Pre-processing visual scenes for retinal prosthesis systems: A comprehensive review.

BACKGROUND: Retinal prostheses offer hope for individuals with degenerative retinal diseases by stimulating the remaining retinal cells to partially restore their vision. This review delves into the current advancements in retinal prosthesis technology, with a special emphasis on the pivotal role that image processing and machine learning techniques play in this evolution. METHODS: We provide a comprehensive analysis of the existing implantable devices and optogenetic strategies, delineating their advantages, limitations, and challenges in addressing complex visual tasks. The review extends to various image processing algorithms and deep learning architectures that have been implemented to enhance the functionality of retinal prosthetic devices. We also illustrate the testing results by demonstrating the clinical trials or using Simulated Prosthetic Vision (SPV) through phosphene simulations, which is a critical aspect of simulating visual perception for retinal prosthesis users. RESULTS: Our review highlights the significant progress in retinal prosthesis technology, particularly its capacity to augment visual perception among the visually impaired. It discusses the integration between image processing and deep learning, illustrating their impact on individual interactions and navigations within the environment through applying clinical trials and also illustrating the limitations of some techniques to be used with current devices, as some approaches only use simulation even on sighted-normal individuals or rely on qualitative analysis, where some consider realistic perception models and others do not. CONCLUSION: This interdisciplinary field holds promise for the future of retinal prostheses, with the potential to significantly enhance the quality of life for individuals with retinal prostheses. Future research directions should pivot towards optimizing phosphene simulations for SPV approaches, considering the distorted and confusing nature of phosphene perception, thereby enriching the visual perception provided by these prosthetic devices. This endeavor will not only improve navigational independence but also facilitate a more immersive interaction with the environment.

A virtual patient simulation modeling the neural and perceptual effects of human visual cortical stimulation, from pulse trains to percepts.

The field of cortical sight restoration prostheses is making rapid progress with three clinical trials of visual cortical prostheses underway. However, as yet, we have only limited insight into the perceptual experiences produced by these implants. Here we describe a computational model or 'virtual patient', based on the neurophysiological architecture of V1, which successfully predicts the perceptual experience of participants across a wide range of previously published human cortical stimulation studies describing the location, size, brightness and spatiotemporal shape of electrically induced percepts in humans. Our simulations suggest that, in the foreseeable future the perceptual quality of cortical prosthetic devices is likely to be limited by the neurophysiological organization of visual cortex, rather than engineering constraints.

Application of Silicone in Ophthalmology: A Review.

This paper reviews the latest trends and applications of silicone in ophthalmology, especially related to intraocular lenses (IOLs). Silicone, or siloxane elastomer, as a synthetic polymer, has excellent biocompatibility, high chemical inertness, and hydrophobicity, enabling wide biomedical applications. The physicochemical properties of silicone are reviewed. A review of methods for mechanical and in vivo characterization of IOLs is presented as a prospective research area, since there are only a few available technologies, even though these properties are vital to ensure medical safety and suitability for clinical use, especially if long-term function is considered. IOLs represent permanent implants to replace the natural lens or for correcting vision, with the first commercial foldable lens made of silicone. Biological aspects of posterior capsular opacification have been reviewed, including the effects of the implanted silicone IOL. However, certain issues with silicone IOLs are still challenging and some conditions can prevent its application in all patients. The latest trends in nanotechnology solutions have been reviewed. Surface modifications of silicone IOLs are an efficient approach to further improve biocompatibility or to enable drug-eluting function. Different surface modifications, including coatings, can provide long-term treatments for various medical conditions or medical diagnoses through the incorporation of sensory functions. It is essential that IOL optical characteristics remain unchanged in case of drug incorporation and the application of nanoparticles can enable it. However, clinical trials related to these advanced technologies are still missing, thus preventing their clinical applications at this moment.

Enhancing emotional expression in cat-like robots: strategies for utilizing tail movements with human-like gazes.

In recent years, there has been a significant growth in research on emotion expression in the field of human-robot interaction. In the process of human-robot interaction, the effect of the robot's emotional expression determines the user's experience and acceptance. Gaze is widely accepted as an important media to express emotions in human-human interaction. But it has been found that users have difficulty in effectively recognizing emotions such as happiness and anger expressed by animaloid robots that use eye contact individually. In addition, in real interaction, effective nonverbal expression includes not only eye contact but also physical expression. However, current animaloid social robots consider human-like eyes as the main emotion expression pathway, which results in a dysfunctional robot appearance and behavioral approach, affecting the quality of emotional expression. Based on retaining the effectiveness of eyes for emotional communication, we added a mechanical tail as a physical expression to enhance the robot's emotional expression in concert with the eyes. The results show that the collaboration between the mechanical tail and the bionic eye enhances emotional expression in all four emotions. Further more, we found that the mechanical tail can enhance the expression of specific emotions with different parameters. The above study is conducive to enhancing the robot's emotional expression ability in human-robot interaction and improving the user's interaction experience.

Do we react differently toward bionic devices vs. cochlear implants and wheelchairs? Possible links with personality traits.

The present study explored the attitudes toward individuals with bionic eyes and limbs, cochlear implants, and people with disabilities that imply using a wheelchair. Our sample consisted of 474 Romanian adults aged 18-61 (M = 27.56, SD = 11.80). Participants were randomly divided into five groups. They all filled scales related to personality characteristics, i.e., agreeableness, neuroticism, openness to experience, comprehension/intellectual efficiency, and previous contact with disability. Then, each group was presented with a vignette describing a character (wheelchair/bionic eye/bionic leg/cochlear implant/control group). Finally, they answered questions about their emotions, cognitions, and behaviors related to that context. Overall, our results suggested that higher agreeability, extraversion, openness to experience, intellectual complexity, and lower neuroticism were generally associated with more positive attitudes toward disability. When examining the differences in participants' emotions, cognitions, and behaviors depending on the target's characteristics, our results generally suggested that the most negative reactions were toward the character with a bionic eye. We discuss these findings considering their importance for shaping positive attitudes related to disability, especially related to the future technological advances in bionic devices.

Quantifying visual acuity for pre-clinical testing of visual prostheses.

Objective.Visual prostheses currently restore only limited vision. More research and pre-clinical work are required to improve the devices and stimulation strategies that are used to induce neural activity that results in visual perception. Evaluation of candidate strategies and devices requires an objective way to convert measured and modelled patterns of neural activity into a quantitative measure of visual acuity.Approach.This study presents an approach that compares evoked patterns of neural activation with target and reference patterns. A d-prime measure of discriminability determines whether the evoked neural activation pattern is sufficient to discriminate between the target and reference patterns and thus provides a quantified level of visual perception in the clinical Snellen and MAR scales. The magnitude of the resulting value was demonstrated using scaled standardized 'C' and 'E' optotypes.Main results.The approach was used to assess the visual acuity provided by two alternative stimulation strategies applied to simulated retinal implants with different electrode pitch configurations and differently sized spreads of neural activity. It was found that when there is substantial overlap in neural activity generated by different electrodes, an estimate of acuity based only upon electrode pitch is incorrect; our proposed method gives an accurate result in both circumstances.Significance.Quantification of visual acuity using this approach in pre-clinical development will allow for more rapid and accurate prototyping of improved devices and neural stimulation strategies.

[Modern concepts of bionic vision]. / Sovremennye kontseptsii bionicheskogo zreniya.

Loss of vision is a pressing medical and social problem leading to profound disability, loss of ability to work, serious alterations in the psycho-emotional state, and a decline of the quality of life. When conservative or surgical treatment can not help restore vision, the use of visual prosthesis - bionic eye - can be an effective solution. This review covers the main modern approaches to the development of visual prosthetic systems. Analysis of publications revealed that there are several main approaches to visual prosthesis differing primarily by the anatomical structure targeted for stimulation in order to activate visual sensations. The most significant among them are retinal prostheses, optic nerve stimulation, and cortical visual prostheses. Currently, retinal prostheses such as ARGUS II demonstrate the most successful results, since the stimulation of the surviving neural structures of the retina is a relatively easy task, but their field of application is limited to diseases associated with pathological changes in photoreceptors. The development of cortical visual prostheses is more difficult, but in the future they may allow using more stimulation channels to obtain a more detailed visual perception. In addition, cortical visual prostheses are universal, as they do not require preservation of any structures of the visual organ, only the primary visual cortex.

NEUROTRANSMISSION IN VISUAL ANALYZER AND BIONIC EYE. A REVIEW.

AIMS: The aim of the work is to point out the transmission of electrical voltage changes in the visual analyser and thus the efficiency of the bionic eye. MATERIAL AND METHODS: The review deals with the question of the transmission of electrical changes in visual path voltage under physiological and pathological conditions. In particular, it points to feedback autoregulatory damage not only of primarily altered cellular structures, but of all other, both horizontally and vertically localized. Based on the results of functional magnetic resonance imaging and electrophysiological methods, it shows the pathology of the entire visual pathway in three eye diseases: retinitis pigmentosa, age-related macular degeneration and glaucoma. RESULTS: The thesis also provides an overview of possible systems that are used to replace lost vision, from epiretinal, subretinal, suprachoroidal implants, through stimulation of the optic nerve, corpus geniculatum laterale to the visual cortex. CONCLUSION: Due to the pathology of neurotransmission, bionic eye systems cannot be expected to be restored after stabilization of binocular functions.

Neural activity shaping utilizing a partitioned target pattern.

Electrical stimulation of neural tissue is used in both clinical and experimental devices to evoke a desired spatiotemporal pattern of neural activity. These devices induce a local field that drives neural activation, referred to as an activating function or generator signal. In visual prostheses, the spread of generator signal from each electrode within the neural tissue results in a spread of visual perception, referred to as a phosphene.Objective.In cases where neighbouring phosphenes overlap, it is desirable to use current steering or neural activity shaping strategies to manipulate the generator signal between the electrodes to provide greater control over the total pattern of neural activity. Applying opposite generator signal polarities in neighbouring regions of the retina forces the generator signal to pass through zero at an intermediate point, thus inducing low neural activity that may be perceived as a high-contrast line. This approach provides a form of high contrast visual perception, but it requires partitioning of the target pattern into those regions that use positive or negative generator signals. This discrete optimization is an NP-hard problem that is subject to being trapped in detrimental local minima.Approach.This investigation proposes a new partitioning method using image segmentation to determine the most beneficial positive and negative generator signal regions. Utilizing a database of 1000 natural images, the method is compared to alternative approaches based upon the mean squared error of the outcome.Main results.Under nominal conditions and with a set computation limit, partitioning provided improvement for 32% of these images. This percentage increased to 89% when utilizing image pre-processing to emphasize perceptual features of the images. The percentage of images that were dealt with most effectively with image segmentation increased as lower computation limits were imposed on the algorithms.Significance.These results provide a new method to increase the resolution of neural stimulating arrays and thus improve the experience of visual prosthesis users.

[Bionic eye prostheses as a means of rehabilitation in case of the loss of both eyes]. / Bionicheskie glaznye protezy kak sredstvo reabilitatsii pri potere oboikh glaznykh yablok.

Currently, there are no effectively working devices for self-orientation of the blind (including those who have lost their eyes anatomically). PURPOSE: To develop a device for helping people with no eyes orient themselves by analyzing the brightness of the light surrounding the user and recording the preserved activity of the oculomotor muscles. MATERIAL AND METHODS: The described device is intended for environmental orientation of blind people who have lost both eye organs anatomically. It consists of the following elements: 1) a video camera with glasses and an information analysis unit (computer with transmitting devices); 2) an eye prosthesis in which microcircuits and a power source are sealed. The user receives the information received by the video camera and the correspondingly processed information by supplying short-term electrical pulses from the electrodes situated on the back surface of the prosthesis. RESULTS: In laboratory conditions, the devices allowed registration of - as example - the direction of a light source coming from the window in a room or a passing car. CONCLUSION: The device will become available for intended usage after carrying out all the prescribed tests and registering in accordance with the established procedures.

Bionic eye review - An update.

PURPOSE: To date, reviews of bionic eye have concentrated on implants which were used in human trials in the developed countries. This is the main restriction of this systematic review examines, however this review discusses worldwide advances in retinal prosthetic research, assesses engineering features and clinical progress of recent implant trials, and identifies potential future research areas in the field of bionic implants. METHODS: A literature review searching PubMed, Google Scholar, and IEEExplore was performed using the PRISMA Guidelines for Systematic Review. We included peer-reviewed papers in the review which demonstrated progress in human or animal trials and papers with described innovative bionic eye engineering design. For each trial, a characteristic of the device, engineering solution, and latest clinical outcomes were presented. RESULTS: Eleven prosthetic projects fulfilled met our inclusion criteria and were ordered by stimulation location. Four have recently finished human trials, three are having conducted multi- or singlecenter human trials, and three are in preclinical animal testing stage. FDA has approved Argus II (FDA 2013, CE 2011); the Alpha-IMS (CE 2013) has been approved and obtained BCVA with Landolt-C test has taken into a multicenter clinical research. New approaches will be presented using alternating magnetic fields, low-intensity focused ultrasounds, optogenetics, implementing ionic gradients across neural cell membranes or influencing neurotransmitter levels will be presented in the review. CONCLUSION: Several bionic eye have successfully achieved visual perception in animals and/or humans. However, many things need to be improved and engineering difficulties are to be resolved before bionic eye will be capable of fully and safely bring back vision functions. New approaches could improve medical outcome of future bionic eye.

Neuroplasticity in adult human visual cortex.

Between 1-5:100 people worldwide have never experienced normotypic vision due to a condition called amblyopia, and about 1:4000 suffer from inherited retinal dystrophies that progressively lead to blindness. While a wide range of technologies and therapies are being developed to restore vision, a fundamental question still remains unanswered: would the adult visual brain retain a sufficient plastic potential to learn how to 'see' after a prolonged period of abnormal visual experience? In this review we summarize studies showing that the visual brain of sighted adults retains a type of developmental plasticity, called homeostatic plasticity, and this property has been recently exploited successfully for adult amblyopia recovery. Next, we discuss how the brain circuits reorganize when blindness occurs and when visual stimulation is partially restored by means of a 'bionic eye' in late blind adults with Retinitis Pigmentosa. The primary visual cortex in these patients slowly became activated by the artificial visual stimulation, indicating that sight restoration therapies can rely on a considerable degree of spared plasticity in adulthood.

Retinal Prostheses and Artificial Vision

In outer retinal degenerative diseases such as retinitis pigmentosa, choroideremia, and geographic atrophy, 30% of the ganglion cell layer in the macula remains intact. With subretinal and epiretinal prostheses, these inner retinal cells are stimulated with controlled electrical current by either a microphotodiode placed in the subretinal area or a microelectrode array tacked to the epiretinal region. As the patient learns to interpret the resulting phosphene patterns created in the brain through special rehabilitation exercises, their orientation, mobility, and quality of life increase. Implants that stimulate the lateral geniculate nucleus or visual cortex are currently being studied for diseases in which the ganglion cells and optic nerve are completely destroyed.

Psychosocial assessment of potential retinal prosthesis trial participants.

BACKGROUND: As the field of retinal prostheses advances, volunteers are required for device trials, and optimal participant recruitment is vital for intervention success. The aims of this study were: (i) to select tests that assess the psychosocial aspects of visual impairment and develop a psychosocial assessment protocol for persons who may be eligible for participation in retinal prostheses trials; (ii) to investigate correlations between these tests; and (iii) to determine associations between psychosocial factors and a person's interest in participating in a retinal prosthesis (bionic eye) trial. METHODS: Cross-sectional study of 72 adults with advanced retinal degeneration. Questionnaire assessments included personality, cognitive ability, social-support, self-efficacy, coping, optimism, depression, and quality of life (Impact of Vision Impairment Profile ([IVI], and Vision and Quality of Life Index [VisQoL]). Level of interest in a retinal prosthesis was also evaluated. RESULTS: All questionnaires were completed without floor or ceiling effects and with minimal respondent burden. Depression correlated with decreased quality of life (rho = -0.37 and 0.40, p < 0.001 for IVI and VisQoL, respectively). Together, depression, gender and vision-specific coping explained 35.2 per cent of variance in IVI quality of life (p < 0.001). Forty-nine per cent of participants were interested in a retinal prosthesis now and 77 per cent in the future. Although the personality trait of 'openness' was somewhat predictive of interest in retinal prostheses (odds ratio 0.78, 95% CI 0.62-0.97), neither severity of vision impairment nor any of the psychosocial measures were strong predictors. CONCLUSIONS: Several existing psychosocial questionnaires can be used for patients with advanced retinal degeneration and may be useful in exploring suitability for a retinal prosthesis or evaluating outcomes. However, the questionnaires used in this study were not good predictors of whether or not a person might be interested in a retinal prosthesis.

[Modern approaches to the retinitis pigmentosa treatment in the older age patients (literature review).]

Retinitis pigmentosa is a hereditary degenerative retina disease, often severe and affecting the retinal pigment epithelium and photoreceptor layer. For the older age group, the disease is increased by the addition of age-related degenerative processes in the retina. Due to the diversity of development factors and forms of retinitis pigmentosa, there is no uniform concept for treating a disease. Applying gene therapy and the optogenetic method is currently impossible because they are at the stage of experimental studies. For patients with terminal stage of retinitis pigmentosa, the implantation of a bionic eye is possible - a device with the ability to restore residual vision. The main treatment method is therapeutic. There were a lot of experimental and clinical studies of various drugs, the efficiency of which varies. Peptide bioregulators are actively used, they support the structural and functional homeostasis of cell populations and have a retinoprotective effect. It is also particularly important to improve the somatic condition of the patient through the use of peptide drugs in the complex.

Paradigm shifts, peregrinations and pixies in ophthalmology.

Human ingenuity is challenged by defending vision, our highest bandwidth sense. Special challenges are presented by the replacement or repair of highly specialized but scarce tissue within the constraints of transparency, tissue shape and alignment, tissue borders and pressure maintenance. Many, mostly destructive, surgical procedures were developed prior to an understanding of underlying pathophysiology. For a number of conditions, both reconstructive and destructive procedures co-exist, yet there are few guidelines as to the better approach. Because the consequences of these procedures may take many years to surface (consistent with a stem cell role in long-term tissue maintenance), guidance may be provided by the elucidation of underlying principles from these approaches. Illustrative examples from clinical, basic research and biotechnology, particularly relating to pterygium, ocular surface squamous neoplasia, dry-eye syndrome, corneal rehabilitation and replacement, cataract surgery, strabismus surgery and bionic eye research, are described. An unexpected consequence of bionic device development has been an appreciation of the sophistication of tissues being replaced, given the limitations of available biomaterials. Examples of how this has provided insights into ocular disease will be illustrated. Stem cell and biomaterial technologies are starting to impact at a time when cost-effectiveness is under scrutiny. Both efficacy and cost will need to be considered as these interventions are introduced. It appears that the paradigm shift rate is accelerating and there is evidence of this in ophthalmology. Lessons learned from the areas of destructive versus reconstructive surgery and the limitations of development of bionic replacements will be used to illustrate how new procedures and technologies can be developed.

Advances in Retinal Prosthetic Research: A Systematic Review of Engineering and Clinical Characteristics of Current Prosthetic Initiatives.

PURPOSE: To date, reviews of retinal prostheses have focused primarily on devices undergoing human trials in the Western Hemisphere and fail to capture significant advances in materials and engineering research in countries such as Japan and Korea, as well as projects in early stages of development. To address these gaps, this systematic review examines worldwide advances in retinal prosthetic research, evaluates engineering characteristics and clinical progress of contemporary device initiatives, and identifies potential directions for future research in the field of retinal prosthetics. METHODS: A literature search using PubMed, Google Scholar, and IEEExplore was conducted following the PRISMA Guidelines for Systematic Review. Inclusion criteria were peer-reviewed papers demonstrating progress in human or animal trials and papers discussing the prosthetic engineering design. For each initiative, a description of the device, its engineering considerations, and recent clinical results were provided. RESULTS: Ten prosthetic initiatives met our inclusion criteria and were organized by stimulation location. Of these initiatives, four have recently completed human trials, three are undergoing multi- or single-center human trials, and three are undergoing preclinical animal testing. Only the Argus II (FDA 2013, CE 2011) has obtained FDA approval for use in the United States; the Alpha-IMS (CE 2013) has achieved the highest visual acuity using a Landolt-C test to date and is the only device presently undergoing a multicenter clinical trial. CONCLUSION: Several distinct approaches to retinal stimulation have been successful in eliciting visual precepts in animals and/or humans. However, many clinical needs are still not met and engineering challenges must be addressed before a retinal prosthesis with the capability to fully and safely restore functional vision can be realized.

The potential of the second sight system bionic eye implant for partial sight restoration.

INTRODUCTION: Second Sight System bionic eye implant, a commercially available visual prosthesis developed by Second Sight Medical Products, has been implanted in over 125 patients with outer retinal dystrophies such as retinitis pigmentosa. The system has gained regulatory approval in both the USA and Europe, and aims to restore vision by electrical stimulation of the nerve cells of the inner retina. AREAS COVERED: In this review, we present the safety profile of this implant from the international clinical trial and discuss the nature and levels of improvement in visual function achieved by patients implanted with the system. Expert commentary: Future developments for the system will be explored following the discussion of the current usefulness of the device, its limitation as and the areas in which further development is necessary.

Progress in the clinical development and utilization of vision prostheses: an update.

Vision prostheses, or "bionic eyes", are implantable medical bionic devices with the potential to restore rudimentary sight to people with profound vision loss or blindness. In the past two decades, this field has rapidly progressed, and there are now two commercially available retinal prostheses in the US and Europe, and a number of next-generation devices in development. This review provides an update on the development of these devices and a discussion on the future directions for the field.

Development of a Magnetic Attachment Method for Bionic Eye Applications.

Successful visual prostheses require stable, long-term attachment. Epiretinal prostheses, in particular, require attachment methods to fix the prosthesis onto the retina. The most common method is fixation with a retinal tack; however, tacks cause retinal trauma, and surgical proficiency is important to ensure optimal placement of the prosthesis near the macula. Accordingly, alternate attachment methods are required. In this study, we detail a novel method of magnetic attachment for an epiretinal prosthesis using two prostheses components positioned on opposing sides of the retina. The magnetic attachment technique was piloted in a feline animal model (chronic, nonrecovery implantation). We also detail a new method to reliably control the magnet coupling force using heat. It was found that the force exerted upon the tissue that separates the two components could be minimized as the measured force is proportionately smaller at the working distance. We thus detail, for the first time, a surgical method using customized magnets to position and affix an epiretinal prosthesis on the retina. The position of the epiretinal prosthesis is reliable, and its location on the retina is accurately controlled by the placement of a secondary magnet in the suprachoroidal location. The electrode position above the retina is less than 50 microns at the center of the device, although there were pressure points seen at the two edges due to curvature misalignment. The degree of retinal compression found in this study was unacceptably high; nevertheless, the normal structure of the retina remained intact under the electrodes.