistic simulations of perception with retinal implants would be useful for future development and evaluation of such systems.Approach.We implemented a retinal prosthetic vision simulation, including temporal features, which have not been previously simulated. In particular, the simulation included temporal aspects such as persistence and perceptual fading of phosphenes and the electrode activation rate.Main results.The simulated phosphene persistence showed an effective reduction in flickering at low electrode activation rates. Although persistence has a positive effect on static scenes, it smears dynamic scenes. Perceptual fading following continuous stimulation affects prosthetic vision of both static and dynamic scenes by making them disappear completely or partially. However, we showed that perceptual fading of a static stimulus might be countered by head-scanning motions, which together with the persistence revealed the contours of the faded object. We also showed that changing the image polarity may improve simulated prosthetic vision in the presence of persistence and perceptual fading.Significance.Temporal aspects have important roles in prosthetic vision, as illustrated by the simulations. Considering these aspects may improve the future design, the training with, and evaluation of retinal prostheses.
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Affiliation(s)
- David Avraham
- Department of Electro-Optical Engineering, School of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer Sheva, Israel.,Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA, United States of America
| | - Jae-Hyun Jung
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA, United States of America
| | - Yitzhak Yitzhaky
- Department of Electro-Optical Engineering, School of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Eli Peli
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA, United States of America
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18
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Parameswarappa DC, Das AV, Dave VP, Agarwal K, Natarajan R, Jalali S. Clinical Presentation and Demographic Distribution of Retinitis Pigmentosa in India and Implications for Potential Treatments: Electronic Medical Records Driven Big Data Analytics: Report I. Semin Ophthalmol 2021; 37:284-290. [PMID: 34404308 DOI: 10.1080/08820538.2021.1957126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
AimTo describe the clinical presentation and demographic distribution of retinitis pigmentosa in patients presenting to a multi-tier ophthalmology hospital network in India and implications for potential treatments.DesignCross-sectional hospital-based study.MethodsThis study included 2,541,810 patients presenting between March 2012 and October 2020. Patients with a clinical diagnosis of retinitis pigmentosa in at least one eye were included as cases. The data were collected using an electronic medical record system.ResultsOverall, 15,062 (0.59%) new patients were diagnosed with retinitis pigmentosa and were included for analysis. The median age was 35 (IQR: 21-49) years and adult age (84.56%) presented more often. The most common presenting age group was between 21 and 30 years (20%). Majority of patients were male (61.68%) and had bilateral (96.39%) affliction. There was a family history in a tenth of the patients (10.46%) and a history of consanguinity in a minority (5.53%). The majority of the eyes had mild or no central visual acuity impairment of <20/70 (34.25%) followed by blindness <20/400 to 20/1200 (21.26%). The predominant retinal signs included disc pallor (76.43%), attenuated arterioles (82.61%) and bony spicule pigmentation (90.15%), and almost all had retinal pigmentary changes. A minority of the eyes underwent a surgical procedure (4.96%).ConclusionRetinitis pigmentosa is commonly bilateral and predominantly affects males. Most patients present in the third decade of life with severe visual acuity impairment. More than half of the eyes from our study are potential candidates for newer therapies. These results have implications for upcoming treatment choices and planning.
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Affiliation(s)
- Deepika C Parameswarappa
- Srimati Kanuri Santhamma Center for Vitreo - Retinal Diseases, L V Prasad Eye Institute, Hyderabad, Telangana, India
| | - Anthony Vipin Das
- Department of eyeSmart EMR & AEye, LV Prasad Eye Institute, Hyderabad, India
| | - Vivek Pravin Dave
- Srimati Kanuri Santhamma Center for Vitreo - Retinal Diseases, L V Prasad Eye Institute, Hyderabad, Telangana, India
| | - Komal Agarwal
- Srimati Kanuri Santhamma Center for Vitreo - Retinal Diseases, L V Prasad Eye Institute, Hyderabad, Telangana, India
| | - Ramya Natarajan
- Department of Ophthalmic Biophysics, Kallam Anji Reddy Campus, L V Prasad Eye Institute, Hyderabad, Telangana, India
| | - Subhadra Jalali
- Srimati Kanuri Santhamma Center for Vitreo - Retinal Diseases, L V Prasad Eye Institute, Hyderabad, Telangana, India
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19
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Petoe MA, Titchener SA, Kolic M, Kentler WG, Abbott CJ, Nayagam DAX, Baglin EK, Kvansakul J, Barnes N, Walker JG, Epp SB, Young KA, Ayton LN, Luu CD, Allen PJ. A Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis: Interim Clinical Trial Results. Transl Vis Sci Technol 2021; 10:12. [PMID: 34581770 PMCID: PMC8479573 DOI: 10.1167/tvst.10.10.12] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To report the initial safety and efficacy results of a second-generation (44-channel) suprachoroidal retinal prosthesis at 56 weeks after device activation. Methods Four subjects, with advanced retinitis pigmentosa and bare-light perception only, enrolled in a phase II trial (NCT03406416). A 44-channel electrode array was implanted in a suprachoroidal pocket. Device stability, efficacy, and adverse events were investigated at 12-week intervals. Results All four subjects were implanted successfully and there were no device-related serious adverse events. Color fundus photography indicated a mild postoperative subretinal hemorrhage in two recipients, which cleared spontaneously within 2 weeks. Optical coherence tomography confirmed device stability and position under the macula. Screen-based localization accuracy was significantly better for all subjects with device on versus device off. Two subjects were significantly better with the device on in a motion discrimination task at 7, 15, and 30°/s and in a spatial discrimination task at 0.033 cycles per degree. All subjects were more accurate with the device on than device off at walking toward a target on a modified door task, localizing and touching tabletop objects, and detecting obstacles in an obstacle avoidance task. A positive effect of the implant on subjects' daily lives was confirmed by an orientation and mobility assessor and subject self-report. Conclusions These interim study data demonstrate that the suprachoroidal prosthesis is safe and provides significant improvements in functional vision, activities of daily living, and observer-rated quality of life. Translational Relevance A suprachoroidal prosthesis can provide clinically useful artificial vision while maintaining a safe surgical profile.
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Affiliation(s)
- Matthew A Petoe
- Bionics Institute, East Melbourne, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Melbourne, Victoria, Australia
| | - Samuel A Titchener
- Bionics Institute, East Melbourne, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Melbourne, Victoria, Australia
| | - Maria Kolic
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - William G Kentler
- Department of Biomedical Engineering, University of Melbourne, Melbourne, Victoria, Australia
| | - Carla J Abbott
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
| | - David A X Nayagam
- Bionics Institute, East Melbourne, Victoria, Australia.,Department of Pathology, University of Melbourne, St. Vincent's Hospital, Victoria, Australia
| | - Elizabeth K Baglin
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - Jessica Kvansakul
- Bionics Institute, East Melbourne, Victoria, Australia.,Medical Bionics Department, University of Melbourne, Melbourne, Victoria, Australia
| | - Nick Barnes
- Research School of Engineering, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Janine G Walker
- Research School of Engineering, Australian National University, Canberra, Australian Capital Territory, Australia.,Health & Biosecurity, CSIRO, Canberra, Australian Capital Territory, Australia
| | | | - Kiera A Young
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - Lauren N Ayton
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia.,Department of Optometry and Vision Sciences, University of Melbourne, Australia
| | - Chi D Luu
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
| | - Penelope J Allen
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia.,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
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20
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Gaillet V, Borda E, Zollinger EG, Ghezzi D. A machine-learning algorithm correctly classifies cortical evoked potentials from both visual stimulation and electrical stimulation of the optic nerve. J Neural Eng 2021; 18. [PMID: 33823498 DOI: 10.1088/1741-2552/abf523] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 04/06/2021] [Indexed: 11/12/2022]
Abstract
Objective. Optic nerve's intraneural stimulation is an emerging neuroprosthetic approach to provide artificial vision to totally blind patients. An open question is the possibility to evoke individual non-overlapping phosphenes via selective intraneural optic nerve stimulation. To begin answering this question, first, we aim at showing in preclinical experiments with animals that each intraneural electrode could evoke a distinguishable activity pattern in the primary visual cortex.Approach. We performed both patterned visual stimulation and patterned electrical stimulation in healthy rabbits while recording evoked cortical activity with an electrocorticogram array in the primary visual cortex. Electrical stimulation was delivered to the optic nerve with the intraneural array OpticSELINE. We used a support vector machine algorithm paired to a linear regression model to classify cortical responses originating from visual stimuli located in different portions of the visual field and electrical stimuli from the different electrodes of the OpticSELINE.Main results. Cortical activity induced by visual and electrical stimulation could be classified with nearly 100% accuracy relative to the specific location in the visual field or electrode in the array from which it originated. For visual stimulation, the accuracy increased with the separation of the stimuli and reached 100% for separation higher than 7°. For electrical stimulation, at low current amplitudes, the accuracy increased with the distance between electrodes, while at higher current amplitudes, the accuracy was nearly 100% already for the shortest separation.Significance. Optic nerve's intraneural stimulation with the OpticSELINE induced discernible cortical activity patterns. These results represent a necessary condition for an optic nerve prosthesis to deliver vision with non-overlapping phosphene. However, clinical investigations will be required to assess the translation of these results into perceptual phenomena.
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Affiliation(s)
- Vivien Gaillet
- Medtronic Chair in Neuroengineering, Center for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique fédérale de Lausanne, Geneva 1202, Switzerland
| | - Eleonora Borda
- Medtronic Chair in Neuroengineering, Center for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique fédérale de Lausanne, Geneva 1202, Switzerland
| | - Elodie Geneviève Zollinger
- Medtronic Chair in Neuroengineering, Center for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique fédérale de Lausanne, Geneva 1202, Switzerland
| | - Diego Ghezzi
- Medtronic Chair in Neuroengineering, Center for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique fédérale de Lausanne, Geneva 1202, Switzerland
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21
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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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22
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Abstract
Visual prostheses aim to restore, at least to some extent, vision that leads to the type of perception available for sighted patients. Their effectiveness is almost always evaluated using clinical tests of vision. Clinical vision tests are designed to measure the limits of parameters of a functioning visual system. I argue here that these tests are rarely suited to determine the ability of prosthetic devices and other therapies to restore vision. This paper describes and explains many limitations of these evaluations. Prosthetic vision testing often makes use of multiple-alternative forced-choice (MAFC) procedures. Although these paradigms are suitable for many studies, they are frequently problematic in vision restoration evaluation. Two main types of problems are identified: (1) where nuisance variables provide spurious cues that can be learned in repeated training, which is common in prosthetic vision, and thus defeat the purpose of the test; and (2) even though a test is properly designed and performed, it may not actually measure what the researchers believe, and thus the interpretation of results is wrong. Examples for both types of problems are presented. Additional problems arise from confounding factors in the administration of tests are pointed as limitations of current device evaluation. For example, head tracing of magnified objects enlarged to compensate for the system's low resolution, in distinction from the scanning head (camera) movements with which users of prosthetic devices expand the limited field of view. Because of these problems, the ability to perform satisfactorily on the clinical tests is necessary but insufficient to prove vision restoration, therefore, additional tests are needed. I propose some directions to pursue in such testing. Translational Relevance Numerous prosthetic devices are being developed and introduced to the market. Proving the utility of these devices is crucial for regulatory and even for post market acceptance, which so far has largely failed, in my opinion. Potential reasons for the failures despite success in regulatory testing and directions for designing improved testing are provided. It is hoped that improved testing will guide improved designs of future prosthetic systems and other vision restoration approaches.
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Affiliation(s)
- Eli Peli
- Schepens Eye Research Institute of Mass Eye & Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
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23
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Song X, Guo T, Shivdasani MN, Dokos S, Lovell NH, Li X, Qiu S, Li T, Zheng S, Li L. Creation of virtual channels in the retina using synchronous and asynchronous stimulation - a modelling study. J Neural Eng 2020; 17. [PMID: 33086210 DOI: 10.1088/1741-2552/abc3a9] [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: 03/01/2020] [Accepted: 10/21/2020] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Implantable retinal prostheses aim to provide artificial vision to those suffering from retinal degenerative diseases by electrically stimulating the remaining retinal neurons using a multi-electrode array. The spatial resolution of these devices can be improved by creation of so-called virtual channels (VCs) that are commonly achieved through synchronized stimulation of multiple electrodes. It is largely unclear though if VCs can be created using asynchronous stimulation, which was the primary aim of this study. APPROACH A computational model of multi-layered retina and epi-retinal dual-electrode stimulation was developed to simulate the neural activity of populations of retinal ganglion cells (RGCs) using the VC strategy under both synchronous and asynchronous stimulation conditions. MAIN RESULTS Our simulation suggests that VCs can be created using asynchronous stimulation. VC performance under both synchronous and asynchronous stimulation conditions can be improved by optimizing stimulation parameters such as current intensity, current ratio (α) between two electrodes, electrode spacing and the stimulation waveform. In particular, two VC performance measures; (1) linear displacement of the centroid of RGC activation, and (2) the RGC activation size consistency as a function of different current ratios α, have comparable performance under asynchronous and synchronous stimulation with appropriately selected stimulation parameters. SIGNIFICANCE Our findings support the possibility of creating VCs in the retina under both synchronous and asynchronous stimulation conditions. The results provide theoretical evidence for future retinal prosthesis designs with higher spatial resolution and power efficiency whilst reducing the number of current sources required to achieve these outcomes.
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Affiliation(s)
- Xiaoyu Song
- , Shanghai Jiao Tong University, Shanghai, 200240, CHINA
| | - Tianruo Guo
- GSBME, UNSW, Sydney, New South Wales, 2052, AUSTRALIA
| | - Mohit N Shivdasani
- Graduate School of Biomedical Engineering, University of New South Wales, Lower Ground, Samuels Building (F25), Kensington, New South Wales, AUSTRALIA
| | - Socrates Dokos
- Graduate School of Biomedical Engineering, The University of New South Wales, Sydney 2052, New South Wales, Sydney, New South Wales, 2052, AUSTRALIA
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW 2052, Sydney, 2052, AUSTRALIA
| | - Xinxin Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, CHINA
| | - Shirong Qiu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, CHINA
| | - Tong Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, CHINA
| | - Shiwei Zheng
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, CHINA
| | - Liming Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, Shanghai, CHINA
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24
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Markan A, Kumar A, Vira J, Gupta V, Agarwal A. Advances in the tools and techniques of vitreoretinal surgery. EXPERT REVIEW OF OPHTHALMOLOGY 2020. [DOI: 10.1080/17469899.2020.1810018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Ashish Markan
- Advanced Eye Center, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
| | - Aman Kumar
- Advanced Eye Center, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
| | - Jayesh Vira
- Department of Ophthalmology, Sankara Eye Hospital, Coimbatore, India
| | - Vishali Gupta
- Department of Ophthalmology, Sankara Eye Hospital, Coimbatore, India
| | - Aniruddha Agarwal
- Advanced Eye Center, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
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25
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Yoon YJ, Lee JI, Jang YJ, An S, Kim JH, Fried SI, Im M. Retinal Degeneration Reduces Consistency of Network-Mediated Responses Arising in Ganglion Cells to Electric Stimulation. IEEE Trans Neural Syst Rehabil Eng 2020; 28:1921-1930. [PMID: 32746297 PMCID: PMC7518787 DOI: 10.1109/tnsre.2020.3003345] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Retinal prostheses use periodic repetition of electrical stimuli to form artificial vision. To enhance the reliability of evoked visual percepts, repeating stimuli need to evoke consistent spiking activity in individual retinal ganglion cells (RGCs). However, it is not well known whether outer retinal degeneration alters the consistency of RGC responses. Hence, here we systematically investigated the trial-to-trial variability in network-mediated responses as a function of the degeneration level. We patch-clamp recorded spikes in ON and OFF types of alpha RGCs from r d10 mice at four different postnatal days (P15, P19, P31, and P60), representing distinct stages of degeneration. To assess the consistency of responses, we analyzed variances in spike count and timing across repeats of the same stimulus delivered multiple times. We found the trial-to-trial variability of network-mediated responses increased considerably as the disease progressed. Compared to responses taken before degeneration onset, those of degenerate retinas showed up to ~70% higher variability (Fano Factor) in spike counts (p < 0.001) and ~95% lower correlation level in spike timing (p < 0.001). These results indicate consistency weakens significantly in electrically-evoked network-mediated responses and therefore raise concerns about the ability of microelectronic retinal implants to elicit consistent visual percepts at advanced stages of retinal degeneration.
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26
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De Silva SR, Arno G, Robson AG, Fakin A, Pontikos N, Mohamed MD, Bird AC, Moore AT, Michaelides M, Webster AR, Mahroo OA. The X-linked retinopathies: Physiological insights, pathogenic mechanisms, phenotypic features and novel therapies. Prog Retin Eye Res 2020; 82:100898. [PMID: 32860923 DOI: 10.1016/j.preteyeres.2020.100898] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 08/07/2020] [Accepted: 08/21/2020] [Indexed: 02/08/2023]
Abstract
X-linked retinopathies represent a significant proportion of monogenic retinal disease. They include progressive and stationary conditions, with and without syndromic features. Many are X-linked recessive, but several exhibit a phenotype in female carriers, which can help establish diagnosis and yield insights into disease mechanisms. The presence of affected carriers can misleadingly suggest autosomal dominant inheritance. Some disorders (such as RPGR-associated retinopathy) show diverse phenotypes from variants in the same gene and also highlight limitations of current genetic sequencing methods. X-linked disease frequently arises from loss of function, implying potential for benefit from gene replacement strategies. We review X-inactivation and X-linked inheritance, and explore burden of disease attributable to X-linked genes in our clinically and genetically characterised retinal disease cohort, finding correlation between gene transcript length and numbers of families. We list relevant genes and discuss key clinical features, disease mechanisms, carrier phenotypes and novel experimental therapies. We consider in detail the following: RPGR (associated with retinitis pigmentosa, cone and cone-rod dystrophy), RP2 (retinitis pigmentosa), CHM (choroideremia), RS1 (X-linked retinoschisis), NYX (complete congenital stationary night blindness (CSNB)), CACNA1F (incomplete CSNB), OPN1LW/OPN1MW (blue cone monochromacy, Bornholm eye disease, cone dystrophy), GPR143 (ocular albinism), COL4A5 (Alport syndrome), and NDP (Norrie disease and X-linked familial exudative vitreoretinopathy (FEVR)). We use a recently published transcriptome analysis to explore expression by cell-type and discuss insights from electrophysiology. In the final section, we present an algorithm for genes to consider in diagnosing males with non-syndromic X-linked retinopathy, summarise current experimental therapeutic approaches, and consider questions for future research.
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Affiliation(s)
- Samantha R De Silva
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Gavin Arno
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Anthony G Robson
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Ana Fakin
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK; Ljubljana University Medical Centre, Ljubljana, Slovenia
| | - Nikolas Pontikos
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Moin D Mohamed
- Department of Ophthalmology, Guy's & St Thomas' NHS Foundation Trust, London, UK
| | - Alan C Bird
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Anthony T Moore
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK; Department of Ophthalmology, UCSF School of Medicine, San Francisco, CA, USA
| | - Michel Michaelides
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Andrew R Webster
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Omar A Mahroo
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK; Department of Ophthalmology, Guy's & St Thomas' NHS Foundation Trust, London, UK; Section of Ophthalmology, King's College London, UK; Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK.
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27
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Talib M, Boon CJF. Retinal Dystrophies and the Road to Treatment: Clinical Requirements and Considerations. Asia Pac J Ophthalmol (Phila) 2020; 9:159-179. [PMID: 32511120 PMCID: PMC7299224 DOI: 10.1097/apo.0000000000000290] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 04/01/2020] [Indexed: 12/15/2022] Open
Abstract
: Retinal dystrophies (RDs) comprise relatively rare but devastating causes of progressive vision loss. They represent a spectrum of diseases with marked genetic and clinical heterogeneity. Mutations in the same gene may lead to different diagnoses, for example, retinitis pigmentosa or cone dystrophy. Conversely, mutations in different genes may lead to the same phenotype. The age at symptom onset, and the rate and characteristics of peripheral and central vision decline, may vary widely per disease group and even within families. For most RD cases, no effective treatment is currently available. However, preclinical studies and phase I/II/III gene therapy trials are ongoing for several RD subtypes, and recently the first retinal gene therapy has been approved by the US Food and Drug Administration for RPE65-associated RDs: voretigene neparvovec-rzyl (Luxturna). With the rapid advances in gene therapy studies, insight into the phenotypic spectrum and long-term disease course is crucial information for several RD types. The vast clinical heterogeneity presents another important challenge in the evaluation of potential efficacy in future treatment trials, and in establishing treatment candidacy criteria. This perspective describes these challenges, providing detailed clinical descriptions of several forms of RD that are caused by genes of interest for ongoing and future gene or cell-based therapy trials. Several ongoing and future treatment options will be described.
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Affiliation(s)
- Mays Talib
- Department of Ophthalmology, Leiden, The Netherlands
| | - Camiel J F Boon
- Department of Ophthalmology, Leiden, The Netherlands
- Department of Ophthalmology, Amsterdam UMC, Academic Medical Center, University of Amsterdam. Amsterdam, The Netherlands
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28
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Yang JW, Yu ZY, Cheng SJ, Chung JHY, Liu X, Wu CY, Lin SF, Chen GY. Graphene Oxide-Based Nanomaterials: An Insight into Retinal Prosthesis. Int J Mol Sci 2020; 21:E2957. [PMID: 32331417 PMCID: PMC7216005 DOI: 10.3390/ijms21082957] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Revised: 04/17/2020] [Accepted: 04/20/2020] [Indexed: 12/27/2022] Open
Abstract
Retinal prosthesis has recently emerged as a treatment strategy for retinopathies, providing excellent assistance in the treatment of age-related macular degeneration (AMD) and retinitis pigmentosa. The potential application of graphene oxide (GO), a highly biocompatible nanomaterial with superior physicochemical properties, in the fabrication of electrodes for retinal prosthesis, is reviewed in this article. This review integrates insights from biological medicine and nanotechnology, with electronic and electrical engineering technological breakthroughs, and aims to highlight innovative objectives in developing biomedical applications of retinal prosthesis.
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Affiliation(s)
- Jia-Wei Yang
- Department of Electrical and Computer Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan; (J.-W.Y.); (S.-J.C.); (S.-F.L.)
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan;
| | - Zih-Yu Yu
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan;
| | - Sheng-Jen Cheng
- Department of Electrical and Computer Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan; (J.-W.Y.); (S.-J.C.); (S.-F.L.)
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan;
| | - Johnson H. Y. Chung
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW 2500, Australia; (J.H.Y.C.); (X.L.)
| | - Xiao Liu
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW 2500, Australia; (J.H.Y.C.); (X.L.)
| | - Chung-Yu Wu
- Department of Electrical Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan;
| | - Shien-Fong Lin
- Department of Electrical and Computer Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan; (J.-W.Y.); (S.-J.C.); (S.-F.L.)
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan;
| | - Guan-Yu Chen
- Department of Electrical and Computer Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan; (J.-W.Y.); (S.-J.C.); (S.-F.L.)
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan;
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 300, Taiwan
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29
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Lyu Q, Lu Z, Li H, Qiu S, Guo J, Sui X, Sun P, Li L, Chai X, Lovell NH. A Three-Dimensional Microelectrode Array to Generate Virtual Electrodes for Epiretinal Prosthesis Based on a Modeling Study. Int J Neural Syst 2020; 30:2050006. [DOI: 10.1142/s0129065720500069] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Despite many advances in the development of retinal prostheses, clinical reports show that current retinal prosthesis subjects can only perceive prosthetic vision with poor visual acuity. A possible approach for improving visual acuity is to produce virtual electrodes (VEs) through electric field modulation. Generating controllable and localized VEs is a crucial factor in effectively improving the perceptive resolution of the retinal prostheses. In this paper, we aimed to design a microelectrode array (MEA) that can produce converged and controllable VEs by current steering stimulation strategies. Through computational modeling, we designed a three-dimensional concentric ring–disc MEA and evaluated its performance with different stimulation strategies. Our simulation results showed that electrode–retina distance (ERD) and inter-electrode distance (IED) can dramatically affect the distribution of electric field. Also the converged VEs could be produced when the parameters of the three-dimensional MEA were appropriately set. VE sites can be controlled by manipulating the proportion of current on each adjacent electrode in a current steering group (CSG). In addition, spatial localization of electrical stimulation can be greatly improved under quasi-monopolar (QMP) stimulation. This study may provide support for future application of VEs in epiretinal prosthesis for potentially increasing the visual acuity of prosthetic vision.
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Affiliation(s)
- Qing Lyu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Zhuofan Lu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Heng Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Shirong Qiu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Jiahui Guo
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Xiaohong Sui
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Pengcheng Sun
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Liming Li
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Xinyu Chai
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Nigel H. Lovell
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, NSW 2052, Australia
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30
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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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31
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Beyeler M, Boynton GM, Fine I, Rokem A. Model-Based Recommendations for Optimal Surgical Placement of Epiretinal Implants. MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION : MICCAI ... INTERNATIONAL CONFERENCE ON MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION 2019; 11768:394-402. [PMID: 35373219 PMCID: PMC8975247 DOI: 10.1007/978-3-030-32254-0_44] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A major limitation of current electronic retinal implants is that in addition to stimulating the intended retinal ganglion cells, they also stimulate passing axon fibers, producing perceptual 'streaks' that limit the quality of the generated visual experience. Recent evidence suggests a dependence between the shape of the elicited visual percept and the retinal location of the stimulating electrode. However, this knowledge has yet to be incorporated into the surgical placement of retinal implants. Here we systematically explored the space of possible implant configurations to make recommendations for optimal intraocular positioning of the electrode array. Using a psychophysically validated computational model, we demonstrate that better implant placement has the potential to reduce the spatial extent of axonal activation in existing implant users by up to ~55%. Importantly, the best implant location, as inferred from a population of simulated virtual patients, is both surgically feasible and is relatively stable across individuals. This study is a first step towards the use of computer simulations in patient-specific planning of retinal implant surgery.
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Affiliation(s)
- Michael Beyeler
- Department of Psychology, University of Washington, Seattle, WA 98195, USA
- Institute for Neuroengineering (UWIN), University of Washington, Seattle, WA 98195, USA
- eScience Institute, University of Washington, Seattle, WA 98195, USA
| | - Geoffrey M Boynton
- Department of Psychology, University of Washington, Seattle, WA 98195, USA
| | - Ione Fine
- Department of Psychology, University of Washington, Seattle, WA 98195, USA
- Institute for Neuroengineering (UWIN), University of Washington, Seattle, WA 98195, USA
| | - Ariel Rokem
- Institute for Neuroengineering (UWIN), University of Washington, Seattle, WA 98195, USA
- eScience Institute, University of Washington, Seattle, WA 98195, USA
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32
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Shalbaf F, Lovell NH, Dokos S, Trew M, Vaghefi E. Foveal eccentricity can influence activation threshold in subretinal electrical stimulation. Biomed Phys Eng Express 2019. [DOI: 10.1088/2057-1976/ab0b85] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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33
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Farvardin M, Afarid M, Attarzadeh A, Johari MK, Mehryar M, Nowroozzadeh MH, Rahat F, Peyvandi H, Farvardin R, Nami M. The Argus-II Retinal Prosthesis Implantation; From the Global to Local Successful Experience. Front Neurosci 2018; 12:584. [PMID: 30237759 PMCID: PMC6136639 DOI: 10.3389/fnins.2018.00584] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 08/03/2018] [Indexed: 12/18/2022] Open
Abstract
Over the past few years, visual prostheses (namely, Argus II retinal implant) and gene therapy have obtained FDA approval in treating blindness resulting from retinitis pigmentosa. Compared to gene therapy; Argus II is less costly with a demonstrated favorable outcome, though the vision is yet artificial. To obtain better results, expectation counseling and preoperative retinal assessment are critical. The global experience with Argus II has enrolled no more than 300 cases so far. The first Argus II retinal prosthesis in Iran was successfully implanted in Shiraz (October 2017). To date, Argus II artificial retina is implanted in four patients in Iran. Beside successful surgery and post-operative care, rehabilitation efforts with validated outcome measures including visual rehabilitation together with neurovisual, visuo-constructive and cognitive rehabilitation/empowerment approaches are expected to boost the functional outcome. A multidisciplinary approach within a cross-functional team would optimize strategies toward better patient outcomes. As such, establishing a collaborative network will foster organized research efforts to better define outcome assessment and rehabilitation strategies. This technology report paper has been an attempt to provide an overview of Argus-II retinal implant global experience as well as the clinical outcome of the so far cases in Iran. Insights from this report were communicated during the first “Brain Engineering and Computational Neuroscience Conference,” 31 January-2 February 2018 in Tehran.
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Affiliation(s)
- Mohsen Farvardin
- Department of Ophthalmology, Poostchi Ophthalmology Research Center, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.,Farvardin Eye Clinic, Shiraz, Iran
| | - Mehrdad Afarid
- Department of Ophthalmology, Poostchi Ophthalmology Research Center, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | | | - Mohammad K Johari
- Department of Ophthalmology, Poostchi Ophthalmology Research Center, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Morsal Mehryar
- Department of Ophthalmology, Poostchi Ophthalmology Research Center, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | - M Hossein Nowroozzadeh
- Department of Ophthalmology, Poostchi Ophthalmology Research Center, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | | | - Hossein Peyvandi
- Computer Engineering Department, Sharif ICT Innovation Center, Sharif University of Technology, Tehran, Iran
| | - Reza Farvardin
- Students' Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Mohammad Nami
- Department of Neuroscience, School of Advanced Medical Sciences and Technologies, Shiraz University of Medical Sciences, Shiraz, Iran.,DANA Brain Health Institute, Iranian Neuroscience Society, Fars Chapter, Shiraz, Iran
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34
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Gamieldien R, Stemmet L, Javer J, Fortuin E, Clarke-Farr PC. Emerging technologies in artificial ocular devices: A systematic review. AFRICAN VISION AND EYE HEALTH 2018. [DOI: 10.4102/aveh.v77i1.428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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35
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Finn AP, Grewal DS, Vajzovic L. Argus II retinal prosthesis system: a review of patient selection criteria, surgical considerations, and post-operative outcomes. Clin Ophthalmol 2018; 12:1089-1097. [PMID: 29942114 PMCID: PMC6005308 DOI: 10.2147/opth.s137525] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Retinitis pigmentosa (RP) is a group of heterogeneous inherited retinal degenerative disorders characterized by progressive rod and cone dysfunction and ensuing photoreceptor loss. Many patients suffer from legal blindness by their 40s or 50s. Artificial vision is considered once patients have lost all vision to the point of bare light perception or no light perception. The Argus II retinal prosthesis system is one such artificial vision device approved for patients with RP. This review focuses on the factors important for patient selection. Careful pre-operative screening, counseling, and management of patient expectations are critical for the successful implantation and visual rehabilitation of patients with the Argus II device.
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Affiliation(s)
- Avni P Finn
- Department of Ophthalmology, Duke University Eye Center, Durham, NC, USA
| | - Dilraj S Grewal
- Department of Ophthalmology, Duke University Eye Center, Durham, NC, USA
| | - Lejla Vajzovic
- Department of Ophthalmology, Duke University Eye Center, Durham, NC, USA
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Ren YM, Weng CH, Zhao CJ, Yin ZQ. Changes in intrinsic excitability of ganglion cells in degenerated retinas of RCS rats. Int J Ophthalmol 2018; 11:756-765. [PMID: 29862172 DOI: 10.18240/ijo.2018.05.07] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2018] [Accepted: 03/16/2018] [Indexed: 11/23/2022] Open
Abstract
AIM To evaluate the intrinsic excitability of retinal ganglion cells (RGCs) in degenerated retinas. METHODS The intrinsic excitability of various morphologically defined RGC types using a combination of patch-clamp recording and the Lucifer yellow tracer in retinal whole-mount preparations harvested from Royal College of Surgeons (RCS) rats, a common retinitis pigmentosa (RP) model, in a relatively late stage of retinal degeneration (P90) were investigated. Several parameters of RGC morphologies and action potentials (APs) were measured and compared to those of non-dystrophic control rats, including dendritic stratification, dendritic field diameter, peak amplitude, half width, resting membrane potential, AP threshold, depolarization to threshold, and firing rates. RESULTS Compared with non-dystrophic control RGCs, more depolarizations were required to reach the AP threshold in RCS RGCs with low spontaneous spike rates and in RCS OFF cells (especially A2o cells), and RCS RGCs maintained their dendritic morphologies, resting membrane potentials and capabilities to generate APs. CONCLUSION RGCs are relatively well preserved morphologically and functionally, and some cells are more susceptible to decreased excitability during retinal degeneration. These findings provide valuable considerations for optimizing RP therapeutic strategies.
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Affiliation(s)
- Yi-Ming Ren
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University); Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing 400038, China
| | - Chuan-Huang Weng
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University); Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing 400038, China
| | - Cong-Jian Zhao
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University); Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing 400038, China
| | - Zheng-Qin Yin
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University); Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing 400038, China
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Han S, Qiu C, Lee KR, Jung JH, Peli E. Word recognition: re-thinking prosthetic vision evaluation. J Neural Eng 2018; 15:055003. [PMID: 29781807 DOI: 10.1088/1741-2552/aac663] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
OBJECTIVE Evaluations of vision prostheses and sensory substitution devices have frequently relied on repeated training and then testing with the same small set of items. These multiple forced-choice tasks produced above chance performance in blind users, but it is unclear if the observed performance represents restoration of vision that transfers to novel, untrained items. APPROACH Here, we tested the generalizability of the forced-choice paradigm on discrimination of low-resolution word images. Extensive visual training was conducted with the same 10 words used in previous BrainPort tongue stimulation studies. The performance on these 10 words and an additional 50 words was measured before and after the training sessions. MAIN RESULTS The results revealed minimal performance improvement with the untrained words, demonstrating instead pattern discrimination limited mostly to the trained words. SIGNIFICANCE These findings highlight the need to reconsider current evaluation practices, in particular, the use of forced-choice paradigms with a few highly trained items. While appropriate for measuring the performance thresholds in acuity or contrast sensitivity of a functioning visual system, performance on such tasks cannot be taken to indicate restored spatial pattern vision.
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Affiliation(s)
- Shui'Er Han
- Department of Ophthalmology, The Schepens Eye Research Institute, Massachusetts Eye and Ear, Harvard Medical School, 20 Staniford Street, Boston, MA 02114-2500, United States of America. School of Psychology, University of Sydney, Sydney, Australia
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Light localization with low-contrast targets in a patient implanted with a suprachoroidal-transretinal stimulation retinal prosthesis. Graefes Arch Clin Exp Ophthalmol 2018; 256:1723-1729. [PMID: 29679170 DOI: 10.1007/s00417-018-3982-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 03/19/2018] [Accepted: 04/06/2018] [Indexed: 10/17/2022] Open
Abstract
PURPOSE To evaluate the improvement in targeted reaching movements toward targets of various contrasts in a patient implanted with a suprachoroidal-transretinal stimulation (STS) retinal prosthesis. METHODS An STS retinal prosthesis was implanted in the right eye of a 42-year-old man with advanced Stargardt disease (visual acuity: right eye, light perception; left eye, hand motion). In localization tests during the 1-year follow-up period, the patient attempted to touch the center of a white square target (visual angle, 10°; contrast, 96, 85, or 74%) displayed at a random position on a monitor. The distance between the touched point and the center of the target (the absolute deviation) was averaged over 20 trials with the STS system on or off. RESULTS With the left eye occluded, the absolute deviation was not consistently lower with the system on than off for high-contrast (96%) targets, but was consistently lower with the system on for low-contrast (74%) targets. With both eyes open, the absolute deviation was consistently lower with the system on than off for 85%-contrast targets. With the system on and 96%-contrast targets, we detected a shorter response time while covering the right eye, which was being implanted with the STS, compared to covering the left eye (2.41 ± 2.52 vs 8.45 ± 3.78 s, p < 0.01). CONCLUSIONS Performance of a reaching movement improved in a patient with an STS retinal prosthesis implanted in an eye with residual natural vision. Patients with a retinal prosthesis may be able to improve their visual performance by using both artificial vision and their residual natural vision. CLINICAL TRIAL REGISTRATION Beginning date of the trial: Feb. 20, 2014 Date of registration: Jan. 4, 2014 Trial registration number: UMIN000012754 Registration site: UMIN Clinical Trials Registry (UMIN-CTR) http://www.umin.ac.jp/ctr/index.htm.
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Yoon CK, Yu HG. Ganglion cell-inner plexiform layer and retinal nerve fibre layer changes within the macula in retinitis pigmentosa: a spectral domain optical coherence tomography study. Acta Ophthalmol 2018; 96:e180-e188. [PMID: 29098796 DOI: 10.1111/aos.13577] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 08/01/2017] [Indexed: 01/05/2023]
Abstract
PURPOSE To investigate how macular ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fibre layer (RNFL) thicknesses within the macula change with retinitis pigmentosa (RP) severity. METHODS Spectral domain optical coherence tomography (SD-OCT) was used to examine 177 patients with RP and 177 normal controls. An optical coherence tomography (OCT) line scan was used to grade RP severity. Retinitis pigmentosa (RP) was categorized as more advanced if there was no identifiable inner segment ellipsoid (ISe) band (NISE) and as less advanced if an ISe band could be identified and peripheral loss of ISe was apparent (IISE). Ganglion cell-inner plexiform layer (GCIPL) and RNFL thicknesses were manually measured on OCT images and analysed. Pearson's correlation analyses were used to examine correlations between GCIPL thickness, RNFL thickness, visual acuity (VA) and visual field extent in patients and controls. RESULTS Ganglion cell-inner plexiform layer (GCIPL) was significantly thicker in IISE than in control eyes (p < 0.001), but significantly thinner in NISE than in IISE eyes (p < 0.001) in both horizontal and vertical OCT scans. Retinal nerve fibre layer (RNFL) was significantly thicker in eyes with IISE and NISE than in control eyes in both horizontal and vertical meridians (all p < 0.001). Ganglion cell-inner plexiform layer (GCIPL) thickness showed a weak positive correlation with vision, and RNFL thickness showed a weak negative correlation with vision and visual field extent. CONCLUSION Based on these results, the inner retina, including the GCIPL and RNFL, maintains its gross integrity longer than the photoreceptor layer in RP. Additionally, thickening of the inner retina may have some functional implications in patients with RP.
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Affiliation(s)
- Chang Ki Yoon
- Department of Ophthalmology; Inje University Busan Paik Hospital; Busan Korea
- Department of Ophthalmology; Seoul National University College of Medicine; Seoul Korea
| | - Hyeong Gon Yu
- Department of Ophthalmology; Seoul National University College of Medicine; Seoul Korea
- Department of Ophthalmology; Seoul National University Hospital; Seoul Korea
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Weiland JD, Humayun MS, Gonzalez Calle A. The Development of Visual Prosthetic Devices to Restore Vision to the Blind. Neuromodulation 2018. [DOI: 10.1016/b978-0-12-805353-9.00101-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Grewal DS, Carrasco-Zevallos OM, Gunther R, Izatt JA, Toth CA, Hahn P. Intra-operative microscope-integrated swept-source optical coherence tomography guided placement of Argus II retinal prosthesis. Acta Ophthalmol 2017; 95:e431-e432. [PMID: 27321093 DOI: 10.1111/aos.13123] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dilraj S. Grewal
- Department of Ophthalmology; Duke University Medical Center; Durham NC USA
| | | | - Randall Gunther
- Department of Biomedical Engineering; Duke University; Durham NC USA
| | - Joseph A. Izatt
- Department of Biomedical Engineering; Duke University; Durham NC USA
| | - Cynthia A. Toth
- Department of Ophthalmology; Duke University Medical Center; Durham NC USA
- Department of Biomedical Engineering; Duke University; Durham NC USA
| | - Paul Hahn
- Department of Ophthalmology; Duke University Medical Center; Durham NC USA
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Wu J, Jin M, Qiao Q. Modeling electrical stimulation of retinal ganglion cell with optimizing additive noises for reducing threshold and energy consumption. Biomed Eng Online 2017; 16:38. [PMID: 28347343 PMCID: PMC5368944 DOI: 10.1186/s12938-017-0333-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2016] [Accepted: 03/20/2017] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Epiretinal prosthesis is one device for the treatment of blindness, which target retinal ganglion cells (RGCs) by electrodes on retinal surface. The stimulating current of epiretinal prosthesis is an important factor that influences the safety threshold and visual perception. Stochastic resonance (SR) can be used to enhance the detection and transmission of subthreshold stimuli in neurons. Here, it was assumed that SR was a potential way to improve the performance of epiretinal prosthesis. The effect of noises on the response of RGCs to electrical stimulation and the energy of stimulating current was studied based on a RGC model. METHODS The RGC was modeled as a multi-compartment model consisting of dendrites and its branches, soma and axon. To evoke SR, a subthreshold signal, a series of bipolar rectangular pulse sequences, plus stochastic biphasic pulse sequences as noises, were used as a stimulus to the model. The SR-type behavior in the model was characterized by a "power norm" measure. To decrease energy consumption of the stimulation waveform, the stochastic biphasic pulse sequences were only added to the cathode and anode phase of the subthreshold pulse and the noise parameters were optimized by using a genetic algorithm (GA). RESULTS When certain intensity of noise is added to the subthreshold signal, RGC model can fire. With the noise's RMS amplitudes increased, more spikes were elicited and the curve of power norm presents the inverted U-like graph. The larger pulse width of stochastic biphasic pulse sequences resulted in higher power norm. The energy consumption and charges of the single bipolar rectangular pulse without noise in threshold level are 468.18 pJ, 15.30 nC, and after adding optimized parameters's noise to the subthreshold signal, they became 314.8174 pJ, 11.9281 nC and were reduced by 32.8 and 22.0%, respectively. CONCLUSIONS The SR exists in the RGC model and can enhance the representation of RGC model to the subthreshold signal. Adding the stochastic biphasic pulse sequences to the cathode and anode phase of the subthreshold signal helps to reduce stimulation threshold, energy consumption and charge of RGC stimulation. These may be helpful for improving the performance of epiretinal prosthesis.
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Affiliation(s)
- Jing Wu
- School of Biomedical Engineering & Technology, Tianjin Medical University, Tianjin, 300070 China
| | - Menghua Jin
- School of Biomedical Engineering & Technology, Tianjin Medical University, Tianjin, 300070 China
| | - Qingli Qiao
- School of Biomedical Engineering & Technology, Tianjin Medical University, Tianjin, 300070 China
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Optical coherence tomography imaging in the management of the Argus II retinal prosthesis system. Eur J Ophthalmol 2017; 27:e16-e21. [PMID: 28009400 DOI: 10.5301/ejo.5000852] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/18/2016] [Indexed: 11/20/2022]
Abstract
PURPOSE To report a real-life experience with the Argus II retinal prosthesis system in blind patients with end-stage retinitis pigmentosa (RP) or choroideremia (CHM), focusing on the pivotal role of optical coherence tomography (OCT) in both preoperative and postoperative management. METHODS This hospital-based case series included 3 blind patients who were uneventfully implanted with Argus II epiretinal device. These patients (2 with RP and 1 with CHM) were selected during the Argus™ II Retinal Prosthesis System PostMarket Surveillance Study Protocol. Complete screening procedures had involved 66 eyes of 33 patients afferent to the Center for Retinitis Pigmentosa of the Veneto Region. RESULTS Preoperative OCT examination resulted in the exclusion of 8 eyes in 4 patients with bilateral posterior staphyloma diagnosing unexpected staphylomatous macular patterns in 2 patients with RP and no sign of pathologic myopia. Postoperative OCT study of Argus II proximity to retinal surface indicated a plausible correlation between electrode-retina distance and perceptual threshold in 2 of our 3 patients. In particular, during the first 6 months of follow-up, the patient with the closest contact between device and macula showed a continuous vision-related improvement in the performance of several real-life tasks. CONCLUSIONS The present findings illustrate the modalities by which each different OCT examination is an essential tool to optimize safety and efficacy profiles during Argus II protocol. Optical coherence tomography will be crucial for future investigative approaches on patient selection criteria and next-generation implant design.
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Bermudez-Cameo J, Badias-Herbera A, Guerrero-Viu M, Lopez-Nicolas G, Guerrero JJ. RGB-D Computer Vision Techniques for Simulated Prosthetic Vision. PATTERN RECOGNITION AND IMAGE ANALYSIS 2017. [DOI: 10.1007/978-3-319-58838-4_47] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Jung JH, Pu T, Peli E. Comparing object recognition from binary and bipolar edge images for visual prostheses. JOURNAL OF ELECTRONIC IMAGING 2016; 25:061619. [PMID: 28458481 PMCID: PMC5407304 DOI: 10.1117/1.jei.25.6.061619] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Visual prostheses require an effective representation method due to the limited display condition which has only 2 or 3 levels of grayscale in low resolution. Edges derived from abrupt luminance changes in images carry essential information for object recognition. Typical binary (black and white) edge images have been used to represent features to convey essential information. However, in scenes with a complex cluttered background, the recognition rate of the binary edge images by human observers is limited and additional information is required. The polarity of edges and cusps (black or white features on a gray background) carries important additional information; the polarity may provide shape from shading information missing in the binary edge image. This depth information may be restored by using bipolar edges. We compared object recognition rates from 16 binary edge images and bipolar edge images by 26 subjects to determine the possible impact of bipolar filtering in visual prostheses with 3 or more levels of grayscale. Recognition rates were higher with bipolar edge images and the improvement was significant in scenes with complex backgrounds. The results also suggest that erroneous shape from shading interpretation of bipolar edges resulting from pigment rather than boundaries of shape may confound the recognition.
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Affiliation(s)
- Jae-Hyun Jung
- Harvard Medical School, Massachusetts Eye and Ear, Department of Ophthalmology, Schepens Eye Research Institute, 20 Staniford Street, Boston, Massachusetts 02114, United States
| | - Tian Pu
- Harvard Medical School, Massachusetts Eye and Ear, Department of Ophthalmology, Schepens Eye Research Institute, 20 Staniford Street, Boston, Massachusetts 02114, United States
- University of Electronic Science and Technology of China, School of Optoelectronic Information, No. 4, Section 2, North Jianshe Road, Chengdu 610054, China
| | - Eli Peli
- Harvard Medical School, Massachusetts Eye and Ear, Department of Ophthalmology, Schepens Eye Research Institute, 20 Staniford Street, Boston, Massachusetts 02114, United States
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Weitz AC, Nanduri D, Behrend MR, Gonzalez-Calle A, Greenberg RJ, Humayun MS, Chow RH, Weiland JD. Improving the spatial resolution of epiretinal implants by increasing stimulus pulse duration. Sci Transl Med 2016; 7:318ra203. [PMID: 26676610 DOI: 10.1126/scitranslmed.aac4877] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Retinal prosthetic implants are the only approved treatment for retinitis pigmentosa, a disease of the eye that causes blindness through gradual degeneration of photoreceptors. An array of microelectrodes triggered by input from a camera stimulates surviving retinal neurons, with each electrode acting as a pixel. Unintended stimulation of retinal ganglion cell axons causes patients to see large oblong shapes of light, rather than focal spots, making it difficult to perceive forms. To address this problem, we performed calcium imaging in isolated retinas and mapped the patterns of cells activated by different electrical stimulation protocols. We found that pulse durations two orders of magnitude longer than those typically used in existing implants stimulated inner retinal neurons while avoiding activation of ganglion cell axons, thus confining retinal responses to the site of the electrode. Multielectrode stimulation with 25-ms pulses can pattern letters on the retina corresponding to a Snellen acuity of 20/312. We validated our findings in a patient with an implanted epiretinal prosthesis by demonstrating that 25-ms pulses evoke focal spots of light.
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Affiliation(s)
- Andrew C Weitz
- Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Devyani Nanduri
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Matthew R Behrend
- Department of Electrical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Alejandra Gonzalez-Calle
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | | | - Mark S Humayun
- Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Robert H Chow
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA. Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
| | - James D Weiland
- Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089, USA.
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Roux S, Matonti F, Dupont F, Hoffart L, Takerkart S, Picaud S, Pham P, Chavane F. Probing the functional impact of sub-retinal prosthesis. eLife 2016; 5. [PMID: 27549126 PMCID: PMC4995098 DOI: 10.7554/elife.12687] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 07/07/2016] [Indexed: 11/27/2022] Open
Abstract
Retinal prostheses are promising tools for recovering visual functions in blind patients but, unfortunately, with still poor gains in visual acuity. Improving their resolution is thus a key challenge that warrants understanding its origin through appropriate animal models. Here, we provide a systematic comparison between visual and prosthetic activations of the rat primary visual cortex (V1). We established a precise V1 mapping as a functional benchmark to demonstrate that sub-retinal implants activate V1 at the appropriate position, scalable to a wide range of visual luminance, but with an aspect-ratio and an extent much larger than expected. Such distorted activation profile can be accounted for by the existence of two sources of diffusion, passive diffusion and activation of ganglion cells’ axons en passant. Reverse-engineered electrical pulses based on impedance spectroscopy is the only solution we tested that decreases the extent and aspect-ratio, providing a promising solution for clinical applications. DOI:http://dx.doi.org/10.7554/eLife.12687.001 One of the most common causes of blindness is a disorder called retinitis pigmentosa. In a healthy eye, the surface at the back of the eye – called the retina – contains cells called photoreceptors that detect light and convert it into electrical signals for the brain to process. In people with retinitis pigmentosa, these photoreceptor cells die off gradually, which leads to loss of vision. The only treatment available for retinitis pigmentosa is to have an artificial retina implanted into the eye. The artificial retina consists of an array of tiny electrodes, which take over from the damaged photoreceptors and generate electrical signals. The person with the implant perceives these electrical signals as bright flashes called “phosphenes”. However, the phosphenes are too large and imprecise to provide the person with vision that is good enough for tasks such as walking unaided or reading. To find out why artificial retinas produce such poor resolution, Roux et al. compared how a rat’s brain responds to either natural visual stimuli or activation of implanted an array of micro-electrodes. Both the micro-electrodes and the natural stimuli activated the same areas of the brain. However, the micro-electrodes produced larger and more elongated patterns of activation. This is because the electrical currents generated by the micro-electrodes diffused throughout the retinal tissue and activated other neurons besides those intended. To overcome this problem, Roux et al. tested different ways of stimulating the micro-electrodes in order to identify those that induce the desired patterns of brain activity. This approach – known as reverse engineering – did indeed improve the performance of the micro-electrode array. The next step is to extend these findings, which were obtained in healthy rats, to non-human primates or animal models of retinitis pigmentosa to better understand the condition in humans. In addition, combining the current approach with other existing techniques should further improve the vision that can be achieved with artificial retinas. DOI:http://dx.doi.org/10.7554/eLife.12687.002
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Affiliation(s)
- Sébastien Roux
- Institut de Neurosciences de la Timone, CNRS, Aix-Marseille Université, Marseille, France
| | - Frédéric Matonti
- Institut de Neurosciences de la Timone, CNRS, Aix-Marseille Université, Marseille, France.,Ophthalmology Department, Aix Marseille Université, Hôpital Nord,Hôpital de la Timone, Marseille, France
| | - Florent Dupont
- CEA-LETI, Grenoble, France.,Université Grenoble Alpes, Grenoble, France
| | - Louis Hoffart
- Institut de Neurosciences de la Timone, CNRS, Aix-Marseille Université, Marseille, France.,Ophthalmology Department, Aix Marseille Université, Hôpital Nord,Hôpital de la Timone, Marseille, France
| | - Sylvain Takerkart
- Institut de Neurosciences de la Timone, CNRS, Aix-Marseille Université, Marseille, France
| | - Serge Picaud
- Inserm, UMRS-986, Institut de la vision, Paris, France
| | - Pascale Pham
- CEA-LETI, Grenoble, France.,Université Grenoble Alpes, Grenoble, France
| | - Frédéric Chavane
- Institut de Neurosciences de la Timone, CNRS, Aix-Marseille Université, Marseille, France
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Matet A, Amar N, Mohand-Said S, Sahel JA, Barale PO. Argus II retinal prosthesis implantation with scleral flap and autogenous temporalis fascia as alternative patch graft material: a 4-year follow-up. Clin Ophthalmol 2016; 10:1565-71. [PMID: 27574397 PMCID: PMC4993412 DOI: 10.2147/opth.s112403] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Introduction The Argus II retinal prosthesis is composed of an epiretinal electrode array positioned over the macula and connected to an extrascleral electronics case via a silicone cable, running through a sclerotomy. During implantation, the manufacturer recommends to cover the sclerotomy site with a patch of processed human pericardium to prevent postoperative hypotony and conjunctival erosion by the underlying electronics case. Due to biomedical regulations prohibiting the use of this material in France, we developed an alternative technique combining a scleral flap protecting the sclerotomy and an autogenous graft of superior temporalis fascia overlying the electronics case. Methods The purpose of this study is to describe the 4-year outcomes of this modified procedure in three subjects who underwent Argus II Retinal Prosthesis System implantation. Clinical data consisting of intraocular pressure measurements and tolerance in terms of conjunctival erosion or inflammation were retrospectively assessed over a 4-year postoperative follow-up. Results None of the three patients implanted with the modified technique developed ocular hypotony over 4 years. A normal, transient conjunctival inflammation occurred during the first postoperative month but conjunctival erosion was not observed in any of the three patients over 4 years. Four years after implantation, the autogenous temporalis fascia graft remained well tolerated and the retinal prosthesis was functional in all three patients. Conclusion The combination of an autograft of superficial temporalis fascia and a scleral flap efficiently prevented leakage through the sclerotomy site, ocular hypotony, and conjunctival erosion by the extrascleral electronics case. This modified technique is suitable for the implantation of existing and forthcoming retinal prostheses. Superficial temporalis fascia may also be used as alternative to commercial tectonic tissues for scleral wound repair in clinical settings where they are not available.
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Affiliation(s)
- Alexandre Matet
- INSERM and DHOS, CHNO des Quinze-Vingts; Sorbonne Universités, UPMC Univ Paris 6, Institut de la Vision
| | - Nawel Amar
- INSERM and DHOS, CHNO des Quinze-Vingts; Sorbonne Universités, UPMC Univ Paris 6, Institut de la Vision
| | - Saddek Mohand-Said
- INSERM and DHOS, CHNO des Quinze-Vingts; Sorbonne Universités, UPMC Univ Paris 6, Institut de la Vision; INSERM; CNRS, Paris, France
| | - José-Alain Sahel
- INSERM and DHOS, CHNO des Quinze-Vingts; Sorbonne Universités, UPMC Univ Paris 6, Institut de la Vision; INSERM; CNRS, Paris, France; Institute of Ophthalmology, University College London, London, UK; Fondation Ophtalmologique Adolphe de Rothschild; Académie des Sciences, Institut de France, Paris, France
| | - Pierre-Olivier Barale
- INSERM and DHOS, CHNO des Quinze-Vingts; Sorbonne Universités, UPMC Univ Paris 6, Institut de la Vision
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Zapf MPH, Boon MY, Lovell NH, Suaning GJ. Assistive peripheral phosphene arrays deliver advantages in obstacle avoidance in simulated end-stage retinitis pigmentosa: a virtual-reality study. J Neural Eng 2016; 13:026022. [PMID: 26902525 DOI: 10.1088/1741-2560/13/2/026022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The prospective efficacy of peripheral retinal prostheses for guiding orientation and mobility in the absence of residual vision, as compared to an implant for the central visual field (VF), was evaluated using simulated prosthetic vision (SPV). APPROACH Sighted volunteers wearing a head-mounted display performed an obstacle circumvention task under SPV. Mobility and orientation performance with three layouts of prosthetic vision were compared: peripheral prosthetic vision of higher visual acuity (VA) but limited VF, of wider VF but limited VA, as well as centrally restricted prosthetic vision. Learning curves using these layouts were compared fitting an exponential model to the mobility and orientation measures. MAIN RESULTS Using peripheral layouts, performance was superior to the central layout. Walking speed with both higher-acuity and wider-angle layouts was 5.6% higher, and mobility errors reduced by 46.4% and 48.6%, respectively, as compared to the central layout. The wider-angle layout yielded the least number of collisions, 63% less than the higher-acuity and 73% less than the central layout. Using peripheral layouts, the number of visual-scanning related head movements was 54.3% (higher-acuity) and 60.7% (wider-angle) lower, as compared to the central layout, and the ratio of time standing versus time walking was 51.9% and 61.5% lower, respectively. Learning curves did not differ between layouts, except for time standing versus time walking, where both peripheral layouts achieved significantly lower asymptotic values compared to the central layout. SIGNIFICANCE Beyond complementing residual vision for an improved performance, peripheral prosthetic vision can effectively guide mobility in the later stages of retinitis pigmentosa (RP) without residual vision. Further, the temporal dynamics of learning peripheral and central prosthetic vision are similar. Therefore, development of a peripheral retinal prosthesis and early implantation to alleviate VF constriction in RP should be considered to extend the target group and the time of benefit for potential retinal prosthesis implantees.
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Affiliation(s)
- Marc Patrick H Zapf
- Graduate School of Biomedical Engineering, UNSW Australia, Sydney 2052, Australia
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Abstract
This review focuses on a description of the Argus II retinal prosthesis system (Argus II; Second Sight Medical Products, Sylmar, CA) that was approved for humanitarian use by the FDA in 2013 in patients with retinitis pigmentosa with bare or no light perception vision. The article describes the components of Argus II, the studies on the implant, and future directions.
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Affiliation(s)
| | - Alex Yuan
- a Cole Eye Institute, Cleveland Clinic Foundation , Cleveland , Ohio , USA
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