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Practical Neurology Oct 2018Ocular neuromyotonia is a rare, albeit treatable, ocular motor disorder, characterised by recurrent brief episodes of diplopia due to tonic extraocular muscle...
Ocular neuromyotonia is a rare, albeit treatable, ocular motor disorder, characterised by recurrent brief episodes of diplopia due to tonic extraocular muscle contraction. Ephaptic transmission in a chronically damaged ocular motor nerve is the possible underlying mechanism. It usually improves with carbamazepine. A 53-year-old woman presented with a 4-month history of recurrent episodes of binocular vertical diplopia (up to 40/day), either spontaneously or after sustained downward gaze. Between episodes she had a mild left fourth nerve palsy. Sustained downward gaze consistently triggered downward left eye tonic deviation, lasting around 1 min. MR scan of the brain was normal. She improved on starting carbamazepine but developed a rash that necessitated stopping the drug. Switching to lacosamide controlled her symptoms.
Topics: Female; Fixation, Ocular; Humans; Isaacs Syndrome; Middle Aged; Ocular Motility Disorders
PubMed: 29467180
DOI: 10.1136/practneurol-2017-001866 -
Journal of Vision Apr 2024This paper reviews projection models and their perception in realistic pictures, and proposes hypotheses for three-dimensional (3D) shape and space perception in... (Review)
Review
This paper reviews projection models and their perception in realistic pictures, and proposes hypotheses for three-dimensional (3D) shape and space perception in pictures. In these hypotheses, eye fixations, and foveal vision play a central role. Many past theories and experimental studies focus solely on linear perspective. Yet, these theories fail to explain many important perceptual phenomena, including the effectiveness of nonlinear projections. Indeed, few classical paintings strictly obey linear perspective, nor do the best distortion-avoidance techniques for wide-angle computational photography. The hypotheses here employ a two-stage model for 3D human vision. When viewing a picture, the first stage perceives 3D shape for the current gaze. Each fixation has its own perspective projection, but, owing to the nature of foveal and peripheral vision, shape information is obtained primarily for a small region of the picture around the fixation. As a viewer moves their eyes, the second stage continually integrates some of the per-gaze information into an overall interpretation of a picture. The interpretation need not be geometrically stable or consistent over time. It is argued that this framework could explain many disparate pictorial phenomena, including different projection styles throughout art history and computational photography, while being consistent with the constraints of human 3D vision. The paper reviews open questions and suggests new studies to explore these hypotheses.
Topics: Humans; Fixation, Ocular; Form Perception; Depth Perception; Space Perception; Eye Movements; Fovea Centralis
PubMed: 38662346
DOI: 10.1167/jov.24.4.23 -
Vision Research Jan 2016During natural viewing large saccades shift the visual gaze from one target to another every few hundreds of milliseconds. The role of microsaccades (MSs), small... (Review)
Review
During natural viewing large saccades shift the visual gaze from one target to another every few hundreds of milliseconds. The role of microsaccades (MSs), small saccades that show up during long fixations, is still debated. A major debate is whether MSs are used to redirect the visual gaze to a new location or to encode visual information through their movement. We argue that these two functions cannot be optimized simultaneously and present several pieces of evidence suggesting that MSs redirect the visual gaze and that the visual details are sampled and encoded by ocular drifts. We show that drift movements are indeed suitable for visual encoding. Yet, it is not clear to what extent drift movements are controlled by the visual system, and to what extent they interact with saccadic movements. We analyze several possible control schemes for saccadic and drift movements and propose experiments that can discriminate between them. We present the results of preliminary analyses of existing data as a sanity check to the testability of our predictions.
Topics: Attention; Fixation, Ocular; Humans; Saccades; Vision, Ocular; Visual Perception
PubMed: 25535005
DOI: 10.1016/j.visres.2014.12.004 -
European Journal of Sport Science Feb 2017Scientists who have examined the gaze strategies employed by athletes have determined that longer quiet eye (QE) durations (QED) are characteristic of skilled compared... (Review)
Review
Scientists who have examined the gaze strategies employed by athletes have determined that longer quiet eye (QE) durations (QED) are characteristic of skilled compared to less-skilled performers. However, the cognitive mechanisms of the QE and, specifically, how the QED affects performance are not yet fully understood. We review research that has examined the functional mechanism underlying QE and discuss the neural networks that may be involved. We also highlight the limitations surrounding QE measurement and its definition and propose future research directions to address these shortcomings. Investigations into the behavioural and neural mechanisms of QE will aid the understanding of the perceptual and cognitive processes underlying expert performance and the factors that change as expertise develops.
Topics: Athletic Performance; Attention; Fixation, Ocular; Humans; Psychomotor Performance; Visual Perception
PubMed: 26356536
DOI: 10.1080/17461391.2015.1075595 -
Eye (London, England) Feb 2015Human saccades and fixations have numerous functions in complex everyday tasks, which have sometimes been neglected in simple experimental situations. In this review I... (Review)
Review
Human saccades and fixations have numerous functions in complex everyday tasks, which have sometimes been neglected in simple experimental situations. In this review I describe some of the characteristics of eye movement behaviour during real-world interactions with objects, while walking in natural environments and while holding a conversation. When performing real-world actions and walking around the world, we fixate relevant features at critical time points during the task. The eye movements between these fixations are planned and coordinated alongside head and body movements, often occurring a short time before the corresponding action. In social interactions, eye movements are both a mechanism for taking in information (for example, when looking at someone's face or following their gaze) and for signalling one's attention to another person. Thus eye movements are specific to a particular task context and subject to high-level planning and control during everyday actions.
Topics: Activities of Daily Living; Fixation, Ocular; Humans; Posture; Saccades
PubMed: 25397783
DOI: 10.1038/eye.2014.275 -
The British Journal of Ophthalmology Nov 1967
Topics: Accommodation, Ocular; Fixation, Ocular; Humans; Miotics; Strabismus; Vision Tests
PubMed: 6060810
DOI: 10.1136/bjo.51.11.786 -
PloS One 2017Binocular vision refers to the integration of images in the two eyes for improved visual performance and depth perception. One aspect of binocular vision is the fixation...
Binocular vision refers to the integration of images in the two eyes for improved visual performance and depth perception. One aspect of binocular vision is the fixation disparity, which is a suboptimal condition in individuals with respect to binocular eye movement control and subsequent neural processing. The objective fixation disparity refers to the vergence angle between the visual axes, which is measured with eye trackers. Subjective fixation disparity is tested with two monocular nonius lines which indicate the physical nonius separation required for perceived alignment. Subjective and objective fixation disparity represent the different physiological mechanisms of motor and sensory fusion, but the precise relation between these two is still unclear. This study measures both types of fixation disparity at viewing distances of 40, 30, and 24 cm while observers fixated a central stationary fusion target. 20 young adult subjects with normal binocular vision were tested repeatedly to investigate individual differences. For heterophoria and subjective fixation disparity, this study replicated that the binocular system does not properly adjust to near targets: outward (exo) deviations typically increase as the viewing distance is shortened. This exo proximity effect-however-was not found for objective fixation disparity, which-on the average-was zero. But individuals can have reliable outward (exo) or inward (eso) vergence errors. Cases with eso objective fixation disparity tend to have less exo states of subjective fixation disparity and heterophoria. In summary, the two types of fixation disparity seem to respond in a different way when the viewing distance is shortened. Motor and sensory fusion-as reflected by objective and subjective fixation disparity-exhibit complex interactions that may differ between individuals (eso versus exo) and vary with viewing distance (far versus near vision).
Topics: Adult; Fixation, Ocular; Humans; Models, Theoretical; Regression Analysis; Reproducibility of Results; Vision Disparity; Young Adult
PubMed: 28135308
DOI: 10.1371/journal.pone.0170190 -
Journal of Vision Nov 2019Accurate positioning of the naked eye is a prerequisite in many ophthalmic measurement and intervention systems. In most of these procedures the eyeball is stabilized...
Accurate positioning of the naked eye is a prerequisite in many ophthalmic measurement and intervention systems. In most of these procedures the eyeball is stabilized through fixation of a target. Fixation is initiated, as well as sustained by a whole set of oculomotor processes: saccadic movements and drift, as well as vergence. Target appearance influences sustained fixation, but the influence of target information on the initiation of fixation has not been evaluated in detail. The current study evaluates the accuracy of fixation initiation as well as sustained fixation under refractive error. Twenty-one ametrope subjects repeatedly fixated a laser speckle-based fixation target for an extended duration of 3 s. Fixational area, fixational saccade rate as well as fixational saccade amplitude were analyzed during two different time intervals, namely in fixation initiation and sustained fixation. Fixation initiation was evaluated within the first 500 ms of fixation, whereas sustained fixation was evaluated 1 s after the eyes were directed toward the fixation target. During fixation initiation, fixation accuracy decreased in comparison to sustained fixation; fixational saccades occurred more frequently, and with larger amplitudes. During sustained fixation, an impact of refractive error was shown. With increasing refractive error, fixational saccade amplitude and fixational saccade rate increased. Fixational area increased in high ametropia through larger and more frequent saccades, but at a rather moderate rate of 10 arcmin/diopter (dpt) radial increase.
Topics: Adult; Female; Fixation, Ocular; Humans; Hyperopia; Male; Myopia; Saccades; Young Adult
PubMed: 31715631
DOI: 10.1167/19.13.8 -
Journal of Vision Jan 2017Microsaccades are high-velocity fixational eye movements, with special roles in perception and cognition. The default microsaccade detection method is to determine when...
Microsaccades are high-velocity fixational eye movements, with special roles in perception and cognition. The default microsaccade detection method is to determine when the smoothed eye velocity exceeds a threshold. We have developed a new method, Bayesian microsaccade detection (BMD), which performs inference based on a simple statistical model of eye positions. In this model, a hidden state variable changes between drift and microsaccade states at random times. The eye position is a biased random walk with different velocity distributions for each state. BMD generates samples from the posterior probability distribution over the eye state time series given the eye position time series. Applied to simulated data, BMD recovers the "true" microsaccades with fewer errors than alternative algorithms, especially at high noise. Applied to EyeLink eye tracker data, BMD detects almost all the microsaccades detected by the default method, but also apparent microsaccades embedded in high noise-although these can also be interpreted as false positives. Next we apply the algorithms to data collected with a Dual Purkinje Image eye tracker, whose higher precision justifies defining the inferred microsaccades as ground truth. When we add artificial measurement noise, the inferences of all algorithms degrade; however, at noise levels comparable to EyeLink data, BMD recovers the "true" microsaccades with 54% fewer errors than the default algorithm. Though unsuitable for online detection, BMD has other advantages: It returns probabilities rather than binary judgments, and it can be straightforwardly adapted as the generative model is refined. We make our algorithm available as a software package.
Topics: Algorithms; Bayes Theorem; Fixation, Ocular; Humans; Saccades; Visual Perception
PubMed: 28114483
DOI: 10.1167/17.1.13 -
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