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artificial retina

Atanu Ghosh, Len Zheleznyak, Antoine Barbot, HaeWon Jung, Geunyoung Yoon
In the presence of optical blur at the fovea, blur adaptation can improve visual acuity (VA) and perceived image quality over time. However, little is known regarding blur adaptation in the peripheral retina. Here, we examined neural adaptation to myopic defocus at the fovea and parafovea (10° temporal retina) in both emmetropes and myopes. During the 60-min adaptation period, subjects (3 emmetropes and 3 myopes) watched movies with +2 diopters of defocus blur through a 6-mm artificial pupil in two separate, counter balanced sessions for each retinal location...
November 8, 2016: Vision Research
Zhisong Lu, Jing Wang, Rui Li, Yan Qiao, Mengyao Zhou, Chang Ming Li
In the past few decades, tremendous effort has been dedicated to develop bacteriorhodopsin (bR)-based photo-electronic devices for generating a stationary photocurrent and further for use as a component of artificial retinas in constant illumination sensing. However, an IR-triggered stationary photocurrent with controllable amplitudes has never been realized to date. Herein, NaYF4:Yb,Er and NaYF4:Yb,Tm upconversion nanoparticles (UCNPs) with green and blue emissions, respectively, were synthesized and further incorporated with bR to build a bionanosystem...
October 26, 2016: Nanoscale
D G A B Oonincx, N Volk, J J E Diehl, J J A van Loon, G Belušič
Mating in the black soldier fly (BSF) is a visually mediated behaviour that under natural conditions occurs in full sunlight. Artificial light conditions promoting mating by BSF were designed based on the spectral characteristics of the compound eye retina. Electrophysiological measurements revealed that BSF ommatidia contained UV-, blue- and green-sensitive photoreceptor cells, allowing trichromatic vision. An illumination system for indoor breeding based on UV, blue and green LEDs was designed and its efficiency was compared with illumination by fluorescent tubes which have been successfully used to sustain a BSF colony for five years...
December 2016: Journal of Insect Physiology
Tamar Arens-Arad, Nairouz Farah, Shai Ben-Yaish, Alex Zlotnik, Zeev Zalevsky, Yossi Mandel
Novel technologies are constantly under development for vision restoration in blind patients. Many of these emerging technologies are based on the projection of high intensity light patterns at specific wavelengths, raising the need for the development of specialized projection systems. Here we present and characterize a novel projection system that meets the requirements for artificial retinal stimulation in rats and enables the recording of cortical responses. The system is based on a customized miniature Digital Mirror Device (DMD) for pattern projection, in both visible (525 nm) and NIR (915 nm) wavelengths, and a lens periscope for relaying the pattern directly onto the animal's retina...
October 12, 2016: Scientific Reports
Zhi Liu, Qiang Li, Gaoyu Cui, Gang Zhu, Weihua Tang, Hengli Zhao, John H Zhang, Yujie Chen, Hua Feng
Previously, it was widely accepted that the delayed ischemic injury and poor clinical outcome following subarachnoid hemorrhage (SAH) was caused by cerebral vasospasm. This classical theory was challenged by a clazosentan clinical trial, which failed to improve patient outcome, despite reversing angiographic vasospasm. One possible explanation for the results of this trial is the changes in microcirculation following SAH, particularly in pericytes, which are the primary cell type controlling microcirculation in the brain parenchyma...
October 2016: Experimental and Therapeutic Medicine
I P Seitz, K Achberger, S Liebau, M D Fischer
In ophthalmology, regenerative medicine is rapidly becoming a reality. Cell based treatment strategies in end stage retinal degeneration may be of therapeutic value, whatever the mechanism of disease mechanism. However, while corneal transplantation is commonly performed with excellent results, many obstacles must be overcome before retinal transplants can become clinically useful. The major problems are the production of appropriate transplants and functional integration in situ. New technologies allow the production of autologous transplants by inducing pluripotency in adult somatic cells...
August 1, 2016: Klinische Monatsblätter Für Augenheilkunde
Tomoyuki Isobe, Taku Kasai, Hiroyuki Kawai
PURPOSE: We evaluated the ocular pharmacokinetics of ripasudil (K-115), a selective Rho-associated coiled-coil containing protein kinase (ROCK) inhibitor, following topical administration to rabbits. METHODS: We determined the ocular distribution of [(14)C]ripasudil by whole-head autoradiography and the radioactivity of each ocular tissue after single and multiple instillation of [(14)C]ripasudil to pigmented rabbits. We also measured the aqueous humor concentrations after concomitant instillation of ripasudil and a combination agent (0...
September 2016: Journal of Ocular Pharmacology and Therapeutics
Antonio Martínez-Álvarez, Rubén Crespo-Cano, Ariadna Díaz-Tahoces, Sergio Cuenca-Asensi, José Manuel Ferrández Vicente, Eduardo Fernández
The retina is a very complex neural structure, which contains many different types of neurons interconnected with great precision, enabling sophisticated conditioning and coding of the visual information before it is passed via the optic nerve to higher visual centers. The encoding of visual information is one of the basic questions in visual and computational neuroscience and is also of seminal importance in the field of visual prostheses. In this framework, it is essential to have artificial retina systems to be able to function in a way as similar as possible to the biological retinas...
November 2016: International Journal of Neural Systems
Ivo G Ros, Andrew A Biewener
Flying birds rely on visual cues for retinal image stabilization by negating rotation-induced optic flow, the motion of the visual panorama across the retina, through corrective eye and head movements. In combination with vestibular and proprioceptive feedback, birds may also use visual cues to stabilize their body during flight. Here, we test whether artificially induced wide-field motion generated through projected visual patterns elicits maneuvers in body orientation and flight position, in addition to stabilizing vision...
August 15, 2016: Journal of Experimental Biology
Maxwell H Turner, Fred Rieke
A central goal in the study of any sensory system is to predict neural responses to complex inputs, especially those encountered during natural stimulation. Nowhere is the transformation from stimulus to response better understood than the vertebrate retina. Nevertheless, descriptions of retinal computation are largely based on stimulation using artificial visual stimuli, and it is unclear how these descriptions map onto the encoding of natural stimuli. We demonstrate that nonlinear spatial integration, a common feature of retinal ganglion cell (RGC) processing, shapes neural responses to natural visual stimuli in primate Off parasol RGCs, whereas On parasol RGCs exhibit surprisingly linear spatial integration...
June 15, 2016: Neuron
Zhi-Jun Pei, Guan-Xin Gao, Bo Hao, Qing-Li Qiao, Hui-Jian Ai
Retinal prosthesis offers a potential treatment for individuals suffering from photoreceptor degeneration diseases. Establishing biological retinal models and simulating how the biological retina convert incoming light signal into spike trains that can be properly decoded by the brain is a key issue. Some retinal models have been presented, ranking from structural models inspired by the layered architecture to functional models originated from a set of specific physiological phenomena. However, Most of these focus on stimulus image compression, edge detection and reconstruction, but do not generate spike trains corresponding to visual image...
April 2016: Neural Regeneration Research
Lucas Theis, Philipp Berens, Emmanouil Froudarakis, Jacob Reimer, Miroslav Román Rosón, Tom Baden, Thomas Euler, Andreas S Tolias, Matthias Bethge
A fundamental challenge in calcium imaging has been to infer spike rates of neurons from the measured noisy fluorescence traces. We systematically evaluate different spike inference algorithms on a large benchmark dataset (>100,000 spikes) recorded from varying neural tissue (V1 and retina) using different calcium indicators (OGB-1 and GCaMP6). In addition, we introduce a new algorithm based on supervised learning in flexible probabilistic models and find that it performs better than other published techniques...
May 4, 2016: Neuron
Berk Gonenc, Peter Gehlbach, Russell H Taylor, Iulian Iordachita
In retinal microsurgery, membrane peeling is a standard procedure requiring the delamination of a thin fibrous membrane adherent to the retina surface by applying very small forces. Robotic devices with combined force-sensing instruments have significant potential to assist this procedure by facilitating membrane delamination through induced micro-vibrations. However, defining the optimal frequency and amplitude for generating such vibrations, and updating these parameters during the procedure is not trivial...
September 2015: Proceedings of the ... IEEE/RSJ International Conference on Intelligent Robots and Systems
Francine Behar-Cohen, Thomas J Wolfensberger
Whilst imaging methods are developed allowing non-invasive analysis and quantification of corneal nerves, retinal nerve fibers and retinal vessels, the eye is considered as an open window on the nervous and vascular system. In the field of therapies, macular edema can be reduced using several drugs with different mechanisms of action and different kinetics. Artificial retina is now available in Switzerland and gene therapy continues to develop but should still be considered rather as a research tool than as a treatment...
January 13, 2016: Revue Médicale Suisse
Massimiliano Giulioni, Xavier Lagorce, Francesco Galluppi, Ryad B Benosman
Estimating the speed and direction of moving objects is a crucial component of agents behaving in a dynamic world. Biological organisms perform this task by means of the neural connections originating from their retinal ganglion cells. In artificial systems the optic flow is usually extracted by comparing activity of two or more frames captured with a vision sensor. Designing artificial motion flow detectors which are as fast, robust, and efficient as the ones found in biological systems is however a challenging task...
2016: Frontiers in Neuroscience
Nicola Martino, Caterina Bossio, Susana Vaquero Morata, Guglielmo Lanzani, Maria Rosa Antognazza
Hybrid interfaces between organic semiconductors and living tissues represent a new tool for in-vitro and in-vivo applications. In particular, conjugated polymers display several optimal properties as substrates for biological systems, such as good biocompatibility, excellent mechanical properties, cheap and easy processing technology, and possibility of deposition on light, thin and flexible substrates. These materials have been employed for cellular interfaces like neural probes, transistors for excitation and recording of neural activity, biosensors and actuators for drug release...
2016: Journal of Visualized Experiments: JoVE
Tom Baden, Philipp Berens, Katrin Franke, Miroslav Román Rosón, Matthias Bethge, Thomas Euler
In the vertebrate visual system, all output of the retina is carried by retinal ganglion cells. Each type encodes distinct visual features in parallel for transmission to the brain. How many such 'output channels' exist and what each encodes are areas of intense debate. In the mouse, anatomical estimates range from 15 to 20 channels, and only a handful are functionally understood. By combining two-photon calcium imaging to obtain dense retinal recordings and unsupervised clustering of the resulting sample of more than 11,000 cells, here we show that the mouse retina harbours substantially more than 30 functional output channels...
January 21, 2016: Nature
Martina Poletti, Murat Aytekin, Michele Rucci
Humans explore static visual scenes by alternating rapid eye movements (saccades) with periods of slow and incessant eye drifts [1-3]. These drifts are commonly believed to be the consequence of physiological limits in maintaining steady gaze, resulting in Brownian-like trajectories [4-7], which are almost independent in the two eyes [8-10]. However, because of the technical difficulty of recording minute eye movements, most knowledge on ocular drift comes from artificial laboratory conditions, in which the head of the observer is strictly immobilized...
December 21, 2015: Current Biology: CB
Henri Lorach, Xin Lei, Ludwig Galambos, Theodore Kamins, Keith Mathieson, Roopa Dalal, Philip Huie, James Harris, Daniel Palanker
PURPOSE: Prosthetic restoration of partial sensory loss leads to interactions between artificial and natural inputs. Ideally, the rehabilitation should allow perceptual fusion of the two modalities. Here we studied the interactions between normal and prosthetic vision in a rodent model of local retinal degeneration. METHODS: Implantation of a photovoltaic array in the subretinal space of normally sighted rats induced local degeneration of the photoreceptors above the chip, and the inner retinal neurons in this area were electrically stimulated by the photovoltaic implant powered by near-infrared (NIR) light...
November 2015: Investigative Ophthalmology & Visual Science
Andrea Bonfiglio, Alberto Lagazzo, Rodolfo Repetto, Alessandro Stocchino
BACKGROUND: During eye rotations the vitreous humour moves with respect to the eye globe. This relative motion has been suggested to possibly have an important role in inducing degradation of the gel structure, which might lead to vitreous liquefaction and/or posterior vitreous detachment. Aim of the present work is to study the characteristics of vitreous motion induced by eye rotations. METHODS: We use an experimental setup, consisting of a Perspex model of the vitreous chamber that, for simplicity, is taken to have a spherical shape...
2015: Eye and Vision (London, England)
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