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Henze D, Majdi JA, Cohen ED. Effect of epiretinal electrical stimulation on the glial cells in a rabbit retinal eyecup model. Front Neurosci 2024; 18:1290829. [PMID: 38318467 PMCID: PMC10839094 DOI: 10.3389/fnins.2024.1290829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 01/03/2024] [Indexed: 02/07/2024] Open
Abstract
Introduction We examined how pulse train electrical stimulation of the inner surface of the rabbit retina effected the resident glial cells. We used a rabbit retinal eyecup preparation model, transparent stimulus electrodes, and optical coherence tomography (OCT). The endfeet of Müller glia processes line the inner limiting membrane (ILM). Methods To examine how epiretinal electrode stimulation affected the Müller glia, we labeled them post stimulation using antibodies against soluble glutamine synthetase (GS). After 5 min 50 Hz pulse train stimulation 30 μm from the surface, the retina was fixed, immunostained for Müller glia, and examined using confocal microscopic reconstruction. Stimulus pulse charge densities between 133-749 μC/cm2/ph were examined. Results High charge density stimulation (442-749 μC/cm2/ph) caused significant losses in the GS immunofluorescence of the Müller glia endfeet under the electrode. This loss of immunofluorescence was correlated with stimuli causing ILM detachment when measured using OCT. Müller cells show potassium conductances at rest that are blocked by barium ions. Using 30 msec 20 μA stimulus current pulses across the eyecup, the change in transretinal resistance was examined by adding barium to the Ringer. Barium caused little change in the transretinal resistance, suggesting under low charge density stimulus pulse conditions, the Müller cell radial conductance pathway for these stimulus currents was small. To examine how epiretinal electrode stimulation affected the microglia, we used lectin staining 0-4 h post stimulation. After stimulation at high charge densities 749 μC/cm2/ph, the microglia under the electrode appeared rounded, while the local microglia outside the electrode responded to the stimulated retina by process orientation inwards in a ring by 30 min post stimulation. Discussion Our study of glial cells in a rabbit eyecup model using transparent electrode imaging suggests that epiretinal electrical stimulation at high pulse charge densities, can injure the Müller and microglia cells lining the inner retinal surface in addition to ganglion cells.
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Affiliation(s)
- Dean Henze
- University of San Diego, San Diego, CA, United States
| | - Joseph A. Majdi
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, MD, United States
| | - Ethan D. Cohen
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, MD, United States
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Vėbraitė I, Bar-Haim C, David-Pur M, Hanein Y. Bi-directional electrical recording and stimulation of the intact retina with a screen-printed soft probe: a feasibility study. Front Neurosci 2024; 17:1288069. [PMID: 38264499 PMCID: PMC10804455 DOI: 10.3389/fnins.2023.1288069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Accepted: 12/14/2023] [Indexed: 01/25/2024] Open
Abstract
Introduction Electrophysiological investigations of intact neural circuits are challenged by the gentle and complex nature of neural tissues. Bi-directional electrophysiological interfacing with the retina, in its intact form, is particularly demanding and currently there is no feasible approach to achieve such investigations. Here we present a feasibility study of a novel soft multi-electrode array suitable for bi-directional electrophysiological study of the intact retina. Methods Screen-printed soft electrode arrays were developed and tested. The soft probes were designed to accommodate the curvature of the retina in the eye and offer an opportunity to study the retina in its intact form. Results For the first time, we show both electrical recording and stimulation capabilities from the intact retina. In particular, we demonstrate the ability to characterize retina responses to electrical stimulation and reveal stable, direct, and indirect responses compared with ex-vivo conditions. Discussion These results demonstrate the unique performances of the new probe while also suggesting that intact retinas retain better stability and robustness than ex-vivo retinas making them more suitable for characterizing retina responses to electrical stimulation.
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Affiliation(s)
- Ieva Vėbraitė
- School of Electrical Engineering, Tel Aviv University, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Chen Bar-Haim
- School of Electrical Engineering, Tel Aviv University, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Moshe David-Pur
- School of Electrical Engineering, Tel Aviv University, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Yael Hanein
- School of Electrical Engineering, Tel Aviv University, Tel Aviv, Israel
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
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Schiavi A, Cuccaro R, Troia A. Functional mechanical attributes of natural and synthetic gel-based scaffolds in tissue engineering: strain-stiffening effects on apparent elastic modulus and compressive toughness. J Mech Behav Biomed Mater 2022; 126:105066. [PMID: 35008012 DOI: 10.1016/j.jmbbm.2021.105066] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 12/14/2021] [Accepted: 12/24/2021] [Indexed: 12/18/2022]
Abstract
The accurate identification and determination of elastic modulus and toughness, as well as other functional mechanical attributes of artificial tissues, are of paramount importance in several fields of tissue science, tissue engineering and technology, since biomechanical and biophysical behavior is strongly linked to biological features of the medical implants and tissue-engineering scaffolds. When soft or ultra-soft materials are investigated, a relevant dispersion of elastic modulus values can be achieved, due to the strain-stiffening effects, inducing a typical non-linear behavior of these materials, as a function of strain-range. In this short communication, the Apparent elastic modulus strain-range dependence is estimated from a segmentation of the strain stiffening curve, and the related compressive toughness is investigated and discussed, based on experimental evidence, for 6 different kinds of gels, used for artificial tissue fabrication; experimental results are compared to mechanical properties of native human tissues.
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Affiliation(s)
- Alessandro Schiavi
- INRiM - Istituto Nazionale di Ricerca Metrologica, Strada Delle Cacce 91, 10135, Torino, Italy.
| | - Rugiada Cuccaro
- INRiM - Istituto Nazionale di Ricerca Metrologica, Strada Delle Cacce 91, 10135, Torino, Italy.
| | - Adriano Troia
- INRiM - Istituto Nazionale di Ricerca Metrologica, Strada Delle Cacce 91, 10135, Torino, Italy.
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Xie H, Wang Y, Ye Z, Fang S, Xu Z, Wu T, Chan LLH. Monitoring Cortical Response and Electrode-Retina Impedance Under Epiretinal Stimulation in Rats. IEEE Trans Neural Syst Rehabil Eng 2021; 29:1178-1187. [PMID: 34152987 DOI: 10.1109/tnsre.2021.3090904] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Retinal prosthesis can restore partial vision in patients with retinal degenerative diseases such as retinitis pigmentosa and age-related macular degeneration. Epiretinal prosthesis is one of three therapeutic approaches, which received regulatory approval several years ago. The thresholds of an epiretinal stimulation is partly determined by the size of the physical gap between the electrode and the retina after implantation. Precise positioning of epiretinal stimulating electrode array is still a challenging task. In this study, we demonstrate an approach to positioning epiretinal prostheses for an optimal response at the cortical output by monitoring both the impedance at the electrode-retina interface and the evoked-potential at the cortical level. We implanted a single-channel electrode on the epiretinal surface in adult rats, acutely, guided by both the impedance at the electrode-retina interface and by electrically evoked potentials (EEPs) in the visual cortex during retinal stimulation. We observe that impedance monotonously increases with decreasing electrode-retina distance, but that the strongest cortical responses were achieved at intermediate impedance levels. When the electrode penetrates the retina, the impedance keeps increasing. The effect of stimulation on the retina changes from epiretinal paradigm to intra-retinal paradigm and a decrease in cortical activation is observed. It is found that high impedance is not always favorable to elicit best cortical responses. Histopathological results showed that the electrode was placed at the intra-retinal space at high impedance value. These results show that monitoring impedance at the electrode-retina interface is necessary but not sufficient in obtaining strong evoked-potentials at the cortical level. Monitoring the cortical EEPs together with the impedance can improve the safety of implantation as well as efficacy of stimulation in the next generation of retinal implants.
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Hadjinicolaou AE, Meffin H, Maturana MI, Cloherty SL, Ibbotson MR. Prosthetic vision: devices, patient outcomes and retinal research. Clin Exp Optom 2021; 98:395-410. [DOI: 10.1111/cxo.12342] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 07/06/2015] [Accepted: 08/04/2015] [Indexed: 12/11/2022] Open
Affiliation(s)
- Alex E Hadjinicolaou
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia,
- ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia,
| | - Hamish Meffin
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia,
- ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia,
| | - Matias I Maturana
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia,
- Department of Electrical and Electronic Engineering, The University of Melbourne, Parkville, Victoria, Australia,
| | - Shaun L Cloherty
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia,
- ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia,
- Department of Electrical and Electronic Engineering, The University of Melbourne, Parkville, Victoria, Australia,
| | - Michael R Ibbotson
- National Vision Research Institute, Australian College of Optometry, Carlton, Victoria, Australia,
- ARC Centre of Excellence for Integrative Brain Function and Department of Optometry and Vision Sciences, University of Melbourne, Parkville, Victoria, Australia,
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Yohannes AR, Jung CY, Shea KI, Wong WT, Beylin A, Cohen ED. The microglia response to electrical overstimulation of the retina imaged under a transparent stimulus electrode. J Neural Eng 2021; 18. [PMID: 33418555 DOI: 10.1088/1741-2552/abda0a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 01/08/2021] [Indexed: 11/12/2022]
Abstract
OBJECTIVE We investigated using the morphological response of retinal microglia as indicators of tissue damage from electrical overstimulation by imaging them through an optically transparent stimulus electrode. APPROACH To track the microglia, we used a transgenic mouse where the microglia expressed a water soluble green fluorescent protein (GFP). The clear stimulus electrode was placed epiretinally on the inner limiting membrane and the microglia layers were imaged using time-lapse confocal microscopy. We examined how the microglia responded both temporally and spatially to local overstimulation of the retinal tissue. Using confocal microscope vertical image stacks, the microglia under the electrode were imaged at 2.5min intervals. The retina was overstimulated for a 5 minute period using 1msec 749μC/cm2/ph biphasic current pulses and changes in the microglia morphology were followed for 1 hour post stimulation. After the imaging period, a label for cellular damage was applied to the retina. MAIN RESULTS The microglia response to overstimulation depended on their spatial location relative to the electrode lumen and could result in 3 different morphological responses. Some microglia were severely injured and became a series of immotile ball-like fluorescent processes. Other microglia survived, and reacted rapidly to the injury by extending filopodia oriented toward the damage zone. This response was seen in inner retinal microglia outside the stimulus electrode edge. A third effect, seen with the deeper outer microglia under the electrode, was a fading of their fluorescent image which appeared to be due to optical scatter caused by overstimulation-induced retinal edema. SIGNIFICANCE The microglial morphological responses to electrical overstimulation injury occur rapidly and can show both direct and indirect effects of the stimulus electrode injury. The microglia injury pattern closely follows models of the electric field distribution under thinly insulated disc electrodes.
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Affiliation(s)
- Alula R Yohannes
- Division of Biomedical Physics, Center for Dev. and Rad. Health, FDA, Bldg. 62 Rm 1204, Silver Spring, Maryland, MD 20993-0002, UNITED STATES
| | - Christopher Yi Jung
- University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland, MD 21250, UNITED STATES
| | - Katherine I Shea
- CDER/Division of Applied Regulatory Science, US Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, Maryland, MD 20993-0002, UNITED STATES
| | - Wai T Wong
- Section on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, 6 Center Drive, Bethesda, Maryland, MD 20814, UNITED STATES
| | - Alexander Beylin
- Office of Product Quality and Evaluation, Center for Dev. and Rad. Health, FDA, Silver Spring, Maryland, UNITED STATES
| | - Ethan D Cohen
- Division of Biomedical Physics, Center for Dev. and Rad. Health, FDA, Office of Science and Engineering Labs, Bld 62 White Oak Fed Res Ctr., 10903 New Hampshire Ave, Silver Spring, Maryland, 20993, UNITED STATES
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Abstract
Developments of new strategies to restore vision and improving on current strategies by harnessing new advancements in material and electrical sciences, and biological and genetic-based technologies are of upmost health priorities around the world. Federal and private entities are spending billions of dollars on visual prosthetics technologies. This review describes the most current and state-of-the-art bioengineering technologies to restore vision. This includes a thorough description of traditional electrode-based visual prosthetics that have improved substantially since early prototypes. Recent advances in molecular and synthetic biology have transformed vision-assisted technologies; For example, optogenetic technologies that introduce light-responsive proteins offer excellent resolution but cortical applications are restricted by fiber implantation and tissue damage. Other stimulation modalities, such as magnetic fields, have been explored to achieve non-invasive neuromodulation. Miniature magnetic coils are currently being developed to activate select groups of neurons. Magnetically-responsive nanoparticles or exogenous proteins can significantly enhance the coupling between external electromagnetic devices and any neurons affiliated with these modifications. The need to minimize cytotoxic effects for nanoparticle-based therapies will likely restrict the number of usable materials. Nevertheless, advances in identifying and utilizing proteins that respond to magnetic fields may lead to non-invasive, cell-specific stimulation and may overcome many of the limitations that currently exist with other methods. Finally, sensory substitution systems also serve as viable visual prostheses by converting visual input to auditory and somatosensory stimuli. This review also discusses major challenges in the field and offers bioengineering strategies to overcome those.
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Affiliation(s)
- Alexander Farnum
- Department of Biomedical Engineering, College of Engineering, Michigan State University, East Lansing, MI, United States
- Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, MI, United States
| | - Galit Pelled
- Department of Biomedical Engineering, College of Engineering, Michigan State University, East Lansing, MI, United States
- Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, MI, United States
- Department of Radiology, College of Human Medicine, Michigan State University, East Lansing, MI, United States
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Qian X, Kang H, Li R, Lu G, Du Z, Shung KK, Humayun MS, Zhou Q. In Vivo Visualization of Eye Vasculature Using Super-Resolution Ultrasound Microvessel Imaging. IEEE Trans Biomed Eng 2020; 67:2870-2880. [PMID: 32054567 DOI: 10.1109/tbme.2020.2972514] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
OBJECTIVE The choroidal vessels, which supply oxygen and nutrient to the retina, may play a pivotal role in eye disease pathogenesis such as diabetic retinopathy and glaucoma. In addition, the retrobulbar circulation that feeds the choroid shows an important pathophysiologic role in myopia and degenerative myopia. Owing to the light-absorbing retinal pigment epithelium (RPE) and optically opaque sclera, choroidal and retrobulbar vasculature were difficult to be observed using clinically accepted optical coherence tomography angiography (OCT-A) technique. Here, we have developed super-resolution ultrasound microvessel imaging technique to visualize the deep ocular vasculature. METHODS An 18-MHz linear array transducer with compounding plane wave imaging technique and contrast agent - microbubble was implemented in this study. The centroid intensity of each microbubble was detected using image deconvolution algorithm with spatially variant point spread function, and then accumulated in successive frames in order to reconstruct microvasculature. The image deconvolution technique was first evaluated in a simulation study and experimental flow phantoms. The performance was then validated on normal rabbit eyes in vivo. RESULTS The image deconvolution based super-resolution ultrasound microvessel imaging technique shows good performance on either simulation study or flow phantoms. In vivo rabbit eye study indicated that the micron-level choroidal and retrobulbar vessels around the optic nerve head were successfully reconstructed in multiple 2D views and 3D volume imaging. CONCLUSIONS Our results demonstrate the capability of using super-resolution ultrasound microvessel imaging technique to image the microvasculature of the posterior pole of the eye. This efficient approach can potentially lead to a routinely performed diagnostic procedure in the field of ophthalmology.
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Rizzo S, Cinelli L, Finocchio L, Tartaro R, Santoro F, Gregori NZ. Assessment of Postoperative Morphologic Retinal Changes by Optical Coherence Tomography in Recipients of an Electronic Retinal Prosthesis Implant. JAMA Ophthalmol 2019; 137:272-278. [PMID: 30605209 PMCID: PMC6439717 DOI: 10.1001/jamaophthalmol.2018.6375] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Accepted: 11/09/2018] [Indexed: 01/10/2023]
Abstract
Importance The postoperative retinal changes at the interface between an implant electrode array and the retina and whether these anatomic changes have an association with the patient visual performance are unknown. Objective To report morphologic changes in recipients of an Argus II Retinal Prosthesis. Design, Setting, and Participants This consecutive, noncomparative case series study included a retrospective review of the preoperative and postoperative optical coherence tomography of 33 eyes among 33 individuals who underwent Argus II Retinal Prosthesis System implantation between October 28, 2011, and June 8, 2017, at 2 different centers, by the same surgeon (S.R.). Thirteen patients received an implant at Azienda Ospedaliero Universitaria Pisana, Pisa, Italy, between October 28, 2011, and October 27, 2014, and 20 patients underwent surgery at Azienda Ospedaliera Universitaria Careggi, Florence, Italy, between December 20, 2014, and June 8, 2017. Patients were excluded if they did not reach the 6-month follow-up. Main Outcomes and Measures All patients were evaluated before surgery, during the first postoperative day, and at 1, 3, 6, 12, and 24 months (subsequently once a year, except for patient-related adverse events), with a comprehensive ophthalmic examination, retinal fundus photography, spectral-domain optical coherence tomography, and visual function tests to evaluate the stability or improvement of their visual performance. Results Of the 20 patients included in the analysis, all were of white race/ethnicity, 12 (60%) were male, and the mean (SD) age was 57.4 (11.6) years. Optical coherence tomography revealed the development of a fibrosislike hyperreflective tissue limited at the interface between the array and retina in 10 eyes (50%). In 9 of 10 patients (90%), fibrosis evolved and progressed to retinal schisis. Despite the development of the fibrosis and schisis, there was no deterioration in the patient's visual performance evaluated prospectively with visual function tests (square localization and direction of motion). Conclusions and Relevance Optical coherence tomography may be used to observe the retinal anatomic changes in patients with an Argus II Prothesis. This analysis revealed the development of a fibrosislike hyperreflective tissue limited at the interface between array and retina that progressed to retinal schisis but with no deterioration in the patients' visual performance.
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Affiliation(s)
- Stanislao Rizzo
- Azienda Ospedaliera Universitaria Careggi, Dipartimento di Medicina e Chirurgia Traslazionale, University of Florence, Florence, Italy
| | - Laura Cinelli
- Azienda Ospedaliera Universitaria Careggi, Dipartimento di Medicina e Chirurgia Traslazionale, University of Florence, Florence, Italy
| | - Lucia Finocchio
- Azienda Ospedaliera Universitaria Careggi, Dipartimento di Medicina e Chirurgia Traslazionale, University of Florence, Florence, Italy
| | - Ruggero Tartaro
- Azienda Ospedaliera Universitaria Careggi, Dipartimento di Medicina e Chirurgia Traslazionale, University of Florence, Florence, Italy
| | - Francesca Santoro
- Azienda Ospedaliera Universitaria Careggi, Dipartimento di Medicina e Chirurgia Traslazionale, University of Florence, Florence, Italy
| | - Ninel Z. Gregori
- Bascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, Florida
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Shepherd RK, Villalobos J, Burns O, Nayagam DAX. The development of neural stimulators: a review of preclinical safety and efficacy studies. J Neural Eng 2018; 15:041004. [PMID: 29756600 PMCID: PMC6049833 DOI: 10.1088/1741-2552/aac43c] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Given the rapid expansion of the field of neural stimulation and the rigorous regulatory approval requirements required before these devices can be applied clinically, it is important that there is clarity around conducting preclinical safety and efficacy studies required for the development of this technology. APPROACH The present review examines basic design principles associated with the development of a safe neural stimulator and describes the suite of preclinical safety studies that need to be considered when taking a device to clinical trial. MAIN RESULTS Neural stimulators are active implantable devices that provide therapeutic intervention, sensory feedback or improved motor control via electrical stimulation of neural or neuro-muscular tissue in response to trauma or disease. Because of their complexity, regulatory bodies classify these devices in the highest risk category (Class III), and they are therefore required to go through a rigorous regulatory approval process before progressing to market. The successful development of these devices is achieved through close collaboration across disciplines including engineers, scientists and a surgical/clinical team, and the adherence to clear design principles. Preclinical studies form one of several key components in the development pathway from concept to product release of neural stimulators. Importantly, these studies provide iterative feedback in order to optimise the final design of the device. Key components of any preclinical evaluation include: in vitro studies that are focussed on device reliability and include accelerated testing under highly controlled environments; in vivo studies using animal models of the disease or injury in order to assess efficacy and, given an appropriate animal model, the safety of the technology under both passive and electrically active conditions; and human cadaver and ex vivo studies designed to ensure the device's form factor conforms to human anatomy, to optimise the surgical approach and to develop any specialist surgical tooling required. SIGNIFICANCE The pipeline from concept to commercialisation of these devices is long and expensive; careful attention to both device design and its preclinical evaluation will have significant impact on the duration and cost associated with taking a device through to commercialisation. Carefully controlled in vitro and in vivo studies together with ex vivo and human cadaver trials are key components of a thorough preclinical evaluation of any new neural stimulator.
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Affiliation(s)
- Robert K Shepherd
- Bionics Institute, East Melbourne, Australia. Medical Bionics Department, University of Melbourne, Melbourne, Australia
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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 2017; 47:999-1003. [PMID: 27842194 DOI: 10.3928/23258160-20161031-03] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [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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Davuluri NS, Nimmagadda K, Petrossians A, Humayun MS, Weiland JD. Strategies to improve stimulation efficiency for retinal prostheses. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2016:3133-3138. [PMID: 28324979 DOI: 10.1109/embc.2016.7591393] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Retinitis Pigmentosa (RP) is a degenerative disease of the retina that leads to vision loss. Retinal prostheses are being developed in order to restore functional vision in patients suffering from RP. We conducted in-vivo experiments in order to identify strategies to efficiently stimulate the retina. We electrically stimulated the retina and measured electrically evoked potentials (EERs) from the superior colliculus of rats. We compared the strength of EERs when voltage-controlled and current-controlled pulses of varying pulse width and charge levels were applied to the retina. In addition to comparing EER strength, we evaluated improvement in power efficiency afforded by a high surface area platinum-iridium material. Voltage-controlled pulses were more efficient than current-controlled pulses when the pulses have a short duration (<; 1 ms) and current-controlled pulses were more efficient than voltage-controlled pulses when the pulse width was greater than 1 ms. The high surface area platinum-iridium stimulation electrode consumed power significantly lower than a standard platinum-iridium electrode.
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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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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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Schiavi A, Cuccaro R, Troia A. Strain-rate and temperature dependent material properties of Agar and Gellan Gum used in biomedical applications. J Mech Behav Biomed Mater 2016; 53:119-130. [DOI: 10.1016/j.jmbbm.2015.08.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 07/28/2015] [Accepted: 08/04/2015] [Indexed: 10/23/2022]
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Leung RT, Shivdasani MN, Nayagam DAX, Shepherd RK. In Vivo and In Vitro Comparison of the Charge Injection Capacity of Platinum Macroelectrodes. IEEE Trans Biomed Eng 2015; 62:849-57. [DOI: 10.1109/tbme.2014.2366514] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Nayagam DAX, Durmo I, McGowan C, Williams RA, Shepherd RK. Techniques for processing eyes implanted with a retinal prosthesis for localized histopathological analysis: Part 2 Epiretinal implants with retinal tacks. J Vis Exp 2015. [PMID: 25798628 PMCID: PMC4370214 DOI: 10.3791/52348] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Retinal prostheses for the treatment of certain forms of blindness are gaining traction in clinical trials around the world with commercial devices currently entering the market. In order to evaluate the safety of these devices, in preclinical studies, reliable techniques are needed. However, the hard metal components utilised in some retinal implants are not compatible with traditional histological processes, particularly in consideration for the delicate nature of the surrounding tissue. Here we describe techniques for assessing the health of the eye directly adjacent to a retinal implant secured epiretinally with a metal tack. Retinal prostheses feature electrode arrays in contact with eye tissue. The most commonly used location for implantation is the epiretinal location (posterior chamber of the eye), where the implant is secured to the retina with a metal tack that penetrates all the layers of the eye. Previous methods have not been able to assess the proximal ocular tissue with the tack in situ, due to the inability of traditional histological techniques to cut metal objects. Consequently, it has been difficult to assess localized damage, if present, caused by tack insertion. Therefore, we developed a technique for visualizing the tissue around a retinal tack and implant. We have modified an established technique, used for processing and visualizing hard bony tissue around a cochlear implant, for the soft delicate tissues of the eye. We orientated and embedded the fixed eye tissue, including the implant and retinal tack, in epoxy resin, to stabilise and protect the structure of the sample. Embedded samples were then ground, polished, stained, and imaged under various magnifications at incremental depths through the sample. This technique allowed the reliable assessment of eye tissue integrity and cytoarchitecture adjacent to the metal tack.
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Affiliation(s)
- David A X Nayagam
- Bionics Institute; Department of Pathology, The University of Melbourne;
| | | | | | - Richard A Williams
- Department of Pathology, The University of Melbourne; Department of Anatomical Pathology, St Vincent's Hospital Melbourne
| | - Robert K Shepherd
- Bionics Institute; Medical Bionics Department, The University of Melbourne
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Davuluri NS, Weiland JD. Time-varying pulse trains limit retinal desensitization caused by continuous electrical stimulation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:414-7. [PMID: 25569984 DOI: 10.1109/embc.2014.6943616] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
An epiretinal prosthesis aims to restore functional vision in patients suffering from retinal degeneration caused by diseases such as Retinitis Pigmentosa (RP) and Age-Related Macular Degeneration (AMD). These diseases result in the loss of photoreceptors but bipolar, amacrine and ganglion cells survive at high rates and can be electrically activate to produce the sensation of light. Continuous application of biphasic stimulus pulses results in desensitization of the retina. In humans, this manifests as decreased brightness and increased stimulus thresholds. This study presents an in vivo model of retinal desensitization caused by continuous electrical stimulation and describes a novel stimulation pattern that limit desensitization.
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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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Petrossians A, Davuluri N, Whalen JJ, Mansfeld F, Weiland JD. Improved Biphasic Pulsing Power Efficiency with Pt-Ir Coated
Microelectrodes. ACTA ACUST UNITED AC 2014. [DOI: 10.1557/opl.2014.267] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTNeuromodulation devices such as deep brain stimulators (DBS), spinal cord
stimulators (SCS) and cochlear implants (CIs) use electrodes in contact with
tissue to deliver electrical pulses to targeted cells. In general, the
neuromodulation industry has been evolving towards smaller, less invasive
devices. Improving power efficiency of these devices can reduce battery storage
requirements. Neuromodulation devices can realize significant power savings if
the impedance to charge transfer at the electrode-tissue interface can be
reduced. High electrochemical impedance at the surface of stimulation
microelectrodes results in larger polarization voltages. Decreasing this
polarization voltage response can reduce power required to deliver the current
pulse. One approach to doing this is to reduce the electrochemical impedance at
the electrode surface. Previously we have reported on a novel electrochemically
deposited 60:40% platinum-iridium (Pt-Ir) electrode material that lowered the
electrode impedance by two orders of magnitude or more.This study compares power consumption of an electrochemically deposited Pt-Ir
stimulating microelectrode to that of standard Pt-Ir probe microelectrode
produced using conventional techniques. Both electrodes were tested using
in-vitro in phosphate buffered saline (PBS) solution and
in-vivo (live rat) models.
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21
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Velikay-Parel M, Ivastinovic D, Georgi T, Richard G, Hornig R. A test method for quantification of stimulus-induced depression effects on perceptual threshold in epiretinal prosthesis. Acta Ophthalmol 2013; 91:e595-602. [PMID: 24112756 DOI: 10.1111/aos.12179] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE As part of a clinical trial, an investigational epiretinal implant (IMI Intelligent Medical Implant) was implanted in a retinitis pigmentosa patient. The prosthesis was wirelessly controlled by a visual interface containing a microcamera, providing wireless data and energy transmission. Forty-nine (49) electrodes were used for pattern recognition. This study examined the changes of perceptual thresholds over time and its relation to long-term stimulation. The goal of the study was to introduce stimulus-related depression of perceptual threshold (StirDepth) measurements as a method to gain further insight into the safety profile of electrical stimulation. METHODS The perceptual threshold was defined as the level of stimulation intensity at which a phosphene perception with a probability of 50% was detected using the Best-PEST method. StirDepth was measured by comparing the threshold changes immediately before and after a stimulation session of using three active electrodes and one passive electrode, which served as control. RESULTS The initial threshold of the day remained stable over the observed period. In StirDepth measurement all thresholds raised significantly after the stimulation sessions. The threshold increase of the active electrodes never exceeded that of the inactive control electrode. CONCLUSIONS StirDepth measurement is feasible in epiretinal implants. The prolonged stimulation raised no safety concerns in the patient. The threshold increase of both the active electrodes and the control electrode leads one to hypothesise that cognitive or neurophysiological effects are the cause rather than the desensitizing of the retinal network or incipient retinal damage.
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Affiliation(s)
- Michaela Velikay-Parel
- Department of Ophthalmology, Medical University Graz, Graz, AustriaDepartment of Ophthalmology, University Medical Center Hamburg-Eppendorf, Hamburg, GermanyIMI Intelligent Medical Implants GmbH, Bonn, Germany
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22
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Nayar VT, Weiland JD, Hodge AM. Macrocompression and Nanoindentation of Soft Viscoelastic Biological Materials. Tissue Eng Part C Methods 2012; 18:968-75. [DOI: 10.1089/ten.tec.2012.0034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Affiliation(s)
- V. Timothy Nayar
- Doheny Eye Institute, University of Southern California, Los Angeles, California
| | - James D. Weiland
- Doheny Eye Institute, University of Southern California, Los Angeles, California
| | - Andrea M. Hodge
- Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, California
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23
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O'Brien EE, Greferath U, Vessey KA, Jobling AI, Fletcher EL. Electronic restoration of vision in those with photoreceptor degenerations. Clin Exp Optom 2012; 95:473-83. [PMID: 22823954 DOI: 10.1111/j.1444-0938.2012.00783.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 06/06/2012] [Accepted: 06/11/2012] [Indexed: 11/27/2022] Open
Abstract
Complete loss of vision is one of the most feared sequelae of retinal disease. Currently, there are few if any treatment options available to patients that may slow or prevent blindness in diseases caused by photoreceptor loss, such as retinitis pigmentosa and age-related macular degeneration. Electronic restoration of vision has emerged over recent years as a safe and viable option for those who have lost substantial numbers of photoreceptors and who are severely vision impaired. Indeed, there has been a dramatic increase in our understanding of what is required to restore vision using an electronic retinal prosthesis. Recent reports show that for some patients, restoration of vision to the point of reading large letters is possible. In this review, we examine the types of implants currently under investigation and the results these devices have achieved clinically. We then consider a range of engineering and biological factors that may need to be considered to improve the visual performance of newer-generation devices. With added research, it is hoped that the level of vision achieved with newer generation devices will steadily improve, resulting in enhanced quality of life for those with severe vision impairment.
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Affiliation(s)
- Emily E O'Brien
- Department of Anatomy and Cell Biology, The University of Melbourne, Parkville, Victoria, Australia.
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24
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Albert ES, Bec JM, Desmadryl G, Chekroud K, Travo C, Gaboyard S, Bardin F, Marc I, Dumas M, Lenaers G, Hamel C, Muller A, Chabbert C. TRPV4 channels mediate the infrared laser-evoked response in sensory neurons. J Neurophysiol 2012; 107:3227-34. [PMID: 22442563 DOI: 10.1152/jn.00424.2011] [Citation(s) in RCA: 132] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Infrared laser irradiation has been established as an appropriate stimulus for primary sensory neurons under conditions where sensory receptor cells are impaired or lost. Yet, development of clinical applications has been impeded by lack of information about the molecular mechanisms underlying the laser-induced neural response. Here, we directly address this question through pharmacological characterization of the biological response evoked by midinfrared irradiation of isolated retinal and vestibular ganglion cells from rodents. Whole cell patch-clamp recordings reveal that both voltage-gated calcium and sodium channels contribute to the laser-evoked neuronal voltage variations (LEVV). In addition, selective blockade of the LEVV by micromolar concentrations of ruthenium red and RN 1734 identifies thermosensitive transient receptor potential vanilloid channels as the primary effectors of the chain reaction triggered by midinfrared laser irradiation. These results have the potential to facilitate greatly the design of future prosthetic devices aimed at restoring neurosensory capacities in disabled patients.
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Affiliation(s)
- E S Albert
- U-1051, INSERM Institut des Neurosciences de Montpellier, Montpellier, France.
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25
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Nayar V, Weiland J, Nelson C, Hodge A. Elastic and viscoelastic characterization of agar. J Mech Behav Biomed Mater 2012; 7:60-8. [DOI: 10.1016/j.jmbbm.2011.05.027] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 04/23/2011] [Accepted: 05/17/2011] [Indexed: 11/26/2022]
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26
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Ray A, Chan LLH, Gonzalez A, Humayun MS, Weiland JD. Impedance as a Method to Sense Proximity at the Electrode-Retina Interface. IEEE Trans Neural Syst Rehabil Eng 2011; 19:696-9. [DOI: 10.1109/tnsre.2011.2169428] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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27
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Di L, Wang LP, Lu YN, He L, Lin ZX, Wu KJ, Ren QS, Wang JY. Protein adsorption and peroxidation of rat retinas under stimulation of a neural probe coated with polyaniline. Acta Biomater 2011; 7:3738-45. [PMID: 21704201 DOI: 10.1016/j.actbio.2011.06.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 05/18/2011] [Accepted: 06/07/2011] [Indexed: 11/27/2022]
Abstract
For the purpose of investigating the potential use of conducting polymers, i.e. polyaniline (PANi), as electrode coating material for improving the function of neural probes, a PANi-coated platinum (Pt) electrode was prepared by the in situ polymerization method. Protein adsorption was observed by atomic force microscopy/scanning electron microscopy and sodium dodecyl sulfate polyacrylamide gel electrophoresis, as well as quantification. Peroxidation of rat retinas was evaluated by determination of conjugated dienes and PLOOH, which were quantified by UV-visible spectrophotometer and high-performance liquid chromatography. The stability of PANi coating for 6 months was also estimated with an in vitro electrical stimulation system. This revealed that: (1) PANi with regular and compact nanoparticles 20-40 nm in diameter was successfully polymerized on the uncoated platinum electrode surface; (2) the PANi-coated Pt electrode adsorbed fewer retinal fragments and induced less peroxidation than the uncoated platinum electrode; (3) in contrast to the uncoated platinum electrode, the PANi-coated Pt electrode surface tended to aggregate retinal fragments rather than spread them, which may help to reduce inflammation and scar formation in long-term implantation; (4) the PANi coating exhibited excellent properties in terms of the intactness and the stable nanoparticle morphology after 6 months' electrical stimulation, while corrosion occurred on the uncoated platinum electrode after 1 month.
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28
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Cohen E, Agrawal A, Connors M, Hansen B, Charkhkar H, Pfefer J. Optical coherence tomography imaging of retinal damage in real time under a stimulus electrode. J Neural Eng 2011; 8:056017. [DOI: 10.1088/1741-2560/8/5/056017] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Ray A, Lee EJ, Humayun MS, Weiland JD. Continuous electrical stimulation decreases retinal excitability but does not alter retinal morphology. J Neural Eng 2011; 8:045003. [PMID: 21775787 DOI: 10.1088/1741-2560/8/4/045003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Retinal prostheses aim to provide visual perception through electrical stimulation of the retina. Hence they have to operate between threshold charge density and maximum safe charge density. To date most studies in the retina have concentrated on understanding the threshold, while stimulation safety has predominantly been studied in structures other than the retina. Toward this end, the present study focuses on determining the effect of continuous electrical stimulation of the retina both on retinal morphology and on the electrically evoked responses in the superior colliculus in a rodent model. The results demonstrate that the retina is able to tolerate 1 h long stimulation with only minor changes evident in retinal histology when examined three to 14 days later, even at charge densities (0.68 mC cm(-2)) above the safe limit of platinum delivered at high stimulus frequency (300 Hz). However, this continuous electrical stimulation causes an elevation in the threshold of the electrically evoked response in the superior colliculus, indicating some form of adaptation to continuous stimulation.
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Affiliation(s)
- A Ray
- University of Southern California, Biomedical Engineering, 1042 Downey Way, DRB 140, Los Angeles, CA 90089-1111, USA
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30
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Characterization of porcine sclera using instrumented nanoindentation. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2011. [DOI: 10.1016/j.msec.2011.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Chan LLH, Lee EJ, Humayun MS, Weiland JD. Both electrical stimulation thresholds and SMI-32-immunoreactive retinal ganglion cell density correlate with age in S334ter line 3 rat retina. J Neurophysiol 2011; 105:2687-97. [PMID: 21411561 DOI: 10.1152/jn.00619.2010] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Electrical stimulation threshold and retinal ganglion cell density were measured in a rat model of retinal degeneration. We performed in vivo electrophysiology and morphometric analysis on normal and S334ter line 3 (RD) rats (ages 84-782 days). We stimulated the retina in anesthetized animals and recorded evoked responses in the superior colliculus. Current pulses were delivered with a platinum-iridium (Pt-Ir) electrode of 75-μm diameter positioned on the epiretinal surface. In the same animals used for electrophysiology, SMI-32 immunolabeling of the retina enabled ganglion cell counting. An increase in threshold currents positively correlated with age of RD rats. SMI-32-labeled retinal ganglion cell density negatively correlated with age of RD rats. ANOVA shows that RD postnatal day (P)100 and P300 rats have threshold and density similar to normal rats, but RD P500 and P700 rats have threshold and density statistically different from normal rats (P < 0.05). Threshold charge densities were within the safety limits of Pt for all groups and pulse configurations, except at RD P600 and RD P700, where pulses were only safe up to 1- and 0.2-ms duration, respectively. Preservation of ganglion cells may enhance the efficiency and safety of electronic retinal implants.
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Affiliation(s)
- Leanne L H Chan
- Doheny Vision Research Center, Doheny Eye Institute, Los Angeles, CA 90033, USA
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32
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Kandagor V, Cela CJ, Sanders CA, Greenbaum E, Lazzi G, Humayun MS, Zhou DM, Castro R, Gaikwad S, Little J. Spatial characterization of electric potentials generated by pulsed microelectrode arrays. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2010; 2010:6243-6246. [PMID: 21097346 DOI: 10.1109/iembs.2010.5628058] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
This presentation is a report on the in situ characterization of stimulating microelectrodes in the context of multielectrode retinal prosthetic implants. The experimental system approximately replicates the geometric and electrical parameters of Second Sight Medical Products' Argus II Retinal Implant. Topographic maps of electric potentials have been prepared for a 60 electrode structure in which selected electrodes were stimulated with biphasic repetitively pulsed charge densities at 100 microC·cm(-2). Surface contour maps were prepared using a 10 microm diameter recording electrode.
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Affiliation(s)
- V Kandagor
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA
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33
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In Situ Characterization of Stimulating Microelectrode Arrays: Study of an Idealized Structure Based on Argus II Retinal implants. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/978-0-387-98120-8_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Basinger BC, Rowley AP, Chen K, Humayun MS, Weiland JD. Finite element modeling of retinal prosthesis mechanics. J Neural Eng 2009; 6:055006. [DOI: 10.1088/1741-2560/6/5/055006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Ni YQ, Gan DK, Xu HD, Xu GZ, Da CD. Neuroprotective effect of transcorneal electrical stimulation on light-induced photoreceptor degeneration. Exp Neurol 2009; 219:439-52. [PMID: 19576889 DOI: 10.1016/j.expneurol.2009.06.016] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2009] [Revised: 06/17/2009] [Accepted: 06/20/2009] [Indexed: 10/20/2022]
Abstract
Direct electrical stimulation of neural tissues is a strategic approach to treat injured axons by accelerating their outgrowth [Al-Majed, A.A., Neumann, C.M., Brushart, T.M., Gordon, T., 2000. Brief electrical stimulation promotes the speed and accuracy of motor axonal regeneration. J. Neurosci. 20, 2602-2608] and promoting their regeneration [Geremia, N.M., Gordon, T., Brushart, T.M., Al-Majed, A.A., Verge, V.M.K., 2007. Electrical stimulation promotes sensory neuron regeneration and growth-associated gene expression. Exp. Neurol. 205, 347-359]. Recently, transcorneal electrical stimulation (TCES), a novel less invasive method, has been shown to rescue axotomized and damaged retinal ganglion cells [Morimoto, T., Miyoshi, T., Matsuda, S., Tano, Y., Fujikado, T., Fukuda, Y., 2005. Transcorneal electrical stimulation rescues axotomized retinal ganglion cells by activating endogenous retinal IGF-1 system. Invest. Ophthalmol. Vis. Sci. 46(6), 2147-2155]. Here, we investigated the neuroprotection of TCES on light-induced photoreceptor degeneration and the underlying mechanism. Adult male Sprague-Dawley (SD) rats received TCES before (pre-TCES) or after (post-TCES) intense light exposure. After fourteen days of light exposure, retinal histology and electroretinography were performed to evaluate the neuroprotective effect of TCES. The mRNA and protein levels of apoptotic-associated genes including Bcl-2, Bax, Caspase-3 as well as ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) in the retinas were determined by real-time PCR and Western blot analysis. The localization of these gene products in the retinas was examined by immunohistochemistry. Both pre- and post-TCES ameliorated the progressive photoreceptor degeneration. The degree of rescue depended on the strength of the electric charge. Post-TCES showed a relatively better and longer-term protective effect than pre-TCES. Real-time PCR and Western blot analysis revealed an upregulation of Bcl-2, CNTF, and BDNF and a downregulation of Bax in the retinas after TCES. Immunohistochemical studies showed that Bcl-2 and CNTF were selectively upregulated in Müller cells. These findings provide a new therapeutic method to prevent or delay photoreceptor degeneration through activating the intrinsic survival system.
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Affiliation(s)
- Ying-qin Ni
- Department of Ophthalmology, Eye and ENT Hospital of Fudan University, 83 Fen Yang Road, Shanghai 200031, People's Republic of China
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Aftab U, Jiang C, Tucker B, Kim JY, Klassen H, Miljan E, Sinden J, Young M. Growth kinetics and transplantation of human retinal progenitor cells. Exp Eye Res 2009; 89:301-10. [PMID: 19524569 DOI: 10.1016/j.exer.2009.03.025] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Revised: 03/20/2009] [Accepted: 03/21/2009] [Indexed: 12/16/2022]
Abstract
We studied the growth kinetics of human retinal progenitor cells (hRPCs) isolated from donor tissue of different gestational ages (G.A.), determined whether hRPCs can be differentiated into mature photoreceptors and assessed their ability to integrate with degenerating host retina upon transplantation. Eyes (12-18 weeks G.A.) were obtained with IRB approval and retinas were enzymatically dissociated. Cells were expanded in vitro, counted at isolation and at each passage, and characterized using immunocytochemistry and PCR. GFP positive hRPCs were co-cultured with retinal explants from rd1 and rhodopsin -/- mice, or transplanted into B6 mice with retinal photocoagulation and rhodopsin -/- mice. Eyes were harvested for histological evaluation following transplantation. Our results show that hRPCs from 16 to 18 weeks G.A. had the longest survival in vitro and yielded the maximum number of cells, proliferating over at least 6 passages. These cells expressed the retinal stem cell markers nestin, Ki-67, PAX6 and Lhx2, and stained positively for photoreceptor markers upon differentiation with serum. Some of the GFP positive cells used for transplantation studies showed evidence of migration into the degenerative host retina and expressed rhodopsin. In conclusion, we have determined the growth kinetics of hRPCs and have shown that cells from donor tissue of 16-18 weeks G.A. exhibit the best proliferative dynamics under the specified conditions, and that hRPCs can also be differentiated along the photoreceptor lineage. Further, we have also demonstrated that following transplantation, some of these cells integrate within the host retina and differentiate to express rhodopsin, thereby supporting the potential utility of hRPC transplantation in the setting of retinal degenerative disorders.
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Affiliation(s)
- Unber Aftab
- Schepens Eye Research Institute, Harvard Medical School, 20 Staniford Street, Boston, MA 02114, USA.
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Immunocytochemical analysis of retinal neurons under electrical stimulation. Brain Res 2008; 1255:89-97. [PMID: 19103179 DOI: 10.1016/j.brainres.2008.11.089] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Revised: 10/30/2008] [Accepted: 11/23/2008] [Indexed: 11/23/2022]
Abstract
To function successfully, a retinal prosthesis needs to provide effective stimulation in a safe manner. To date, most studies have been dedicated to assessing proper stimulation parameters, for example, determining stimulus threshold. Few studies have looked at the effects of prolonged stimulation on retinal morphology. One previous study did show gross morphological changes in the rat retina due to mechanical pressure, with and without electrical stimulation (Colodetti, L., Weiland, J.D., Colodetti, S., Ray, A., Seiler, M.J., Hinton, D.R., Humayun, M.S., 2007). Here, we used immunocytochemistry to investigate the effects of the same experimental conditions on neuronal structure in finer detail. For this purpose, we first defined four experimental groups. In Group 1, the stimulating electrode was near but did not contact the retina, and we did not apply current pulses. In Group 2, the electrode also did not contact the retina, but we applied current pulses of 0.09 microC/phase. In Group 3, the stimulating electrode directly contacted the retina, but we did not apply current pulses. In Group 4, the stimulating electrode directly contacted the retina, and we applied current pulses of 0.09 microC/phase. We found neural damage only in the outer retina, including a disturbance of synaptic vesicle proteins in the photoreceptor terminals and a remodeling of horizontal and rod bipolar cells' processes. These results show that, although gross morphological changes are mainly concentrated around the area of electrode contact, immunocytochemistry can reveal changes in adjacent areas as well.
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A review of in vivo animal studies in retinal prosthesis research. Graefes Arch Clin Exp Ophthalmol 2008; 246:1505-17. [PMID: 18709385 DOI: 10.1007/s00417-008-0891-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2008] [Revised: 06/12/2008] [Accepted: 06/16/2008] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND The development of a functional retinal prosthesis for acquired blindness is a great challenge. Rapid progress in the field over the last 15 years would not have been possible without extensive animal experimentation pertaining to device design and fabrication, biocompatibility, stimulation parameters and functional responses. This paper presents an overview of in vivo animal research related to retinal prosthetics, and aims to summarize the relevant studies. METHODS A Pubmed search of the English language literature was performed. The key search terms were: retinal implant, retinal prosthesis, artificial vision, rat, rabbit, cat, dog, sheep, pig, minipig. In addition a manual search was performed based on references quoted in the articles retrieved through Pubmed. RESULTS We identified 50 articles relevant to in vivo animal experimentation directly related to the development of a retinal implant. The highest number of publications related to the cat (n = 18). CONCLUSION The contribution of animal models to the development of retinal prosthetic devices has been enormous, and has led to human feasibility studies. Grey areas remain regarding long-term tissue-implant interactions, biomaterials, prosthesis design and neural adaptation. Animals will continue to play a key role in this rapidly evolving field.
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