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Journal of Vision 2016During visual fixation, we constantly move our eyes. These microscopic eye movements are composed of tremor, drift, and microsaccades. Early studies concluded that...
During visual fixation, we constantly move our eyes. These microscopic eye movements are composed of tremor, drift, and microsaccades. Early studies concluded that microsaccades, like larger saccades, are binocular and conjugate, as expected from Hering's law of equal innervation. Here, we document the existence of monocular microsaccades during both fixation and a discrimination task, reporting the location of the gap in a foveal, low-contrast letter C. Monocular microsaccades differ in frequency, amplitude, and peak velocity from binocular microsaccades. Our analyses show that these differences are robust to different velocity and duration criteria that have been used previously to identify microsaccades. Also, the frequency of monocular microsaccades differs systematically according to the task: monocular microsaccades occur more frequently during fixation than discrimination, the opposite of their binocular equivalents. However, during discrimination, monocular microsaccades occur more often around the discrimination threshold, particularly for each subject's dominant eye and in case of successful discrimination. We suggest that monocular microsaccades play a functional role in the production of fine corrections of eye position and vergence during demanding visual tasks.
Topics: Adult; Discrimination Learning; Female; Fixation, Ocular; Humans; Male; Saccades; Task Performance and Analysis; Visual Perception; Young Adult
PubMed: 26913629
DOI: 10.1167/16.3.37 -
Developments in Ophthalmology 2007To foveate targets in different depths, the movements of the two eyes must be disconjugate. Fine measurements of eye rotations about the three principal axes have... (Review)
Review
To foveate targets in different depths, the movements of the two eyes must be disconjugate. Fine measurements of eye rotations about the three principal axes have demonstrated that disconjugate eye movements may appear not only in the horizontal, but also in the vertical and torsional directions. In the presence of visual targets, disconjugate eye movements are driven by the vergence system, but they may also appear during vestibular stimulation. Disconjugate eye movements are highly adaptable by visual disparities, but under normal condition the effects of adaptation only persist when one eye is covered. Finally, disorders of the brainstem and cerebellum may lead to abnormal disconjugate eye movements that are often specific for the topography of the lesion. This chapter reviews the literature on the phenomenology of disconjugate eye movements over the last 15 years.
Topics: Adaptation, Ocular; Eye Movements; Fixation, Ocular; Humans; Vision, Binocular
PubMed: 17314481
DOI: 10.1159/000100351 -
Ophthalmic & Physiological Optics : the... Sep 2001The reliability and validity of new tests of fixation disparity were investigated as a function of viewing distance (100, 60, 40, and 30 cm). The 'nonius offset card'...
The reliability and validity of new tests of fixation disparity were investigated as a function of viewing distance (100, 60, 40, and 30 cm). The 'nonius offset card' presents a set of paired dichoptic nonius (vernier) lines with different offset simultaneously: the subject has to indicate the coinciding lines. The 'computer test' uses a psychophysical procedure that presents one pair of nonius lines sequentially with varying offset; the effect of the number of short-term nonius test trials is investigated. As a reference, the Mallett unit and the Sheedy disparometer were used. Despite different group means, the methods had significant test-retest correlations and inter-correlations, as tested at 40 cm. All methods showed an increase in exo fixation disparity as the viewing distance was shortened; the slope of this proximity-fixation-disparity curve, however, was different between the nonius offset card and the computer test.
Topics: Computer Graphics; Fixation, Ocular; Humans; Optometry; Psychophysics; Reproducibility of Results; Vision Disparity
PubMed: 11563424
DOI: 10.1046/j.1475-1313.2001.00600.x -
Optica Acta 1968
Topics: Fixation, Ocular; Form Perception; Humans
PubMed: 5661779
DOI: 10.1080/713818090 -
Perception 2007
Topics: Depth Perception; Eye Movements; Fixation, Ocular; Head Movements; Humans; Motion Perception; Vision Disparity
PubMed: 17844961
DOI: 10.1068/p3607ed -
Graefe's Archive For Clinical and... Oct 2006To investigate the effect of unsteady fixation on the multifocal electroretinogram (mfERG) measurement in normal subjects.
PURPOSE
To investigate the effect of unsteady fixation on the multifocal electroretinogram (mfERG) measurement in normal subjects.
METHODS
The mfERGs of 20 subjects with normal vision (mean age=23.5 years) were recorded with different levels of voluntary eye movements made to mimic unsteady fixation. Subjects were required to move their fixation regularly every 2 s between the center and the ends of a fixation cross, so that 51.2% of the time fixation was at the center and 12.2% of the time it was at each end of the fixation cross. Four different conditions were performed: central fixation (without voluntary eye movements) and with 2 degrees, 4 degrees and 6 degrees magnitude of unsteady fixation. First-order kernel mfERG findings are presented.
RESULTS
Analysis of the ring responses indicated that the central mfERG amplitude was most affected by unsteady fixation. There was significantly reduced amplitude for 4 degrees unsteady fixation and as expected, this reduction became larger with 6 degrees unstable fixation. However, there was no significant effect on the center hexagon amplitude for 2 degrees unsteady fixation. The amplitudes of the ring-2 responses were only affected in the 6 degrees unsteady fixation condition. No significant change in implicit time was found for any level of unsteady fixation.
CONCLUSION
These results suggest that mfERG amplitude is not substantially affected if fixation is maintained within the central stimulus hexagon. We conclude that, for patients with poor fixation, the accuracy of mfERG results may be difficult to interpret and the use of a fixation-monitoring system is desirable for ideal measurement. The depth of depression at the blind spot area may be another useful parameter to interpret the accuracy of mfERG results in patients with poor fixation.
Topics: Adult; Electroretinography; Eye Movements; Fixation, Ocular; Humans; Retina
PubMed: 16550403
DOI: 10.1007/s00417-006-0304-8 -
Psychonomic Bulletin & Review Oct 2020Gaze-where one looks, how long, and when-plays an essential part in human social behavior. While many aspects of social gaze have been reviewed, there is no... (Review)
Review
Gaze-where one looks, how long, and when-plays an essential part in human social behavior. While many aspects of social gaze have been reviewed, there is no comprehensive review or theoretical framework that describes how gaze to faces supports face-to-face interaction. In this review, I address the following questions: (1) When does gaze need to be allocated to a particular region of a face in order to provide the relevant information for successful interaction; (2) How do humans look at other people, and faces in particular, regardless of whether gaze needs to be directed at a particular region to acquire the relevant visual information; (3) How does gaze support the regulation of interaction? The work reviewed spans psychophysical research, observational research, and eye-tracking research in both lab-based and interactive contexts. Based on the literature overview, I sketch a framework for future research based on dynamic systems theory. The framework holds that gaze should be investigated in relation to sub-states of the interaction, encompassing sub-states of the interactors, the content of the interaction as well as the interactive context. The relevant sub-states for understanding gaze in interaction vary over different timescales from microgenesis to ontogenesis and phylogenesis. The framework has important implications for vision science, psychopathology, developmental science, and social robotics.
Topics: Facial Recognition; Fixation, Ocular; Humans; Social Interaction; Social Perception
PubMed: 32367351
DOI: 10.3758/s13423-020-01715-w -
Vision Research Oct 1996Saccades are often elicited in the laboratory by the abrupt step-displacement of a single lit point which is initially the foveolar fixation point and then the eccentric...
Saccades are often elicited in the laboratory by the abrupt step-displacement of a single lit point which is initially the foveolar fixation point and then the eccentric refixation target. This was our Control condition. Four experiments modified the fixation arrangements to examine the effect of altered foveolar stimulation on saccadic latency and accuracy to targets within the central +/- 6 deg of the visual field. (1) No foveolar fixation point: The subject fixated the empty space midway between a pair of fixation guides, which later collapsed into a single refixation target. Latencies for small saccades were similar to the Control values. (2) No foveolar fixation point and no real refixation target: A pair of fixation guides underwent a yoked displacement, and it was easy to fixate and track the invisible midpoint. The smallest saccades were hypermetric, and the typical pattern of latency variation with retinal eccentricity was exaggerated in scale. (3) Spatial effects of a persistent non-target: The precise position of a non-target was important, latency increases being in the ipsilateral hemifield when the non-target was intrafoveolar and unilateral, bilateral when intrafoveolar and on the midline, and local when the non-target was extrafoveolar. (4) Temporal effects of a foveolar fixation point: Blanking an otherwise persistent fixation point for as little as 1 msec at the time of target presentation reduced the expected latency increase. We conclude that the position and timing of foveolar illumination can be critical for saccades of all sizes.
Topics: Fixation, Ocular; Fovea Centralis; Humans; Saccades; Time Factors; Visual Fields
PubMed: 8917779
DOI: 10.1016/0042-6989(96)00029-6 -
Journal of Vision Jun 2018Micromovements of the eye during visual fixations provide clues about how our visual system acquires information. The analysis of fixational eye movements can thus serve...
Micromovements of the eye during visual fixations provide clues about how our visual system acquires information. The analysis of fixational eye movements can thus serve as a noninvasive means to detect age-related or pathological changes in visual processing, which can in turn reflect associated cognitive or neurological disorders. However, the utility of such diagnostic approaches relies on the quality and usability of detection methods applied for the eye movement analysis. Here, we propose a novel method for (micro)saccade detection that is resistant to high-frequency recording noise, a frequent problem in video-based eye tracking in either aged subjects or subjects suffering from a vision-related pathology. The method is fast, it does not require manual noise removal, and it can work with position, velocity, or acceleration features, or a combination thereof. The detection accuracy of the proposed method is assessed on a new dataset of manually labeled recordings acquired from 14 subjects of advanced age (69-81 years old), performing an ocular fixation task. It is demonstrated that the detection accuracy of the new method compares favorably to that of two frequently used reference methods and that it is comparable to the best of the two algorithms when tested on an existing low-noise eye-tracking dataset.
Topics: Aged; Aged, 80 and over; Algorithms; Female; Fixation, Ocular; Humans; Male; Noise; Saccades; Visual Pathways; Visual Perception
PubMed: 30029229
DOI: 10.1167/18.6.19 -
Progress in Brain Research 2009The present chapter suggests that while there is strong evidence that specific brain systems are preferentially biased toward processing gaze information, this...
The present chapter suggests that while there is strong evidence that specific brain systems are preferentially biased toward processing gaze information, this specificity is not mirrored by the behavioral data as measured in highly controlled impoverished model tasks. In less controlled tasks, however, such as when observers are left free to look at whatever they want in complex natural scenes, observers focus on people and their eyes. This agrees with one's intuition, and with the neural evidence, that eyes are special. We discuss the implications of these data, including that there is much to be gained by examining brain and behavioral processes to social stimuli as they occur in complex real-world settings.
Topics: Attention; Cues; Fixation, Ocular; Humans; Imitative Behavior; Orientation; Social Behavior; Social Environment; Social Perception; Space Perception
PubMed: 19733765
DOI: 10.1016/S0079-6123(09)17618-5