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https://www.readbyqxmd.com/read/27900949/prediction-of-cortical-responses-to-simultaneous-electrical-stimulation-of-the-retina
#1
Kerry J Halupka, Mohit N Shivdasani, Shaun L Cloherty, David B Grayden, Yan T Wong, Anthony N Burkitt, Hamish Meffin
OBJECTIVE: Simultaneous electrical stimulation of multiple electrodes has shown promise in diversifying the responses that can be elicited by retinal prostheses compared to interleaved single electrode stimulation. However, the effects of interactions between electrodes are not well understood and clinical trials with simultaneous stimulation have produced inconsistent results. We investigated the effects of multiple electrode stimulation of the retina by developing a model of cortical responses to retinal stimulation...
November 30, 2016: Journal of Neural Engineering
https://www.readbyqxmd.com/read/27874058/perceptual-learning-in-a-non-human-primate-model-of-artificial-vision
#2
Nathaniel J Killian, Milena Vurro, Sarah B Keith, Margee J Kyada, John S Pezaris
Visual perceptual grouping, the process of forming global percepts from discrete elements, is experience-dependent. Here we show that the learning time course in an animal model of artificial vision is predicted primarily from the density of visual elements. Three naïve adult non-human primates were tasked with recognizing the letters of the Roman alphabet presented at variable size and visualized through patterns of discrete visual elements, specifically, simulated phosphenes mimicking a thalamic visual prosthesis...
November 22, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27855446/-technological-set-up-of-epiretinal-implants
#3
W Mokwa, M Görtz
In blinded patients, visual prostheses can restore visual perception by appropriate electrical stimulation of retinal nerve cells. This article presents the basic technological principles of retinal prostheses, using an epiretinal implantable visual prosthesis as example. An implantable visual prosthesis typically consists of extraocular and intraocular sections. The extraocular section is responsible for detecting the image. The information is derived from this image that is needed for appropriate electrical stimulation of the retinal nerve cells...
November 2016: Klinische Monatsblätter Für Augenheilkunde
https://www.readbyqxmd.com/read/27835711/one-year-outcome-of-49-channel-suprachoroidal-transretinal-stimulation-prosthesis-in-patients-with-advanced-retinitis-pigmentosa
#4
Takashi Fujikado, Motohiro Kamei, Hirokazu Sakaguchi, Hiroyuki Kanda, Takao Endo, Masakazu Hirota, Takeshi Morimoto, Kentaro Nishida, Haruhiko Kishima, Yasuo Terasawa, Koji Oosawa, Motoki Ozawa, Kohji Nishida
Purpose: To determine the feasibility of a 49-channel suprachoroidal-transretinal stimulation (STS) retinal prosthesis that was implanted for 1 year. Methods: Three patients with advanced retinitis pigmentosa (RP) and with less than or equal to hand motion (HM) vision were studied. A 49-channel STS system was implanted in a scleral pocket, and the stability of the prosthesis, adverse events, and its efficacy were investigated. Results: The electrode array was implanted in a scleral pocket located under the parafoveal area through a scleral incision at 14 mm in patient (Pt) 1, 16 mm in Pt 2, and 18 mm in Pt 3 from the sclerocorneal limbus...
November 1, 2016: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/27780207/visual-bold-response-in-late-blind-subjects-with-argus-ii-retinal-prosthesis
#5
E Castaldi, G M Cicchini, L Cinelli, L Biagi, S Rizzo, M C Morrone
Retinal prosthesis technologies require that the visual system downstream of the retinal circuitry be capable of transmitting and elaborating visual signals. We studied the capability of plastic remodeling in late blind subjects implanted with the Argus II Retinal Prosthesis with psychophysics and functional MRI (fMRI). After surgery, six out of seven retinitis pigmentosa (RP) blind subjects were able to detect high-contrast stimuli using the prosthetic implant. However, direction discrimination to contrast modulated stimuli remained at chance level in all of them...
October 2016: PLoS Biology
https://www.readbyqxmd.com/read/27701633/stimulation-of-a-suprachoroidal-retinal-prosthesis-drives-cortical-responses-in-a-feline-model-of-retinal-degeneration
#6
Felix P Aplin, Erica L Fletcher, Chi D Luu, Kirstan A Vessey, Penelope J Allen, Robyn H Guymer, Robert K Shepherd, Mohit N Shivdasani
Purpose: Retinal prostheses have emerged as a promising technology to restore vision in patients with severe photoreceptor degeneration. To better understand how neural degeneration affects the efficacy of electronic implants, we investigated the function of a suprachoroidal retinal implant in a feline model. Methods: Unilateral retinal degeneration was induced in four adult felines by intravitreal injection of adenosine triphosphate (ATP). Twelve weeks post injection, animals received suprachoroidal electrode array implants in each eye, and responses to electrical stimulation were obtained using multiunit recordings from the visual cortex...
October 1, 2016: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/27664290/the-bionic-eye-a-quarter-century-of-retinal-prosthesis-research-and-development
#7
Mark S Humayun, Eugene de Juan, Gislin Dagnelie
This article describes the history of visual prostheses, with emphasis on the development of the Argus II retinal prosthesis system (Second Sight Medical Products, Inc., Sylmar, CA). A brief overview of cortical electrical stimulation in the blind is provided, followed by an account of the design and development of retinal stimulation equipment at the Duke Eye Center in the late 1980s; the first human intraoperative tests there and the subsequent 8 years of tests at the Wilmer Eye Institute; the transfer of the project to the Doheny Eye Institute at the University of Southern California and the founding of Second Sight Medical Products; and the development and clinical trials of the Argus I and Argus II systems...
October 2016: Ophthalmology
https://www.readbyqxmd.com/read/27612691/monitoring-the-evolution-of-boron-doped-porous-diamond-electrode-on-flexible-retinal-implant-by-oct-and-in-vivo-impedance-spectroscopy
#8
Clément Hébert, Myline Cottance, Julie Degardin, Emmanuel Scorsone, Lionel Rousseau, Gaelle Lissorgues, Philippe Bergonzo, Serge Picaud
Nanocrystalline Boron doped Diamond proved to be a very attractive material for neural interfacing, especially with the retina, where reduce glia growth is observed with respect to other materials, thus facilitating neuro-stimulation over long terms. In the present study, we integrated diamond microelectrodes on a polyimide substrate and investigated their performances for the development of neural prosthesis. A full description of the microfabrication of the implants is provided and their functionalities are assessed using cyclic voltammetry and electrochemical impedance spectroscopy...
December 1, 2016: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/27575757/the-argus-ii-retinal-prosthesis-a-comprehensive-review
#9
Lisa C Olmos de Koo, Ninel Z Gregori
No abstract text is available yet for this article.
2016: International Ophthalmology Clinics
https://www.readbyqxmd.com/read/27574397/argus-ii-retinal-prosthesis-implantation-with-scleral-flap-and-autogenous-temporalis-fascia-as-alternative-patch-graft-material-a-4-year-follow-up
#10
Alexandre Matet, Nawel Amar, Saddek Mohand-Said, José-Alain Sahel, Pierre-Olivier Barale
INTRODUCTION: The Argus II retinal prosthesis is composed of an epiretinal electrode array positioned over the macula and connected to an extrascleral electronics case via a silicone cable, running through a sclerotomy. During implantation, the manufacturer recommends to cover the sclerotomy site with a patch of processed human pericardium to prevent postoperative hypotony and conjunctival erosion by the underlying electronics case. Due to biomedical regulations prohibiting the use of this material in France, we developed an alternative technique combining a scleral flap protecting the sclerotomy and an autogenous graft of superior temporalis fascia overlying the electronics case...
2016: Clinical Ophthalmology
https://www.readbyqxmd.com/read/27565989/characteristics-and-vitreoretinal-management-of-retinal-detachment-in-eyes-with-boston-keratoprosthesis
#11
Petros Petrou, Philip J Banerjee, Mark Wilkins, Mandeep Singh, Karen Eastlake, G Astrid Limb, David G Charteris
PURPOSE: To review the incidence and features of vitreoretinal complications of a permanent Boston keratoprosthesis and to report the use and outcomes of 23-gauge vitrectomy to manage vitreoretinal pathology. DESIGN: Retrospective non-comparative, interventional case series. SUBJECT, PARTICIPANTS: 27 eyes of 27 patients managed with a Boston keratoprosthesis at Moorfields Eye Hospital over a 3-year period. METHODS: All eyes that underwent pars plana vitrectomy (PPV) and had at least 6 months follow-up were analysed with a specific focus on the anatomical and histological characteristics of retinal detachment and outcomes of surgery...
August 26, 2016: British Journal of Ophthalmology
https://www.readbyqxmd.com/read/27558213/improvements-in-vision-related-quality-of-life-in-blind-patients-implanted-with-the-argus-ii-epiretinal-prosthesis
#12
Jacque L Duncan, Thomas P Richards, Aries Arditi, Lyndon da Cruz, Gislin Dagnelie, Jessy D Dorn, Allen C Ho, Lisa C Olmos de Koo, Pierre-Olivier Barale, Paulo E Stanga, Gabriele Thumann, Yizhong Wang, Robert J Greenberg
BACKGROUND: The purpose of this analysis is to report the change in quality of life (QoL) after treatment with the Argus II Epiretinal Prosthesis in patients with end-stage retinitis pigmentosa. METHODS: The Vision and Quality of Life Index (VisQoL) was used to assess changes in QoL dimensions and overall utility score in a prospective 30-patient single-arm clinical study. VisQoL is a multi-attribute instrument consisting of six dimensions (injury, life, roles, assistance, activity and friendship) that may be affected by visual impairment...
August 25, 2016: Clinical & Experimental Optometry: Journal of the Australian Optometrical Association
https://www.readbyqxmd.com/read/27549126/probing-the-functional-impact-of-sub-retinal-prosthesis
#13
Sébastien Roux, Frédéric Matonti, Florent Dupont, Louis Hoffart, Sylvain Takerkart, Serge Picaud, Pascale Pham, Frédéric Chavane
Retinal prostheses are promising tools for recovering visual functions in blind patients but, unfortunately, with still poor gains in visual acuity. Improving their resolution is thus a key challenge that warrants understanding its origin through appropriate animal models. Here, we provide a systematic comparison between visual and prosthetic activations of the rat primary visual cortex (V1). We established a precise V1 mapping as a functional benchmark to demonstrate that sub-retinal implants activate V1 at the appropriate position, scalable to a wide range of visual luminance, but with an aspect-ratio and an extent much larger than expected...
2016: ELife
https://www.readbyqxmd.com/read/27529371/towards-high-resolution-retinal-prostheses-with-direct-optical-addressing-and-inductive-telemetry
#14
Sohmyung Ha, Massoud L Khraiche, Abraham Akinin, Yi Jing, Samir Damle, Yanjin Kuang, Sue Bauchner, Yu-Hwa Lo, William R Freeman, Gabriel A Silva, Gert Cauwenberghs
OBJECTIVE: Despite considerable advances in retinal prostheses over the last two decades, the resolution of restored vision has remained severely limited, well below the 20/200 acuity threshold of blindness. Towards drastic improvements in spatial resolution, we present a scalable architecture for retinal prostheses in which each stimulation electrode is directly activated by incident light and powered by a common voltage pulse transferred over a single wireless inductive link. APPROACH: The hybrid optical addressability and electronic powering scheme provides separate spatial and temporal control over stimulation, and further provides optoelectronic gain for substantially lower light intensity thresholds than other optically addressed retinal prostheses using passive microphotodiode arrays...
October 2016: Journal of Neural Engineering
https://www.readbyqxmd.com/read/27495262/performance-of-real-world-functional-vision-tasks-by-blind-subjects-improves-after-implantation-with-the-argus%C3%A2-ii-retinal-prosthesis-system
#15
Gislin Dagnelie, Punita Christopher, Aries Arditi, Lyndon da Cruz, Jacque L Duncan, Allen C Ho, Lisa C Olmos de Koo, José-Alain Sahel, Paulo E Stanga, Gabriele Thumann, Yizhong Wang, Maura Arsiero, Jessy D Dorn, Robert J Greenberg
BACKGROUND: The main objective of this study was to test Argus II subjects on three real-world Functional Vision tasks. DESIGN: The study was designed to be randomized and prospective. Testing was conducted in a hospital/research laboratory setting at the various participating centers. PARTICIPANTS: Twenty eight Argus II subjects, all profoundly blind, participated in this study. METHODS: Subjects were tested on the three real-world Functional Vision tasks: Sock Sorting, Sidewalk Tracking, and Walking Direction Discrimination task MAIN OUTCOME MEASURES: For the Sock Sorting task, percentage correct was computed based on how accurately subjects sorted the piles on a cloth-covered table and on a bare table...
August 6, 2016: Clinical & Experimental Ophthalmology
https://www.readbyqxmd.com/read/27491695/long-term-repeatability-and-reproducibility-of-phosphene-characteristics-in-chronically-implanted-argus-ii-retinal-prosthesis-subjects
#16
Yvonne H-L Luo, Joe Jiangjian Zhong, Monica Clemo, Lyndon da Cruz
PURPOSE: Previously published literatures of acute studies on few subjects have shown contradictory evidence on the reproducibility and characteristics of the elicited phosphenes, despite using the same stimulating parameters with epiretinal electrode arrays. In this study, we set out to investigate the long-term repeatilibity and reproducibility of phosphenes in subjects chronically implanted with the Argus II retinal prosthesis (Second Sight Medical Products, Inc., Sylmar, CA, USA)...
October 2016: American Journal of Ophthalmology
https://www.readbyqxmd.com/read/27468325/retinal-prosthesis-system-for-advanced-retinitis-pigmentosa-a-health-technology-assessment
#17
(no author information available yet)
BACKGROUND: Retinitis pigmentosa is a group of genetic disorders that involves the breakdown and loss of photoreceptors in the retina, resulting in progressive retinal degeneration and eventual blindness. The Argus II Retinal Prosthesis System is the only currently available surgical implantable device approved by Health Canada. It has been shown to improve visual function in patients with severe visual loss from advanced retinitis pigmentosa. The objective of this analysis was to examine the clinical effectiveness, cost-effectiveness, budget impact, and safety of the Argus II system in improving visual function, as well as exploring patient experiences with the system...
2016: Ontario Health Technology Assessment Series
https://www.readbyqxmd.com/read/27453256/five-year-safety-and-performance-results-from-the-argus-ii-retinal-prosthesis-system-clinical-trial
#18
Lyndon da Cruz, Jessy D Dorn, Mark S Humayun, Gislin Dagnelie, James Handa, Pierre-Olivier Barale, José-Alain Sahel, Paulo E Stanga, Farhad Hafezi, Avinoam B Safran, Joel Salzmann, Arturo Santos, David Birch, Rand Spencer, Artur V Cideciyan, Eugene de Juan, Jacque L Duncan, Dean Eliott, Amani Fawzi, Lisa C Olmos de Koo, Allen C Ho, Gary Brown, Julia Haller, Carl Regillo, Lucian V Del Priore, Aries Arditi, Robert J Greenberg
PURPOSE: The Argus II Retinal Prosthesis System (Second Sight Medical Products, Inc, Sylmar, CA) was developed to restore some vision to patients blind as a result of retinitis pigmentosa (RP) or outer retinal degeneration. A clinical trial was initiated in 2006 to study the long-term safety and efficacy of the Argus II System in patients with bare or no light perception resulting from end-stage RP. DESIGN: Prospective, multicenter, single-arm clinical trial. Within-patient controls included the nonimplanted fellow eye and patients' native residual vision compared with their vision with the Argus II...
October 2016: Ophthalmology
https://www.readbyqxmd.com/read/27382477/virtual-electrode-design-for-increasing-spatial-resolution-in-retinal-prosthesis
#19
Kyle Loizos, Carlos Cela, Robert Marc, Gianluca Lazzi
Retinal prostheses systems are currently used to restore partial vision to patients blinded by degenerative diseases by electrically stimulating surviving retinal cells. To obtain likely maximum resolution, electrode size is minimised, allowing for a large quantity on an array and localised stimulation regions. Besides the small size leading to fabrication difficulties and higher electrochemical charge density, there are challenges associated with the number of drivers needed for a large electrode count as well as the strategies to deliver sufficient power to these drivers wirelessly...
June 2016: Healthcare Technology Letters
https://www.readbyqxmd.com/read/27323882/sic-protective-coating-for-photovoltaic-retinal-prosthesis
#20
Xin Lei, Sheryl Kane, Stuart Cogan, Henri Lorach, Ludwig Galambos, Philip Huie, Keith Mathieson, Theodore Kamins, James Harris, Daniel Palanker
OBJECTIVE: To evaluate plasma-enhanced, chemically vapor deposited (PECVD) amorphous silicon carbide (α-SiC:H) as a protective coating for retinal prostheses and other implantable devices, and to study their failure mechanisms in vivo. APPROACH: Retinal prostheses were implanted in rats sub-retinally for up to 1 year. Degradation of implants was characterized by optical and scanning electron microscopy. Dissolution rates of SiC, SiN x and thermal SiO2 were measured in accelerated soaking tests in saline at 87 °C...
August 2016: Journal of Neural Engineering
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