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At least 811 records · Page 45Linked to original sources
PubMed1975

Vestibulo-ocular function in patients with cerebellar atrophy.

Eye movement abnormalities were quantiatively assessed in four patients with clinically pure cerebellar atrophy (group A), six patients with brainstem plus cerebellar atrophy (group B), and five patients with Friedreich's ataxia (group C). Twelve patients had one or more types of spontaneous nystagmus; eight gaze nystagmus, three rebound nystagmus, wo positional nystagmus, and one vestibular nystagmus. Catoric-induced and rotatory-induced nystagmus was hyperactive in group A and diminished in group C. Group B had mixed responses. All patients demonstrated significant fixation instability and impaired smooth pursuit. There was dysmetria of voluntary saccades, with flutter and "rebound" saccades. Nine of 15 patients had significant slowing of induced saccades, including two patients in group A. It is concluded that quantitative vestibulocular tests can be useful in classifying the cerebellar atrophy syndromes.

Cerebellar Ataxia↗
PubMed1979

Periodic alternating gaze.

A 77-year-old man with autopsy-proven bilateral cerebral infarction had a periodic alternating conjugate horizontal ocular deviation for 2 days, which ceased shortly before death. There have been four previously reported patients with this disorder. The phenomenon suggests acute bilateral cerebral disease with a relatively intact brainstem.

Aged↗
PubMed2005

Smooth pursuit in patients with downbeat nystagmus.

Smooth pursuit and gaze holding in light and darkness was investigated in 19 patients with downbeat nystagmus (DBN) and 17 control subjects. Vertical downward smooth pursuit was selectively impaired in patients, and gaze holding with a visible target was only slightly better than in darkness. The selective impairment of downward pursuit and the poor visual suppression of ocular drift in DBN support the involvement of the floccular lobe, which participates in gaze holding and contains gaze-velocity Purkinje cells with a downward on-direction for smooth pursuit.

Adult↗
PubMed1990

Color perimetry for assessment of primary open-angle glaucoma.

The authors report the development of a color perimetry procedure which compares sensitivity of the short-wavelength color-vision mechanism in the peripheral visual field for normal eyes, eyes with ocular hypertension, and eyes with primary open-angle glaucoma. To isolate the short-wavelength cone mechanism, they modified an automatic projection perimeter to blue-on-yellow color perimetry and used a monochromatic 440-nm stimulus and a broad-band bright yellow background. The three groups of subjects were matched for age and lens density. Refraction, pupil size, acuity, and medication were controlled. Under these conditions, most glaucomatous eyes showed reduced sensitivities more than two standard deviations below normal. Normal control eyes were significantly different from eyes with ocular hypertension only in the superior nasal field (P less than 0.05), but normal eyes differed from eyes with primary open-angle glaucoma in all areas of the field (P less than 0.01).

Aged↗
PubMed1982

Resetting fast phases of head and eye and their linkage in the frog.

(1) Compensatory slow phase movements were evoked by optokinetic, vestibular and combined optokinetic and vestibular stimulation. Superimposed fast phases resetting the position of the head (in space) and of the eye (in head) were recorded with a magnetic field search coil in unrestrained and head fixed frogs, respectively. (2) Head fast phases recorded during optokinetic stimulation covaried in the frequency of their occurrence with slow phase head velocity. Their amplitude was large (average 18.9 +/- 8.9 degrees), maximal velocity increased with amplitude by 6.6 degrees/s/deg, and duration (average 230 +/- 33 ms) was almost independent on amplitude. (3) Ocular fast phases rarely occurred during sinusoidal stimulation and neither optokinetic after nystagmus nor postrotatory nystagmus were observed. Fast phases, evoked by constant velocity optokinetic or acceleratory stimuli, consisted of two components: a primary resetting fast phase and a smaller fast movement in the opposite direction. The primary fast phase had a small amplitude (average 2.2 +/- 1.3 degrees). In different stimulus conditions fast phase parameters were very similar. Maximal velocity increased by 6.5 degrees/s/deg. Duration (average 165 +/- 23.4 ms) was variable. (4) During ocular fast phases the vestibulo-collic and the optokinetic-collic reflexes were suppressed. The slow phase head velocity either became zero or a small head fast phase in the direction of the ocular fast phase occurred. Fast phase head movements were accompanied by an ocular fast phase or by a retraction of one or both eyes, depending on the amplitude of the head fast phase. At the end of a head fast phase eye position was always recentered.

Animals↗
PubMed1992

Overlooking: a sign of bilateral central scotomata in children.

Four children are reported who always looked above objects of visual interest (overlooking). All had bilateral central scotomata (loss of central visual field). Three had optic nerve disease selectively affecting the papillomacular fibers; the fourth had ocular colobomata affecting the maculae. Overlooking is an important sign of bilateral central scotomata in children: it is an adaptation to loss of central vision.

Adolescent↗
PubMed1978

Eye-movements of six-year-old children in two memorization tasks.

Eye movements, during the viewing phase of two memorization tasks, of 12 boys and 12 girls in a transitional period of memory development are described. The findings suggest that the development of ocular strategies parallels closely the emergence of other strategic behaviors and that information on eye movements would provide a necessary complement to the data on emerging ability to plan.

Child↗
PubMed1979

Interocular alignment following visual deprivation in the cat.

Kittens were placed in the dark just after birth and then removed at various ages for the study of interocular alignment. It was found that kittens dark-reared for 4 months or longer were characteristically incyclotorted with respect to normal animals. Deprivation periods of less than 2 months were ineffective in producing these changes. Divergence of the visual axes was also observed in some dark-reared cats. Pupillary constriction in response to light was much more pronounced in dark-reared cats than in normal cats. This enhanced pupillary reaction persisted for at least 3 weeks after the deprived animals were brought into an illuninated environment. When dark-reared cats were allowed a recovery period in a normally lit visual environment, their ocular alignment changed markedly. The incyclotorsion and divergence of the visual axes disappeared, and instead cats allowed recovery from deprivation could display excyclotorsion and/or convergence of the visual axes. These anomalies of ocular alignment associated with the recovery from visual deprivation could occur following periods of initial deprivation as short as 30 days or as long as 2 years. The mechanisms and possible significance of such anomalies are considered.

Animals↗
PubMed1980

Giant axonal neuropathy: visual and oculomotor deficits.

Giant axonal neuropathy, a generalised disorder or neurofilaments, presents as a chronic, progressive peripheral neuropathy in childhood. Evidence for central nervous system involvement is demonstrated in this study of four male patients with giant axonal neuropathy who had defective visual function and abnormal ocular motility. The visual system was studied by electroretinography, which showed normal retinal function, and by visual evoked potentials, which showed disease of both optic nerves and retrochiasmal visual pathways. The ocular motility disorder, studied by electrooculography, comprised defective pursuit, inability to maintain eccentric gaze with gaze paretic and rebound nystagmus, abnormal optokinetic responses and failure of suppression of the vestibulo-ocular reflex by fixation. These findings suggested involvement by giant axonal neuropathy of the cerebellar and brain stem pathways important in the control of ocular motility.

Axons↗
PubMed1979

Retinal rivalry in functional amblyopia.

Thirteen patients with varying degrees of amblyopia were examined for perception of retinal rivalry with the use of the phase difference haploscope. Visual acuity was varied in the fixing eye by the addition of plus lenses, equalizing ocular dominance. Retinal rivalry could be detected over wide ranges of visual acuity disparity by amblyopic patients with visual acuity better than 20/50. Rivalry could not be detected, however, by patients with less than 20/50 visual acuity in their amblyopic eye.

Amblyopia↗
PubMed1993

Vestibular function and sensory interaction in space flight.

The vestibular system and vestibulo-visual interaction were examined in 11 astronauts by the electrooculographic (EOG) method during short- and long-term flights on days 2, 3, 5, 9, 22, 50, 164, and 169 (experiments OPTOKINES and LABYRINTH). In space (flight days 2 and 3), they showed enhanced spontaneous vertical nystagmus, and disorders of tracking of vertical and diagonal movements of the stimulus which improved after active head movements. Early increasing of the reactivity of the cupulo-endolymphatic system (flight days 2-3) was replaced after 5 days of flight with a reduction of the vestibular function and an increase of the significance of the visual input in the formation of oculomotor responses to combined vestibulo-optokinetic stimulation. The type of spontaneous ocular reaction and vestibular stimulation of oculomotor activity under the conditions of weightlessness represented, on one hand, the general responses of sensory systems to weightlessness and, on the other hand, specificity of integrating and adaptive processes.

Electrooculography↗
PubMedDate not supplied

Skew deviation revisited.

Skew deviation is a vertical misalignment of the eyes caused by damage to prenuclear vestibular input to ocular motor nuclei. The resultant vertical ocular deviation is relatively comitant in nature, and is usually seen in the context of brainstem or cerebellar injury from stroke, multiple sclerosis, or trauma. Skew deviation is usually accompanied by binocular torsion, torticollis, and a tilt in the subjective visual vertical. This constellation of findings has been termed the ocular tilt reaction. In the past two decades, a clinical localizing value for skew deviation has been assigned, and a cogent vestibular mechanism for comitant and incomitant variants of skew deviation has been proposed. Our understanding of skew deviation as a manifestation of central otolithic dysfunction in different planes of three-dimensional space is evolving. The similar spectrum of vertical ocular deviations arising in patients with congenital strabismus may further expand the nosology of skew deviation to include vergence abnormalities caused by the effects of early binocular visual imbalance on the developing visual system.

Diplopia↗
PubMed1980

Ocular dominance, eye alignment and visual acuity in kittens reared with an optically induced squint.

A horizontal concomitant strabismus produced optically in kittens with prisms caused a decrease in the proportion of binocularly excitable striate neurons with approximately equal percentages of neurons being driven by each eye. In addition, preventing fusion with prisms resulted in alterations in interocular alignment and in some cases a mild strabismic amblyopia. The changes in ocular dominance were dependent on the amount and direction of the prism induced deviation; however, regardless of the type of prisms worn, the kittens which demonstrated interocular misalignments were esotropic.

Animals↗
PubMed2001

Gaze anchoring to a pointing target is present during the entire pointing movement and is driven by a non-visual signal.

A well-coordinated pattern of eye and hand movements can be observed during goal-directed arm movements. Typically, a saccadic eye movement precedes the arm movement, and its occurrence is temporally correlated with the start of the arm movement. Furthermore, the coupling of gaze and aiming movements is also observable after pointing initiation. It has recently been observed that saccades cannot be directed to new target stimuli, away from a pointing target stimulus. Saccades directed to targets presented during the final phase of a pointing movement were delayed until after pointing movement offset ("gaze anchoring"). The present study investigated whether ocular gaze is anchored to a pointing target during the entire pointing movement. In experiment 1, new targets were presented at various times during the duration of a pointing movement, triggered by the kinematics arm moment itself (movement onset, peak acceleration/velocity/deceleration, and offset). Subjects had to make a saccade to the new target as fast as possible while maintaining the pointing movement to the initial target. Saccadic latencies were increased by an amount of time that approximately equaled the remaining pointing time after saccadic target presentation, with the majority of saccades executed after pointing movement offset. The nature of the signal driving gaze stabilization during pointing was investigated in experiment 2. In previous experiments where ocular gaze was anchored to a pointing target, subjects could always see their moving arm, thus it was unknown whether a visual image of the moving arm, an afferent (proprioceptive) signal or an efferent (motor control related) signal produced gaze anchoring. In experiment 2 subjects had to point with or without vision of the moving arm to test whether a visual signal is used to anchor gaze to a pointing target. Results indicate that gaze anchoring was also observed without vision of the moving arm. The findings support the existence of a mechanism enforcing ocular gaze anchoring during the entire duration of a pointing movement. Moreover, such a mechanism uses an internally generated, or proprioceptive, nonvisual signal. Possible neural substrates underlying these processes are discussed, as well as the role of selective attention.

Adolescent↗
PubMed2000

Asymmetry of ocular motor and perceptual vestibular processing in humans with unilateral vestibular deafferentation.

To investigate the effect of asymmetrical vestibular input on the perceived straight-ahead direction, we compared 7 subjects (age 59 +/- 8 yrs, mean +/- SD) who had chronic (>10 mos) unilateral vestibular deafferentation with 10 age matched controls (age 61+/-6 younger controls (age 28 +/- 7 yrs). Despite the age difference, the two control groups performed similarly and were therefore pooled. Eye and head movements were recorded using search coils as subjects underwent 30 s trials of sinusoidal, whole body oscillation (0.4-2 Hz, peak velocities 0-120 degrees /s) in darkness while attempting to maintain gaze on a remembered target 5 m distant. As a control, most stimulus oscillations were randomly superimposed on an imperceptible, constant velocity of +/-0.5 degrees /s that produced a whole-body offset of 15 degrees by the end of the trial. Following oscillation, subjects remained motionless in darkness and were asked to orient both gaze and a manipulandum to the remembered target location. In control subjects, mean final gaze and manipulandum positions were within 15 degrees of the target for all testing conditions. There was no dependence of final gaze and manipulandum positions on the frequency or velocity of the preceding whole-body oscillations (p > 0.05). In four of seven unilaterally deafferented subjects there was an ipsilesional bias of final eye position of > or =10 degrees. These subjects moved both eye and manipulandum to the ipsilesional side, with the error increasing at higher stimulus velocities. For the 120 degrees /s peak head velocity, mean ipsilesional gaze bias ranged from 10-37 degrees and mean manipulandum bias ranged from 26-108 degrees. Although the errors depended on velocity p < 0.01), errors were independent of frequency (p > 0.1). In the remaining three subjects with vestibular deafferentation, final gaze and manipulandum positions [were not statistically different from controls.] Early gain (eye velocity / head velocity) of the VOR averaged 0.82 +/- 0.01 for the first 10 s of all trials and was similar in all groups (p > 0.1). Gain during the final 10 s gain averaged 0.78 +/- 0.01 for control subjects, but was significantly lower at 0.70 +/- 0.01 for unilaterally deafferented subjects, whose eye positions reached the limit of the ocular motor range. We conclude that many humans with chronic unilateral vestibular deafferentation have a large ipsilesional dynamic bias of eye position and the perceived straight ahead direction reflecting persistent asymmetry of vestibular processing.

Adult↗
PubMed1984

Adaptive modification of the vestibulo-ocular reflex by mental effort in darkness.

The vestibulo-ocular reflex (VOR) can be suppressed in darkness if a subject tries to imagine that he looks at a head fixed target. This mental suppression of VOR was used to induce adaptive changes in VOR gain during 3 h of active head oscillations in complete darkness. VOR gain changes were tested by asking the subject to look at a visual target; then passively or actively the head was turned in darkness while the subject "fixated" the same target. Corrective saccades occurring at the end of the movement when lights were turned on give an elegant measure of VOR gain. Three hours of training induced in 3 subjects a mean of 10.9% and 11.4% decrease of VOR gain for passive and active conditions, respectively. This demonstrates that reflex adaptation can be obtained without external cues, and probably with only an internal reconstruction of target and eye movement.

Adaptation, Physiological↗
PubMed1997

Visual responses of neurons from areas V1 and MT in a monkey with late onset strabismus: a case study.

One adult monkey (Macaca fascicularis) was investigated psychophysically and electrophysiologically after at least 5 years of late onset esotropic macrostrabismus (squint angle 52 deg). Behavioural tests revealed normal monocular visual and visuomotor functions. No indications of deep amblyopia or oculomotor asymmetry were found. The monkey used the left or right eye alternately at about equal frequencies. Single unit recordings from area VI disclosed a normal ocular dominance distribution. Most VI neurons from both hemispheres received binocular input. Thus, discordant visual information from corresponding retinal locations of the two eyes converged onto the cortical neurons. No evidence for anomalous retinal correspondence was found. Diplopia and confusion must therefore be avoided by suppression of vision through one eye to allow stable, unambiguous perception. Possible suppression was investigated by stimulating a neuron through the same eye when it was actively used for fixation in one set of trials, and when it was not used for fixation in another set of trials. Significant differences in these two stimulus conditions were found in 20/39 neurons from area VI and in 11/34 motion sensitive neurons recorded in the middle superior temporal area (MT). The normalized population activity in VI and MT was higher if cells were stimulated through the fixating eye. The data are discussed with respect to possible suppressive mechanisms helping to prevent double vision in strabismus and in binocular rivalry.

Action Potentials↗