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Abbott CJ, Allen PJ, Williams CE, Williams RA, Epp SB, Burns O, Thomas R, Harrison M, Thien PC, Saunders A, McGowan C, Sloan C, Luu CD, Nayagam DAX. Chronic electrical stimulation with a peripheral suprachoroidal retinal implant: a preclinical safety study of neuroprotective stimulation. Front Cell Dev Biol 2024; 12:1422764. [PMID: 38966426 PMCID: PMC11222648 DOI: 10.3389/fcell.2024.1422764] [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: 04/24/2024] [Accepted: 06/05/2024] [Indexed: 07/06/2024] Open
Abstract
Purpose Extraocular electrical stimulation is known to provide neuroprotection for retinal cells in retinal and optic nerve diseases. Currently, the treatment approach requires patients to set up extraocular electrodes and stimulate potentially weekly due to the lack of an implantable stimulation device. Hence, a minimally-invasive implant was developed to provide chronic electrical stimulation to the retina, potentially improving patient compliance for long-term use. The aim of the present study was to determine the surgical and stimulation safety of this novel device designed for neuroprotective stimulation. Methods Eight normally sighted adult feline subjects were monocularly implanted in the suprachoroidal space in the peripheral retina for 9-39 weeks. Charge balanced, biphasic, current pulses (100 μA, 500 µs pulse width and 50 pulses/s) were delivered continuously to platinum electrodes for 3-34 weeks. Electrode impedances were measured hourly. Retinal structure and function were assessed at 1-, 2-, 4-, 6- and 8-month using electroretinography, optical coherence tomography and fundus photography. Retina and fibrotic thickness were measured from histological sections. Randomized, blinded histopathological assessments of stimulated and non-stimulated retina were performed. Results All subjects tolerated the surgical and stimulation procedure with no evidence of discomfort or unexpected adverse outcomes. The device position was stable after a post-surgery settling period. Median electrode impedance remained within a consistent range (5-10 kΩ) over time. There was no change in retinal thickness or function relative to baseline and fellow eyes. Fibrotic capsule thickness was equivalent between stimulated and non-stimulated tissue and helps to hold the device in place. There was no scarring, insertion trauma, necrosis, retinal damage or fibroblastic response in any retinal samples from implanted eyes, whilst 19% had a minimal histiocytic response, 19% had minimal to mild acute inflammation and 28% had minimal to mild chronic inflammation. Conclusion Chronic suprathreshold electrical stimulation of the retina using a minimally invasive device evoked a mild tissue response and no adverse clinical findings. Peripheral suprachoroidal electrical stimulation with an implanted device could potentially be an alternative approach to transcorneal electrical stimulation for delivering neuroprotective stimulation.
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Affiliation(s)
- Carla J. Abbott
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
- Department of Surgery (Ophthalmology), University of Melbourne, East Melbourne, VIC, Australia
| | - Penelope J. Allen
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
- Department of Surgery (Ophthalmology), University of Melbourne, East Melbourne, VIC, Australia
- Vitreoretinal Unit, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
| | - Chris E. Williams
- Bionics Institute, East Melbourne, VIC, Australia
- Medical Bionics Department, University of Melbourne, Fitzroy, VIC, Australia
| | - Richard A. Williams
- Department of Clinical Pathology, University of Melbourne, Parkville, VIC, Australia
- Dorevitch Pathology, Heidelberg, VIC, Australia
| | | | - Owen Burns
- Bionics Institute, East Melbourne, VIC, Australia
| | - Ross Thomas
- Bionics Institute, East Melbourne, VIC, Australia
| | | | - Patrick C. Thien
- Bionics Institute, East Melbourne, VIC, Australia
- Medical Bionics Department, University of Melbourne, Fitzroy, VIC, Australia
| | | | | | | | - Chi D. Luu
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
- Department of Surgery (Ophthalmology), University of Melbourne, East Melbourne, VIC, Australia
| | - David A. X. Nayagam
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
- Department of Clinical Pathology, University of Melbourne, Parkville, VIC, Australia
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Allen PJ. Retinal prostheses: Where to from here? Clin Exp Ophthalmol 2021; 49:418-429. [PMID: 34021959 DOI: 10.1111/ceo.13950] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 05/05/2021] [Accepted: 05/09/2021] [Indexed: 11/29/2022]
Abstract
Researchers have been working towards the development of retinal prostheses, so called "bionic eyes" since the 1960s in an effort to restore functional vision to severely visually impaired patients. Groups from all around the world are involved in this research but in particular, groups from the United States, Germany, France, Japan and Australia have conducted clinical trials of these devices and three of these devices have achieved either FDA HDE (U.S. Food and Drug Administration Humanitarian Device Exception) or CE mark approval for commercial production. Despite this, all three of these devices are now not in commercial production. There are many challenges to overcome to develop devices suitable to implant in human patients and then reach commercial distribution. This is an exacting process and many hurdles need to be overcome to reach this point so that leaving the market after achieving this goal is a significant decision. Ongoing research is exploring the possibility of less complicated surgery with better visual processing algorithms to provide more useful visual information for our patients to provide a commercial alternative.
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Affiliation(s)
- Penelope J Allen
- The Centre for Eye Research Australia, East Melbourne, Australia.,Department of Surgery (Ophthalmology), University of Melbourne, Melbourne, Australia.,The Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
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Theil JH, Johns JL, Chen P, Theil DM, Albertelli MA. Hematology and Culture Assessment of Cranially Implanted Rhesus Macaques ( Macaca mulatta). Comp Med 2021; 71:166-176. [PMID: 33536115 PMCID: PMC8063204 DOI: 10.30802/aalas-cm-20-000084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 10/14/2020] [Accepted: 10/30/2020] [Indexed: 12/25/2022]
Abstract
The use of percutaneous cranial implants in rhesus macaques (Macaca mulatta) has long been a valuable tool for neuroscience research. However, when treating and assessing these animals, veterinarians are required to make assumptions about diagnostic results due to a lack of research into how these implants affect physiology. Microbial cultures of cranial implant sites show an abundance of colonizing bacteria, but whether these microbes affect animal health and wellbeing is poorly understood. In addition, microbial antibiotic resistance can present significant health concerns for both the animals and the researchers. To help elucidate the relationship between percutaneous cranial implants and blood parameters, complete blood cell counts and serum chemistry results were assessed on 57 nonhuman primates at our institution from September 2001 to March 2017. Generalized estimating equations were used to compare the results before and after an animal's first implant surgery. This modelling showed that cranial implants were a significant predictor of alterations in the number of neutrophils, lymphocytes, and red blood cells, and in the concentration of hemoglobin, alkaline phosphatase, creatinine, calcium, phos- phorus, total protein, albumin, and globulin. Anaerobic and aerobic bacterial cultures were performed to identify bacteria associated with cranial implants. Staphylococcus spp., Streptococcus spp., and Corynebacterium spp. comprised the majority of the aerobic bacterial isolates, while Fusobacterium spp., Peptostreptococcus spp. and Bacterioides fragilis comprised the majority of anaerobic bacterial isolates. Using a Pearson r correlation for statistical analysis, we assessed whether any of these bacterial isolates developed antibiotic resistances over time. Cefazolin, the most frequently used antibiotic in monkeys in this study, was the only antimicrobial out of 41 agents tested to which bacteria developed resistance over time. These results indicate that percutaneous implants are associated with a generalized inflammatory state, multiple bacterial species are present at the implant site, and these bacteria may contribute to the inflammatory response.
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Key Words
- cbc, complete blood cell count
- chem, serum chemistry
- wbc, white blood cell
- rbc, red blood cell
- hgb, hemoglobin
- hct, hematocrit
- mcv, mean cell volume
- mchc, mean cell hemoglobin concentration
- ast, aspartate aminotransferase
- alt, alanine aminotransferase
- alp, alkaline phosphatase
- ggt, γ-glutamyl transferase
- bun, blood urea nitrogen
- ck, creatine kinase
- gee, generalized estimating equation
- aid, anemia of inflammatory disease
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Affiliation(s)
- Jacob H Theil
- Campus Veterinary Services, University of California, Davis, Davis, California; Department of Comparative Medicine, Stanford University, Stanford, California;,
| | - Jennifer L Johns
- Department of Biomedical Sciences, Oregon State University Carlson College of Veterinary Medicine, Corvallis, Oregon
| | - Poyin Chen
- Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts; Department of Microbiology and Immunology, Harvard University, Boston, Massachusetts
| | | | - Megan A Albertelli
- Department of Comparative Medicine, Stanford University, Stanford, California
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Su X, Guo J, Zhou M, Chen J, Li L, Chen Y, Sui X, Li H, Chai X. Computational Modeling of Spatially Selective Retinal Stimulation With Temporally Interfering Electric Fields. IEEE Trans Neural Syst Rehabil Eng 2021; 29:418-428. [PMID: 33507871 DOI: 10.1109/tnsre.2021.3055203] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Retinal electrical stimulation is a widely utilized method to restore visual function for patients with retinal degenerative diseases. Transcorneal electrical stimulation (TES) represents an effective way to improve the visual function due to its potential neuroprotective effect. However, TES with single electrode fails to spatially and selectively stimulate retinal neurons. Herein, a computational modeling method was proposed to explore the feasibility of spatially selective retinal stimulation via temporally interfering electric fields. An eyeball model with multiple electrodes was constructed to simulate the interferential electric fields with various electrode montages and current ratios. The results demonstrated that the temporal interference (TI) stimulation would gradually generate an increasingly localized high-intensity region on retina as the return electrodes moved towards the posterior of the eyeball and got closer. Additionally, the position of the convergent region could be modulated by regulating the current ratio of different electrode channels. The TI strategy with multisite and steerable stimulation can stimulate local retinal region with certain convergence and a relatively large stimulation range, which would be a feasible approach for the spatially selective retinal neuromodulation.
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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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Zapf MPH, Boon MY, Lovell NH, Suaning GJ. Assistive peripheral phosphene arrays deliver advantages in obstacle avoidance in simulated end-stage retinitis pigmentosa: a virtual-reality study. J Neural Eng 2016; 13:026022. [PMID: 26902525 DOI: 10.1088/1741-2560/13/2/026022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The prospective efficacy of peripheral retinal prostheses for guiding orientation and mobility in the absence of residual vision, as compared to an implant for the central visual field (VF), was evaluated using simulated prosthetic vision (SPV). APPROACH Sighted volunteers wearing a head-mounted display performed an obstacle circumvention task under SPV. Mobility and orientation performance with three layouts of prosthetic vision were compared: peripheral prosthetic vision of higher visual acuity (VA) but limited VF, of wider VF but limited VA, as well as centrally restricted prosthetic vision. Learning curves using these layouts were compared fitting an exponential model to the mobility and orientation measures. MAIN RESULTS Using peripheral layouts, performance was superior to the central layout. Walking speed with both higher-acuity and wider-angle layouts was 5.6% higher, and mobility errors reduced by 46.4% and 48.6%, respectively, as compared to the central layout. The wider-angle layout yielded the least number of collisions, 63% less than the higher-acuity and 73% less than the central layout. Using peripheral layouts, the number of visual-scanning related head movements was 54.3% (higher-acuity) and 60.7% (wider-angle) lower, as compared to the central layout, and the ratio of time standing versus time walking was 51.9% and 61.5% lower, respectively. Learning curves did not differ between layouts, except for time standing versus time walking, where both peripheral layouts achieved significantly lower asymptotic values compared to the central layout. SIGNIFICANCE Beyond complementing residual vision for an improved performance, peripheral prosthetic vision can effectively guide mobility in the later stages of retinitis pigmentosa (RP) without residual vision. Further, the temporal dynamics of learning peripheral and central prosthetic vision are similar. Therefore, development of a peripheral retinal prosthesis and early implantation to alleviate VF constriction in RP should be considered to extend the target group and the time of benefit for potential retinal prosthesis implantees.
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Affiliation(s)
- Marc Patrick H Zapf
- Graduate School of Biomedical Engineering, UNSW Australia, Sydney 2052, Australia
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Zapf MPH, Boon MY, Matteucci PB, Lovell NH, Suaning GJ. Towards an assistive peripheral visual prosthesis for long-term treatment of retinitis pigmentosa: evaluating mobility performance in immersive simulations. J Neural Eng 2015; 12:036001. [DOI: 10.1088/1741-2560/12/3/036001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Ayton LN, Blamey PJ, Guymer RH, Luu CD, Nayagam DAX, Sinclair NC, Shivdasani MN, Yeoh J, McCombe MF, Briggs RJ, Opie NL, Villalobos J, Dimitrov PN, Varsamidis M, Petoe MA, McCarthy CD, Walker JG, Barnes N, Burkitt AN, Williams CE, Shepherd RK, Allen PJ. First-in-human trial of a novel suprachoroidal retinal prosthesis. PLoS One 2014; 9:e115239. [PMID: 25521292 PMCID: PMC4270734 DOI: 10.1371/journal.pone.0115239] [Citation(s) in RCA: 199] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 11/18/2014] [Indexed: 11/19/2022] Open
Abstract
Retinal visual prostheses (“bionic eyes”) have the potential to restore vision to blind or profoundly vision-impaired patients. The medical bionic technology used to design, manufacture and implant such prostheses is still in its relative infancy, with various technologies and surgical approaches being evaluated. We hypothesised that a suprachoroidal implant location (between the sclera and choroid of the eye) would provide significant surgical and safety benefits for patients, allowing them to maintain preoperative residual vision as well as gaining prosthetic vision input from the device. This report details the first-in-human Phase 1 trial to investigate the use of retinal implants in the suprachoroidal space in three human subjects with end-stage retinitis pigmentosa. The success of the suprachoroidal surgical approach and its associated safety benefits, coupled with twelve-month post-operative efficacy data, holds promise for the field of vision restoration. Trial Registration Clinicaltrials.gov NCT01603576
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Affiliation(s)
- Lauren N. Ayton
- Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
- * E-mail:
| | - Peter J. Blamey
- Bionics Institute, East Melbourne, Australia
- Department of Medical Bionics, University of Melbourne, East Melbourne, Australia
| | - Robyn H. Guymer
- Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | - Chi D. Luu
- Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | - David A. X. Nayagam
- Bionics Institute, East Melbourne, Australia
- Department of Pathology, University of Melbourne, St Vincent's Hospital Melbourne, Fitzroy, Australia
| | | | - Mohit N. Shivdasani
- Bionics Institute, East Melbourne, Australia
- Department of Medical Bionics, University of Melbourne, East Melbourne, Australia
| | - Jonathan Yeoh
- Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | - Mark F. McCombe
- Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | - Robert J. Briggs
- Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | - Nicholas L. Opie
- Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | | | - Peter N. Dimitrov
- Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | - Mary Varsamidis
- Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
| | | | - Chris D. McCarthy
- NICTA, Computer Vision Research Group, Canberra, Australia
- National Institute for Mental Health Research, Australian National University, Canberra, Australia
| | - Janine G. Walker
- NICTA, Computer Vision Research Group, Canberra, Australia
- National Institute for Mental Health Research, Australian National University, Canberra, Australia
| | - Nick Barnes
- NICTA, Computer Vision Research Group, Canberra, Australia
- National Institute for Mental Health Research, Australian National University, Canberra, Australia
| | - Anthony N. Burkitt
- Bionics Institute, East Melbourne, Australia
- Centre for Neural Engineering, University of Melbourne, National Information and Communications Technology Australia (NICTA), Ltd., Melbourne, Australia
| | | | - Robert K. Shepherd
- Bionics Institute, East Melbourne, Australia
- Department of Medical Bionics, University of Melbourne, East Melbourne, Australia
| | - Penelope J. Allen
- Centre for Eye Research Australia, University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
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