Nystagmus

2008 ◽  
Author(s):  
Agnes Wong
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
The Other ◽  
Whipple’S Disease ◽  
Internuclear Ophthalmoplegia ◽  
Optokinetic System ◽  
Gaze Holding ◽  
Slow Eye Movements ◽  
Ocular System ◽  
System 1

Nystagmus is involuntary eye oscillations initiated by slow eye movements that drive the eye away from the target. In contrast, saccadic dyskinesia consists of involuntary, fast eye movements that take the fovea off target. Nystagmus usually arises from lesions in the 1. Vestibulo-ocular system (VOR) 2. Gaze-holding system 3. Smooth pursuit and optokinetic system. 1. Pendular versus jerk ■ Pendular (see A in the figure below): both phases are slow eye movements. ■ Jerk (see B, C, and D in the figure below): one phase consists of fast eye movements (quick phase), and the other consists of slow eye movements. By convention, the direction of nystagmus is named after the direction of quick phases that return the eye to the target. 2. Plane: horizontal, vertical, torsional, or combined form (e.g., rotary, elliptical) 3. Conjugacy ■ Conjugate: Both eyes move in the same direction with similar amplitude and frequency. ■ Disconjugate: Both eyes move in the same direction with different amplitude and frequency (e.g., internuclear ophthalmoplegia). ■ Disjunctive: The eyes move in opposite directions (e.g., oculomasticatory myorhythmia seen in Whipple’s disease).

Visually evoked slow eye movements, visual-vestibular interaction, and infratentorial lesions

1983 ◽  
Vol 91 (1) ◽  
pp. 76-80 ◽  
Author(s):  
Carsten Wennmo ◽  
Nils Gunnar Henriksson ◽  
Bengt Hindfelt ◽  
Ilmari PyykkÖ ◽  
MÅNs Magnusson
Keyword(s):  
Eye Movements ◽  
Phase Velocity ◽  
Brain Stem ◽  
Smooth Pursuit ◽  
Maximum Velocity ◽  
Slow Phase ◽  
Slow Phase Velocity ◽  
Velocity Gain ◽  
Visual Vestibular Interaction ◽  
Slow Eye Movements

The maximum velocity gain of smooth pursuit and optokinetic, vestibular, and optovestibular slow phases was examined in 15 patients with pontine, 10 with medullary, 10 with cerebellar, and 5 with combined cerebello — brain stem disorders. Marked dissociations were observed between smooth pursuit and optokinetic slow phases, especially in medullary disease. A cerebellar deficit enhanced slow phase velocity gain during rotation in darkness, whereas the corresponding gain during rotation in light was normal.

Lidocaine-induced unilateral internuclear ophthalmoplegia: effects on convergence and conjugate eye movements

1989 ◽  
Vol 62 (1) ◽  
pp. 82-95 ◽  
Author(s):  
P. D. Gamlin ◽  
J. W. Gnadt ◽  
L. E. Mays
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Open Loop ◽  
Medial Longitudinal Fasciculus ◽  
Slow Phase ◽  
Internuclear Ophthalmoplegia ◽  
Unaffected Side ◽  
Affected Side ◽  
Position Signal ◽  
Slow Drift

1. To characterize the vergence signal carried by the medial longitudinal fasciculus (MLF), it was subjected to reversible blockade by small injections of 10% lidocaine hydrochloride. The effects of these blockades on both conjugate and vergence eye movements were studied. 2. With this procedure, experimentally induced internuclear ophthalmoplegia (INO) and its effects on conjugate eye movements could be studied acutely, without possible contamination from long-term oculomotor adaptation. In the eye contralateral to the MLF blockade, saccadic and horizontal smooth-pursuit eye movements were normal. Horizontal abducting nystagmus, often seen in patients with INO, was not observed in this eye. 3. As previously reported for INO, profound oculomotor deficits were seen in the eye ipsilateral to the MLF blockade. During maximal blockade, adducting saccades and horizontal smooth-pursuit movements in this eye did not cross the midline. Adducting saccades were reduced in amplitude and peak velocity and showed significantly increased durations. Abducting saccades, which were slightly hypometric, displayed a marked postsaccadic centripetal drift. 4. The eye ipsilateral to the blockade displayed a pronounced, upward, slow drift, whereas the eye contralateral to the blockade showed virtually no drift. Furthermore, although vertical saccades to visual targets remained essentially conjugate, the size of the resetting quick phases in each eye was related to the amplitude of the slow phase movement in that eye. Thus the eye on the affected side displayed large quick phases, whereas the eye on the unaffected side showed only slight movements. On occasion, unilateral downbeating nystagmus was seen. This strongly suggests that the vertical saccade generators for the two eyes can act independently. 5. The effect of MLF blockade on the vergence gain of the eye on the affected side was investigated. As a measure of open-loop vergence gain, the relationship of accommodative convergence to accommodation (AC/A) was measured before, during, and after reversible lidocaine block of the MLF. After taking conjugate deficits into account, the net vergence signal to the eye ipsilateral to the injection was found to increase significantly during the reversible blockade. 6. The most parsimonious explanation for this increased vergence signal is suggested by the accompanying single-unit study. This study showed that abducens internuclear neurons, whose axons course in the MLF, provide medial rectus motoneurons with an appropriate horizontal conjugate eye position signal but an inappropriate vergence signal. Ordinarily, this incorrect vergence signal is overcome by another, more potent, v

Binocular interaction in the optokinetic system of the crab Carcinus maenas (L.): Optokinetic gain modified by bilateral image flow

1993 ◽  
Vol 10 (5) ◽  
pp. 873-885 ◽  
Author(s):  
Hans-Ortwin Nalbach ◽  
Peter Thier ◽  
Dezsö Varjú
Keyword(s):  
Eye Movements ◽  
Phase Shift ◽  
Carcinus Maenas ◽  
The Other ◽  
Rotational Component ◽  
Control Loop ◽  
Optokinetic System ◽  
Image Flow ◽  
Binocular Interaction ◽  
Better Than

AbstractWe recorded optokinetic eye movements of the crab, Carcinus maenas, in split-drum experiments. The patterns were either oscillated in antiphase on both sides mimicking translational image flow or they were oscillated in phase producing rotational image flow. Eye movements elicited by the rotational stimulus were larger than those produced by the pseudotranslational pattern movements. The smaller response to the latter is mainly a consequence of binocular interaction, the strength of which depends on both the phase-shift and amplitude of pattern oscillation. We develop two hypotheses to explain our results: either (1) signals from each eye modify the gain of the linkage signals coming from the other eye, or (2) the signals coming from the other eye modify the gain of the control loop itself. Quantitative evaluation of the data favors the second of these two hypotheses, which comprises the models of Barnes and Horridge (1969) and Nalbach et al. (1985). In addition, we found that it is the signals from the two slow channels of the crab's movement-detecting system that are transferred from one eye to the other, while signals of the fastest channel act almost exclusively ipsilaterally. We discuss our results as an adaptation by which an animal with panoramic vision compensates exclusively the rotational component of image flow during locomotion. The fact that freely walking crabs distinguish the two components of image flow better than restrained crabs indicates that further visual and nonvisual signals help to disentangle image flow.

Cranial Neuropathies & Brainstem Syndromes

Neuroanatomy ◽  
2017 ◽  
pp. 206-244
Author(s):  
Adam J Fisch
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Facial Palsy ◽  
Internuclear Ophthalmoplegia ◽  
Smooth Pursuit Eye Movements ◽  
Pupillary Reflex ◽  
Pursuit Eye Movements ◽  
Gag Reflex ◽  
Cranial Neuropathies ◽  
Specific Disorders

This chapter addresses the various cranial neuropathies and brainstem syndromes and their respective anatomical components. Included among these disorders are pupillary reflex pathologies, oral-palatal deviations, gag reflex, facial palsy, Bell’s palsy, internuclear ophthalmoplegia, midbrain syndromes, pontine syndromes, and medullary syndromes. Instructions are presented on how to draw the elements of the neuropathies and syndromes, as well as the trigeminal nerve, central pathways, central somatotopic maps, and smooth pursuit eye movements. Finally, case histories of specific disorders are presented along with discussion of the elements involved in making the diagnosis.

Spatial but Not Temporal Cueing Influences the Mislocalisation of a Target Flashed during Smooth Pursuit

Perception ◽  
10.1068/p3411 ◽  
2002 ◽  
Vol 31 (10) ◽  
pp. 1195-1203 ◽  
Author(s):  
Gerben Rotman ◽  
Eli Brenner ◽  
Jeroen B J Smeets
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Normal Condition ◽  
Smooth Pursuit ◽  
Human Subjects ◽  
The Other ◽  
Moving Target ◽  
Pursuit Eye Movements

Human subjects misjudge the position of a target that is flashed during a pursuit eye movement. Their judgments are biased in the direction in which the eyes are moving. We investigated whether this bias can be reduced by making the appearance of the flash more predictable. In the normal condition, subjects pursued a moving target that flashed somewhere along its trajectory. After the presentation, they indicated where they had seen the flash. The mislocalisations in this condition were compared to mislocalisations in conditions in which the subjects were given information about when or where the flash would come. This information consisted of giving two warning flashes spaced at equal intervals before the target flash, of giving two warning beeps spaced at equal intervals before the target flash, or of showing the same stimulus twice. Showing the same stimulus twice significantly reduced the mislocalisation. The other conditions did not. We interpret this as indicating that it is not predictability as such that influences the performance, but the fact that the target appears at a spatially cued position. This was supported by a second experiment, in which we examined whether subjects make smaller mis-judgments when they have to determine the distance between a target flashed during pursuit and a reference seen previously, than when they have to determine the distance between the flashed target and a reference seen afterwards. This was indeed the case, presumably because the reference provided a spatial cue for the flash when it was presented first. We conclude that a spatial cue reduces the mislocalisation of targets that are flashed during pursuit eye movements. The cue does not have to be exactly at the same position as the flash.

Ocular Motor Disorders Caused by Lesions in the Brainstem

2008 ◽  
Author(s):  
Agnes Wong
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Head Tracking ◽  
Dorsomedial Nucleus ◽  
Abducens Nucleus ◽  
Burst Neurons ◽  
Gaze Holding ◽  
Clinical Correlate ◽  
Cerebellar Peduncle ◽  
Ventral Paraflocculus

Oculopalatal tremor usually occurs many months after an initial insult, due to neural deafferentation. It rarely resolves spontaneously. Treatment is with gabapentin, ceruletide, or anticolinergic agents. The y-group is a small group of cells that lies rostral to the inferior cerebellar peduncle. It receives inputs from the saccule (part of the otolith) and from Purkinje cells of the flocculus, and it projects to the oculomotor and trochlear nuclei via the superior cerebellar peduncle and a crossing ventral tegmental tract. 1. Discharge during upward smooth pursuit, optokinetic, and combined eye-head tracking (VOR cancellation), but not during VOR in darkness (see sections 3.14 and 5.2) 2. Together with the flocculus and ventral paraflocculus, may contribute to vertical VOR adaptation (see section 3.12) No known documented clinical correlate Collections of neurons scattered along the midline fiber tracts in the pons and medulla, including: 1. The nucleus pararaphales in the medulla, which receives vertical eye position signals from the INC, and projects to the flocculus and ventral paraflocculus 2. The nucleus incertus in the pons, which contains burst-tonic neurons that mainly discharge in relation to horizontal eye movements, and projects to the flocculus Function: may send an “efference copy” of eye movement commands to the flocculus for gaze holding or longer term adaptation No known documented clinical correlate The abducens nucleus contains: 1. Abducens motoneurons that innervate the ipsilateral lateral rectus 2. Abducens internuclear neurons, the axons of which cross the midline and ascend via the MLF to innervate the contralateral medial rectus motoneurons in the oculomotor nucleus. 3. Neurons that project to the cerebeller flocculus The abducens nucleus is the final common motor pathway for horizontal conjugate eye movements, as it receives input for horizontal saccades, VOR, and smooth pursuit. The paramedian pontine reticular formation (PPRF) contains: Excitatory burst neurons (EBN) in the dorsomedial nucleus reticularis pontis caudalis (NRPC) that ■ Project to the ipsilateral abducens nucleus to generate ipsilateral, conjugate, horizontal saccades ■ Project to inhibitory burst neurons in the nucleus paragigantocellularis dorsalis (PGD) and receive inhibitory inputs from omnipause neurons in nucleus raphe interpositus (rip)

Supranuclear Ocular Motor Systems

2021 ◽  
pp. 105-114
Author(s):  
Scott D. Eggers
Keyword(s):  
Eye Movements ◽  
Basal Ganglia ◽  
Smooth Pursuit ◽  
Saccadic Eye Movements ◽  
Ocular Motor ◽  
Motor Systems ◽  
Slow Eye Movements ◽  
Vestibulocerebellar Input

Properly functioning eye movements facilitate a clear, stable view of the environment. Saccadic eye movements and nystagmus fast phases are 2 types of fast eye movements. Slow eye movements include smooth pursuit, vestibular, optokinetic, and vergence. Reflexive and voluntary conjugate eye movements incorporate cortical, subcortical (basal ganglia), and vestibulocerebellar input to the final common pathways of horizontal and vertical eye movements. The present chapter reviews the anatomy and dysfunction of the supranuclear input to conjugate gaze.

Chromatic Contrast Sensitivity During Optokinetic Nystagmus, Visually Enhanced Vestibulo-ocular Reflex, and Smooth Pursuit Eye Movements

2009 ◽  
Vol 101 (5) ◽  
pp. 2317-2327 ◽  
Author(s):  
Alexander C. Schütz ◽  
Doris I. Braun ◽  
Karl R. Gegenfurtner
Keyword(s):  
Eye Movements ◽  
Contrast Sensitivity ◽  
Smooth Pursuit ◽  
Optokinetic Nystagmus ◽  
Slow Phase ◽  
Smooth Pursuit Eye Movements ◽  
Pursuit Eye Movements ◽  
Ocular Reflex ◽  
Vestibulo Ocular Reflex ◽  
Slow Eye Movements

Recently we showed that sensitivity for chromatic- and high-spatial frequency luminance stimuli is enhanced during smooth-pursuit eye movements (SPEMs). Here we investigated whether this enhancement is a general property of slow eye movements. Besides SPEM there are two other classes of eye movements that operate in a similar range of eye velocities: the optokinetic nystagmus (OKN) is a reflexive pattern of alternating fast and slow eye movements elicited by wide-field visual motion and the vestibulo-ocular reflex (VOR) stabilizes the gaze during head movements. In a natural environment all three classes of eye movements act synergistically to allow clear central vision during self- and object motion. To test whether the same improvement of chromatic sensitivity occurs during all of these eye movements, we measured human detection performance of chromatic and luminance line stimuli during OKN and contrast sensitivity during VOR and SPEM at comparable velocities. For comparison, performance in the same tasks was tested during fixation. During the slow phase of OKN we found a similar enhancement of chromatic detection rate like that during SPEM, whereas no enhancement was observable during VOR. This result indicates similarities between slow-phase OKN and SPEM, which are distinct from VOR.

Visual asymmetries during face encoding Increased dwell time and fixations in the upper and left hemifields

2018 ◽  
Author(s):  
Fatima Maria Felisberti
Keyword(s):  
Face Recognition ◽  
Eye Movements ◽  
Visual Field ◽  
Face Processing ◽  
Dwell Time ◽  
The Other ◽  
Environmental Cues ◽  
Reading Habits ◽  
The Right

Visual field asymmetries (VFA) in the encoding of groups rather than individual faces has been rarely investigated. Here, eye movements (dwell time (DT) and fixations (Fix)) were recorded during the encoding of three groups of four faces tagged with cheating, cooperative, or neutral behaviours. Faces in each of the three groups were placed in the upper left (UL), upper right (UR), lower left (LL), or lower right (LR) quadrants. Face recognition was equally high in the three groups. In contrast, the proportion of DT and Fix were higher for faces in the left than the right hemifield and in the upper rather than the lower hemifield. The overall time spent looking at the UL was higher than in the other quadrants. The findings are relevant to the understanding of VFA in face processing, especially groups of faces, and might be linked to environmental cues and/or reading habits.

Sign in / Sign up

Export Citation Format

Share Document