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vergence adaptation

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https://www.readbyqxmd.com/read/27876513/are-high-lags-of-accommodation-in-myopic-children-due-to-motor-deficits
#1
Vivek Labhishetty, William R Bobier
Children with a progressing myopia exhibit an abnormal pattern of high accommodative lags coupled with high accommodative convergence (AC/A) and high accommodative adaptation. This is not predicted by the current models of accommodation and vergence. Reduced accommodative plant gain and reduced sensitivity to blur have been suggested as potential causes for this abnormal behavior. These etiologies were tested by altering parameters (sensory, controller and plant gains) in the Simulink model of accommodation...
November 25, 2016: Vision Research
https://www.readbyqxmd.com/read/27867718/temporal-multiplexing-with-adaptive-optics-for-simultaneous-vision
#2
Eleni Papadatou, Antonio J Del Águila-Carrasco, Iván Marín-Franch, Norberto López-Gil
We present and test a methodology for generating simultaneous vision with a deformable mirror that changed shape at 50 Hz between two vergences: 0 D (far vision) and -2.5 D (near vision). Different bifocal designs, including toric and combinations of spherical aberration, were simulated and assessed objectively. We found that typical corneal aberrations of a 60-year-old subject changes the shape of objective through-focus curves of a perfect bifocal lens. This methodology can be used to investigate subjective visual performance for different multifocal contact or intraocular lens designs...
October 1, 2016: Biomedical Optics Express
https://www.readbyqxmd.com/read/27756701/tonic-accommodation-predicts-closed-loop-accommodation-responses
#3
Chunming Liu, Stefanie A Drew, Eric Borsting, Amy Escobar, Lawrence Stark, Christopher Chase
The purpose of this study is to examine the potential relationship between tonic accommodation (TA), near work induced TA-adaptation and the steady state closed-loop accommodation response (AR). Forty-two graduate students participated in the study. Various aspects of their accommodation system were objectively measured using an open-field infrared auto-refractor (Grand Seiko WAM-5500). Tonic accommodation was assessed in a completely dark environment. The association between TA and closed-loop AR was assessed using linear regression correlations and t-test comparisons...
December 2016: Vision Research
https://www.readbyqxmd.com/read/27643747/cerebellar-control-of-eye-movements
#4
Shin C Beh, Teresa C Frohman, Elliot M Frohman
BACKGROUND: The cerebellum plays a central role in the online, real-time control, and long-term modulation of eye movements. EVIDENCE ACQUISITION: We reviewed the latest (fifth) edition of Leigh and Zee's textbook, The Neurology of Eye Movements, and literature in PUBMED using the following terms: cerebellum, flocculus, paraflocculus, vermis, oculomotor vermis, dorsal vermis, caudal fastigial nucleus, fastigial oculomotor region, uvula, nodulus, ansiform lobule, eye movements, saccades, ipsipulsion, contrapulsion, smooth pursuit, vergence, convergence, divergence, gaze-holding, down beat nystagmus, vestibulo-ocular reflex (VOR), angular VOR, translational VOR, skew deviation, velocity storage...
September 16, 2016: Journal of Neuro-ophthalmology: the Official Journal of the North American Neuro-Ophthalmology Society
https://www.readbyqxmd.com/read/27552410/stereoscopic-viewing-can-induce-changes-in-the-ca-c-ratio
#5
Pascaline Neveu, Corinne Roumes, Matthieu Philippe, Philippe Fuchs, Anne-Emmanuelle Priot
PURPOSE: Stereoscopic displays challenge the neural cross-coupling between accommodation and vergence by inducing a constant accommodative demand and a varying vergence demand. Stereoscopic viewing calls for a decrease in the gain of vergence accommodation, which is the accommodation caused by vergence, quantified by using the convergence-accommodation to convergence (CA/C) ratio. However, its adaptability is still a subject of debate. METHODS: Cross-coupling (CA/C and AC/A ratios) and tonic components of vergence and accommodation were assessed in 12 participants (27...
August 1, 2016: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/27548084/adaptation-of-horizontal-eye-alignment-in-the-presence-of-prism-in-young-children
#6
Yifei Wu, Vidhyapriya Sreenivasan, Erin E Babinsky, T Rowan Candy
Young children experience decreased convergence and increased accommodation demands relative to adults, as a result of their small interpupillary distance and hyperopic refraction. Those with typical amounts of hyperopic refractive error must accommodate more than an emmetrope to achieve focused retinal images, which may also drive additional convergence through the neural coupling. Adults and older children have demonstrated vergence adaptation to a variety of visual stimuli. Can vergence adaptation help younger children achieve alignment in the presence of these potentially conflicting demands? Purkinje image eye tracking and eccentric photorefraction were used to record simultaneous vergence and accommodation responses in adults and young children (3-6 years)...
August 1, 2016: Journal of Vision
https://www.readbyqxmd.com/read/27341089/short-term-adaptation-of-accommodative-responses-in-myopes-fitted-with-multifocal-contact-lenses
#7
Jerome Ozkan, Cathleen Fedtke, Jiyoon Chung, Varghese Thomas, Ravi Chandra Bakaraju
OBJECTIVES: To investigate whether adaptation of accommodative responses occurred in non-presbyopic myopes fitted with four multifocal contact lens (MFCL) designs. METHODS: Prospective, subject-masked clinical investigation comprising 40 experienced myopic lens wearers (18-25 years) fitted bilaterally with single-vision (SV) control lens (Air Optix Aqua [Alcon, Fort Worth, TX]) and randomized to two of four test MFCL (Proclear MFCL [Distance and Near] [CooperVision, Pleasanton, CA], Air Optix Aqua MFCL, Purevision MFCL [Bausch & Lomb, Rochester, NY])...
June 20, 2016: Eye & Contact Lens
https://www.readbyqxmd.com/read/26991129/unmasking-the-linear-behaviour-of-slow-motor-adaptation-to-prolonged-convergence
#8
Ian M Erkelens, Benjamin Thompson, William R Bobier
Adaptation to changing environmental demands is central to maintaining optimal motor system function. Current theories suggest that adaptation in both the skeletal-motor and oculomotor systems involves a combination of fast (reflexive) and slow (recalibration) mechanisms. Here we used the oculomotor vergence system as a model to investigate the mechanisms underlying slow motor adaptation. Unlike reaching with the upper limbs, vergence is less susceptible to changes in cognitive strategy that can affect the behaviour of motor adaptation...
June 2016: European Journal of Neuroscience
https://www.readbyqxmd.com/read/26943155/vergence-adaptation-to-short-duration-stimuli-in-early-childhood
#9
Erin Babinsky, Vidhyapriya Sreenivasan, T Rowan Candy
PURPOSE: To investigate whether nonstrabismic typically developing young children are capable of exhibiting vergence adaptation. METHODS: Fifteen adults (19.5-35.8 years) and 34 children (2.5-7.3 years) provided usable data. None wore habitual refractive correction. Eye position and accommodation were recorded using Purkinje image eye tracking and eccentric photorefraction (MCS PowerRefractor). Vergence was measured in three conditions while the participant viewed naturalistic targets at 33 cm...
March 2016: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/26830708/gaze-dependent-phoria-and-vergence-adaptation
#10
Muriel Dysli, Mathias Abegg
Incomitance is a condition with gaze-dependent deviations of ocular alignment and is common in strabismus patients. The physiological mechanisms that maintain equal horizontal ocular alignment in all gaze directions (concomitance) in healthy individuals are poorly explored. We investigate adaptive processes in the vergence system that are induced by horizontal incomitant vergence stimuli (stimuli that require a gaze-dependent vergence response in order to re-establish binocular single vision). We measured horizontal vergence responses elicited after healthy subjects shifted their gaze from a position that required no vergence to a position that required convergence...
2016: Journal of Vision
https://www.readbyqxmd.com/read/26431525/effects-of-prism-eyeglasses-on-objective-and-subjective-fixation-disparity
#11
Volkhard Schroth, Roland Joos, Wolfgang Jaschinski
In optometry of binocular vision, the question may arise whether prisms should be included in eyeglasses to compensate an oculomotor and/or sensory imbalance between the two eyes. The corresponding measures of objective and subjective fixation disparity may be reduced by the prisms, or the adaptability of the binocular vergence system may diminish effects of the prisms over time. This study investigates effects of wearing prisms constantly for about 5 weeks in daily life. Two groups of 12 participants received eyeglasses with prisms having either a base-in direction or a base-out direction with an amount up to 8 prism diopters...
2015: PloS One
https://www.readbyqxmd.com/read/26326968/differential-saccadic-adaptation-controlled-by-the-target-color
#12
Laurent Madelain, Jeremie Jozefowiez, Sohir Rahmouni
Saccade adaptation is a form of motor learning that maintains saccade accuracy in response to new sensorimotor contingencies. Several studies have shown that saccade gain can be adapted separately in double-step paradigms depending on cues affecting the motor command (velocity or direction of target motion, orbital eccentricity, or vergence). However, purely visual cues such as target color and shape consistently failed to drive different gain states during saccadic adaptation. These results are consistent with the dominant view that saccade adaptation is a simple motor recalibration process...
2015: Journal of Vision
https://www.readbyqxmd.com/read/26326513/gaze-dependent-vergence-adaptation
#13
Muriel Dysli, Mathias Abegg
PURPOSE: The innervational pattern of extraocular muscles that maintain ocular alignment vary with gaze direction, age, and orbital anatomy. A muscle paresis, for example, may cause a misalignment, which is characterized by a gaze dependent deviation of the ocular alignment. Clinically this is termed incomitant strabismus. In this study we aimed at investigating the physiological mechanisms that enable orthophoria, i.e. good ocular alignment, in all directions of gaze. For this purpose we explored the physiological response to vergence stimuli and assessed their directional specificity...
2015: Journal of Vision
https://www.readbyqxmd.com/read/26325955/age-related-changes-in-accommodation-predict-perceptual-tolerance-to-vergence-accommodation-conflicts-in-stereo-displays
#14
Simon Watt, Louise Ryan
Conventional stereoscopic imagery presents conflicting stimuli to vergence and accommodation. With sufficient conflict, vergence-accommodation coupling causes inaccurate responses in one or both systems, impairing stereoscopic depth perception, or preventing it altogether. We examined tolerance of stereo depth perception to stimuli presented in-front-of and behind the screen, and examined factors that might predict it, including phoria, and decreased ability to accommodate with age (presbyopia). We characterised accommodation of observers aged 20 to 68 years using the slope of the linear portion of their stimulus-response functions...
2015: Journal of Vision
https://www.readbyqxmd.com/read/25891521/increased-onset-of-vergence-adaptation-reduces-excessive-accommodation-during-the-orthoptic-treatment-of-convergence-insufficiency
#15
Vidhyapriya Sreenivasan, William R Bobier
This research tested the hypothesis that the successful treatment of convergence insufficiency (CI) with vision-training (VT) procedures, leads to an increased capacity of vergence adaptation (VAdapt) allowing a more rapid downward adjustment of the convergence accommodation cross-link. Nine subjects with CI were recruited from a clinical population, based upon reduced fusional vergence amplitudes, receded near point of convergence or symptomology. VAdapt and the resulting changes to convergence accommodation (CA) were measured at specific intervals over 15 min (pre-training)...
June 2015: Vision Research
https://www.readbyqxmd.com/read/25788706/acute-onset-incomitant-image-disparity-modifies-saccadic-and-vergence-eye-movements
#16
Muriel Dysli, Fabian Keller, Mathias Abegg
New-onset impairment of ocular motility will cause incomitant strabismus, i.e., a gaze-dependent ocular misalignment. This ocular misalignment will cause retinal disparity, that is, a deviation of the spatial position of an image on the retina of both eyes, which is a trigger for a vergence eye movement that results in ocular realignment. If the vergence movement fails, the eyes remain misaligned, resulting in double vision. Adaptive processes to such incomitant vergence stimuli are poorly understood. In this study, we have investigated the physiological oculomotor response of saccadic and vergence eye movements in healthy individuals after shifting gaze from a viewing position without image disparity into a field of view with increased image disparity, thus in conditions mimicking incomitance...
2015: Journal of Vision
https://www.readbyqxmd.com/read/25600699/-how-does-the-brain-control-eye-movements-motor-and-premotor-neurons-of-the-brainstem
#17
REVIEW
O A Coubard
Knowledge of cognitive and neural architecture and processes that control eye movements has advanced enough to allow precise and quantitative analysis of hitherto unsolved phenomena. In this review, we revisit from a neuropsychological viewpoint Hering vs. Helmholtz' hypotheses on binocular coordination. Specifically, we reexamine the behavior and the neural bases of saccade-vergence movement, to move the gaze in both direction and depth under natural conditions. From the psychophysical viewpoint, neo-Heringian and neo-Helmholtzian authors have accumulated arguments favoring distinct conjugate (for saccades) and disconjugate (for vergence) systems, as well as advocating for monocularly programmed eye movements...
April 2015: Revue Neurologique
https://www.readbyqxmd.com/read/25360355/comparison-of-binocular-through-focus-visual-acuity-with-monovision-and-a-small-aperture-inlay
#18
Christina Schwarz, Silvestre Manzanera, Pedro M Prieto, Enrique J Fernández, Pablo Artal
Corneal small aperture inlays provide extended depth of focus as a solution to presbyopia. As this procedure is becoming more popular, it is interesting to compare its performance with traditional approaches, such as monovision. Here, binocular visual acuity was measured as a function of object vergence in three subjects by using a binocular adaptive optics vision analyzer. Visual acuity was measured at two luminance levels (photopic and mesopic) under several optical conditions: 1) natural vision (4 mm pupils, best corrected distance vision), 2) pure-defocus monovision ( + 1...
October 1, 2014: Biomedical Optics Express
https://www.readbyqxmd.com/read/25250983/control-of-binocular-gaze-in-a-high-precision-manual-task
#19
Matteo Valsecchi, Karl R Gegenfurtner
We investigated the precision of binocular gaze control while observers performed a high-precision manual movement, which involved hitting a target hole in a plate with a hand-held needle. Binocular eye movements and the 3D-position of the needle tip were tracked. In general the observers oriented their gaze to the target before they reached it with the needle. The amplitude of microsaccades scaled with the distance of the needle tip. We did not find evidence for the coordination of version and vergence during microsaccades which could be expected if those movements displaced gaze between the needle and the target hole...
May 2015: Vision Research
https://www.readbyqxmd.com/read/25211041/supranuclear-eye-movement-disorders
#20
REVIEW
João Lemos, Eric Eggenberger
PURPOSE OF REVIEW: This work reviews supranuclear ocular motor disorders, highlighting new data published during the past year. RECENT FINDINGS: Perceptional adaptative mechanisms may explain recent research concerning the discrepancy between objective measurement of saccade abnormalities and their putative functional visual impairment. Eye movement classes seem to be selectively disrupted by different neurodegenerative disorders. Deep brain stimulation in Parkinson's disease patients may improve pursuit deficits, highlighting the role of basal ganglia in the control of smooth pursuit...
November 2014: Current Opinion in Ophthalmology
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