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phoria adaptation

Tara L Alvarez, Eun H Kim, Bérangère Granger-Donetti
People develop presbyopia as part of the normal aging process. Most presbyopes adapt to progressive additive lens (PALs), while others do not. This investigation sought to determine whether the ability to modify disparity vergence or phoria was correlated to PALs adaptation. In experiment 1, a double-step paradigm quantified the ability to modify convergence responses in sixteen presbyopes. In experiment 2, thirty-one incipient presbyopes participated in a 5-minute sustained fixation task to evoke phoria adaptation where the magnitude and rate of phoria adaptation were measured...
May 31, 2017: Scientific Reports
Tara L Alvarez, Eun H Kim, Chang Yaramothu, Bérangère Granger-Donetti
A paucity of research exists to investigate whether the normal aging process influences the ability to adapt disparity vergence and phoria. Vergence eye movements and dissociated phoria were recorded from 49 healthy subjects (ages 20-70years) using an objective eye movement tracking system. Four-degree vergence responses were modified using a double-step protocol. Dynamics of vergence were quantified via peak velocity. The phoria adaptation experiment measured the magnitude (net change in phoria level) and rate (magnitude divided by the time constant) of phoria adaption during 5min of sustained fixation on a binocular target (40cm/8...
April 2017: Vision Research
Celia R Gong, David Troilo, Kathryn Richdale
PURPOSE: To determine the effect of multifocal contact lenses on accommodation and phoria in children. METHODS: This was a prospective, non-dispensing, randomized, crossover, single-visit study. Myopic children with normal accommodation and binocularity and no history of myopia control treatment were enrolled and fitted with CooperVision Biofinity single vision (SV) and multifocal (MF, +2.50D center distance add) contact lenses. Accommodative responses (photorefraction) and phorias (modified Thorington) were measured at four distances (>3 m, 100 cm, 40 cm, 25 cm)...
March 2017: Optometry and Vision Science: Official Publication of the American Academy of Optometry
Jaeho Jung, Lindsay Klaehn, Michael C Brodsky
PURPOSE: To evaluate the stability of human binocular alignment under conditions of altered fixation and luminance. METHODS: Horizontal binocular alignment in 8 healthy orthotropic subjects was measured using infrared video-oculography (VOG) under conditions of binocular fixation and luminance change. Each testing condition was preceded by a binocular fixation period in room light (475 lux) to define the baseline binocular alignment. Binocular alignment was then measured in darkness without fixation, in room light through a semitranslucent filter that precluded fixation, and in darkness with a distant fixational target...
August 2016: Journal of AAPOS: the Official Publication of the American Association for Pediatric Ophthalmology and Strabismus
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
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
Jinhua Bao, Yuwen Wang, Zuopao Zhuo, Xianling Yang, Renjing Tan, Björn Drobe, Hao Chen
AIMS: To determine the influence of single-vision lenses (SVLs) and progressive addition lenses (PALs) on the near vision posture of myopic children based on their near phoria. METHODS: Sixty-two myopic children were assigned to wear SVLs followed by PALs. Eighteen children were esophoric (greater than +1), 18 were orthophoric (-1 to 1) and 26 were exophoric (less than -1) at near. Reading distance, head tilt and ocular gaze angles were measured using an electromagnetic system after adaptation to each lens type...
August 2016: British Journal of Ophthalmology
Xinping Yu, Jinhua Bao, Björn Drobe, Wenhui Lv, Ge Wu, Jinling Xu, Hao Chen
PURPOSE: To compare personalized near addition values for myopic children that induce a reasonable phoria (Ph) (meeting Sheard's criterion) and induce a null lag of accommodation at near and to evaluate changes in these metrics after lens adaptation. METHODS: Fifty-three myopic children participated in this study. Accommodative response, Ph, and fusional amplitudes (FAs) were measured at 33 cm through multiple addition lenses (0D, +1.00D, +1.50D, +2.00D, +2.50D, +3...
January 2016: Optometry and Vision Science: Official Publication of the American Academy of Optometry
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
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
Vidhyapriya Sreenivasan, Elizabeth L Irving, William R Bobier
Investigations into the progression of myopia in children have long considered the role of accommodation as a cause and solution. Myopic children show high levels of accommodative adaptation, coupled with accommodative lag and high response AC/A (accommodative convergence per diopter of accommodation). This pattern differs from that predicted by current models of interaction between accommodation and vergence, where weakened reflex responses and a high AC/A would be associated with a low not high levels of accommodative adaptation...
August 2014: Vision Research
Hamed Momeni-Moghaddam, Frank Eperjesi, James Kundart, Kazem Mostafavi-Nam
PURPOSE: The purpose of this study was to determine whether stereoacuity can be used as an indicator of prism adaptation. In particular, we wanted to know whether the time required for stereoacuity to return to the initial level after viewing through a prism can be used to determine the degree of adaptation. MATERIALS AND METHODS: Eighteen subjects participated in this study. Stereoacuity and dissociated phoria were determined using the TNO stereotest and the Maddox rod, respectively...
August 2014: Current Eye Research
Horst Mayer
BACKGROUND: During many years of occupational stress research, mostly within the German governmental program for "Humanization of Work Life'', remarkable deficits concerning visual work were seen, the most striking being the lack of cooperation between the different experts. OBJECTIVE: With regard to this article hard arguments and ideas for solutions had to be found. METHODS/PARTICIPANTS: A pilot study in 21 enterprises was realized (1602 employees with different visual work tasks)...
January 1, 2014: Work: a Journal of Prevention, Assessment, and Rehabilitation
Edyta Karpicka, Peter Alan Howarth
PURPOSE: In this experiment two hypotheses were tested. The first hypothesis was that viewing 3D stereoscopic stimuli which are located geometrically beyond the screen on which the images are displayed would induce exophoric heterophoria (phoria) changes (adaptation). The second hypothesis was that participants whose phoria changed as a consequence of adaptation during the viewing of the stereoscopic stimuli would experience less visual discomfort than people whose phoria did not adapt...
September 2013: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
Eun H Kim, Tara L Alvarez
BACKGROUND: This study sought to investigate whether eye dominance and age are related to the stimulus-free oculomotor resting state described via the dark disconjugate position (near or far), the dark conjugate position (left to right), and the near dissociated phoria. METHODS: Nineteen non-presbyopes and 25 presbyopes with normal binocular vision participated in two identical sessions. The left-eye and the right-eye positions were recorded using a video-based infrared eye tracker while the subjects were in total darkness...
September 2013: Graefe's Archive for Clinical and Experimental Ophthalmology
Vidhyapriya Sreenivasan, Elizabeth L Irving, William R Bobier
The influence of phoria-type and myopia on changes to vergence and accommodation during prolonged near-task was examined in 53 children. Participants were classified into phoria and refractive categories based on near phoria and cycloplegic refraction respectively. Measures of near phoria, binocular (BA) and monocular accommodation (MA) were obtained before and during a 20 min task when children binocularly fixated a high-contrast target at 33 cm through best corrective lenses. Vergence adaptation and accommodative adaptation were quantified using changes to near phoria and tonic accommodation respectively...
March 15, 2012: Vision Research
Aurora Torrents Gómez, Núria Lupón, Genís Cardona, J Antonio Aznar-Casanova
BACKGROUND: Single image random dot stereograms (SIRDS) have been used to study diverse visual parameters and skills. The aim of the present study was to identify the main optometric factors involved in the perception of SIRDS and to obtain a discriminant model to categorise our participants in terms of their skill in perceiving SIRDS. METHODS: Response time was determined to assess the ability of 69 participants to perceive the hidden three-dimensional shape in an auto-stereogram presented under controlled conditions, whereupon three skill level groups were defined...
March 2012: Clinical & Experimental Optometry: Journal of the Australian Optometrical Association
Eun H Kim, Vincent R Vicci, Sang J Han, Tara L Alvarez
PURPOSE: This study sought to investigate the influence of phoria adaptation on convergence peak velocity from responses located at different initial vergence positions. METHODS: Symmetrical 4° convergence step responses and near dissociated phoria (measured at 40 cm from the subject's midline) were recorded from six subjects with normal binocular vision using an infrared limbus tracking system with a haploscope. Two different sustained fixations (1° and 16° convergent rotation along the subject's midline) were used to study whether phoria had an influence on the peak velocity of convergence responses located at two initial vergence positions (1° or 'far' steps and 12° or 'near' steps)...
2011: PloS One
Eun H Kim, Vincent R Vicci, Bérangère Granger-Donetti, Tara L Alvarez
The ability to adapt is critical to survival and varies between individuals. Adaptation of one motor system may be related to the ability to adapt another. This study sought to determine whether phoria adaptation was correlated with the ability to modify the dynamics of disparity vergence. Eye movements from ten subjects were recorded during dynamic disparity vergence modification and phoria adaptation experiments. Two different convergent stimuli were presented during the dynamic vergence modification experiment: a test stimulus (4° step) and a conditioning stimulus (4° double step)...
July 2011: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
A T Berk, A O Saatci, E Kir, I Durak, S Kaynak
Postoperative muscle imbalance was prospectively evaluated in 44 patients who underwent conventional scleral buckling operations. Strabismus was present in 27 of 44 patients (61%). Heterotropia resolved spontaneously during the first six postoperative months in nine of 27 patients (33%). Diplopia persisted in six patients (13.6%) and limitation of ductions occurred in 22 of 44 patients (50%). The risk of developing postoperative strabismus was 2.5 times longer if an implant was placed under a rectus muscle...
1996: Strabismus
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