Retinal Prostheses

2017 ◽  
Vol 1 (3) ◽  
pp. 204-213 ◽  
Author(s):  
Hossein Nazari ◽  
Paulo Falabella ◽  
Lan Yue ◽  
James Weiland ◽  
Mark S. Humayun
Keyword(s):  
Retinal Degeneration ◽  
Visual Information ◽  
Microelectrode Array ◽  
Electrode Array ◽  
Lateral Geniculate Body ◽  
Occipital Cortex ◽  
Artificial Vision ◽  
Retinal Neurons ◽  
Retinal Prostheses ◽  
Retinal Stimulation

Artificial vision is restoring sight by electrical stimulation of the visual system at the level of retina, optic nerve, lateral geniculate body, or occipital cortex. The development of artificial vision began with occipital cortex prosthesis; however, retinal prosthesis has advanced faster in recent years. Currently, multiple efforts are focused on finding the optimal approach for restoring vision through an implantable retinal microelectrode array system. Retinal prostheses function by stimulating the inner retinal neurons that survive retinal degeneration. In these devices, the visual information, gathered by a light detector, is transformed into controlled patterns of electrical pulses, which are in turn delivered to the surviving retinal neurons by an electrode array. Retinal prostheses are classified based on where the stimulating array is implanted (ie, epiretinal, subretinal, suprachoroidal, or episcleral). Recent regulatory approval of 2 retinal prostheses has greatly escalated interest in the potential of these devices to treat blindness secondary to outer retinal degeneration. This review will focus on the technical and operational features and functional outcomes of clinically tested retinal prostheses. We will discuss the major barriers and some of the more promising solutions to improve the outcomes of restoring vision with electrical retinal stimulation.

scholarly journals Retinal Prosthetic Approaches to Enhance Visual Perception for Blind Patients

Micromachines ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 535 ◽  
Author(s):  
Shinyong Shim ◽  
Kyungsik Eom ◽  
Joonsoo Jeong ◽  
Sung Kim
Keyword(s):  
Visual Acuity ◽  
Implantable Devices ◽  
Artificial Vision ◽  
Retinal Neurons ◽  
Electrode Arrays ◽  
Retinal Prostheses ◽  
Future Directions ◽  
Retinal Stimulation ◽  
Made In ◽  
Blind Patients

Retinal prostheses are implantable devices that aim to restore the vision of blind patients suffering from retinal degeneration, mainly by artificially stimulating the remaining retinal neurons. Some retinal prostheses have successfully reached the stage of clinical trials; however, these devices can only restore vision partially and remain insufficient to enable patients to conduct everyday life independently. The visual acuity of the artificial vision is limited by various factors from both engineering and physiological perspectives. To overcome those issues and further enhance the visual resolution of retinal prostheses, a variety of retinal prosthetic approaches have been proposed, based on optimization of the geometries of electrode arrays and stimulation pulse parameters. Other retinal stimulation modalities such as optics, ultrasound, and magnetics have also been utilized to address the limitations in conventional electrical stimulation. Although none of these approaches have been clinically proven to fully restore the function of a degenerated retina, the extensive efforts made in this field have demonstrated a series of encouraging findings for the next generation of retinal prostheses, and these could potentially enhance the visual acuity of retinal prostheses. In this article, a comprehensive and up-to-date overview of retinal prosthetic strategies is provided, with a specific focus on a quantitative assessment of visual acuity results from various retinal stimulation technologies. The aim is to highlight future directions toward high-resolution retinal prostheses.

scholarly journals Photovoltaic retinal prosthesis restores high-resolution responses to single-pixel stimulation in blind retinas

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Naïg Aurelia Ludmilla Chenais ◽  
Marta Jole Ildelfonsa Airaghi Leccardi ◽  
Diego Ghezzi
Keyword(s):  
High Resolution ◽  
Ganglion Cells ◽  
Artificial Vision ◽  
Wide Field ◽  
Retinal Ganglion ◽  
Retinal Neurons ◽  
Retinal Prostheses ◽  
Retinal Stimulation ◽  
Single Pixel ◽  
Pixel Pitch

AbstractRetinal prostheses hold the promise of restoring vision in totally blind people. However, a decade of clinical trials highlighted quantitative limitations hampering the possibility of reaching this goal. A key challenge in retinal stimulation is to independently activate retinal neurons over a large portion of the subject’s visual field. Reaching such a goal would significantly improve the perception accuracy in retinal implants’ users, along with their spatial cognition, attention, ambient mapping and interaction with the environment. Here we show a wide-field, high-density and high-resolution photovoltaic epiretinal prosthesis for artificial vision (POLYRETINA). The prosthesis embeds 10,498 physically and functionally independent photovoltaic pixels, allowing for wide retinal coverage and high-resolution stimulation. Single-pixel illumination reproducibly induced network-mediated responses from retinal ganglion cells at safe irradiance levels. Furthermore, POLYRETINA allowed response discrimination with a high spatial resolution equivalent to the pixel pitch (120 µm) thanks to the network-mediated stimulation mechanism. This approach could allow mid-peripheral artificial vision in patients with retinitis pigmentosa.

scholarly journals Early Feasibility Study of a Neurostimulator to Create Artificial Vision

Neurosurgery ◽  
2019 ◽  
Vol 66 (Supplement_1) ◽  
Author(s):  
Nader Pouratian ◽  
Daniel Yoshor ◽  
Soroush Niketeghad ◽  
Jessy Dornm ◽  
Robert Greenberg
Keyword(s):  
Video Processing ◽  
Visual Information ◽  
Electrode Array ◽  
Video Camera ◽  
Artificial Vision ◽  
Processing Unit ◽  
New Device ◽  
Pediatric Glaucoma ◽  
Functional Vision ◽  
And Performance

Abstract INTRODUCTION Stimulation of human visual cortex is known to elicit visual perceptions that could potentially be used for creating artificial vision. The Orion Visual Cortical Prosthesis is a new device that is intended to restore some functional vision to blind patients. METHODS The device comprises an implant (consisting of an electronics package, receiving antenna, and an electrode array with 60 electrodes); glasses with a video camera; and a video processing unit (VPU). The camera collects real-time visual information, which is then processed by the VPU and converted to stimulation patterns sent to electrode array. The electronics are skull mounted with the subdural array implanted through a posterior interhemispheric approach. This is a 5-yr study of subjects who are bilaterally blind with bare light or no light perception due to non-cortical etiology. RESULTS A total of 6 subjects have been implanted in 2 centers. As of May 1, 2019, average implant duration was 11.1 mo (range 3.4-15.0 mo). Average age at time of implant was 50.3 yr. Cause of blindness included trauma (2), pediatric glaucoma (2), optic neuropathy (1), and endophthalmitis (1). One serious adverse device event (seizure) has been reported. Average thresholds ranged from 1.6 to 3.7 mA across the 6 subjects. At 6 mo postimplant, 3 of 5 subjects performed significantly better with the system on than off on a light localization task; 2 subjects performed better on a direction of motion task, and no subjects had measurable visual acuity. All 5 subjects were rated as receiving “positive” or “mild positive” benefit on a functional vision assessment. One-year adverse event and visual performance data for the first 5 subjects will be presented and compared to results from a commercially-available retinal prosthesis. CONCLUSION Safety and performance results of the first 5 subjects as of 6 mo postimplantation appear encouraging.

scholarly journals Epiretinal stimulation with local returns enhances selectivity at cellular resolution

2018 ◽  
Author(s):  
Victoria H. Fan ◽  
Lauren E. Grosberg ◽  
Sasidhar S. Madugula ◽  
Pawel Hottowy ◽  
Wladyslaw Dabrowski ◽  
...  
Keyword(s):  
Ganglion Cells ◽  
Electrode Array ◽  
Artificial Vision ◽  
Retinal Ganglion ◽  
Retinal Neurons ◽  
Cellular Resolution ◽  
Electrode Recording ◽  
Current Spread ◽  
Evoked Activity

AbstractObjectiveEpiretinal prostheses are designed to restore vision in people blinded by photoreceptor degenerative diseases, by directly activating retinal ganglion cells (RGCs) using an electrode array implanted on the retina. In present-day clinical devices, current spread from the stimulating electrode to a distant return electrode often results in the activation of many cells, potentially limiting the quality of artificial vision. In the laboratory, epiretinal activation of RGCs with cellular resolution has been demonstrated with small electrodes, but distant returns may still cause undesirable current spread. Here, the ability of local return stimulation to improve the selective activation of RGCs at cellular resolution was evaluated.ApproachA custom multi-electrode array (512 electrodes, 10 μm diameter, 60 μm pitch) was used to simultaneously stimulate and record from RGCs in isolated primate retina. Stimulation near the RGC soma with a single electrode and a distant return was compared to stimulation in which the return was provided by six neighboring electrodes.Main resultsLocal return stimulation enhanced the capability to activate cells near the central electrode (<30 μm) while avoiding cells farther away (>30 μm). This resulted in an improved ability to selectively activate ON and OFF cells, including cells encoding immediately adjacent regions in the visual field.SignificanceThese results suggest that a device that restricts the electric field through local returns could optimize activation of neurons at cellular resolution, improving the quality of artificial vision.Novelty & SignificanceThe effectiveness of local return stimulation for enhancing the electrical activation of retinal neurons was tested using high-density multi-electrode recording and stimulation in isolated macaque retina. The results suggest that local returns may reduce unwanted evoked activity and thus optimize the selectivity of stimulation at cellular resolution. Similar patterns could be implemented in a future high-resolution prosthesis to permit a more faithful replication of normal retinal activity for the treatment of incurable blindness.

scholarly journals Differential stimulation of the retina with glutamate toward a neurotransmitter-based retinal prosthesis

2016 ◽  
Author(s):  
Corey M. Rountree ◽  
Samsoon Inayat ◽  
John B. Troy ◽  
Laxman Saggere
Keyword(s):  
Visual Information ◽  
Ganglion Cells ◽  
Retinal Ganglion ◽  
Retinal Prostheses ◽  
Retinal Stimulation ◽  
Stimulation Parameters ◽  
Normal Means ◽  
Retinal Pathways ◽  
Pulsatile Delivery ◽  
Stimulation Of

ABSTRACTSubretinal 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 retinal stimulation study exploiting the inner retinal pathways exists. 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. We show that controlled pulsatile delivery of glutamate into the subsurface of explanted wild-type rat retinas elicits highly localized simultaneous inhibitory and excitatory spike rate responses in OFF and ON RGCs. We also present the spatiotemporal characteristics of RGC responses to subretinally injected glutamate and the therapeutic stimulation parameters. Our findings could pave the way for future development of a neurotransmitter-based subretinal prosthesis offering more naturalistic vision and better visual acuity than electrical prostheses.

scholarly journals Changes in thalamocortical connectivity as a potential mechanism of cross-modal plasticity in congenitally blind individuals

2018 ◽  
Author(s):  
Theo Marins ◽  
Maite Russo ◽  
Erika Rodrigues ◽  
jorge Moll ◽  
Daniel Felix ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Cortical Thickness ◽  
Visual Information ◽  
Brain Plasticity ◽  
Temporal Cortex ◽  
Occipital Cortex ◽  
Brain Structures ◽  
Congenitally Blind ◽  
Blind Individuals ◽  
Neuroimaging Techniques

ABSTRACTEvidence of cross-modal plasticity in blind individuals has been reported over the past decades showing that non-visual information is carried and processed by classical “visual” brain structures. This feature of the blind brain makes it a pivotal model to explore the limits and mechanisms of brain plasticity. However, despite recent efforts, the structural underpinnings that could explain cross-modal plasticity in congenitally blind individuals remain unclear. Using advanced neuroimaging techniques, we mapped the thalamocortical connectivity and assessed cortical thickness and integrity of white matter of congenitally blind individuals and sighted controls to test the hypothesis that aberrant thalamocortical pattern of connectivity can pave the way for cross-modal plasticity. We described a direct occipital takeover by the temporal projections from the thalamus, which would carry non-visual information (e.g. auditory) to the visual cortex in congenitally blinds. In addition, the amount of thalamo-occipital connectivity correlated with the cortical thickness of primary visual cortex (V1), supporting a probably common (or related) reorganization phenomena. Our results suggest that aberrant thalamocortical connectivity as one possible mechanism of cross-modal plasticity in blinds, with potential impact on cortical thickness of V1.SIGNIFICANT STATEMENTCongenitally blind individuals often develop greater abilities on spared sensory modalities, such as increased acuity in auditory discrimination and voice recognition, when compared to sighted controls. These functional gains have been shown to rely on ‘visual’ cortical areas of the blind brain, characterizing the phenomenon of cross-modal plasticity. However, its anatomical underpinnings in humans have been unsuccessfully pursued for decades. Recent advances of non-invasive neuroimaging techniques allowed us to test the hypothesis of abnormal thalamocortical connectivity in congenitally blinds. Our results showed an expansion of the thalamic connections to the temporal cortex over those that project to the occipital cortex, which may explain, the cross-talk between the visual and auditory systems in congenitally blind individuals.

Biocompatibility of polyimide microelectrode array for retinal stimulation

2004 ◽  
Vol 24 (1-2) ◽  
pp. 185-189 ◽  
Author(s):  
Jong-Mo Seo ◽  
Sung June Kim ◽  
Hum Chung ◽  
Eui Tae Kim ◽  
Hyeong Gon Yu ◽  
...  
Keyword(s):  
Microelectrode Array ◽  
Retinal Stimulation

Electric Field-Assisted Positioning of Neurons on Pt Microelectrode Arrays

2003 ◽  
Vol 773 ◽  
Author(s):  
Shalini Prasad ◽  
Mo Yang ◽  
Xuan Zhang ◽  
Yingchun Ni ◽  
Vladimir Parpura ◽  
...  
Keyword(s):  
Electric Field ◽  
Electrical Activity ◽  
Electric Fields ◽  
Microelectrode Array ◽  
Electrode Array ◽  
Sprague Dawley ◽  
A Cell ◽  
Neuron Patterning

AbstractCharacterization of electrical activity of individual neurons is the fundamental step in understanding the functioning of the nervous system. Single cell electrical activity at various stages of cell development is essential to accurately determine in in-vivo conditions the position of a cell based on the procured electrical activity. Understanding memory formation and development translates to changes in the electrical activity of individual neurons. Hence, there is an enormous need to develop novel ways for isolating and positioning individual neurons over single recording sites. To this end, we used a 3x3 multiple microelectrode array system to spatially arrange neurons by applying a gradient AC field. We characterized the electric field distribution inside our test platform by using two dimensiona l finite element modeling (FEM) and determined the location of neurons over the electrode array. Dielectrophoretic AC fields were utilized to separate the neurons from the glial cells and to position the neurons over the electrodes. The neurons were obtained from 0-2-day-old rat (Sprague-Dawley) pups. The technique of using electric fields to achieve single neuron patterning has implications in neural engineering, elucidating a new and simpler method to develop and study neuronal activity as compared to conventional microelectrode array techniques.

Design of a Prototype for Vision Prosthesis

2018 ◽  
Vol 7 (2) ◽  
pp. 1-13
Author(s):  
V. Bhujanga Rao ◽  
P. Seetharamaiah ◽  
Nukapeyi Sharmili
Keyword(s):  
Visual Information ◽  
Ganglion Cells ◽  
Electrode Array ◽  
Laboratory Model ◽  
Electric Pulses ◽  
Embedded Computer ◽  
Field Of Vision ◽  
Led Array ◽  
Electrical Pulses ◽  
Computer Based

This article describes how the field of vision prostheses is currently being developed around the world to restore useful vision for people suffering from retinal degenerative diseases. The vision prosthesis system (VPS) maps visual images to electrical pulses and stimulates the surviving healthy parts in the retina of the eye, i.e. ganglion cells, using electric pulses applied through an electrode array. The retinal neurons send visual information to the brain. This article presents the design of a prototype vision prosthesis system which converts images/video into biphasic electric stimulation pulses for the excitation of electrodes simulated by an LED array. The proposed prototype laboratory model has been developed for the design of flexible high-resolution 1024-electrode VPS, using an embedded computer-based efficient control algorithm for better visual prediction. The prototype design for the VPS is verified visually through a video display on an LCD/LED array. The experimental results of VPS are enumerated for the test objects, such as, palm, human face and large font characters. The results were found to be satisfactory.

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