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https://www.readbyqxmd.com/read/28227741/eye-movements-as-a-marker-for-visual-prosthesis-spatial-mapping-a-feasibility-study-using-a-blind-patient-implanted-with-the-argus-ii-retinal-prosthesis
#1
Avi Caspi, Jessy Dorn, John B Helder, Kapil D Katyal, Arup Roy, Avi Caspi, Jessy Dorn, John B Helder, Kapil D Katyal, Arup Roy, John B Helder, Kapil D Katyal, Jessy Dorn, Arup Roy, Avi Caspi
Spatial mapping, the location in space of a perceived location due to an implanted electrode's electrical stimulation is important in the design of visual prostheses. Generally, a visual prosthesis system consists of an implanted electrode array, an external camera that acquires the image, and a transmitter that sends the information to the implanted electrodes. In cortical visual implant, the layout of the implanted array in most cases does not match the retinotopic map and it is necessary to find the location of the percept of each electrode in world coordinates...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28227738/tuning-electrical-stimulation-for-thalamic-visual-prosthesis-an-autoencoder-based-approach
#2
Amr Jawwad, Hossam H Abolfotuh, Bassem Abdullah, Hani M K Mahdi, Seif Eldawlatly, Amr Jawwad, Hossam H Abolfotuh, Bassem Abdullah, Hani M K Mahdi, Seif Eldawlatly, Amr Jawwad, Hani M K Mahdi, Bassem Abdullah, Seif Eldawlatly, Hossam H Abolfotuh
Visual prosthesis holds hope of vision restoration for millions with retinal degenerative diseases. Machine learning techniques such as artificial neural networks could help in improving prosthetic devices as they could learn how the brain encodes information and imitate that code. This paper introduces an autoencoder-based approach for tuning thalamic visual prostheses. The objective of the proposed approach is to estimate electrical stimuli that are equivalent to a given natural visual stimulus, in a way such that they both elicit responses that are as similar as possible when introduced to a Lateral Geniculate Nucleus (LGN) population...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28226523/embedded-clutter-reduction-and-face-detection-algorithms-for-a-visual-prosthesis
#3
Derek M Rollend, Paul E Rosendall, Kevin C Wolfe, Dean M Kleissas, Seth D Billings, Jonathan M Oben, John B Helder, Francesco V Tenore, Philippe M Burlina, Arup Roy, Robert Greenberg, Kapil D Katyal, Derek M Rollend, Paul E Rosendall, Kevin C Wolfe, Dean M Kleissas, Seth D Billings, Jonathan M Oben, John B Helder, Francesco V Tenore, Philippe M Burlina, Arup Roy, Robert Greenberg, Kapil D Katyal, Arup Roy, Dean M Kleissas, John B Helder, Seth D Billings, Robert Greenberg, Philippe M Burlina, Derek M Rollend, Paul E Rosendall, Jonathan M Oben, Kapil D Katyal, Francesco V Tenore, Kevin C Wolfe
Retinal prosthetic devices can significantly and positively impact the ability of visually challenged individuals to live a more independent life. We describe a visual processing system which leverages image analysis techniques to produce visual patterns and allows the user to more effectively perceive their environment. These patterns are used to stimulate a retinal prosthesis to allow self guidance and a higher degree of autonomy for the affected individual. Specifically, we describe an image processing pipeline that allows for object and face localization in cluttered environments as well as various contrast enhancement strategies in the "implanted image...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28209965/high-amplitude-electrical-stimulation-can-reduce-elicited-neuronal-activity-in-visual-prosthesis
#4
Alejandro Barriga-Rivera, Tianruo Guo, Chih-Yu Yang, Amr Al Abed, Socrates Dokos, Nigel H Lovell, John W Morley, Gregg J Suaning
Retinal electrostimulation is promising a successful therapy to restore functional vision. However, a narrow stimulating current range exists between retinal neuron excitation and inhibition which may lead to misperformance of visual prostheses. As the conveyance of representation of complex visual scenes may require neighbouring electrodes to be activated simultaneously, electric field summation may contribute to reach this inhibitory threshold. This study used three approaches to assess the implications of relatively high stimulating conditions in visual prostheses: (1) in vivo, using a suprachoroidal prosthesis implanted in a feline model, (2) in vitro through electrostimulation of murine retinal preparations, and (3) in silico by computing the response of a population of retinal ganglion cells...
February 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28203188/endoscope-assisted-and-controlled-argus-ii-epiretinal-prosthesis-implantation-in-late-stage-retinitis-pigmentosa-a-report-of-2-cases
#5
Emin Özmert, Sibel Demirel
Several different approaches for restoring sight in subjects who are blind due to outer retinal degeneration are currently under investigation, including stem cell therapy, gene therapy, and visual prostheses. Although many different types of visual prostheses have shown promise, to date, the Argus II Epiretinal Prosthesis System, developed in a clinical setting over the course of 10 years, is the world's first and only retinal prosthesis that has been approved by the United States Food and Drug Administration (FDA) and has been given the CE-Mark for sale within the European Economic Area (EEA)...
September 2016: Case Reports in Ophthalmology
https://www.readbyqxmd.com/read/28181076/visual-evoked-potential-in-rcs-rats-with-okayama-university-type-retinal-prosthesis-ourep%C3%A2-implantation
#6
Alamusi, Toshihiko Matsuo, Osamu Hosoya, Tetsuya Uchida
Photoelectric dye-coupled polyethylene film, designated Okayama University type-retinal prosthesis or OUReP™, generates light-evoked surface electric potentials and stimulates neurons. The dye-coupled films or plain films were implanted subretinally in both eyes of 10 Royal College of Surgeons rats with hereditary retinal dystrophy at the age of 6 weeks. Visual evoked potentials in response to monocular flashing light stimuli were recorded from cranially-fixed electrodes, 4 weeks and 8 weeks after the implantation...
February 8, 2017: Journal of Artificial Organs: the Official Journal of the Japanese Society for Artificial Organs
https://www.readbyqxmd.com/read/28135031/retinal-prosthesis-that-incorporates-the-organization-of-the-nerve-fibre-layer
#7
REVIEW
Thomas FitzGibbon
Recent efforts to restore partial vision in blind patients have made significant progress. Currently, prosthetic design concentrates on stimulating as many foveal retinal ganglion cells as possible but is hampered by stimulation of the nerve fibre layer. This results in a nonvisuotopic arrangement of phosphenes (stimulation percepts). This article suggests that by extending the stimulation area well beyond the fovea and stimulating the nerve fibre layer, axons from any remaining ganglion cells in more peripheral regions of the retina (low acuity) can be used to generate a visuotopic map...
January 30, 2017: Clinical & Experimental Ophthalmology
https://www.readbyqxmd.com/read/28114567/retinotopic-to-spatiotopic-mapping-in-blind-patients-implanted-with-the-argus-ii-retinal-prosthesis
#8
Avi Caspi, Arup Roy, Jessy D Dorn, Robert J Greenberg
Purpose: To quantify the precision of mapping from retinotopic (retina-centered) to spatiotopic (world-centered) coordinates in blind humans implanted with a retinal prosthesis device. Additionally, to demonstrate that an eye tracker can be calibrated on sightless patients based on the percept from a visual implant. Methods: We directly activated epiretinal electrodes to create retinotopic stimuli and recorded the location of the percept at world-based coordinates...
January 1, 2017: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/28113816/versatile-stimulation-back-end-with-programmable-exponential-current-pulse-shapes-for-a-retinal-visual-prosthesis
#9
Mohammad Hossein Maghami, Amir M Sodagar, Mohamad Sawan
No abstract text is available yet for this article.
March 30, 2016: IEEE Transactions on Neural Systems and Rehabilitation Engineering
https://www.readbyqxmd.com/read/28009400/optical-coherence-tomography-imaging-in-the-management-of-the-argus-ii-retinal-prosthesis-system
#10
Francesco Parmeggiani, Katia De Nadai, Angela Piovan, Andrea Binotto, Sara Zamengo, Marzio Chizzolini
PURPOSE: To report a real-life experience with the Argus II retinal prosthesis system in blind patients with end-stage retinitis pigmentosa (RP) or choroideremia (CHM), focusing on the pivotal role of optical coherence tomography (OCT) in both preoperative and postoperative management. METHODS: This hospital-based case series included 3 blind patients who were uneventfully implanted with Argus II epiretinal device. These patients (2 with RP and 1 with CHM) were selected during the Argus™ II Retinal Prosthesis System PostMarket Surveillance Study Protocol...
January 19, 2017: European Journal of Ophthalmology
https://www.readbyqxmd.com/read/27942525/are-long-stimulus-pulse-durations-the-answer-to-improving-spatial-resolution-in-retinal-prostheses
#11
COMMENT
Matthew A Petoe, Mohit N Shivdasani
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...
November 2016: Annals of Translational Medicine
https://www.readbyqxmd.com/read/27929043/differential-stimulation-of-the-retina-with-subretinally-injected-exogenous-neurotransmitter-a-biomimetic-alternative-to-electrical-stimulation
#12
Corey M Rountree, Samsoon Inayat, John B Troy, Laxman Saggere
Subretinal stimulation of the retina with neurotransmitters, the normal means of conveying visual information, is a potentially better alternative to electrical stimulation widely used in current retinal prostheses for treating blindness from photoreceptor degenerative diseases. Yet, no subretinal electrical or chemical stimulation study has stimulated the OFF and ON pathways differentially through inner retinal activation. Here, we demonstrate the feasibility of differentially stimulating retinal ganglion cells (RGCs) through the inner nuclear layer of the retina with glutamate, a primary neurotransmitter chemical, in a biomimetic way...
December 8, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27916963/neuron-stimulation-device-integrated-with-silicon-nanowire-based-photodetection-circuit-on-a-flexible-substrate
#13
Suk Won Jung, Jong Yoon Shin, Kilwha Pi, Yong Sook Goo, Dong-Il Dan Cho
This paper proposes a neural stimulation device integrated with a silicon nanowire (SiNW)-based photodetection circuit for the activation of neurons with light. The proposed device is comprised of a voltage divider and a current driver in which SiNWs are used as photodetector and field-effect transistors; it has the functions of detecting light, generating a stimulation signal in proportion to the light intensity, and transmitting the signal to a micro electrode. To show the applicability of the proposed neural stimulation device as a high-resolution retinal prosthesis system, a high-density neural stimulation device with a unit cell size of 110 × 110 μ m and a resolution of 32 × 32 was fabricated on a flexible film with a thickness of approximately 50 μm...
December 1, 2016: Sensors
https://www.readbyqxmd.com/read/27900949/prediction-of-cortical-responses-to-simultaneous-electrical-stimulation-of-the-retina
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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