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https://www.readbyqxmd.com/read/29453455/temporal-structure-in-spiking-patterns-of-ganglion-cells-defines-perceptual-thresholds-in-rodents-with-subretinal-prosthesis
#1
Elton Ho, Henri Lorach, Georges Goetz, Florian Laszlo, Xin Lei, Theodore Kamins, Jean-Charles Mariani, Alexander Sher, Daniel Palanker
Subretinal prostheses are designed to restore sight in patients blinded by retinal degeneration using electrical stimulation of the inner retinal neurons. To relate retinal output to perception, we studied behavioral thresholds in blind rats with photovoltaic subretinal prostheses stimulated by full-field pulsed illumination at 20 Hz, and measured retinal ganglion cell (RGC) responses to similar stimuli ex-vivo. Behaviorally, rats exhibited startling response to changes in brightness, with an average contrast threshold of 12%, which could not be explained by changes in the average RGC spiking rate...
February 16, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29443363/sheets-glide-assisted-intraocular-placement-of-the-argus-ii-retinal-prosthesis
#2
Avni P Finn, Lejla Vajzovic
BACKGROUND AND OBJECTIVE: As an increasing number of vitreoretinal surgeons are implanting retinal prosthesis devices, the need to share surgical techniques to ease implantation in challenging scenarios grows. The authors share a technique to aide in overcoming a challenge associated with uveal prolapse in a patient undergoing Argus II retinal prosthesis (Second Sight Medical Products, Sylmar, CA) implantation. PATIENTS AND METHODS: A surgical technique is discussed and demonstrated using a video (Video available at www...
February 1, 2018: Ophthalmic Surgery, Lasers & Imaging Retina
https://www.readbyqxmd.com/read/29438279/recent-updates-on-treatment-of-ocular-microbial-infections-by-stem-cell-therapy-a-review
#3
REVIEW
Seoh Wei Teh, Pooi Ling Mok, Munirah Abd Rashid, Mae-Lynn Catherine Bastion, Normala Ibrahim, Akon Higuchi, Kadarkarai Murugan, Rajan Mariappan, Suresh Kumar Subbiah
Ocular microbial infection has emerged as a major public health crisis during the past two decades. A variety of causative agents can cause ocular microbial infections; which are characterized by persistent and destructive inflammation of the ocular tissue; progressive visual disturbance; and may result in loss of visual function in patients if early and effective treatments are not received. The conventional therapeutic approaches to treat vision impairment and blindness resulting from microbial infections involve antimicrobial therapy to eliminate the offending pathogens or in severe cases; by surgical methods and retinal prosthesis replacing of the infected area...
February 13, 2018: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/29426448/the-toronto-experience-with-the-argus-ii-retinal-prosthesis-new-technology-new-hope-for-patients
#4
Robert G Devenyi, Joshua Manusow, Beatrice E Patino, Mohamed Mongy, Michelle Markowitz, Samuel N Markowitz
Surgical restoration of vision with retinal prostheses is a new and developing technology currently available in a select group of countries, Canada among them. The Argus II retinal prosthesis is the first commercially available device for restoration of vision in patients with Retinitis Pigmentosa or with similar retinal pathology who still have minimal residual native vision. The surgery is complex and requires training however it is within the abilities of any experienced retina surgeon. Surgical experience builds up with each case and in our patients length of surgery constantly went down...
February 2018: Canadian Journal of Ophthalmology. Journal Canadien D'ophtalmologie
https://www.readbyqxmd.com/read/29426432/rehabilitation-of-lost-functional-vision-with-the-argus-ii-retinal-prosthesis
#5
Michelle Markowitz, Mark Rankin, Mohamed Mongy, Beatrice E Patino, Joshua Manusow, Robert G Devenyi, Samuel N Markowitz
The Argus II retinal prosthesis is the first commercially available device for restoration of vision in patients with Retinitis Pigmentosa or with similar retinal pathology who still have minimal residual native vision. The technology is able to restore vision with production of artificial visual percepts which usually are given adequate useful interpretation by the visual system in most implanted patients. The technology usually produces visual perception at the level of shape identification or better in some cases enabling in many less dependence on vision substitution devices and skills...
February 2018: Canadian Journal of Ophthalmology. Journal Canadien D'ophtalmologie
https://www.readbyqxmd.com/read/29392324/eye-movement-control-in-the-argus-ii-retinal-prosthesis-enables-reduced-head-movement-and-better-localization-precision
#6
Avi Caspi, Arup Roy, Varalakshmi Wuyyuru, Paul E Rosendall, Jason W Harper, Kapil D Katyal, Michael P Barry, Gislin Dagnelie, Robert J Greenberg
Purpose: Visual scanning by sighted individuals is done using eye and head movements. In contrast, scanning using the Argus II is solely done by head movement, since eye movements can introduce localization errors. Here, we tested if a scanning mode utilizing eye movements increases visual stability and reduces head movements in Argus II users. Methods: Eye positions were measured in real-time and were used to shift the region of interest (ROI) that is sent to the implant within the wide field of view (FOV) of the scene camera...
February 1, 2018: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/29388561/optimization-of-pillar-electrodes-in-subretinal-prosthesis-for-enhanced-proximity-to-target-neurons
#7
Thomas Anthony Flores, Xin Lei, Tiffany Wanshing Huang, Henri Lorach, Roopa Dalal, Ludwig Galambos, Ted I Kamins, Keith Mathieson, Daniel Palanker
High-resolution prosthetic vision requires dense stimulating arrays with small electrodes. However, such miniaturization reduces electrode capacitance and penetration of electric field into tissue. We evaluate potential solutions to these problems with subretinal implants based on utilization of pillar electrodes. Approach. To study integration of three-dimensional (3-D) implants with retinal tissue, we fabricated arrays with varying pillar diameter, pitch, and height, and implanted beneath the degenerate retina in rats (Royal College of Surgeons, RCS)...
February 1, 2018: Journal of Neural Engineering
https://www.readbyqxmd.com/read/29311491/visual-evoked-potential-in-rabbits-eyes-with-subretinal-implantation-by-vitrectomy-of-okayama-university-type-retinal-prosthesis-oureptm
#8
Toshihiko Matsuo, Tetsuya Uchida, Koichiro Yamashita, Shigiko Takei, Daisuke Ido, Mamoru Tanaka, Masao Oguchi, Toshinori Furukawa
Okayama University-type retinal prosthesis (OURePTM) is a photoelectric dye-coupled polyethylene film which generates electric potential in response to light and stimulates nearby neurons. This study aims to test surgical feasibility for subretinal film implantation and to examine functional durability of films in subretinal space. Dye-coupled films were implanted subretinally by vitrectomy in the right eye of normal white rabbits: 8 rabbits for 1 month and 8 rabbits for 6 months. The implanted films were removed by vitrectomy in 4 of these 8 rabbits in 1-month or 6-month implantation group...
January 1, 2018: Journal of Veterinary Medical Science
https://www.readbyqxmd.com/read/29304268/multimodal-imaging-including-optical-coherence-tomography-angiography-of-a-patient-with-argus-ii-retinal-prosthesis-one-year-after-implantation
#9
Dilek Güven, Mehmet Demir, Delil Özcan, Hakan Kaçar, Semra Tiryaki Demir, Saniye Üke Uzun
A 58-year-old man with end-stage retinitis pigmentosa (RP) and visual acuity of light perception in both eyes received simultaneous phacoemulsification with intraocular lens implantation and implantation of the Argus II Retinal Prosthesis System (Second Sight Medical Products, Sylmar, CA) to his right eye 1 year ago. He accomplished the fitting and rehabilitation sessions, and no extraocular or intraocular complications were encountered perioperatively, postoperatively, or during the follow-up. The patient used the prosthesis actively for 2...
January 1, 2018: Ophthalmic Surgery, Lasers & Imaging Retina
https://www.readbyqxmd.com/read/29201260/retinal-prosthesis-system-for-advanced-retinitis-pigmentosa-a-health-technology-assessment-update
#10
(no author information available yet)
Background: Retinitis pigmentosa is a group of inherited disorders characterized by the degeneration of the photoreceptors in the retina, resulting in progressive vision loss. The Argus II system is designed to restore partial functional vision in patients with profound vision loss from advanced retinitis pigmentosa. At present, it is the only treatment option approved by Health Canada for this patient population. In June 2016, Health Quality Ontario published a health technology assessment of the Argus II retinal prosthesis system for patients with advanced retinitis pigmentosa...
2017: Ontario Health Technology Assessment Series
https://www.readbyqxmd.com/read/29184478/visual-prosthesis-interfacing-stimulating-electrodes-with-retinal-neurons-to-restore-vision
#11
REVIEW
Alejandro Barriga-Rivera, Lilach Bareket, Josef Goding, Ulises A Aregueta-Robles, Gregg J Suaning
The bypassing of degenerated photoreceptors using retinal neurostimulators is helping the blind to recover functional vision. Researchers are investigating new ways to improve visual percepts elicited by these means as the vision produced by these early devices remain rudimentary. However, several factors are hampering the progression of bionic technologies: the charge injection limits of metallic electrodes, the mechanical mismatch between excitable tissue and the stimulating elements, neural and electric crosstalk, the physical size of the implanted devices, and the inability to selectively activate different types of retinal neurons...
2017: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/29148158/long-term-anesthetic-protocol-in-rats-feasibility-in-electrophysiology-studies-in-visual-prosthesis
#12
Alejandro Barriga-Rivera, Veronica Tatarinoff, Nigel H Lovell, John W Morley, Gregg J Suaning
Electrical stimulation of excitable cells provides therapeutic benefits for a variety of medical conditions, including restoration of partial vision to those blinded via some types of retinal degeneration. To improve visual percepts elicited by the current technology, researchers are conducting acute electrophysiology experiments, mainly in cats. However, the rat can provide a model of a range of retinal diseases and possesses a sufficiently large eye to be used in this field. This article presents a long-term anesthetic protocol to enable electrophysiology experiments to further the development of visual prostheses...
November 17, 2017: Veterinary Ophthalmology
https://www.readbyqxmd.com/read/29076459/an-optimized-content-aware-image-retargeting-method-toward-expanding-the-perceived-visual-field-of-the-high-density-retinal-prosthesis-recipients
#13
Heng Li, Yajie Zeng, Zhuofan Lu, Xiaofei Cao, Xiaofan Su, Xiaohong Sui, Jing Wang, Xinyu Chai
Retinal prosthesis devices have shown great value in restoring some sight for individuals with profoundly impaired vision, but the visual acuity and visual field provided by prostheses greatly limit recipients' visual experience. In this paper, we employ computer vision approaches to seek to expand the perceptible visual field in patients implanted potentially with a high-density retinal prosthesis while maintaining visual acuity as much as possible. Approach. We propose an optimized content-aware image retargeting method, by introducing salient object detection based on color and intensity-difference contrast, aiming to remap important information of a scene into a small visual field and preserve their original scale as much as possible...
October 27, 2017: Journal of Neural Engineering
https://www.readbyqxmd.com/read/29060685/information-transmission-in-the-primary-visual-cortex-of-retinal-degenerated-rats
#14
Yi Wang, Ke Chen, Leanne L H Chan
To study the information transmission in the primary visual cortex (V1) of retinal degenerated (RD) models, wild type (WT) and RD rats were used in the experiments. The neural response in V1 was recorded extracellularly while the flicker with varied intensity levels was given as the visual stimulus. The mutual information (MI) and normalized mutual information (NMI) were determined for every isolated neuron, in order to quantify the amount and efficiency of information transmission in V1 of both control and experimental groups...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/29060083/testing-stimulus-protocols-in-retinal-prosthesis-patients
#15
A Gonzalez-Calle, J D Weiland
Retinal prostheses have demonstrated the capability to give blind patients the ability to detect motion and locate large objects. High-resolution retinal prostheses require precise activation of retinal cells to elicit a small visual phosphine that can serve as a building block to make patterns. Each electrode should activate only nearby cells, however patients receiving single electrode stimulation often report a streak-shaped phosphene rather than a focal spot. It is important to investigate stimulus paradigms that will provide better control over the spatial patterns of activation...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/29060067/a-comparative-study-of-light-and-electrically-evoked-response-of-retinal-ganglion-cells
#16
Satarupa Biswas, Debdeep Sikdar, Soumen Das, Manjunatha Mahadevappa
Understanding of the evoked neural discharges from retinal tissues is vital for designing of any retinal prosthesis. In this study, retinal ganglion cell activity to light and electrical stimulus is recorded using multielectrode arrays. For an effective epiretinal prosthetic device, the electrical stimulus through the prosthesis should be able to evoke responses similar to those of light response in normal condition. This pilot study was intended to design the experimental protocol for in-vitro retinal stimulation...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/29060066/flexible-microelectrode-array-for-retinal-prosthesis
#17
Bin Sun, Tengyue Li, Kai Xia, Qi Zeng, Tianzhun Wu, Mark S Humayun
fMEA (flexible microelectrode array) is one of the key implantable components for neural stimulating and recording. For its specific implanted environment, it should be designed and fabricated to meet following requirements such as biocompatibility, high-resolution, flexible and low impedance to ensure safety and long-term effective stimulation. Here we proposed a high resolution (1025-channel) fMEA for artificial retina. The adhesion between its substrate polyimide (PI) and metal was enhanced by using plasma treatment...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/29046507/subretinal-implantation-of-okayama-university-type-retinal-prosthesis-ourep-tm-in-canine-eyes-by-vitrectomy
#18
Toshihiko Matsuo, Tetsuya Uchida, Makoto Nitta, Koichiro Yamashita, Shigiko Takei, Daisuke Ido, Mamoru Tanaka, Masao Oguchi, Toshinori Furukawa
Okayama University-type retinal prosthesis (OUReP(TM)) is a photoelectric dye-coupled polyethylene film which generates electric potential in response to light and stimulates nearby neurons. This study aims to test surgical feasibility of subretinal implantation and functional durability of dye-coupled films in the subretinal space. The dye-coupled films were implanted subretinally by 25-gauge vitrectomy in the right eye of 11 normal beagle dogs: 2 dogs served for film removal after 5-month film implantation, 3 dogs for film removal after 3-month film implantation, 3 dogs for 3-month film implantation and pathological examination, and 3 dogs for sham surgery...
October 18, 2017: Journal of Veterinary Medical Science
https://www.readbyqxmd.com/read/28883759/the-advantage-of-topographic-prominence-adopted-filter-for-the-detection-of-short-latency-spikes-of-retinal-ganglion-cells
#19
Jungryul Ahn, Myoung-Hwan Choi, Kwangsoo Kim, Solomon S Senok, Dong-Il Dan Cho, Kyo-In Koo, Yongsook Goo
Electrical stimulation through retinal prosthesis elicits both short and long-latency retinal ganglion cell (RGC) spikes. Because the short-latency RGC spike is usually obscured by electrical stimulus artifact, it is very important to isolate spike from stimulus artifact. Previously, we showed that topographic prominence (TP) discriminator based algorithm is valid and useful for artifact subtraction. In this study, we compared the performance of forward backward (FB) filter only vs. TP-adopted FB filter for artifact subtraction...
September 2017: Korean Journal of Physiology & Pharmacology
https://www.readbyqxmd.com/read/28878616/interim-results-of-a-multicenter-trial-with-the-new-electronic-subretinal-implant-alpha-ams-in-15-patients-blind-from-inherited-retinal-degenerations
#20
Katarina Stingl, Ruth Schippert, Karl U Bartz-Schmidt, Dorothea Besch, Charles L Cottriall, Thomas L Edwards, Florian Gekeler, Udo Greppmaier, Katja Kiel, Assen Koitschev, Laura Kühlewein, Robert E MacLaren, James D Ramsden, Johann Roider, Albrecht Rothermel, Helmut Sachs, Greta S Schröder, Jan Tode, Nicole Troelenberg, Eberhart Zrenner
Purpose: We assessed the safety and efficacy of a technically advanced subretinal electronic implant, RETINA IMPLANT Alpha AMS, in end stage retinal degeneration in an interim analysis of two ongoing prospective clinical trials. The purpose of this article is to describe the interim functional results (efficacy). Methods: The subretinal visual prosthesis RETINA IMPLANT Alpha AMS (Retina Implant AG, Reutlingen, Germany) was implanted in 15 blind patients with hereditary retinal degenerations at four study sites with a follow-up period of 12 months (www...
2017: Frontiers in Neuroscience
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