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https://www.readbyqxmd.com/read/28060395/design-and-validation-of-a-training-simulator-for-laser-capsulotomy-peripheral-iridotomy-and-retinopexy
#1
Sarah M Simpson, Kelly D Schweitzer, Davin E Johnson
BACKGROUND AND OBJECTIVES: Ophthalmology trainees commonly learn laser procedures on live patients. A simulator for learning peripheral iridotomy (PI), posterior capsulotomy, and retinopexy may improve patient outcomes. MATERIALS AND METHODS: A model eye with artificial tissues was designed. The tissues reacted to laser similarly to human tissues. Inexperienced (n = 6; first- to third-year residents) and experienced (n = 7; fourth- to fifth-year residents and staff) ophthalmic personal were compared on performance of the above laser procedures...
January 1, 2017: Ophthalmic Surgery, Lasers & Imaging Retina
https://www.readbyqxmd.com/read/27958724/engineering-an-artificial-flavoprotein-magnetosensor
#2
Chris Bialas, Lauren E Jarocha, Kevin B Henbest, Tilo M Zollitsch, Goutham Kodali, Christiane R Timmel, Stuart R Mackenzie, P Leslie Dutton, Christopher C Moser, P J Hore
Migratory birds use the Earth's magnetic field as a source of navigational information. This light-dependent magnetic compass is thought to be mediated by cryptochrome proteins in the retina. Upon light activation, electron transfer between the flavin adenine dinucleotide cofactor and tryptophan residues leads to the formation of a spin-correlated radical pair, whose subsequent fate is sensitive to external magnetic fields. To learn more about the functional requirements of this complex chemical compass, we have created a family of simplified, adaptable proteins-maquettes-that contain a single tryptophan residue at different distances from a covalently bound flavin...
December 28, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27942525/are-long-stimulus-pulse-durations-the-answer-to-improving-spatial-resolution-in-retinal-prostheses
#3
COMMENT
Matthew A Petoe, Mohit N Shivdasani
Retinal prostheses can provide artificial vision to patients with degenerate retinae by electrically stimulating the remaining inner retinal neurons. The evoked perception is generally adequate for light localization, but of limited spatial resolution owing to the indiscriminate activation of multiple retinal cell types, leading to distortions in the perceived image. Here we present a perspective on a recent work by Weitz and colleagues who demonstrate a focal confinement of retinal ganglion cell (RGC) activation when using extended pulse durations in the stimulation waveform...
November 2016: Annals of Translational Medicine
https://www.readbyqxmd.com/read/27936751/effective-retinal-penetration-of-lipophilic-and-lipid-conjugated-hydrophilic-agents-delivered-by-engineered-liposomes
#4
Junsung Lee, Unbyeol Goh, Hyoung-Jin Lee, Jiyoung Kim, Moonkyoung Jeong, Ji-Ho Park
Efficient delivery of drugs to the retina is critical but difficult to achieve with current methods. There have been a number of attempts to use intravitreal injection of liposomes, artificial vesicles composed of a phospholipid bilayer, to overcome the limitations of conventional intravitreal injection (short retention time, toxicity, poor penetration, etc.). Here, we report an optimal liposomal formulation that can diffuse through the vitreous humor, deliver the incorporated agents to all retinal layers effectively, and maintain them for a relatively long time...
December 27, 2016: Molecular Pharmaceutics
https://www.readbyqxmd.com/read/27919674/neural-adaptation-to-peripheral-blur-in-myopes-and-emmetropes
#5
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 a 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...
December 17, 2016: Vision Research
https://www.readbyqxmd.com/read/27836334/enhanced-neural-function-in-highly-aberrated-eyes-following-perceptual-learning-with-adaptive-optics
#6
Ramkumar Sabesan, Antoine Barbot, Geunyoung Yoon
Highly aberrated keratoconic (KC) eyes do not elicit the expected visual advantage from customized optical corrections. This is attributed to the neural insensitivity arising from chronic visual experience with poor retinal image quality, dominated by low spatial frequencies. The goal of this study was to investigate if targeted perceptual learning with adaptive optics (AO) can stimulate neural plasticity in these highly aberrated eyes. The worse eye of 2 KC subjects was trained in a contrast threshold test under AO correction...
November 25, 2016: Vision Research
https://www.readbyqxmd.com/read/27782261/controllable-stationary-photocurrents-generated-from-a-bacteriorhodopsin-upconversion-nanoparticle-based-bionanosystem-under-nir-illumination
#7
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
https://www.readbyqxmd.com/read/27751886/photoreceptor-spectral-sensitivity-of-the-compound-eyes-of-black-soldier-fly-hermetia-illucens-informing-the-design-of-led-based-illumination-to-enhance-indoor-reproduction
#8
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
https://www.readbyqxmd.com/read/27731346/head-mounted-dmd-based-projection-system-for-natural-and-prosthetic-visual-stimulation-in-freely-moving-rats
#9
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
https://www.readbyqxmd.com/read/27698742/blood-filled-cerebrospinal-fluid-enhanced-pericyte-microvasculature-contraction-in-rat-retina-a-novel-in-vitro-study-of-subarachnoid-hemorrhage
#10
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
https://www.readbyqxmd.com/read/27479580/-stem-cells-for-retina-replacement
#11
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...
December 2016: Klinische Monatsblätter Für Augenheilkunde
https://www.readbyqxmd.com/read/27463221/ocular-penetration-and-pharmacokinetics-of-ripasudil-following-topical-administration-to-rabbits
#12
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
https://www.readbyqxmd.com/read/27354187/automatic-tuning-of-a-retina-model-for-a-cortical-visual-neuroprosthesis-using-a-multi-objective-optimization-genetic-algorithm
#13
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
https://www.readbyqxmd.com/read/27284072/optic-flow-stabilizes-flight-in-ruby-throated-hummingbirds
#14
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
https://www.readbyqxmd.com/read/27263968/synaptic-rectification-controls-nonlinear-spatial-integration-of-natural-visual-inputs
#15
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
https://www.readbyqxmd.com/read/27212929/a-cascade-model-of-information-processing-and-encoding-for-retinal-prosthesis
#16
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
https://www.readbyqxmd.com/read/27151639/benchmarking-spike-rate-inference-in-population-calcium-imaging
#17
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
https://www.readbyqxmd.com/read/27110431/effects-of-micro-vibratory-modulation-during-robot-assisted-membrane-peeling
#18
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
https://www.readbyqxmd.com/read/26946708/-ophthalmolgy-what-s-new-in-2015
#19
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
https://www.readbyqxmd.com/read/26909015/event-based-computation-of-motion-flow-on-a-neuromorphic-analog-neural-platform
#20
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
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