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Ho E, Lei X, Flores T, Lorach H, Huang T, Galambos L, Kamins T, Harris J, Mathieson K, Palanker D. Characteristics of prosthetic vision in rats with subretinal flat and pillar electrode arrays. J Neural Eng 2019; 16:066027. [PMID: 31341094 PMCID: PMC7192047 DOI: 10.1088/1741-2552/ab34b3] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Objective Retinal prostheses aim to restore sight by electrically stimulating the surviving retinal neurons. In clinical trials of the current retinal implants, prosthetic visual acuity does not exceed 20/550. However, to provide meaningful restoration of central vision in patients blinded by age-related macular degeneration (AMD), prosthetic acuity should be at least 20/200, necessitating a pixel pitch of about 50 μm or lower. With such small pixels, stimulation thresholds are high due to limited penetration of electric field into tissue. Here, we address this challenge with our latest photovoltaic arrays and evaluate their performance in vivo. Approach We fabricated photovoltaic arrays with 55 and 40 μm pixels (a) in flat geometry, and (b) with active electrodes on 10 μm tall pillars. The arrays were implanted subretinally into rats with degenerate retina. Stimulation thresholds and grating acuity were evaluated using measurements of the visually evoked potentials (VEP). Main results With 55 μm pixels, we measured grating acuity of 48 ± 11 μm, which matches the linear pixel pitch of the hexagonal array. This geometrically corresponds to a visual acuity of 20/192 in a human eye, matching the threshold of legal blindness in the US (20/200). With pillar electrodes, the irradiance threshold was nearly halved, and duration threshold reduced by more than three-fold, compared to flat pixels. With 40 μm pixels, VEP was too low for reliable measurements of the grating acuity, even with pillar electrodes. Significance While being helpful for treating a complete loss of sight, current prosthetic technologies are insufficient for addressing the leading cause of untreatable visual impairment—AMD. Subretinal photovoltaic arrays may provide sufficient visual acuity for restoration of central vision in patients blinded by AMD.
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Affiliation(s)
- Elton Ho
- Department of Physics, Stanford University, Stanford, CA 94305, United States of America. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, United States of America
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He Y, Huang NT, Caspi A, Roy A, Montezuma SR. Trade-Off Between Field-of-View and Resolution in the Thermal-Integrated Argus II System. Transl Vis Sci Technol 2019; 8:29. [PMID: 31440426 PMCID: PMC6701876 DOI: 10.1167/tvst.8.4.29] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 06/21/2019] [Indexed: 12/18/2022] Open
Abstract
Purpose To investigate the effect of a wider field-of-view (FOV) of a retinal prosthesis on the users' performance in locating objects. Methods One female and four male subjects who were blind due to end-stage retinitis pigmentosa and had been implanted with the Argus II retinal prosthesis participated (aged 63.4 ± 15.4). Thermal imaging was captured by an external sensor and converted to electrical stimulation to the retina. Subjects were asked to localize and to reach for heat-emitting objects using two different FOV mappings: a normal 1:1 mapping (no zoom) that provided 18° × 11° FOV and a 3:1 mapping (zoom out) that provided 49° × 35° FOV. Their accuracy and response time were recorded. Results Subjects were less accurate and took longer to complete the tasks with zoom out compared to no zoom. Localization accuracy decreased from 83% (95% confidence interval, 75%, 90%) with no zoom to 76% (67%, 83%) with zoom out (P = 0.07). Reaching accuracy differed between the two mappings only in one subject. Response time increased by 43% for the localization task (24%, 66%; P < 0.001) and by 20% for the reaching task (0%, 45%; P = 0.055). Conclusions Argus II wearers can efficiently find heat-emitting objects with the default 18° × 11° FOV of the current Argus II. For spatial localization, a higher spatial resolution may be preferred over a wider FOV. Translational Relevance Understanding the trade-off between FOV and spatial resolution in retinal prosthesis users can guide device optimization.
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Affiliation(s)
- Yingchen He
- Department of Psychology, University of Minnesota, Minneapolis, MN, USA
| | - Natalie T Huang
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, MN, USA
| | - Avi Caspi
- Department of Electrical and Electronic Engineering, Jerusalem College of Technology, Jerusalem, Israel.,Second Sight Medical Products, Inc., Sylmar, CA, USA
| | - Arup Roy
- Second Sight Medical Products, Inc., Sylmar, CA, USA
| | - Sandra R Montezuma
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, MN, USA
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Schaffrath K, Schellhase H, Walter P, Augustin A, Chizzolini M, Kirchhof B, Grisanti S, Wiedemann P, Szurman P, Richard G, Greenberg RJ, Dorn JD, Parmeggiani F, Rizzo S. One-Year Safety and Performance Assessment of the Argus II Retinal Prosthesis: A Postapproval Study. JAMA Ophthalmol 2019; 137:896-902. [PMID: 31145440 DOI: 10.1001/jamaophthalmol.2019.1476] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Importance The Argus II Retinal Prosthesis System is indicated for patients with vision loss due to severe to profound outer retinal degeneration, a group with few treatment options. Objectives To collect postapproval safety and visual function data for the Argus II. Design, Setting, and Participants Multicenter, postapproval clinical trial conducted at 9 sites in Germany and Italy. Data were collected from December 2, 2011, to September 30, 2017, and patients were followed-up for 12 months or longer. Patients were 25 years or older with severe to profound outer retinal degeneration, some residual light perception or the ability of the retina to respond to electrical stimulation, and a history of useful form vision and were already planning to undergo Argus II implantation. Main Outcomes and Measures The primary end point of this study was the nature and rate of adverse events. Secondary end points included 3 visual function tests: square localization (SL), direction of motion, and grating visual acuity (GVA). Results Forty-seven patients were followed for 12 months or longer after implant. Mean (SD) age was 56 (12) years, 37 (79%) had retinitis pigmentosa, and 27 (57%) were male. Through the first 12 months postimplantation, 23 patients (49%) experienced 51 nonserious adverse events and 12 (26%) experienced 13 serious adverse events (SAEs), 9 of which were judged to be related to the Argus II, and 4 of which were judged to be related to the procedure. The most common SAE was conjunctival erosion, reported in 4 patients. No significance testing was done for group analysis for the SL or direction-of-motion tests. When averaged across the group, patients' accuracy on the SL test, but not on the direction-of-motion test, appeared better when the Argus II was on than when it was switched off. For GVA, more patients at each point in time achieved the 2.9 GVA cutoff in the implanted eye when the Argus II was on compared with it switched off. Conclusions and Relevance Safety and visual function outcomes in this clinical practice setting cohort of patients with Argus II implants were consistent with previously reported results. Longer follow-up of these patients and data from additional patients are required to better outline the risks and benefits of this approach to addressing blindness secondary to severe-to-profound outer retinal degeneration. Trial Registration ClinicalTrials.gov identifier: NCT01490827.
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Affiliation(s)
- Kim Schaffrath
- Department of Ophthalmology, RWTH Aachen University, Aachen, Germany
| | - Hannah Schellhase
- Department of Ophthalmology, RWTH Aachen University, Aachen, Germany
| | - Peter Walter
- Department of Ophthalmology, RWTH Aachen University, Aachen, Germany
| | - Albert Augustin
- Department of Ophthalmology, Karlsruhe Memorial Hospital, Karlsruhe, Germany
| | - Marzio Chizzolini
- Center for Retinitis Pigmentosa of Veneto Region, Camposampiero Hospital, Padova, Italy
| | - Bernd Kirchhof
- Department of Vitreo-retinal Surgery, Center of Ophthalmology, University of Cologne, Cologne, Germany
| | - Salvatore Grisanti
- University Eye Clinic, University Hospital Schleswig-Holstein, University of Luebeck, Luebeck, Germany
| | - Peter Wiedemann
- Department of Ophthalmology, Leipzig University, Leipzig, Germany
| | - Peter Szurman
- Eye Clinic Sulzbach, Knappschaft Hospital Saar, Sulzbach/Saar, Germany
| | | | - Robert J Greenberg
- Second Sight Medical Products Inc, Sylmar, California.,Alfred Mann Foundation for Scientific Research, Valencia, California
| | - Jessy D Dorn
- Second Sight Medical Products Inc, Sylmar, California
| | - Francesco Parmeggiani
- Center for Retinitis Pigmentosa of Veneto Region, Camposampiero Hospital, Padova, Italy.,Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy
| | - Stanislao Rizzo
- Department of Neuroscience, University of Florence, Florence, Italy.,Department of Ophthalmology, Careggi University Hospital, Florence, Italy
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Hsu PC, Chen PY, Chung YS, Lin TC, Hwang DK, Chen SJ, Kao CL. First implantation of retinal prosthesis in a patient with high myopia after surgery and rehabilitation program in Taiwan. J Chin Med Assoc 2019; 82:599-602. [PMID: 30893253 DOI: 10.1097/jcma.0000000000000091] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The implantation of the Argus II retinal prosthesis system in a 54-year-old woman with retinitis pigmentosa who presented with an eye of long axial length at 26.82 mm was successful. Postoperative examination revealed a gap of 700 µm between the electrode array and the retina, which caused decreased visual perception. A modified strategy with quad and quinary electrode stimulation was introduced to generate higher perceptual thresholds. The patient experienced visual functional changes during the first half of the year after surgery, although no remarkable difference was observed in terms of implant-retina distance. Fibrosis around the tack developed and extended between the gap with the retina elevated from the tack toward the center array, 8 months after the surgery. Schisis of the retina developed and filled the gap, resulting in decreased threshold, and the strategy was then shifted back to single electrode stimulation mode. Rehabilitation program is an evolving process that depends on the distance between the array and the retina in the eye with staphyloma. This study first showed the implantation in a patient with high myopia who presented with long axial length after surgery and rehabilitation program in Taiwan.
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Affiliation(s)
- Po-Cheng Hsu
- Department of Physical Medicine and Rehabilitation, Taipei Veterans General Hospital, Taipei, Taiwan, ROC
- School of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC
| | - Po-Yin Chen
- Department of Physical Medicine and Rehabilitation, Taipei Veterans General Hospital, Taipei, Taiwan, ROC
- School of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC
| | - Yi-Shun Chung
- Department of Physical Medicine and Rehabilitation, Taipei Veterans General Hospital, Taipei, Taiwan, ROC
- School of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC
| | - Tai-Chi Lin
- School of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC
- Department of Ophthalmology, Taipei Veterans General Hospital, Taipei, Taiwan, ROC
| | - De-Kuang Hwang
- School of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC
- Department of Ophthalmology, Taipei Veterans General Hospital, Taipei, Taiwan, ROC
| | - Shih-Jen Chen
- School of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC
- Department of Ophthalmology, Taipei Veterans General Hospital, Taipei, Taiwan, ROC
| | - Chung-Lan Kao
- Department of Physical Medicine and Rehabilitation, Taipei Veterans General Hospital, Taipei, Taiwan, ROC
- School of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC
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A model of ganglion axon pathways accounts for percepts elicited by retinal implants. Sci Rep 2019; 9:9199. [PMID: 31235711 PMCID: PMC6591412 DOI: 10.1038/s41598-019-45416-4] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 06/04/2019] [Indexed: 11/09/2022] Open
Abstract
Degenerative retinal diseases such as retinitis pigmentosa and macular degeneration cause irreversible vision loss in more than 10 million people worldwide. Retinal prostheses, now implanted in over 250 patients worldwide, electrically stimulate surviving cells in order to evoke neuronal responses that are interpreted by the brain as visual percepts ('phosphenes'). However, instead of seeing focal spots of light, current implant users perceive highly distorted phosphenes that vary in shape both across subjects and electrodes. We characterized these distortions by asking users of the Argus retinal prosthesis system (Second Sight Medical Products Inc.) to draw electrically elicited percepts on a touchscreen. Using ophthalmic fundus imaging and computational modeling, we show that elicited percepts can be accurately predicted by the topographic organization of optic nerve fiber bundles in each subject's retina, successfully replicating visual percepts ranging from 'blobs' to oriented 'streaks' and 'wedges' depending on the retinal location of the stimulating electrode. This provides the first evidence that activation of passing axon fibers accounts for the rich repertoire of phosphene shape commonly reported in psychophysical experiments, which can severely distort the quality of the generated visual experience. Overall our findings argue for more detailed modeling of biological detail across neural engineering applications.
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Wood EH, Tang PH, De la Huerta I, Korot E, Muscat S, Palanker DA, Williams GA. STEM CELL THERAPIES, GENE-BASED THERAPIES, OPTOGENETICS, AND RETINAL PROSTHETICS: Current State and Implications for the Future. Retina 2019; 39:820-835. [PMID: 30664120 PMCID: PMC6492547 DOI: 10.1097/iae.0000000000002449] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
PURPOSE To review and discuss current innovations and future implications of promising biotechnology and biomedical offerings in the field of retina. We focus on therapies that have already emerged as clinical offerings or are poised to do so. METHODS Literature review and commentary focusing on stem cell therapies, gene-based therapies, optogenetic therapies, and retinal prosthetic devices. RESULTS The technologies discussed herein are some of the more recent promising biotechnology and biomedical developments within the field of retina. Retinal prosthetic devices and gene-based therapies both have an FDA-approved product for ophthalmology, and many other offerings (including optogenetics) are in the pipeline. Stem cell therapies offer personalized medicine through novel regenerative mechanisms but entail complex ethical and reimbursement challenges. CONCLUSION Stem cell therapies, gene-based therapies, optogenetics, and retinal prosthetic devices represent a new era of biotechnological and biomedical progress. These bring new ethical, regulatory, care delivery, and reimbursement challenges. By addressing these issues proactively, we may accelerate delivery of care to patients in a safe, efficient, and value-based manner.
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Affiliation(s)
| | - Peter H Tang
- Department of Ophthalmology, Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
| | | | - Edward Korot
- Oakland University William Beaumont School of Medicine, Rochester, Michigan
| | | | - Daniel A Palanker
- Department of Ophthalmology, Hansen Experimental Physics Laboratory, Stanford University, Stanford, California
| | - George A Williams
- Associated Retinal Consultants, Royal Oak, Michigan
- Oakland University William Beaumont School of Medicine, Rochester, Michigan
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Ronchi S, Fiscella M, Marchetti C, Viswam V, Müller J, Frey U, Hierlemann A. Single-Cell Electrical Stimulation Using CMOS-Based High-Density Microelectrode Arrays. Front Neurosci 2019; 13:208. [PMID: 30918481 PMCID: PMC6424875 DOI: 10.3389/fnins.2019.00208] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 02/22/2019] [Indexed: 01/24/2023] Open
Abstract
Non-invasive electrical stimulation can be used to study and control neural activity in the brain or to alleviate somatosensory dysfunctions. One intriguing prospect is to precisely stimulate individual targeted neurons. Here, we investigated single-neuron current and voltage stimulation in vitro using high-density microelectrode arrays featuring 26,400 bidirectional electrodes at a pitch of 17.5 μm and an electrode area of 5 × 9 μm2. We determined optimal waveforms, amplitudes and durations for both stimulation modes. Owing to the high spatial resolution of our arrays and the close proximity of the electrodes to the respective neurons, we were able to stimulate the axon initial segments (AIS) with charges of less than 2 pC. This resulted in minimal artifact production and reliable readout of stimulation efficiency directly at the soma of the stimulated cell. Stimulation signals as low as 70 mV or 100 nA, with pulse durations as short as 18 μs, yielded measurable action potential initiation and propagation. We found that the required stimulation signal amplitudes decreased with cell growth and development and that stimulation efficiency did not improve at higher electric fields generated by simultaneous multi-electrode stimulation.
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Affiliation(s)
- Silvia Ronchi
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
| | - Michele Fiscella
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
- MaxWell Biosystems AG, Basel, Switzerland
| | - Camilla Marchetti
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
| | - Vijay Viswam
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
- MaxWell Biosystems AG, Basel, Switzerland
| | - Jan Müller
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
- MaxWell Biosystems AG, Basel, Switzerland
| | - Urs Frey
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
- MaxWell Biosystems AG, Basel, Switzerland
| | - Andreas Hierlemann
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
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Gregori NZ, Callaway NF, Hoeppner C, Yuan A, Rachitskaya A, Feuer W, Ameri H, Arevalo JF, Augustin AJ, Birch DG, Dagnelie G, Grisanti S, Davis JL, Hahn P, Handa JT, Ho AC, Huang SS, Humayun MS, Iezzi R, Jayasundera KT, Kokame GT, Lam BL, Lim JI, Mandava N, Montezuma SR, Olmos de Koo L, Szurman P, Vajzovic L, Wiedemann P, Weiland J, Yan J, Zacks DN. Retinal Anatomy and Electrode Array Position in Retinitis Pigmentosa Patients After Argus II Implantation: An International Study. Am J Ophthalmol 2018; 193:87-99. [PMID: 29940167 DOI: 10.1016/j.ajo.2018.06.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Revised: 06/12/2018] [Accepted: 06/13/2018] [Indexed: 01/26/2023]
Abstract
PURPOSE To assess the retinal anatomy and array position in Argus II retinal prosthesis recipients. DESIGN Prospective, noncomparative cohort study. METHODS Setting: International multicenter study. PATIENTS Argus II recipients enrolled in the Post-Market Surveillance Studies. PROCEDURES Spectral-domain optical coherence tomography images collected for the Surveillance Studies (NCT01860092 and NCT01490827) were reviewed. Baseline and postoperative macular thickness, electrode-retina distance (gap), optic disc-array overlap, and preretinal membrane presence were recorded at 1, 3, 6, and 12 months. MAIN OUTCOME MEASURES Axial retinal thickness and axial gap along the array's long axis (a line between the tack and handle); maximal retinal thickness and maximal gap along a B-scan near the tack, midline, and handle. RESULTS Thirty-three patients from 16 surgical sites in the United States and Germany were included. Mean axial retinal thickness increased from month 1 through month 12 at each location, but reached statistical significance only at the array midline (P = .007). The rate of maximal thickness increase was highest near the array midline (slope = 6.02, P = .004), compared to the tack (slope = 3.60, P < .001) or the handle (slope = 1.93, P = .368). The mean axial and maximal gaps decreased over the study period, and the mean maximal gap size decrease was significant at midline (P = .032). Optic disc-array overlap was seen in the minority of patients. Preretinal membranes were common before and after implantation. CONCLUSIONS Progressive macular thickening under the array was common and corresponded to decreased electrode-retina gap over time. By month 12, the array was completely apposed to the macula in approximately half of the eyes.
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Bareket L, Barriga-Rivera A, Zapf MP, Lovell NH, Suaning GJ. Progress in artificial vision through suprachoroidal retinal implants. J Neural Eng 2018; 14:045002. [PMID: 28541930 DOI: 10.1088/1741-2552/aa6cbb] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Retinal implants have proven their ability to restore visual sensation to people with degenerative retinopathy, characterized by photoreceptor cell death and the retina's inability to sense light. Retinal bionics operate by electrically stimulating the surviving neurons in the retina, thus triggering the transfer of visual sensory information to the brain. Suprachoroidal implants were first investigated in Australia in the 1950s. In this approach, the neuromodulation hardware is positioned between the sclera and the choroid, thus providing significant surgical and safety benefits for patients, with the potential to maintain residual vision combined with the artificial input from the device. Here we review the latest advances and state of the art devices for suprachoroidal prostheses, highlight future technologies and discuss challenges and perspectives towards improved rehabilitation of vision.
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Affiliation(s)
- Lilach Bareket
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia
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60
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Abstract
Vision begins when the eye's optical system-the cornea, iris, and crystalline lens-projects an image onto the retina, the thin and nearly transparent sheet of neural tissue that lines the back of the eye (see figure 1). Photoreceptors located at the back of the retina transduce incident photons into neural signals that are relayed to the brain. Those signals form the basis for visual perception. In humans, cone photoreceptors, which number about 6 million, dominate the central region of the visual field and are responsible for color and high-resolution day vision. Rod photoreceptors, which number about 120 million, dominate the periphery and mediate night vision.
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61
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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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Loizos K, Marc R, Humayun M, Anderson JR, Jones BW, Lazzi G. Increasing Electrical Stimulation Efficacy in Degenerated Retina: Stimulus Waveform Design in a Multiscale Computational Model. IEEE Trans Neural Syst Rehabil Eng 2018; 26:1111-1120. [PMID: 29877835 PMCID: PMC6005361 DOI: 10.1109/tnsre.2018.2832055] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A computational model of electrical stimulation of the retina is proposed for investigating current waveforms used in prosthetic devices for restoring partial vision lost to retinal degenerative diseases. The model framework combines a connectome-based neural network model characterized by accurate morphological and synaptic properties with an admittance method model of bulk tissue and prosthetic electronics. In this model, the retina was computationally "degenerated," considering cellular death and anatomical changes that occur early in disease, as well as altered neural behavior that develops throughout the neurodegeneration and is likely interfering with current attempts at restoring vision. A resulting analysis of stimulation range and threshold of ON ganglion cells within the retina that are either healthy or in beginning stages of degeneration is presented for currently used stimulation waveforms, and an asymmetric biphasic current stimulation for subduing spontaneous firing to allow increased control over ganglion cell firing patterns in degenerated retina is proposed. Results show that stimulation thresholds of retinal ganglion cells do not notably vary after beginning stages of retina degeneration. In addition, simulation of proposed asymmetric waveforms showed the ability to enhance the control of ganglion cell firing via electrical stimulation.
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63
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Delyfer MN, Gaucher D, Govare M, Cougnard-Grégoire A, Korobelnik JF, Ajana S, Mohand-Saïd S, Ayello-Scheer S, Rezaiguia-Studer F, Dollfus H, Sahel JA, Barale PO. Adapted Surgical Procedure for Argus II Retinal Implantation: Feasibility, Safety, Efficiency, and Postoperative Anatomic Findings. ACTA ACUST UNITED AC 2018; 2:276-287. [DOI: 10.1016/j.oret.2017.08.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 08/01/2017] [Accepted: 08/08/2017] [Indexed: 11/17/2022]
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Flores T, Lei X, Huang T, Lorach H, Dalal R, Galambos L, Kamins T, Mathieson K, Palanker D. Optimization of pillar electrodes in subretinal prosthesis for enhanced proximity to target neurons. J Neural Eng 2018; 15:036011. [PMID: 29388561 DOI: 10.1088/1741-2552/aaac39] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE High-resolution prosthetic vision requires dense stimulating arrays with small electrodes. However, such miniaturization reduces electrode capacitance and penetration of electric field into tissue. We evaluate potential solutions to these problems with subretinal implants based on utilization of pillar electrodes. APPROACH To study integration of three-dimensional (3D) implants with retinal tissue, we fabricated arrays with varying pillar diameter, pitch, and height, and implanted beneath the degenerate retina in rats (Royal College of Surgeons, RCS). Tissue integration was evaluated six weeks post-op using histology and whole-mount confocal fluorescence imaging. The electric field generated by various electrode configurations was calculated in COMSOL, and stimulation thresholds assessed using a model of network-mediated retinal response. MAIN RESULTS Retinal tissue migrated into the space between pillars with no visible gliosis in 90% of implanted arrays. Pillars with 10 μm height reached the middle of the inner nuclear layer (INL), while 22 μm pillars reached the upper portion of the INL. Electroplated pillars with dome-shaped caps increase the active electrode surface area. Selective deposition of sputtered iridium oxide onto the cap ensures localization of the current injection to the pillar top, obviating the need to insulate the pillar sidewall. According to computational model, pillars having a cathodic return electrode above the INL and active anodic ring electrode at the surface of the implant would enable six times lower stimulation threshold, compared to planar arrays with circumferential return, but suffer from greater cross-talk between the neighboring pixels. SIGNIFICANCE 3D electrodes in subretinal prostheses help reduce electrode-tissue separation and decrease stimulation thresholds to enable smaller pixels, and thereby improve visual acuity of prosthetic vision.
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Affiliation(s)
- Thomas Flores
- Department of Applied Physics, Stanford University, Stanford, CA, United States of America
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Güven D, Demir M, Özcan D, Kaçar H, Demir ST, Uzun SÜ. Multimodal Imaging Including Optical Coherence Tomography Angiography of a Patient With Argus II Retinal Prosthesis One Year After Implantation. Ophthalmic Surg Lasers Imaging Retina 2018; 49:55-59. [PMID: 29304268 DOI: 10.3928/23258160-20171215-09] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 06/02/2017] [Indexed: 11/20/2022]
Abstract
A 58-year-old man with end-stage retinitis pigmentosa (RP) and visual acuity of light perception in both eyes received simultaneous phacoemulsification with intraocular lens implantation and implantation of the Argus II Retinal Prosthesis System (Second Sight Medical Products, Sylmar, CA) to his right eye 1 year ago. He accomplished the fitting and rehabilitation sessions, and no extraocular or intraocular complications were encountered perioperatively, postoperatively, or during the follow-up. The patient used the prosthesis actively for 2.5 to 3 hours per day. In this report, the authors compare the multimodal imaging findings including optical coherence tomography angiography of the chronic electrically stimulated retinal prosthesis implanted eye with the fellow eye. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:55-59.].
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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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Chan LLH, Bermak A. Novel structure of carbon nanotube micro electrode for high-resolution stimulation of neurons. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2016:6170-6173. [PMID: 28269661 DOI: 10.1109/embc.2016.7592137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This paper proposes a novel method to fabricate high resolution flexible electrodes. Among the steps, the carbon nanotube (CNT) electrodes synthesized facing down shows impedance improvement of about 90 times comparing with the normal facing up synthesized samples. Meanwhile, section impedance of electrodes is also defined in this paper to compare the area efficiency of impedance between electrodes with different sizes. In addition and to the best of our knowledge, high performance electrodes embedded inside parylene is reported for the first time taking into consideration the hydrophobicity change of the CNT surface.
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Wang J, Xie H, Chung T, Chan LLH, Pang SW. Neural Probes with Integrated Temperature Sensors for Monitoring Retina and Brain Implantation and Stimulation. IEEE Trans Neural Syst Rehabil Eng 2017; 25:1663-1673. [PMID: 28362612 DOI: 10.1109/tnsre.2016.2634584] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Gold (Au) resistive temperature sensors were integrated on flexible polyimide-based neural probes to monitor temperature changes during neural probe implantation and stimulation. Temperature changes were measured as neural probes were implanted to infer the positions of the neural probes, and as the retina or the deep brain region was stimulated electrically. The temperature sensor consisted of a serpentine Au resistor and surrounded by four Au electrodes with 200 and [Formula: see text] diameter (dia.). The Au temperature sensors had temperature coefficient of 0.32%, and they were biocompatible and small in size. In vivo measurements of temperature changes during implantation and stimulation were carried out in the retina and deep brain region in rats. The desired implantation position was reached when temperature measured by the sensor increased to the calibrated level and became stable. There was no temperature increase when low level stimulation current of 8 and [Formula: see text] each for the two 200- and 400- [Formula: see text]-dia. electrodes, respectively, were applied. When higher level stimulation current of 100 and [Formula: see text] each were applied to the two 200- and 400- [Formula: see text]-dia. electrodes, respectively, maximum temperature increases of 1.2 °C in retina and 1 °C in deep brain region were found.
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Petoe MA, Shivdasani MN. Are long stimulus pulse durations the answer to improving spatial resolution in retinal prostheses? ANNALS OF TRANSLATIONAL MEDICINE 2016; 4:434. [PMID: 27942525 DOI: 10.21037/atm.2016.11.24] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Retinal prostheses can provide artificial vision to patients with degenerate retinae by electrically stimulating the remaining inner retinal neurons. The evoked perception is generally adequate for light localization, but of limited spatial resolution owing to the indiscriminate activation of multiple retinal cell types, leading to distortions in the perceived image. Here we present a perspective on a recent work by Weitz and colleagues who demonstrate a focal confinement of retinal ganglion cell (RGC) activation when using extended pulse durations in the stimulation waveform. Using real-time calcium imaging, they provide evidence that long pulse durations selectively stimulate inner retinal neurons, whilst avoiding unwanted axonal activations. The application of this stimulation technique may provide enhanced spatial resolution for retinal prosthesis users. These experiments provide a robust analysis of the effects of increasing pulse duration and introduce the potential for alternative stimulation paradigms in retinal prostheses.
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Affiliation(s)
- Matthew A Petoe
- Bionics Institute, Department of Medical Bionics, University of Melbourne, Melbourne, Australia
| | - Mohit N Shivdasani
- Bionics Institute, Department of Medical Bionics, University of Melbourne, Melbourne, Australia
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Rountree CM, Inayat S, Troy JB, Saggere L. Differential stimulation of the retina with subretinally injected exogenous neurotransmitter: A biomimetic alternative to electrical stimulation. Sci Rep 2016; 6:38505. [PMID: 27929043 PMCID: PMC5144088 DOI: 10.1038/srep38505] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 11/09/2016] [Indexed: 12/19/2022] Open
Abstract
Subretinal stimulation of the retina with neurotransmitters, the normal means of conveying visual information, is a potentially better alternative to electrical stimulation widely used in current retinal prostheses for treating blindness from photoreceptor degenerative diseases. Yet, no subretinal electrical or chemical stimulation study has stimulated the OFF and ON pathways differentially through inner retinal activation. Here, we demonstrate the feasibility of differentially stimulating retinal ganglion cells (RGCs) through the inner nuclear layer of the retina with glutamate, a primary neurotransmitter chemical, in a biomimetic way. We show that controlled pulsatile delivery of glutamate into the subsurface of explanted wild-type rat retinas elicits highly localized simultaneous inhibitory and excitatory spike rate responses in OFF and ON RGCs. We also present the spatiotemporal characteristics of RGC responses to subretinally injected glutamate and the therapeutic stimulation parameters. Our findings could pave the way for future development of a neurotransmitter-based subretinal prosthesis offering more naturalistic vision and better visual acuity than electrical prostheses.
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Affiliation(s)
- Corey M Rountree
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Samsoon Inayat
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, USA
| | - John B Troy
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Laxman Saggere
- Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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Rachitskaya AV, Yuan A, Marino MJ, Reese J, Ehlers JP. Intraoperative OCT Imaging of the Argus II Retinal Prosthesis System. Ophthalmic Surg Lasers Imaging Retina 2016; 47:999-1003. [PMID: 27842194 PMCID: PMC5546736 DOI: 10.3928/23258160-20161031-03] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Accepted: 09/16/2016] [Indexed: 11/20/2022]
Abstract
BACKGROUND AND OBJECTIVE Optimal placement of the Argus II Retinal Prosthesis System (Second Sight Medical Products, Sylmar, CA) is critical. Intraoperative optical coherence tomography (OCT) allows for intrasurgical visualization and confirmation of array placement. In this study, two different OCT systems were evaluated to assess the feasibility and utility of this technology during Argus II surgery. PATIENTS AND METHODS Intraoperative OCT was performed on five patients undergoing Argus II implantation at Cole Eye Institute from June 2015 to July 2016. The EnVisu portable OCT (Bioptigen, Morrisville, NC) and microscope-integrated RESCAN 700 (Zeiss, Oberkochen, Germany) intraoperative OCT systems were utilized. The EnVisu was used in three patients and the RESCAN 700 in three of the five patients. Following array tacking, intraoperative OCT was performed over the entire array including the edges and tack. RESULTS Intraoperative OCT allowed for visualization of the array/retina interface. Microscope integration of the OCT system facilitated ease of focusing, real-time feedback, surgeon-directed OCT scanning to the areas of interest, and enhanced image quality at points of interest. CONCLUSIONS Intraoperative imaging of the Argus II electrode array is feasible and provides information about electrode array-retina interface and distance to help guide a surgeon. Microscope integration of OCT appears to provide an optimal and efficient approach to intraoperative OCT during Argus II array placement. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:999-1003.].
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Eleftheriou CG, Zimmermann JB, Kjeldsen HD, David-Pur M, Hanein Y, Sernagor E. Carbon nanotube electrodes for retinal implants: A study of structural and functional integration over time. Biomaterials 2016; 112:108-121. [PMID: 27760395 PMCID: PMC5123641 DOI: 10.1016/j.biomaterials.2016.10.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 10/08/2016] [Accepted: 10/11/2016] [Indexed: 12/15/2022]
Abstract
The choice of electrode material is of paramount importance in neural prosthetic devices. Electrodes must be biocompatible yet able to sustain repetitive current injections in a highly corrosive environment. We explored the suitability of carbon nanotube (CNT) electrodes to stimulate retinal ganglion cells (RGCs) in a mouse model of outer retinal degeneration. We investigated morphological changes at the bio-hybrid interface and changes in RGC responses to electrical stimulation following prolonged in vitro coupling to CNT electrodes. We observed gradual remodelling of the inner retina to incorporate CNT assemblies. Electrophysiological recordings demonstrate a progressive increase in coupling between RGCs and the CNT electrodes over three days, characterized by a gradual decrease in stimulation thresholds and increase in cellular recruitment. These results provide novel evidence for time-dependent formation of viable bio-hybrids between CNTs and the retina, demonstrating that CNTs are a promising material for inclusion in retinal prosthetic devices.
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Affiliation(s)
- Cyril G Eleftheriou
- Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle-upon-Tyne, NE2 4HH, United Kingdom
| | - Jonas B Zimmermann
- Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle-upon-Tyne, NE2 4HH, United Kingdom
| | - Henrik D Kjeldsen
- Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle-upon-Tyne, NE2 4HH, United Kingdom
| | - Moshe David-Pur
- School of Electrical Engineering, Tel-Aviv University, Ramat-Aviv, Tel-Aviv, 69978, Israel
| | - Yael Hanein
- School of Electrical Engineering, Tel-Aviv University, Ramat-Aviv, Tel-Aviv, 69978, Israel
| | - Evelyne Sernagor
- Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Framlington Place, Newcastle-upon-Tyne, NE2 4HH, United Kingdom.
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75
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Brandli A, Luu CD, Guymer RH, Ayton LN. Progress in the clinical development and utilization of vision prostheses: an update. Eye Brain 2016; 8:15-25. [PMID: 28539798 PMCID: PMC5398739 DOI: 10.2147/eb.s70822] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Vision prostheses, or "bionic eyes", are implantable medical bionic devices with the potential to restore rudimentary sight to people with profound vision loss or blindness. In the past two decades, this field has rapidly progressed, and there are now two commercially available retinal prostheses in the US and Europe, and a number of next-generation devices in development. This review provides an update on the development of these devices and a discussion on the future directions for the field.
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Affiliation(s)
- Alice Brandli
- Centre for Eye Research Australia, Department of Surgery (Ophthalmology), The University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, VIC, Australia
| | - Chi D Luu
- Centre for Eye Research Australia, Department of Surgery (Ophthalmology), The University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, VIC, Australia
| | - Robyn H Guymer
- Centre for Eye Research Australia, Department of Surgery (Ophthalmology), The University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, VIC, Australia
| | - Lauren N Ayton
- Centre for Eye Research Australia, Department of Surgery (Ophthalmology), The University of Melbourne, Royal Victorian Eye and Ear Hospital, Melbourne, VIC, Australia
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Worldwide Argus II implantation: recommendations to optimize patient outcomes. BMC Ophthalmol 2016; 16:52. [PMID: 27154461 PMCID: PMC4858839 DOI: 10.1186/s12886-016-0225-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 04/21/2016] [Indexed: 01/27/2023] Open
Abstract
Background A position paper based on the collective experiences of Argus II Retinal Prosthesis System investigators to review strategies to optimize outcomes in patients with retinitis pigmentosa undergoing retinal prosthesis implantation. Methods Retinal surgeons, device programmers, and rehabilitation specialists from Europe, Canada, Middle East, and the United States were convened to the first international Argus II Investigator Meeting held in Ann Arbor, MI in March 2015. The recommendations from the collective experiences were collected. Factors associated with successful outcomes were determined. Results Factors leading to successful outcomes begin with appropriate patient selection, expectation counseling, and preoperative retinal assessment. Challenges to surgical implantation include presence of staphyloma and inadequate Tenon’s capsule or conjunctiva. Modified surgical technique may reduce risks of complications such as hypotony and conjunctival erosion. Rehabilitation efforts and correlation with validated outcome measures following implantation are critical. Conclusions Bringing together Argus II investigators allowed the identification of strategies to optimize patient outcomes. Establishing an on-line collaborative network will foster coordinated research efforts to advance outcome assessment and rehabilitation strategies.
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Cho A, Ratliff C, Sampath A, Weiland J. Changes in ganglion cell physiology during retinal degeneration influence excitability by prosthetic electrodes. J Neural Eng 2016; 13:025001. [PMID: 26905177 DOI: 10.1088/1741-2560/13/2/025001] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Here we investigate ganglion cell physiology in healthy and degenerating retina to test its influence on threshold to electrical stimulation. APPROACH Age-related Macular Degeneration and Retinitis Pigmentosa cause blindness via outer retinal degeneration. Inner retinal pathways that transmit visual information to the central brain remain intact, so direct electrical stimulation from prosthetic devices offers the possibility for visual restoration. Since inner retinal physiology changes during degeneration, we characterize physiological properties and responses to electrical stimulation in retinal ganglion cells (RGCs) of both wild type mice and the rd10 mouse model of retinal degeneration. MAIN RESULTS Our aggregate results support previous observations that elevated thresholds characterize diseased retinas. However, a physiology-driven classification scheme reveals distinct sub-populations of ganglion cells with thresholds either normal or strongly elevated compared to wild-type. When these populations are combined, only a weakly elevated threshold with large variance is observed. The cells with normal threshold are more depolarized at rest and exhibit periodic oscillations. SIGNIFICANCE During degeneration, physiological changes in RGCs affect the threshold stimulation currents required to evoke action potentials.
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Affiliation(s)
- Alice Cho
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90033, USA
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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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79
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Luo YHL, da Cruz L. The Argus® II Retinal Prosthesis System. Prog Retin Eye Res 2016; 50:89-107. [PMID: 26404104 DOI: 10.1016/j.preteyeres.2015.09.003] [Citation(s) in RCA: 179] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2015] [Revised: 08/25/2015] [Accepted: 09/17/2015] [Indexed: 11/25/2022]
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OPTOMAP WIDEFIELD IMAGING OF THE ARGUS II RETINAL PROSTHESIS IN PATIENTS WITH RETINITIS PIGMENTOSA. Retin Cases Brief Rep 2015; 10:382-5. [PMID: 26705237 DOI: 10.1097/icb.0000000000000269] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To explore the utility of using ultra-widefield imaging to visualize the Argus II implant in the eyes of three patients with retinitis pigmentosa. METHODS Case series of three patients with retinitis pigmentosa who were implanted with the Argus II Retinal Prosthesis System; two of whom were enrolled in the Argus II clinical trial and one received the implant after the commercial release of the device. Optomap widefield fundus autofluorescence and color images of both eyes were taken in all three patients by an experienced technician using the Optos 200Tx imaging system. Analysis focused on fundus autofluorescence images of the implanted eyes and consisted of assessing the location and configuration of the Argus II electrode array and cable, and also the condition of the surrounding retina. Analysis was led by an experienced vitreoretinal surgeon. RESULTS Optos fundus autofluorescence images of the implanted eyes in all 3 patients gave a wide-angle view of the retina, with the electrode array and cable clearly visible. The status of the array and cable was able to be determined without difficulty. All 3 cases showed an appropriate mild-to-moderate bowing of the cable, and also the electrode array being positioned on or near the macula with a superotemporal tilt. Other features, such as "bone spicules," were also clearly seen. Optos color images were not as useful in the analysis because of an exaggerated green light artifact seen in the implanted versus the nonimplanted eyes. CONCLUSION Optomap fundus autofluorescence widefield images are useful in determining the configuration of the Argus II cable and the position of the electrode array on the retina and therefore are a useful component of the postoperative surveillance of patients implanted with the device. Using autofluorescence avoids the generation of a light reflection artifact often seen with Optos color imaging.
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81
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Seider MI, Hahn P. Argus II retinal prosthesis malrotation and repositioning with intraoperative optical coherence tomography in a posterior staphyloma. Clin Ophthalmol 2015; 9:2213-6. [PMID: 26648688 PMCID: PMC4664517 DOI: 10.2147/opth.s96570] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Introduction The Argus II retinal prosthesis may improve visual function in patients with severe vision loss from retinitis pigmentosa. Optimal centration of the electrode array over the macula is important to achieve optimal visual results. Argus tack malrotation is a novel entity that may be encountered during placement, especially in patients with posterior staphyloma. Methods Retrospective case review. Results During tacking of the electronics array a clockwise rotation occurred resulting in malposition. We hypothesize this was secondary to undue rotation or posterior pressure applied during tack insertion in conjunction with placement over a previously unrecognized posterior staphyloma. Intraoperative optical coherence tomography, because of the cross-sectional images provided, was helpful in visualizing the distance between the electronics array and the retina, which was difficult to assess using the surgical microscope alone. Repositioning was achieved by adjusting the tack without removal. The patient experienced an improvement in vision as a result of the surgery. Conclusion Malrotation may occur when tacking the Argus II prosthesis, and the presence of a posterior staphyloma may increase this risk. It is important to differentiate malrotation from tack misplacement – the former may be addressed with array unrotation or partial tack withdrawal and the latter may require tack removal and reinsertion. Also, intraoperative optical coherence tomography may be helpful in characterizing electronics array position during surgery.
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Affiliation(s)
| | - Paul Hahn
- Duke University Eye Center, Durham, NC, USA
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82
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Fox K, Meffin H, Burns O, Abbott CJ, Allen PJ, Opie NL, McGowan C, Yeoh J, Ahnood A, Luu CD, Cicione R, Saunders AL, McPhedran M, Cardamone L, Villalobos J, Garrett DJ, Nayagam DAX, Apollo NV, Ganesan K, Shivdasani MN, Stacey A, Escudie M, Lichter S, Shepherd RK, Prawer S. Development of a Magnetic Attachment Method for Bionic Eye Applications. Artif Organs 2015; 40:E12-24. [DOI: 10.1111/aor.12582] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Kate Fox
- School of Physics; University of Melbourne; Melbourne Victoria Australia
- School of Aerospace, Mechanical and Manufacturing Engineering; RMIT University; Melbourne Victoria Australia
| | - Hamish Meffin
- Department of Electrical and Electronic Engineering; University of Melbourne; Melbourne Victoria Australia
- National Vision Research Institute; Australian College of Optometry; Melbourne Victoria Australia
| | - Owen Burns
- The Bionics Institute; Melbourne Victoria Australia
| | - Carla J. Abbott
- Centre for Eye Research Australia (CERA) Royal Victorian Eye and Ear Hospital; Melbourne Victoria Australia
| | - Penelope J. Allen
- Centre for Eye Research Australia (CERA) Royal Victorian Eye and Ear Hospital; Melbourne Victoria Australia
| | - Nicholas L. Opie
- Centre for Eye Research Australia (CERA) Royal Victorian Eye and Ear Hospital; Melbourne Victoria Australia
| | | | - Jonathan Yeoh
- Centre for Eye Research Australia (CERA) Royal Victorian Eye and Ear Hospital; Melbourne Victoria Australia
| | - Arman Ahnood
- School of Physics; University of Melbourne; Melbourne Victoria Australia
| | - Chi D. Luu
- Centre for Eye Research Australia (CERA) Royal Victorian Eye and Ear Hospital; Melbourne Victoria Australia
| | - Rosemary Cicione
- School of Physics; University of Melbourne; Melbourne Victoria Australia
| | | | | | | | | | - David J. Garrett
- School of Physics; University of Melbourne; Melbourne Victoria Australia
- The Bionics Institute; Melbourne Victoria Australia
| | | | - Nicholas V. Apollo
- School of Physics; University of Melbourne; Melbourne Victoria Australia
- The Bionics Institute; Melbourne Victoria Australia
| | - Kumaravelu Ganesan
- School of Physics; University of Melbourne; Melbourne Victoria Australia
| | | | - Alastair Stacey
- School of Physics; University of Melbourne; Melbourne Victoria Australia
| | - Mathilde Escudie
- School of Physics; University of Melbourne; Melbourne Victoria Australia
| | - Samantha Lichter
- School of Physics; University of Melbourne; Melbourne Victoria Australia
| | | | - Steven Prawer
- School of Physics; University of Melbourne; Melbourne Victoria Australia
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Majdi JA, Minnikanti S, Peixoto N, Agrawal A, Cohen ED. Access resistance of stimulation electrodes as a function of electrode proximity to the retina. J Neural Eng 2014; 12:016006. [DOI: 10.1088/1741-2560/12/1/016006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abramian M, Lovell NH, Morley JW, Suaning GJ, Dokos S. Activation and inhibition of retinal ganglion cells in response to epiretinal electrical stimulation: a computational modelling study. J Neural Eng 2014; 12:016002. [PMID: 25426958 DOI: 10.1088/1741-2560/12/1/016002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Retinal prosthetic devices aim to restore sight in visually impaired people by means of electrical stimulation of surviving retinal ganglion cells (RGCs). This modelling study aims to demonstrate that RGC inhibition caused by high-intensity cathodic pulses greatly influences their responses to epiretinal electrical stimulation and to investigate the impact of this inhibition on spatial activation profiles as well as their implications for retinal prosthetic device design. Another aim is to take advantage of this inhibition to reduce axonal activation in the nerve fibre layer. APPROACH A three-dimensional finite-element model of epiretinal electrical stimulation was utilized to obtain RGC activation and inhibition threshold profiles for a range of parameters. MAIN RESULTS RGC activation and inhibition thresholds were highly dependent on cell and stimulus parameters. Activation thresholds were 1.5, 3.4 and 11.3 μA for monopolar electrodes with 5, 20 and 50 μm radii, respectively. Inhibition to activation threshold ratios were mostly within the range 2-10. Inhibition significantly altered spatial patterns of RGC activation. With concentric electrodes and appropriately high levels of stimulus amplitudes, activation of passing axons was greatly reduced. SIGNIFICANCE RGC inhibition significantly impacts their spatial activation profiles, and therefore it most likely influences patterns of perceived phosphenes induced by retinal prosthetic devices. Thus this inhibition should be taken into account in future studies concerning retinal prosthesis development. It might be possible to utilize this inhibitory effect to bypass activation of passing axons and selectively stimulate RGCs near their somas and dendrites to achieve more localized phosphenes.
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Affiliation(s)
- Miganoosh Abramian
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia
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85
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Weitz AC, Behrend MR, Ahuja AK, Christopher P, Wei J, Wuyyuru V, Patel U, Greenberg RJ, Humayun MS, Chow RH, Weiland JD. Interphase gap as a means to reduce electrical stimulation thresholds for epiretinal prostheses. J Neural Eng 2014; 11:016007. [PMID: 24654269 DOI: 10.1088/1741-2560/11/1/016007] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Epiretinal prostheses are designed to restore functional vision to the blind by electrically stimulating surviving retinal neurons. These devices have classically employed symmetric biphasic current pulses in order to maintain a balance of charge. Prior electrophysiological and psychophysical studies in peripheral nerve show that adding an interphase gap (IPG) between the two phases makes stimulation more efficient than pulses with no gap. This led us to investigate the effect of IPG duration on retinal stimulation thresholds. APPROACH We measured retinal ganglion cell (RGC) electrical thresholds in salamander retina and phosphene perceptual thresholds in epiretinal prosthesis patients during stimulation with different IPG lengths. We also built Hodgkin-Huxley-type models of RGCs to further study how IPG affects thresholds. MAIN RESULTS In general, there was a negative exponential correlation between threshold and IPG duration. Durations greater than or equal to ~0.5 ms reduced salamander RGC thresholds by 20-25%. Psychophysical testing in five retinal prosthesis patients indicated that stimulating with IPGs can decrease perceptual thresholds by 10-15%. Results from computational models of RGCs corroborated the observed behavior. SIGNIFICANCE Incorporating interphase gaps can reduce the power consumption of epiretinal prostheses and increase the available dynamic range of phosphene size and brightness.
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86
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Rizzo S, Belting C, Cinelli L, Allegrini L, Genovesi-Ebert F, Barca F, di Bartolo E. The Argus II Retinal Prosthesis: 12-month outcomes from a single-study center. Am J Ophthalmol 2014; 157:1282-90. [PMID: 24560994 DOI: 10.1016/j.ajo.2014.02.039] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 02/14/2014] [Accepted: 02/15/2014] [Indexed: 12/25/2022]
Abstract
PURPOSE To study the anatomic and functional outcomes of Argus II Retinal Prosthesis System implantation in patients with retinitis pigmentosa. DESIGN Interventional case series. METHODS The study population included 6 patients with visual acuity no better than light perception. After the Argus II Retinal Prosthesis System was implanted, complications and anatomic and functional results were studied. The main outcome measures were mobility, square localization, direction of motion, grating visual acuity, and Goldmann visual field, all of which were assessed. Optical coherence tomography was performed. RESULTS Implantation of the Argus II Retinal Prosthesis System was safely performed in all patients. One patient experienced postoperative elevation in intraocular pressure, which was controlled medically. In 1 patient, moderate detachment of the choroid occurred postoperatively, and it resolved spontaneously. One patient withdrew from the study. Wound dehiscence, endophthalmitis or retinal detachment was not observed. All patients were able to locate a bright light on the ceiling and a dark line on the floor after the surgery. Performance in square localization tests improved in 4 patients, and direction of motion improved in 3 patients. One patient achieved grating visual acuity. Goldmann visual field test results improved in all patients. CONCLUSIONS The patients showed improvement in visual tasks after the surgery, and the device was well tolerated and functional over a 1-year follow-up period. A rigorous patient-selection process is necessary to maximize patient compliance with the rigorous follow-up testing schedule. Both patients and medical staff should be prepared for a lengthy, arduous rehabilitation process.
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Affiliation(s)
- Stanislao Rizzo
- Azienda Ospedaliero-Universitaria Pisana, Unità Operativa Chirurgia Oftalmica, Via Paradisa 2, 56124 Pisa, Italy.
| | - Claudia Belting
- Azienda Ospedaliero-Universitaria Pisana, Unità Operativa Chirurgia Oftalmica, Via Paradisa 2, 56124 Pisa, Italy
| | - Laura Cinelli
- Azienda Ospedaliero-Universitaria Pisana, Unità Operativa Chirurgia Oftalmica, Via Paradisa 2, 56124 Pisa, Italy
| | - Luca Allegrini
- Azienda Ospedaliero-Universitaria Pisana, Unità Operativa Chirurgia Oftalmica, Via Paradisa 2, 56124 Pisa, Italy
| | - Federica Genovesi-Ebert
- Azienda Ospedaliero-Universitaria Pisana, Unità Operativa Chirurgia Oftalmica, Via Paradisa 2, 56124 Pisa, Italy
| | - Francesco Barca
- Azienda Ospedaliero-Universitaria Pisana, Unità Operativa Chirurgia Oftalmica, Via Paradisa 2, 56124 Pisa, Italy
| | - Emanuele di Bartolo
- Azienda Ospedaliero-Universitaria Pisana, Unità Operativa Chirurgia Oftalmica, Via Paradisa 2, 56124 Pisa, Italy
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87
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Nayagam DAX, Williams RA, Allen PJ, Shivdasani MN, Luu CD, Salinas-LaRosa CM, Finch S, Ayton LN, Saunders AL, McPhedran M, McGowan C, Villalobos J, Fallon JB, Wise AK, Yeoh J, Xu J, Feng H, Millard R, McWade M, Thien PC, Williams CE, Shepherd RK. Chronic electrical stimulation with a suprachoroidal retinal prosthesis: a preclinical safety and efficacy study. PLoS One 2014; 9:e97182. [PMID: 24853376 PMCID: PMC4031073 DOI: 10.1371/journal.pone.0097182] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 04/16/2014] [Indexed: 11/23/2022] Open
Abstract
Purpose To assess the safety and efficacy of chronic electrical stimulation of the retina with a suprachoroidal visual prosthesis. Methods Seven normally-sighted feline subjects were implanted for 96–143 days with a suprachoroidal electrode array and six were chronically stimulated for 70–105 days at levels that activated the visual cortex. Charge balanced, biphasic, current pulses were delivered to platinum electrodes in a monopolar stimulation mode. Retinal integrity/function and the mechanical stability of the implant were assessed monthly using electroretinography (ERG), optical coherence tomography (OCT) and fundus photography. Electrode impedances were measured weekly and electrically-evoked visual cortex potentials (eEVCPs) were measured monthly to verify that chronic stimuli were suprathreshold. At the end of the chronic stimulation period, thresholds were confirmed with multi-unit recordings from the visual cortex. Randomized, blinded histological assessments were performed by two pathologists to compare the stimulated and non-stimulated retina and adjacent tissue. Results All subjects tolerated the surgical and stimulation procedure with no evidence of discomfort or unexpected adverse outcomes. After an initial post-operative settling period, electrode arrays were mechanically stable. Mean electrode impedances were stable between 11–15 kΩ during the implantation period. Visually-evoked ERGs & OCT were normal, and mean eEVCP thresholds did not substantially differ over time. In 81 of 84 electrode-adjacent tissue samples examined, there were no discernible histopathological differences between stimulated and unstimulated tissue. In the remaining three tissue samples there were minor focal fibroblastic and acute inflammatory responses. Conclusions Chronic suprathreshold electrical stimulation of the retina using a suprachoroidal electrode array evoked a minimal tissue response and no adverse clinical or histological findings. Moreover, thresholds and electrode impedance remained stable for stimulation durations of up to 15 weeks. This study has demonstrated the safety and efficacy of suprachoroidal stimulation with charge balanced stimulus currents.
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Affiliation(s)
- David A. X. Nayagam
- Bionics Institute, East Melbourne, Victoria, Australia
- Department of Pathology, University of Melbourne, Parkville, Victoria, Australia
- * E-mail:
| | - Richard A. Williams
- Department of Pathology, University of Melbourne, Parkville, Victoria, Australia
- Department of Anatomical Pathology, St Vincent’s Hospital Melbourne, Fitzroy, Victoria, Australia
| | - Penelope J. Allen
- Centre for Eye Research Australia, University of Melbourne, East Melbourne, Victoria, Australia
- Department of Ophthalmology, The University of Melbourne, East Melbourne, Victoria, Australia
| | - Mohit N. Shivdasani
- Bionics Institute, East Melbourne, Victoria, Australia
- Medical Bionics Department, University of Melbourne, East Melbourne, Victoria, Australia
| | - Chi D. Luu
- Centre for Eye Research Australia, University of Melbourne, East Melbourne, Victoria, Australia
| | - Cesar M. Salinas-LaRosa
- Department of Anatomical Pathology, St Vincent’s Hospital Melbourne, Fitzroy, Victoria, Australia
| | - Sue Finch
- Statistical Consulting Centre, The University of Melbourne, Parkville, Victoria, Australia
| | - Lauren N. Ayton
- Centre for Eye Research Australia, University of Melbourne, East Melbourne, Victoria, Australia
| | | | | | - Ceara McGowan
- Bionics Institute, East Melbourne, Victoria, Australia
| | | | - James B. Fallon
- Bionics Institute, East Melbourne, Victoria, Australia
- Medical Bionics Department, University of Melbourne, East Melbourne, Victoria, Australia
| | - Andrew K. Wise
- Bionics Institute, East Melbourne, Victoria, Australia
- Department of Otolaryngology, The University of Melbourne, East Melbourne, Victoria, Australia
- Medical Bionics Department, University of Melbourne, East Melbourne, Victoria, Australia
| | - Jonathan Yeoh
- Centre for Eye Research Australia, University of Melbourne, East Melbourne, Victoria, Australia
- Department of Ophthalmology, The University of Melbourne, East Melbourne, Victoria, Australia
| | - Jin Xu
- Bionics Institute, East Melbourne, Victoria, Australia
- The HEARing Cooperative Research Centre, The University of Melbourne, East Melbourne, Victoria, Australia
- Department of Otolaryngology, The University of Melbourne, East Melbourne, Victoria, Australia
| | - Helen Feng
- Bionics Institute, East Melbourne, Victoria, Australia
- Department of Otolaryngology, The University of Melbourne, East Melbourne, Victoria, Australia
| | | | - Melanie McWade
- Bionics Institute, East Melbourne, Victoria, Australia
- Biomedical Engineering Department, Vanderbilt University, Nashville, Tennessee, United States of America
| | | | - Chris E. Williams
- Bionics Institute, East Melbourne, Victoria, Australia
- Department of Pathology, University of Melbourne, Parkville, Victoria, Australia
- Medical Bionics Department, University of Melbourne, East Melbourne, Victoria, Australia
| | - Robert K. Shepherd
- Bionics Institute, East Melbourne, Victoria, Australia
- Medical Bionics Department, University of Melbourne, East Melbourne, Victoria, Australia
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88
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Aspinall PA, Borooah S, Al Alouch C, Roe J, Laude A, Gupta R, Gupta M, Montarzino A, Dhillon B. Gaze and pupil changes during navigation in age-related macular degeneration. Br J Ophthalmol 2014; 98:1393-7. [DOI: 10.1136/bjophthalmol-2014-305032] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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89
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Boinagrov D, Pangratz-Fuehrer S, Goetz G, Palanker D. Selectivity of direct and network-mediated stimulation of the retinal ganglion cells with epi-, sub- and intraretinal electrodes. J Neural Eng 2014; 11:026008. [PMID: 24608166 DOI: 10.1088/1741-2560/11/2/026008] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVE Intra-retinal placement of stimulating electrodes can provide close and stable proximity to target neurons. We assessed improvement in stimulation thresholds and selectivity of the direct and network-mediated retinal stimulation with intraretinal electrodes, compared to epiretinal and subretinal placements. APPROACH Stimulation thresholds of the retinal ganglion cells (RGCs) in wild-type rat retina were measured using the patch-clamp technique. Direct and network-mediated responses were discriminated using various synaptic blockers. MAIN RESULTS Three types of RGC responses were identified: short latency (SL, τ < 5 ms) originating in RGCs, medium latency (ML, 3 < τ < 70 ms) originating in the inner nuclear layer and long latency (LL, τ > 40 ms) originating in photoreceptors. Cathodic epiretinal stimulation exhibited the lowest threshold for direct RGC response and the highest direct selectivity (network/direct thresholds ratio), exceeding a factor of 3 with pulse durations below 0.5 ms. For network-mediated stimulation, the lowest threshold was obtained with anodic pulses in OPL position, and its network selectivity (direct/network thresholds ratio) increased with pulse duration, exceeding a factor of 4 at 10 ms. Latency of all three types of responses decreased with increasing strength of the stimulus. SIGNIFICANCE These results define the optimal range of pulse durations, pulse polarities and electrode placement for the retinal prostheses aiming at direct or network-mediated stimulation of RGCs.
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Affiliation(s)
- David Boinagrov
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA. Department of Physics, Stanford University, Stanford, CA 94305, USA
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90
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Waschkowski F, Hesse S, Rieck AC, Lohmann T, Brockmann C, Laube T, Bornfeld N, Thumann G, Walter P, Mokwa W, Johnen S, Roessler G. Development of very large electrode arrays for epiretinal stimulation (VLARS). Biomed Eng Online 2014; 13:11. [PMID: 24502253 PMCID: PMC3976033 DOI: 10.1186/1475-925x-13-11] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 01/29/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Retinal implants have been developed to treat blindness causing retinal degenerations such as Retinitis pigmentosa (RP). The retinal stimulators are covering only a small portion of the retina usually in its center. To restore not only central vision but also a useful visual field retinal stimulators need to cover a larger area of the retina. However, large area retinal stimulators are much more difficult to implant into an eye. Some basic questions concerning this challenge should be answered in a series of experiments. METHODS Large area retinal stimulators were fabricated as flexible multielectrode arrays (MEAs) using silicon technology with polyimide as the basic material for the substrate. Electrodes were made of gold covered with reactively sputtered iridium oxide. Several prototype designs were considered and implanted into enucleated porcine eyes. The prototype MEAs were also used as recording devices. RESULTS Large area retinal stimulator MEAs were fabricated with a diameter of 12 mm covering a visual angle of 37.6° in a normal sighted human eye. The structures were flexible enough to be implanted in a folded state through an insertion nozzle. The implants could be positioned onto the retinal surface and fixated here using a retinal tack. Recording of spontaneous activity of retinal neurons was possible in vitro using these devices. CONCLUSIONS Large flexible MEAs covering a wider area of the retina as current devices could be fabricated using silicon technology with polyimide as a base material. Principal surgical techniques were established to insert such large devices into an eye and the devices could also be used for recording of retinal neural activity.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Peter Walter
- Department of Ophthalmology, University Hospital Aachen, RWTH Aachen University, Pauwelsstr 30, 52074 Aachen, Germany.
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91
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Mandel Y, Goetz G, Lavinsky D, Huie P, Mathieson K, Wang L, Kamins T, Galambos L, Manivanh R, Harris J, Palanker D. Cortical responses elicited by photovoltaic subretinal prostheses exhibit similarities to visually evoked potentials. Nat Commun 2013; 4:1980. [PMID: 23778557 PMCID: PMC4249937 DOI: 10.1038/ncomms2980] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2012] [Accepted: 04/29/2013] [Indexed: 01/23/2023] Open
Abstract
We have previously developed a wireless photovoltaic retinal prosthesis, in which camera-captured images are projected onto the retina using pulsed near-IR light. Each pixel in the subretinal implant directly converts pulsed light into local electric current to stimulate the nearby inner retinal neurons. Here we report that implants having pixel sizes of 280, 140 and 70 μm implanted in the subretinal space in rats with normal and degenerate retina elicit robust cortical responses upon stimulation with pulsed near-IR light. Implant-induced eVEP has shorter latency than visible light-induced VEP, its amplitude increases with peak irradiance and pulse duration, and decreases with frequency in the range of 2-20 Hz, similar to the visible light response. Modular design of the arrays allows scalability to a large number of pixels, and combined with the ease of implantation, offers a promising approach to restoration of sight in patients blinded by retinal degenerative diseases.
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Affiliation(s)
- Yossi Mandel
- Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305, USA.
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