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Delayed saccadic eye movements in glaucoma
Kanjee R, Yücel YH, Steinbach MJ, González EG, Gupta N
Eye and Brain , 2012, DOI: http://dx.doi.org/10.2147/EB.S38467
Abstract: yed saccadic eye movements in glaucoma Original Research (1411) Total Article Views Authors: Kanjee R, Yücel YH, Steinbach MJ, González EG, Gupta N Published Date November 2012 Volume 2012:4 Pages 63 - 68 DOI: http://dx.doi.org/10.2147/EB.S38467 Received: 24 September 2012 Accepted: 29 October 2012 Published: 27 November 2012 Raageen Kanjee,1 Yeni H Yücel,1,2 Martin J Steinbach,3,4 Esther G González,3,4 Neeru Gupta1,2,5 1Ophthalmology and Vision Sciences, Laboratory Medicine and Pathobiology, St Michael's Hospital, University of Toronto, 2Keenan Research Centre at the Li Ka Shing Knowledge Institute of St Michael's Hospital, 3Toronto Western Hospital, University Health Network, 4Centre for Vision Research, York University, 5Glaucoma and Nerve Protection Unit, St Michael's Hospital, Toronto, ON, Canada Purpose: To determine whether saccadic eye movements are altered in glaucoma patients. Patients and methods: Sixteen patients with glaucoma and 21 control subjects were prospectively studied. Patients participated in a pro-saccade step task. Saccades were recorded using a noninvasive infrared oculometric device with head-mounted target projection. Medians of saccade reaction time, duration, amplitude, and peak velocity; frequency of express saccades; and percentage of trials with direction error were recorded. t-tests were used to compare the glaucoma and age-matched control groups. A correlation analysis of saccade parameters with visual field loss was also performed. Results: Median saccade reaction times were significantly prolonged in glaucoma patients compared with controls (220.9 ± 49.02 ms vs 192.1 ± 31.24 ms; t-test: P = 0.036). Median duration, median amplitude, and median peak velocity of saccades did not show significant differences between glaucoma and control groups (P > 0.05). Frequency of express saccades was significantly decreased in glaucoma patients compared with controls (1.75 ± 2.32 vs 7.0 ± 6.99; t-test: P = 0.007). Saccade parameters in glaucoma patients showed no significant correlation with visual field loss. Conclusion: Saccadic eye movements are significantly delayed in patients with early, moderate, or advanced glaucoma. Determination of median saccade reaction time may offer a novel functional test to quantify visual function in glaucoma patients. Further studies are needed to determine pathological processes implicated in delayed initiation of saccades, and to assess whether alteration of saccades affects daily activities in glaucoma patients.
Delayed saccadic eye movements in glaucoma  [cached]
Kanjee R,Yücel YH,Steinbach MJ,González EG
Eye and Brain , 2012,
Abstract: Raageen Kanjee,1 Yeni H Yücel,1,2 Martin J Steinbach,3,4 Esther G González,3,4 Neeru Gupta1,2,51Ophthalmology and Vision Sciences, Laboratory Medicine and Pathobiology, St Michael's Hospital, University of Toronto, 2Keenan Research Centre at the Li Ka Shing Knowledge Institute of St Michael's Hospital, 3Toronto Western Hospital, University Health Network, 4Centre for Vision Research, York University, 5Glaucoma and Nerve Protection Unit, St Michael's Hospital, Toronto, ON, CanadaPurpose: To determine whether saccadic eye movements are altered in glaucoma patients.Patients and methods: Sixteen patients with glaucoma and 21 control subjects were prospectively studied. Patients participated in a pro-saccade step task. Saccades were recorded using a noninvasive infrared oculometric device with head-mounted target projection. Medians of saccade reaction time, duration, amplitude, and peak velocity; frequency of express saccades; and percentage of trials with direction error were recorded. t-tests were used to compare the glaucoma and age-matched control groups. A correlation analysis of saccade parameters with visual field loss was also performed.Results: Median saccade reaction times were significantly prolonged in glaucoma patients compared with controls (220.9 ± 49.02 ms vs 192.1 ± 31.24 ms; t-test: P = 0.036). Median duration, median amplitude, and median peak velocity of saccades did not show significant differences between glaucoma and control groups (P > 0.05). Frequency of express saccades was significantly decreased in glaucoma patients compared with controls (1.75 ± 2.32 vs 7.0 ± 6.99; t-test: P = 0.007). Saccade parameters in glaucoma patients showed no significant correlation with visual field loss.Conclusion: Saccadic eye movements are significantly delayed in patients with early, moderate, or advanced glaucoma. Determination of median saccade reaction time may offer a novel functional test to quantify visual function in glaucoma patients. Further studies are needed to determine pathological processes implicated in delayed initiation of saccades, and to assess whether alteration of saccades affects daily activities in glaucoma patients.Keywords: visual field, latency, visual dysfunction, brain, superior colliculus, quality of life
Distortion of Space and Time during Saccadic Eye Movements  [PDF]
M. Suzuki, Y. Yamazaki
Intelligent Information Management (IIM) , 2010, DOI: 10.4236/iim.2010.22011
Abstract: The space-time distortion perceived subjectively during saccadic eye movements is an associative phenomenon of a transient shift of observer’s visual frame of reference from one position to another. Here we report that the lines of subjective simultaneity defined as two spatially separated flashes perceived during saccades were nearly uniformly tilted along the physical time-course. The causality of the resulting space-time compression may be explained by the Minkowski space-time diagram in physics.
Saccadic Eye Movements Minimize the Consequences of Motor Noise  [PDF]
Robert J. van Beers
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002070
Abstract: The durations and trajectories of our saccadic eye movements are remarkably stereotyped. We have no voluntary control over these properties but they are determined by the movement amplitude and, to a smaller extent, also by the movement direction and initial eye orientation. Here we show that the stereotyped durations and trajectories are optimal for minimizing the variability in saccade endpoints that is caused by motor noise. The optimal duration can be understood from the nature of the motor noise, which is a combination of signal-dependent noise favoring long durations, and constant noise, which prefers short durations. The different durations of horizontal vs. vertical and of centripetal vs. centrifugal saccades, and the somewhat surprising properties of saccades in oblique directions are also accurately predicted by the principle of minimizing movement variability. The simple and sensible principle of minimizing the consequences of motor noise thus explains the full stereotypy of saccadic eye movements. This suggests that saccades are so stereotyped because that is the best strategy to minimize movement errors for an open-loop motor system.
Production, Control, and Visual Guidance of Saccadic Eye Movements  [PDF]
Jeffrey D. Schall
ISRN Neurology , 2013, DOI: 10.1155/2013/752384
Abstract: Primate vision is served by rapid shifts of gaze called saccades. This review will survey current knowledge and particular problems concerning the neural control and guidance of gaze shifts. 1. Introduction Being primates endowed with a fovea providing acute vision over a very small range of the visual field, we must shift gaze to explore the world. Rapid eye movements called saccades direct the line of sight onto objects of interest in the visual field, often conspicuous objects like a berry among leaves and sometimes important objects like the family member among a social group. More is understood about visually guided saccade production than any other sensory motor system for several reasons. First, movements of the eyes are simpler than movements of the limbs or vocal apparatus because they have fewer degrees of freedom and can ignore gravity. Second, every neuron from the sensory through the motor is accessible to inquiry within the cranium. Third, advances in technology have provided accurate measurements and manipulations of the fine details of eye movements. Eye movement research with macaque monkeys has profoundly influenced clinical neurology and ophthalmology, and this translational interface runs both directions. On the one hand, insights from monkey studies have been essential for clinicians to interpret neurological examinations. On the other hand, properties of human eye movements have stimulated neurophysiological studies that have, in turn, informed clinical practice. While the neural control of movements is certainly instantiated through molecular mechanisms, it has become clear that knowledge at the level of neural systems is most useful for this clinical translation. For example, monkey models of strabismus and amblyopia (e.g., [1–5]), fourth nerve palsy (e.g., [6]), nystagmus (e.g., [7, 8]), and Parkinson’s disease (e.g., [9, 10]) have provided precise information that would otherwise have been left to clinical guesswork. These monkey models have furthermore provided refinements of new treatments such as deep brain stimulation for Parkinson’s disease, optical treatments for developmental strabismus, and drugs for nystagmus. Similarly, many neuropsychiatric disorders are associated with problems of gaze control (e.g., [11]), so obtaining neurophysiological data from monkeys performing tasks in which these problems are expressed by patients (and their relatives) will provide information that can improve the diagnosis and possibly treatment of these disorders. The literature on the production, guidance, and effects of saccades is very
Saccadic Eye Movements and the Generalized Pareto Distribution  [PDF]
Reiner Lenz
Computer Science , 2014,
Abstract: We describe a statistical analysis of the eye tracker measurements in a database with 15 observers viewing 1003 images under free-viewing conditions. In contrast to the common approach of investigating the properties of the fixation points we analyze the properties of the transition phases between fixations. We introduce hyperbolic geometry as a tool to measure the step length between consecutive eye positions. We show that the step lengths, measured in hyperbolic and euclidean geometry, follow a generalized Pareto distribution. The results based on the hyperbolic distance are more robust than those based on euclidean geometry. We show how the structure of the space of generalized Pareto distributions can be used to characterize and identify individual observers.
Both Lexical and Non-Lexical Characters Are Processed during Saccadic Eye Movements  [PDF]
Hao Zhang, Hong-Mei Yan, Keith M. Kendrick, Chao-Yi Li
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046383
Abstract: On average our eyes make 3–5 saccadic movements per second when we read, although their neural mechanism is still unclear. It is generally thought that saccades help redirect the retinal fovea to specific characters and words but that actual discrimination of information only occurs during periods of fixation. Indeed, it has been proposed that there is active and selective suppression of information processing during saccades to avoid experience of blurring due to the high-speed movement. Here, using a paradigm where a string of either lexical (Chinese) or non-lexical (alphabetic) characters are triggered by saccadic eye movements, we show that subjects can discriminate both while making saccadic eye movement. Moreover, discrimination accuracy is significantly better for characters scanned during the saccadic movement to a fixation point than those not scanned beyond it. Our results showed that character information can be processed during the saccade, therefore saccades during reading not only function to redirect the fovea to fixate the next character or word but allow pre-processing of information from the ones adjacent to the fixation locations to help target the next most salient one. In this way saccades can not only promote continuity in reading words but also actively facilitate reading comprehension.
Reading “Sun” and Looking Up: The Influence of Language on Saccadic Eye Movements in the Vertical Dimension  [PDF]
Carolin Dudschig, Jan Souman, Martin Lachmair, Irmgard de la Vega, Barbara Kaup
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056872
Abstract: Traditionally, language processing has been attributed to a separate system in the brain, which supposedly works in an abstract propositional manner. However, there is increasing evidence suggesting that language processing is strongly interrelated with sensorimotor processing. Evidence for such an interrelation is typically drawn from interactions between language and perception or action. In the current study, the effect of words that refer to entities in the world with a typical location (e.g., sun, worm) on the planning of saccadic eye movements was investigated. Participants had to perform a lexical decision task on visually presented words and non-words. They responded by moving their eyes to a target in an upper (lower) screen position for a word (non-word) or vice versa. Eye movements were faster to locations compatible with the word's referent in the real world. These results provide evidence for the importance of linguistic stimuli in directing eye movements, even if the words do not directly transfer directional information.
Do Horizontal Saccadic Eye Movements Increase Interhemispheric Coherence? Investigation of a Hypothesized Neural Mechanism Underlying EMDR  [PDF]
Zoe Samara,Bernet M. Elzinga,Heleen A. Slagter
Frontiers in Psychiatry , 2011, DOI: 10.3389/fpsyt.2011.00004
Abstract: Series of horizontal saccadic eye movements (EMs) are known to improve episodic memory retrieval in healthy adults and to facilitate the processing of traumatic memories in eye movement desensitization and reprocessing (EMDR) therapy. Several authors have proposed that EMs achieve these effects by increasing the functional connectivity of the two brain hemispheres, but direct evidence for this proposal is lacking. The aim of this study was to investigate whether memory enhancement following bilateral EMs is associated with increased interhemispheric coherence in the electroencephalogram (EEG). Fourteen healthy young adults were asked to freely recall lists of studied neutral and emotional words after a series of bilateral EMs and a control procedure. Baseline EEG activity was recorded before and after the EM and control procedures. Phase and amplitude coherence between bilaterally homologous brain areas were calculated for six frequency bands and electrode pairs across the entire scalp. Behavioral analyses showed that participants recalled more emotional (but not neutral) words following the EM procedure than following the control procedure. However, the EEG analyses indicated no evidence that the EMs altered participants’ interhemispheric coherence or that improvements in recall were correlated with such changes in coherence. These findings cast doubt on the interhemispheric interaction hypothesis, and therefore may have important implications for future research on the neurobiological mechanism underlying EMDR.
Saccadic movements using eye-tracking technology in individuals with autism spectrum disorders: pilot study
Mercadante, Marcos T.;Macedo, Elizeu C.;Baptista, Patrícia M.;Paula, Cristiane S.;Schwartzman, José S.;
Arquivos de Neuro-Psiquiatria , 2006, DOI: 10.1590/S0004-282X2006000400003
Abstract: objective: to verify differences in the visual scanning strategies between pervasive developmental disorders (pdd) and controls when they are observing social and non-social pictures. method: pdd group (pddg) comprised by 10 non-retarded subjects (age from 4 to 41) and age-matched control group (cg). nine social pictures with human beings (including two pictures of cat mask), and 3 nonsocial pictures of objects were presented for 5 seconds. saccadic movements and fixation were recorded with equipment eyegaze? (lc technologies inc.). results: pddg (mean=292.73, se=67.62) presented longer duration of saccadic movements for social pictures compared to cg (mean=136.06, se=14.01) (p=0.04). the cg showed a higher number of fixations in the picture 7 (a women using a cat mask, with the eyes erased) (cg: mean=3.40; pddg: mean=1.80; p=0.007). conclusion: the results suggest differences in strategies that pdd explore human picture. moreover, these strategies seem not to be affected by the lack of expected part of the face (the eyes).
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