scholarly journals Fixational Saccades and Their Relation to Fixation Instability in Strabismic Monkeys

2017 ◽  
Vol 58 (13) ◽  
pp. 5743 ◽  
Author(s):  
Suraj Upadhyaya ◽  
Mythri Pullela ◽  
Santoshi Ramachandran ◽  
Samuel Adade ◽  
Anand C. Joshi ◽  
...  
Keyword(s):  
Fixational Saccades

scholarly journals Fixation eye movement abnormalities and stereopsis recovery following strabismus repair

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Talora L. Martin ◽  
Jordan Murray ◽  
Kiran Garg ◽  
Charles Gallagher ◽  
Aasef G. Shaikh ◽  
...  
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Functional Improvement ◽  
Slow Phase ◽  
Fixational Eye Movements ◽  
Movement Characteristics ◽  
Adaptive Mechanisms ◽  
Before And After ◽  
Gaze Holding ◽  
Fixational Saccades

AbstractWe evaluated the effects of strabismus repair on fixational eye movements (FEMs) and stereopsis recovery in patients with fusion maldevelopment nystagmus (FMN) and patients without nystagmus. Twenty-one patients with strabismus, twelve with FMN and nine without nystagmus, were tested before and after strabismus repair. Eye-movements were recorded during a gaze-holding task under monocular viewing conditions. Fast (fixational saccades and quick phases of nystagmus) and slow (inter-saccadic drifts and slow phases of nystagmus) FEMs and bivariate contour ellipse area (BCEA) were analyzed in the viewing and non-viewing eye. Strabismus repair improved the angle of strabismus in subjects with and without FMN, however patients without nystagmus were more likely to have improvement in stereoacuity. The fixational saccade amplitudes and intersaccadic drift velocities in both eyes decreased after strabismus repair in subjects without nystagmus. The slow phase velocities were higher in patients with FMN compared to inter-saccadic drifts in patients without nystagmus. There was no change in the BCEA after surgery in either group. In patients without nystagmus, the improvement of the binocular function (stereopsis), as well as decreased fixational saccade amplitude and intersaccadic drift velocity, could be due, at least partially, to central adaptive mechanisms rendered possible by surgical realignment of the eyes. The absence of improvement in patients with FMN post strabismus repair likely suggests the lack of such adaptive mechanisms in patients with early onset infantile strabismus. Assessment of fixation eye movement characteristics can be a useful tool to predict functional improvement post strabismus repair.

scholarly journals Fixational saccades are more disconjugate in adults than in children

PLoS ONE ◽  
2017 ◽  
Vol 12 (4) ◽  
pp. e0175295 ◽  
Author(s):  
Aasef G. Shaikh ◽  
Fatema F. Ghasia
Keyword(s):  
Fixational Saccades

scholarly journals Suppressive interactions underlying visually evoked fixational saccades

2016 ◽  
Vol 118 ◽  
pp. 70-82 ◽  
Author(s):  
Helena X. Wang ◽  
Shlomit Yuval-Greenberg ◽  
David J. Heeger
Keyword(s):  
Fixational Saccades

scholarly journals Figure-Ground Processing during Fixational Saccades in V1: Indication for Higher-Order Stability

2014 ◽  
Vol 34 (9) ◽  
pp. 3247-3252 ◽  
Author(s):  
A. Gilad ◽  
Y. Pesoa ◽  
I. Ayzenshtat ◽  
H. Slovin
Keyword(s):  
Higher Order ◽  
Fixational Saccades

Fixational saccades alter the gap effect

2014 ◽  
Vol 39 (12) ◽  
pp. 2098-2106 ◽  
Author(s):  
Masayuki Watanabe ◽  
Yuka Matsuo ◽  
Ling Zha ◽  
Michael R. MacAskill ◽  
Yasushi Kobayashi
Keyword(s):  
Gap Effect ◽  
Fixational Saccades

scholarly journals Reading Specific Small Saccades Predict Individual Phonemic Awareness and Reading Speed

2021 ◽  
Vol 15 ◽  
Author(s):  
Samy Rima ◽  
Michael C. Schmid
Keyword(s):  
Eye Movements ◽  
Short Story ◽  
Phonemic Awareness ◽  
Developmental Dyslexia ◽  
Reading Skill ◽  
Fundamental Aspect ◽  
Fixational Eye Movements ◽  
Free Viewing ◽  
Wide Range ◽  
Fixational Saccades

Small fixational eye-movements are a fundamental aspect of vision and thought to reflect fine shifts in covert attention during active viewing. While the perceptual benefits of these small eye movements have been demonstrated during a wide range of experimental tasks including during free viewing, their function during reading remains surprisingly unclear. Previous research demonstrated that readers with increased microsaccade rates displayed longer reading speeds. To what extent increased fixational eye movements are, however, specific to reading and might be indicative of reading skill deficits remains, however, unknown. To address this topic, we compared the eye movement scan paths of 13 neurotypical individuals and 13 subjects diagnosed with developmental dyslexia during short story reading and free viewing of natural scenes. We found that during reading only, dyslexics tended to display small eye movements more frequently compared to neurotypicals, though this effect was not significant at the population level, as it could also occur in slow readers not diagnosed as dyslexics. In line with previous research, neurotypical readers had twice as many regressive compared to progressive microsaccades, which did not occur during free viewing. In contrast, dyslexics showed similar amounts of regressive and progressive small fixational eye movements during both reading and free viewing. We also found that participants with smaller fixational saccades from both neurotypical and dyslexic samples displayed reduced reading speeds and lower scores during independent tests of reading skill. Slower readers also displayed greater variability in the landing points and temporal occurrence of their fixational saccades. Both the rate and spatio-temporal variability of fixational saccades were associated with lower phonemic awareness scores. As none of the observed differences between dyslexics and neurotypical readers occurred during control experiments with free viewing, the reported effects appear to be directly related to reading. In summary, our results highlight the predictive value of small saccades for reading skill, but not necessarily for developmental dyslexia.

The role of fixation disengagement and oculomotor preparation in gap saccade task is gap-duration dependent

2021 ◽  
Author(s):  
Bing Li ◽  
Jing Guang ◽  
Mingsha Zhang
Keyword(s):  
Spatial Information ◽  
Brain State ◽  
Primary Role ◽  
Express Saccade ◽  
Long Latency ◽  
Theory Versus ◽  
Saccade Direction ◽  
Saccade Task ◽  
Disengagement Theory ◽  
Fixational Saccades

The influence of internal brain state on behavioral performance is well illustrated by the gap-saccade task, in which saccades might be initiated with short latency (express saccade) or with long latency (regular saccade) even though the external visual condition is identical. Accumulated evidence has demonstrated that the internal brain state is different before the initiation of an express saccade than of a regular saccade. However, the reported origin of the fluctuation of internal brain state is disputed among previous studies, e.g., the fixation disengagement theory versus the oculomotor preparation theory. In the present study, we examined these two theories by analyzing the rate and direction of fixational saccades, i.e., small amplitude saccades during fixation period, because they could be modulated by internal brain state. Since fixation disengagement is not spatially tuned, it might affect the rate but not direction of fixational saccade. In contrast, oculomotor preparation can contain the spatial information for upcoming saccade, thus, it might have a distinct effect on fixational saccade direction. We found that the different spatiotemporal characteristics of fixational saccades among tasks with different gap durations reveals different driven force to change the internal brain state. Under short gap duration (100 ms), fixation disengagement plays a primary role in switching internal brain state. Conversely, under medium (200 ms) and long (400 ms) gap durations, oculomotor preparation plays a primary role. These results suggest that both fixation disengagement and oculomotor preparation can change the internal brain state, but their relative contributions are gap-duration dependent.

Effects of fixational saccades on response timing in macaque lateral geniculate nucleus

2010 ◽  
Vol 27 (5-6) ◽  
pp. 171-181 ◽  
Author(s):  
ALAN B. SAUL
Keyword(s):  
Eye Movements ◽  
Lateral Geniculate Nucleus ◽  
Alert Monkey ◽  
Visual Thalamus ◽  
Lateral Geniculate ◽  
Cortical Responses ◽  
The Times ◽  
Response Timing ◽  
Fixational Saccades ◽  
Display Monitor

AbstractEven during active fixation, small eye movements persist that might be expected to interfere with vision. Numerous brain mechanisms probably contribute to discounting this jitter. Changes in the timing of responses in the visual thalamus associated with fixational saccades are considered in this study. Activity of single neurons in alert monkey lateral geniculate nucleus (LGN) was recorded during fixation while pseudorandom visual noise stimuli were presented. The position of the stimulus on the display monitor was adjusted based on eye position measurements to control for changes in retinal locations due to eye movements. A method for extracting nonstationary first-order response mechanisms was applied, so that changes around the times of saccades could be observed. Saccade-related changes were seen in both amplitude and timing of geniculate responses. Amplitudes were greatly reduced around saccades. Timing was retarded slightly during a window of about 200 ms around saccades. That is, responses became more sustained. These effects were found in both parvocellular and magnocellular neurons. Timing changes in LGN might play a role in maintaining cortical responses to visual stimuli in the presence of eye movements, compensating for the spatial shifts caused by saccades via these shifts in timing.

Abnormal fixational eye movements in strabismus

2017 ◽  
Vol 102 (2) ◽  
pp. 253-259 ◽  
Author(s):  
Fatema F Ghasia ◽  
Jorge Otero-Millan ◽  
Aasef G Shaikh
Keyword(s):  
Eye Movements ◽  
Large Angle ◽  
Fine Tuning ◽  
Eye Position ◽  
Visually Guided ◽  
Binocular Fusion ◽  
The Gaze ◽  
Fixational Eye Movements ◽  
The Stability ◽  
Fixational Saccades

IntroductionFixational saccades are miniature eye movements that constantly change the gaze during attempted visual fixation. Visually guided saccades and fixational saccades represent an oculomotor continuum and are produced by common neural machinery. Patients with strabismus have disconjugate binocular horizontal saccades. We examined the stability and variability of eye position during fixation in patients with strabismus and correlated the severity of fixational instability with strabismus angle and binocular vision.MethodsEye movements were measured in 13 patients with strabismus and 16 controls during fixation and visually guided saccades under monocular viewing conditions. Fixational saccades and intersaccadic drifts were analysed in the viewing and non-viewing eye of patients with strabismus and controls.ResultsWe found an increase in fixational instability in patients with strabismus compared with controls. We also found an increase in the disconjugacy of fixational saccades and intrasaccadic ocular drift in patients with strabismus compared with controls. The disconjugacy was worse in patients with large-angle strabismus and absent stereopsis. There was an increase in eye position variance during drifts in patients with strabismus. Our findings suggest that both fixational saccades and intersaccadic drifts are abnormal and likely contribute to the fixational instability in patients with strabismus.DiscussionFixational instability could be a useful tool for mass screenings of children to diagnose strabismus in the absence of amblyopia and latent nystagmus. The increased disconjugacy of fixational eye movements and visually guided saccades in patients with strabismus reflects the disruption of the fine-tuning of the motor and visual systems responsible for achieving binocular fusion in these patients.

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