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.

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 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 Naturalistic spatiotemporal stimulus modulation during epiretinal stimulation increases the persistence of retinal ganglion cell responsivity

2020 ◽  
Author(s):  
Naïg Aurélia Ludmilla Chenais ◽  
Marta Jole Ildelfonsa Airaghi Leccardi ◽  
Diego Ghezzi
Keyword(s):  
Retinal Ganglion Cells ◽  
Ganglion Cells ◽  
Artificial Vision ◽  
Retinal Ganglion ◽  
Electric Pulses ◽  
Retinal Stimulation ◽  
Electrophysiological Recordings ◽  
Stimulus Modulation ◽  
Stimulation Of ◽  
Blind Patients

AbstractObjectiveRetinal stimulation in blind patients evokes the sensation of discrete points of light called phosphenes, which allows them performing visual guided tasks, such as orientation, navigation, object recognition, object manipulation and reading. However, the clinical benefit of artificial vision in profoundly blind patients is still tenuous, as several engineering and biophysical obstacles keep it away from natural perception. The relative preservation of the inner retinal neurons in hereditary degenerative retinal diseases, such as retinitis pigmentosa, supports artificial vision through the network-mediated stimulation of retinal ganglion cells. However, the response of retinal ganglion cells to repeated electrical stimulation rapidly declines, primarily because of the intrinsic desensitisation of their excitatory network. In patients, upon repetitive stimulation, phosphenes fade out in less than half of a second, which drastically limits the understanding of the percept.ApproachA more naturalistic stimulation strategy, based on spatiotemporal modulation of electric pulses, could overcome the desensitisation of retinal ganglion cells. To investigate this hypothesis, we performed network-mediated epiretinal stimulations paired to electrophysiological recordings in retinas explanted from both male and female retinal degeneration 10 mice.Main resultsThe results showed that the spatial and temporal modulation of the network-mediated epiretinal stimulation prolonged the responsivity of retinal ganglion cells from 400 ms up to 4.2 s.SignificanceA time-varied, non-stationary and interrupted stimulation of the retinal network, mimicking involuntary microsaccades, might reduce the fading of the visual percept and improve the clinical efficacy of retinal implants.

scholarly journals Virtual reality simulation of epi-retinal prosthetic vision highlights the relevance of the visual angle

2020 ◽  
Author(s):  
Jacob Thomas Thorn ◽  
Enrico Migliorini ◽  
Diego Ghezzi
Keyword(s):  
Virtual Reality ◽  
Visual Angle ◽  
Life Experience ◽  
Word Reading ◽  
Real Life ◽  
Retinal Prosthesis ◽  
Optimal Number ◽  
Artificial Vision ◽  
Retinal Prostheses ◽  
Blind Patients

AbstractObjectiveRetinal prostheses hold the potential to restore artificial vision in blind patients suffering from outer retinal dystrophies. The optimal number, density, and coverage of the electrodes that a retinal prosthesis should have to provide adequate artificial vision in daily activities is still an open question and an important design parameter needed to develop better implants.ApproachTo address this question, we investigated the interaction between the visual angle, the pixel number and the pixel density without being limited by a small electrode count, as in previous research reports. We implemented prosthetic vision in a virtual reality environment in order to simulate the real-life experience of using a retinal prosthesis. We designed four different tasks simulating: object recognition, word reading, perception of a descending step and crossing a street.Main resultsThe results of our study showed that in all the tasks the visual angle played the most significant role in improving the performance of the participant.SignificanceThe design of new retinal prostheses should take into account the relevance of the restored visual angle to provide a helpful and valuable visual aid to profoundly or totally blind patients.

Inflammatory Markers Associated With Diabetes Mellitus – Old and New Players

2020 ◽  
Vol 26 ◽  
Author(s):  
Emir Muzurović ◽  
Zoja Stanković ◽  
Zlata Kovačević ◽  
Benida Šahmanović Škrijelj ◽  
Dimitri P Mikhailidis
Keyword(s):  
Diabetes Mellitus ◽  
Inflammatory Markers ◽  
High Specificity ◽  
Future Directions ◽  
Effective Strategies ◽  
Advantages And Disadvantages ◽  
Type 2 Dm ◽  
Increased Risk ◽  
Made In

: Diabetes mellitus (DM) is a chronic and complex metabolic disorder, and also an important cause of cardiovascular (CV) diseases (CVDs). Subclinical inflammation, observed in patients with type 2 DM (T2DM), cannot be considered the sole or primary cause of T2DM in the absence of classical risk factors, but it represents an important mechanism that serves as a bridge between primary causes of T2DM and its manifestation. Progress has been made in the identification of effective strategies to prevent or delay the onset of T2DM. It is important to identify those at increased risk for DM by using specific biomarkers. Inflammatory markers correlate with insulin resistance (IR) and glycoregulation in patients with DM. Also, several inflammatory markers have been shown to be useful in assessing the risk of developing DM and its complications. However, the intertwining of pathophysiological processes and the not-quite-specificity of inflammatory markers for certain clinical entities limits their practical use. In this review we consider the advantages and disadvantages of various inflammatory biomarkers of DM that have been investigated to date as well as possible future directions. Key features of such biomarkers should be high specificity, non-invasiveness and cost-effectiveness.

Philippine Archaeology: Status and Prospects

1987 ◽  
Vol 18 (2) ◽  
pp. 235-249 ◽  
Author(s):  
Karl L. Hutterer
Keyword(s):  
Present Form ◽  
Historical Events ◽  
Research Practices ◽  
Future Directions ◽  
Historical Perspectives ◽  
Present Essay ◽  
History Of ◽  
Future Potential ◽  
Made In

The purpose of the present essay is not to present a history of Philippine archaeology; several preliminary attempts have been made in this regard which may be consulted. Rather, the aim of this paper is to pause for a moment and look across the landscape of Philippine archaeology to assess what has been accomplished to date, to ponder strength and weaknesses of the field at this time, and to consider future directions. Nevertheless, the shape of any landscape is the result of historical events and processes that need to be taken into account if we want to understand its present form and assess its future potential and development. Thus, it will be necessary to include in the following thoughts historical perspectives which will help to explain how and why certain concepts, methods and research practices arose in the context of Philippine archaeology and came to determine our picture of Philippine prehistory.

scholarly journals Molecular Transport Junctions: An Introduction

MRS Bulletin ◽  
2004 ◽  
Vol 29 (6) ◽  
pp. 376-384 ◽  
Author(s):  
Cherie R. Kagan ◽  
Mark A. Ratner
Keyword(s):  
Thin Film ◽  
Charge Transport ◽  
Single Molecule ◽  
Molecular Transport ◽  
Molecular Junction ◽  
Theoretical Understanding ◽  
Future Directions ◽  
Molecular Scale ◽  
Molecular Charge ◽  
Made In

AbstractThis issue of MRS Bulletin on molecular transport junctions highlights the current experimental and theoretical understanding of molecular charge transport and its extension to the rapidly growing areas of molecular and carbon nanotube electronics. This introduction will outline the progress that has been made in understanding the mechanisms of molecular junction transport and the challenges and future directions in exploring charge transport on the molecular scale. In spite of the substantial challenges, molecular charge transport is of great interest for its intrinsic importance to potential single-molecule electronic, thin-film electronic, and optoelectronic applications.

A Review of Measurement Equivalence in Organizational Research: What's Old, What's New, What's Next?

2021 ◽  
pp. 109442812110565
Author(s):  
Ajay V. Somaraju ◽  
Christopher D. Nye ◽  
Jeffrey Olenick
Keyword(s):  
Review Paper ◽  
Measurement Equivalence ◽  
Future Directions ◽  
Organizational Research ◽  
Potential Sources ◽  
Organizational Constructs ◽  
Organizational Literature ◽  
Over Time ◽  
Made In ◽  
Highly Cited

The study of measurement equivalence has important implications for organizational research. Nonequivalence across groups or over time can affect the results of a study and the conclusions that are drawn from it. As a result, the review paper by Vandenberg & Lance (2000) has been highly cited and has played an important role in understanding the measurement of organizational constructs. However, that paper is now 20 years old, and a number of advances have been made in the application and interpretation of measurement equivalence (ME) since its publication. Therefore, the goal of the present paper is to provide an updated review of ME techniques that describes recent advances in testing for ME and proposes a taxonomy of potential sources of nonequivalence. Finally, we articulate recommendations for applying these newer methods and consider future directions for measurement equivalence research in the organizational literature.

scholarly journals Sarcoma Immunotherapy: Past Approaches and Future Directions

Sarcoma ◽  
2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
S. P. D'Angelo ◽  
W. D. Tap ◽  
G. K. Schwartz ◽  
R. D. Carvajal
Keyword(s):  
Malignant Tumors ◽  
Therapeutic Option ◽  
Interleukin 2 ◽  
Hematologic Malignancies ◽  
Clinical Activity ◽  
Antigen Receptors ◽  
Curative Intent ◽  
Future Directions ◽  
Metastatic Setting ◽  
Made In

Sarcomas are heterogeneous malignant tumors of mesenchymal origin characterized by more than 100 distinct subtypes. Unfortunately, 25–50% of patients treated with initial curative intent will develop metastatic disease. In the metastatic setting, chemotherapy rarely leads to complete and durable responses; therefore, there is a dire need for more effective therapies. Exploring immunotherapeutic strategies may be warranted. In the past, agents that stimulate the immune system such as interferon and interleukin-2 have been explored and there has been evidence of some clinical activity in selected patients. In addition, many cancer vaccines have been explored with suggestion of benefit in some patients. Building on the advancements made in other solid tumors as well as a better understanding of cancer immunology provides hope for the development of new and exciting therapies in the treatment of sarcoma. There remains promise with immunologic checkpoint blockade antibodies. Further, building on the success of autologous cell transfer in hematologic malignancies, designing chimeric antigen receptors that target antigens that are over-expressed in sarcoma provides a great deal of optimism. Exploring these avenues has the potential to make immunotherapy a real therapeutic option in this orphan disease.

Sign in / Sign up

Export Citation Format

Share Document