Towards photosensor movement-adaptive image analysis in an electronic retinal prosthesis
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By way of extracellular, stimulating electrodes, electronic vision prosthesis aims to render discrete light spots - so-called phosphenes - in the visual field, thereby providing a phosphene image serving as a rudimentary remediation of profound blindness. It is proposed that a digital camera, or some other photosensitive array, captures frames, the frames be analyzed, and phosphenes be actuated accordingly. We present a numerical experiment wherein we observed the phosphene image in response to a set of stimuli for various image analysis schemes. We used the mutual-information function to quantify the efficacy of analysis schemes; the function penalizes a scheme for introducing redundancy to the phosphene image, while accounting for the probability of each stimulus. We demonstrate an effective scheme involving Laplacian of Gaussian (/spl nabla/2G) kernels geometrically transformed in accordance with phosphene layout. Further, we propose adapting the kernels comprising a scheme in accordance with photosensor movement.Keywords:
Phosphene
Retinal Prosthesis
Blob detection
By way of extracellular, stimulating electrodes, electronic vision prosthesis aims to render discrete light spots - so-called phosphenes - in the visual field, thereby providing a phosphene image serving as a rudimentary remediation of profound blindness. It is proposed that a digital camera, or some other photosensitive array, captures frames, the frames be analyzed, and phosphenes be actuated accordingly. We present a numerical experiment wherein we observed the phosphene image in response to a set of stimuli for various image analysis schemes. We used the mutual-information function to quantify the efficacy of analysis schemes; the function penalizes a scheme for introducing redundancy to the phosphene image, while accounting for the probability of each stimulus. We demonstrate an effective scheme involving Laplacian of Gaussian (/spl nabla/2G) kernels geometrically transformed in accordance with phosphene layout. Further, we propose adapting the kernels comprising a scheme in accordance with photosensor movement.
Phosphene
Retinal Prosthesis
Blob detection
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A retinal prosthesis capable of restoring face recognition, reading, and mobility to blind patients is within the capability of microsystems technology. Electrode arrays can be made dense enough to be able to place thousands of pixels into the macula. Electrode materials can supply safe and effective stimulus current. This review examines some prior work in electrical stimulation of the retina and simulations of phosphene-based vision as a basis to produce design constraints for a biomimetic retinal-stimulating array. An array is designed considering the needs of the end users (blind individuals), the biology of diseased retina, and the limits of electrode technology. Other technology to support the system such as high-density stimulus generation circuitry and hermetic packaging face significant challenges but solutions can likely be realized to some degree.
Phosphene
Retinal Prosthesis
Electrode array
Retinal implant
Visual prosthesis
Microsystem
Stimulus (psychology)
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Phosphene
Retinal Prosthesis
Visual prosthesis
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Clinical trials have shown different irregular characteristics of phosphene maps can be elicited by retinal prostheses. This study investigated the effect of distortion and dropout percentage on two novel eye-hand coordination tasks. 16 volunteers participated in two tasks on a touch screen: drawing geometric shapes and writing Chinese characters. The accuracy and efficiency in both tasks were recorded and compared while one irregular characteristic was changed. Results show that the accuracy and efficiency of both tasks decrease as the variability of distortion and dropout percentage increase, which may provide theoretical and practical significance for the clinical research on retinal prostheses.
Phosphene
Visual prosthesis
Retinal Prosthesis
Distortion (music)
Dropout (neural networks)
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By way of extracellular, electrical stimulation of the visual pathway, the various approaches to vision prosthesis aim to provide crude, patterned vision to individuals with profound blindness. Common to all approaches is the implantable electrode array and the rendering of phosphenes-the actuated percepts occupying the visual field of the implantee. Thus prosthetic vision may be simulated, and underlying theories as to how to render it efficacious developed. We review the field of simulated prosthetic vision. Furthermore, with retinal prosthesis in mind, we suggest a revised approach-an approach with regard to sampling theory, the vertebrate central visual pathway, and eye movements. The parallel development of prosthetic vision theory, explored via simulation and bioengineering issues surrounding neurostimulator design and implantation has bearing on the success of clinical trials by numerous groups in coming years.
Phosphene
Retinal Prosthesis
Visual prosthesis
Retinal implant
Electrode array
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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. During this study a 55 year old patient implanted with the Argus II system on August 2015 was tested with single electrode stimulation and pattern stimulation experiments. Tasks were performed using Argus II normal parameters.
Retinal Prosthesis
Phosphene
Visual prosthesis
Argus
Stimulus (psychology)
Streak
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Researchers in the field of visual prostheses need a Simulated Prosthetic Vision (SPV) setup to evaluate their image processing algorithms on people with normal vision before implanting any retinal prostheses. In this paper, an SPV developed for a visual prosthesis is introduced and the associated experimental results are reported. These experiments are designed to examine the efficacy of two down sampling methods, the mode down sampling (MDS) and the nearest neighbor method. The experiments are conducted in a corridor including some obstacles. Three levels of difficulties are considered for each of the two methods and two measures are used to compare the efficiency of the methods: Percentage of Preferred Walking Speed (PPWS), and Total Hit Count (THC). The qualitative and quantitative results reported in this paper reveal that the controlled blinking of phosphenes would present additional information to help the patients.
Phosphene
Retinal Prosthesis
Visual prosthesis
Feature (linguistics)
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Phosphene
Visual prosthesis
Retinal Prosthesis
Ocular prosthesis
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The first deaf-blind patient in Russia with Argus II retinal prosthesis system: what he sees and why
In this study, we propose a new method for evaluating the functional results based on the sizes of phosphenes that the patient drew which were then digitalized. We also describe the methodology of psychological testing and support for a deaf-blind patient.A 59-year-old man with retinitis pigmentosa and hearing loss (clinical Usher syndrome) underwent surgery to implant the Argus II retinal prosthesis system in his right eye.Correlation analysis showed a weak dependency between the size of a phosphene and the perceptual threshold. Significant correlations between a phosphene and the height of the interface, impedance or retinal thickness was not found. The patient with the retinal prosthesis felt more independent and confident, and more healthy. This is the first case of retinal implant surgery in Russia.The results of this study add to the understanding in the field of retinal implants functioning. The experience of the successful rehabilitation of the deaf-blind patient after implantation of Argus II allowed us to design a methodology that can be used in future similar cases.
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Argus
Visual prosthesis
Retinal implant
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A retinal prosthesis is one of the candidate technologies to help blind patients regain their vision. Electrical stimulation of the retinal cells evokes a visual sensation such as phosphene. We have proposed retinal stimulators using a smart electrode embedded with CMOS microchips. A large-scale array, which is required for high-resolution restoration of vision, can be achieved using the smart electrode. Because CMOS microchips have a multiplexer function, many smart electrodes can be controlled using a few wires. Stimulus current generators are also integrated into the microchips to realize electrical stimulation without an external stimulator. We have demonstrated prototypes based on the smart electrode architecture. A high-density electrode array was fabricated using built-in CMOS microchips that were embedded in stimulus electrodes. The prototype was implanted into an extracted eyeball, and functional validation was performed.
Phosphene
Retinal Prosthesis
Visual prosthesis
Electrode array
Neural Prosthesis
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