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PubMed1998

Abnormal head posture associated with high hyperopia.

BACKGROUND: An abnormal head posture may be adopted for ocular or nonocular reasons. The most common ocular reasons are to maintain binocularity and to obtain the best possible visual acuity. Patients with undercorrected or overcorrected refractive errors have been reported to adopt a variety of head positions, thought to be an attempt to obtain the best possible visual acuity. METHODS: Five patients with symmetric high hyperopia (at least + 5.00 D) and an abnormal head posture are presented. RESULTS: All five patients demonstrated an abnormal head posture of chin down for fixation without the spectacle correction in place. This abnormal head posture was eliminated by occlusion of either eye and also by wearing of the refractive correction. No patient demonstrated significant strabismus. CONCLUSION: An abnormal head posture when not wearing spectacle correction can occur in children who have high hyperopia and insignificant strabismus. This may be a mechanism by which the best visual acuity is obtained (indicated by the disappearance of the abnormal head posture on wearing of the glasses) and also to maintain binocularity (indicated by the disappearance of the abnormal head posture under monocular testing conditions). The presence of a chin-down abnormal head posture should alert the examiner to the possible presence of high hyperopia and therefore the necessity for a cycloplegic refraction.

Child↗
PubMed1986

Nonius horopter in projected viewing.

Nonius horopter measurements were made on three normal subjects using both physically displaced (real viewing) and stereogrammetrically displaced (projected viewing) test objects. Three subjects with ocular anomalies were tested using the projected viewing arrangement with and without 5% overall magnifier before the right eye, and seven complete measurements of the projected viewing horopter were made on a fourth subject with an ocular anomaly over the period of 1 month. These latter individual plots showed large irregularities that changed location from day to day. Plotting the mean and standard error of the means of these seven sets of data produced a smoothing out of the horopter locus. Plotting each individual horopter setting in the sequence of measurement and monitoring eye position indicated that all of the irregularities and regional horopter changes found are most likely introduced by changes in fixation disparity (vergence eye movements).

Depth Perception↗
PubMed1995

Eye stabilization by vestibulo-ocular reflex (VOR) and optokinetic reflex (OKR) in macaque monkey: which helps which?

VOR-OKR interaction was studied in macaque monkey in the frequency domain, using various vestibular-visual stimulus combinations in the horizontal plane. At low stimulus frequencies (< 0.1 Hz), the eyes were always stabilized on the optokinetic pattern, irrespective of whether the head, the pattern, or both were rotated. At higher frequencies, the gain of the OKR attenuated, and concomitantly the eyes became increasingly stabilized in space. These findings show that the VOR becomes functionally relevant only at high frequencies. It compensates for the limited bandwidth of the OKR, thereby improving vision provided the pattern to be fixated is stationary in space.

Animals↗
PubMed1982

Progressive supranuclear palsy: the relationship between ocular motor dysfunction and psychological test performance.

The performance of patients with progressive supranuclear palsy on visual search and scanning tasks was related to the pattern of ocular deficits observed in these patients during horizontal refixation. Comparisons were made to age-matched normals and patients with Parkinson disease or cerebellar damage. The poor performance of the progressive supranuclear palsy group on visual search and scanning could not be attributed to the restricted range of vertical gaze or the large number of hypometric saccades during horizontal refixation. Instead, we believe that their impaired scanning resulted from the presence of square-wave jerks during attempted fixation.

Bulbar Palsy, Progressive↗
PubMed2006

Upward gaze-evoked nystagmus with organoarsenic poisoning.

The authors report assessment of abnormal ocular movements in three patients after organoarsenic poisoning from diphenylarsinic acid. The characteristic and principal sign is upward gaze-evoked nystagmus. Moreover, vertical gaze holding impairment was shown by electronystagmography on direct current recording.

Adolescent↗
PubMed1995

Illusory localization of stimuli flashed in the dark before saccades.

A photic stimulus flashed just before a saccade in the dark tends to be mislocalized in the direction of the saccade. This mislocalization is not only perceptual; it is also expressed by errors of ocular targeting. A particular situation arises if the point of light is flashed twice at the same place, the second time, just before a saccade. The point of light may appear at two different places even though neither the site of its retinal image nor the direction of gaze change between the flashes. Experiments were run on five human subjects, head fixed in the dark, with flashes repeated at the site of the saccade goal or at the initial point of fixation. In both cases, the test stimulus was mislocalized. However, its apparent displacement never produced the perception of a streak. Streaks were reported only when there was an actual stimulus movement on the retina (e.g. by flashing the stimulus during the saccade). Mislocalization did not occur if the two flashes were not separated by a dark interval. This implies that, as long as a steady stimulus remains continually visible, there is no updating of the internal representation of eye position assumed to be used for stimulus localization.

Fixation, Ocular↗
PubMed1998

Optimizing gaze control in three dimensions.

Horizontal and vertical movements of the human eye bring new objects to the center of the visual field, but torsional movements rotate the visual world about its center. Ocular torsion stays near zero during head-fixed gaze shifts, and eye movements to visual targets are thought to be driven by purely horizontal and vertical commands. Here, analysis of eye-head gaze shifts revealed that gaze commands were three-dimensional, with a separate neural control system for torsion. Active torsion optimized gaze control as no two-dimensional system could have, stabilizing the retinal image as quickly as possible when it would otherwise have spun around the fixation point.

Adult↗
PubMed1997

Distinguishing subcortical and cortical influences in visual attention. Subcortical attentional processing.

PURPOSE: The purpose of the study was to investigate the role of subcortical processing in human visual attention. The midbrain contribution to visual attention is unclear. Although evidence exists for a subcortical attentional advantage in ocular motor tasks, such an advantage has not been shown in perceptual tasks. Because retinotectal projections arise predominantly from nasal retina (i.e., temporal hemifield), subcortical attention should be distributed asymmetrically for monocular viewing conditions with an advantage to the temporal hemifield. METHODS: To test for a subcortical attentional effect, the authors compared the results of binocular and monocular viewing conditions using the split priming motion induction paradigm. In this perceptual attention paradigm, priming cues are presented to the left and right of fixation followed by an instantaneously presented horizontal bar. As a result of attention to the priming cues, motion is perceived within the bar as it appears to draw in from the two lateral cues toward a central collision point. Asymmetrically distributed attention results in an asymmetry in the perception of motion within the bar, and thus the perceived collision point will be shifted away from the center. RESULTS: In two separate studies, one with and one without control of eye movements, the authors found significant differences between the results for monocular and binocular presentation. When the stimulus configuration is presented to the left eye, the perceived collision point is shifted toward the center consistent with a subcortical attentional effect. However, presentation of the stimulus configuration to the right eye yields the same results as those of binocular presentation. CONCLUSIONS: This pattern of results can be explained by a separate and additive interaction between cortical and subcortical attentional effects in the visual field. Dominance of the left visual field for cortical attention and dominance of the temporal visual field for subcortical attention act together when the initial priming cue occurs in the temporal (left) visual field of the left eye. However, these influences compete when the same stimulus configuration is presented to the right eye, where cortical attention predominates in the left visual field and subcortical attention predominates in the temporal (right) visual field.

Adult↗
PubMed1975

Absence of spontaneous head tilt in superior oblique muscle palsy.

We used the head-tilt test--based on an imbalance between the function of a paretic superior oblique muscle and its homonymous superior rectus muscle, rather than on an anomaly of cycloversion-to test three patients with superior oblique muscle palsies. Spontaneous ocular torticollis was absent if a patient had poor vision in one eye or if his vertical fusional amplitudes were of such magnitude that he was able to overcome his vertical deviation in all positions of gaze. These latter instances, though rare, may be more common than reports indicate.

Adult↗
PubMed2005

Characteristics and course of patients with deteriorated monofixation syndrome.

BACKGROUND: Monofixation syndrome is characterized by small-angle strabismus with vergence fusional amplitudes and "peripheral fusion." Although it is thought to be a relatively stable condition, some patients with this syndrome deteriorate, resulting in an increasing heterotropia, sometimes associated with diplopia. Deteriorated monofixation syndrome is well known among clinicians; however, there are no studies describing the course and outcomes for these patients. PURPOSE: To assess the clinical characteristics, course, and response to therapy of patients with deteriorated monofixation syndrome. METHODS: We identified all patients from our database that had an ocular deviation of < or =8 Delta on simultaneous prism cover testing, peripheral fusion, and between 3000 and 67 seconds of stereoacuity (monofixators) who subsequently had an increase in their deviation to >8 Delta, loss of fusion, or diplopia. From this group we assessed patient clinical characteristics, course, and response to therapy. RESULTS: We identified 29 patients with deteriorated monofixation syndrome who subsequently underwent treatment. Treatment consisted of surgery in 28 patients and minus lens therapy in one patient. Of the study group, 28 (97%) of the patients had a history of esotropia and 20 patients (69%) had a history of amblyopia. Nine patients noted diplopia at the time of deterioration, which persisted in four patients after treatment. In all, 14 patients (48%) met the criteria for monofixation again after therapy, while 20 patients (69%) had successful motor alignment (< or =8 Delta). There was a trend toward poorer outcomes in the diplopic group when compared with the patients who did not have diplopia, although this was not statistically significant (P = 0.26 for regaining monofixation syndrome). Follow-up ranged from 1 month to 21 years. CONCLUSION: Though monofixation is considered a stable condition, some patients will deteriorate over time as demonstrated by an increase in the ocular deviation and loss of fusion. In this study 31% of our patients noted the onset of diplopia. Following treatment, 48% of the patients regained monofixation. Patients with diplopia following deterioration of their alignment may be less likely to regain good alignment or monofixation after treatment.

Amblyopia↗
PubMed1976

Normal values in clinical electrooculography. II. Analysis of potential and time parameters and their relation to other variables.

The following EOG potential and time parameters from 72 normal subjects were analysed: base value B, dark trough D, light peak L, light induced potential rise L-D, interval between beginning of dark adaptation and occurrence of dark through d and interval between dark trough and light peak l. Their relations to sex, age pupillary diameter, degree of iris pigmentation, refractive error, axial length, corneal curvature and diameter, ocular protrusion and interpupillary distance were assessed. Right eye and left eye samples of the EOG parameters were congruent, although individual differences were sometimes appreciable. The levels of B and D were higher in the female half of the sample. A positive correlation existed between age and D level. L-D was negatively correlated to the degree of refractive error and positively correlated to the ocular protrusion. A positive correlation was found between d and the four potential parameters, and there was a positive correlation between age and l. Practical consequences of the statistical analysis relating to the interpretation of such EOG data are discussed.

Action Potentials↗
PubMed1989

Oculogyric crisis after metoclopramide therapy.

Oculogyric crisis developed in a 21-year-old girl after 5 oral doses of 10 mg of metoclopramide. The symptoms were relieved by i.v. administration of diphenhydramine hydrochloride. Although ocular side effects of metoclopramide are rare, it can induce an alarming oculogyric crisis in some sensitive subjects. The mechanism of oculogyric crises is unclear but the characteristics of the condition and some known causes are discussed. Advice is given on optometric management.

Adult↗
PubMed1995

Imaginary gaze effects on eye movements induced by linear acceleration: involvement of vestibular induced smooth pursuit eye movement.

We investigated smooth eye movements elicited i) by linear acceleration in a space-fixed imaginary gaze condition (smooth component of eye movement induced by linear motion: LSEM) and ii) during acoustic pursuit of a moving sound source (smooth component of eye movement induced by acoustic pursuit of a sound source: SSPEM). The two conditions were examined using the same test subjects. LSEM and SSPEM performance was found to be positively correlated across the subject population. From the comparison of LSEM and SSPEM we propose the following hypothesis: LSEM consists not only of a pure translational vestibular-ocular reflex (tVOR) component but also of a component based on the perception of otolithic information. Accordingly, this second component is instrumental in the pursuit of an imaginary visual target during linear self-motion.

Acceleration↗
PubMed1984

Rivalry with continuous and flashed stimuli as a measure of ocular dominance across the visual field.

Two measures of sensory ocular dominance were compared. Both involved dichoptic presentation of orthogonal gratings--a situation which results in binocular rivalry. The gratings were presently briefly in experiment 1 and continuously in experiment 2 and by the predominance of one grating over the other a quantitative estimation of ocular dominance was obtained in both cases. Comparison of the results showed that (a) binocular rivalry suppression was present for exposures of 250 ms and (b) the briefly presented gratings were a more sensitive test for ocular dominance than conventional continuously presented stimuli. The variation of dominance over the horizontal meridian of the visual field was considered. For many subjects a consistent different in the ocular dominance in the two halves of the visual field, and therefore of the cortex, was found. Some showed dominance of the ipsilateral eye in each hemisphere while others showed dominance of the contralateral eye. It was found that there is, in fact, a continuum of types of dominance pattern amongst individuals.

Adult↗
PubMed2003

Acquired brown syndrome secondary to superior oblique muscle cysticercosis.

BACKGROUND: Acquired Brown syndrome is known to occur after trauma, iatrogenic events, cysts of superior oblique muscle tendon, and inflammation. The purpose of this study is to report a large series of patients with acquired Brown syndrome secondary to superior oblique muscle cysticercosis and to discuss its management. METHODS: Retrospective analysis was performed of clinical and imaging features, management, and outcome in seven patients with cysticercosis of the superior oblique muscle presenting clinically as Brown syndrome. RESULTS: Seven patients were identified (five male and two female) ranging in age from 6 to 45 years. All patients had the ocular motility limitation, ie, limitation of elevation in adduction., characteristic of Brown syndrome. This was associated with pain and swelling in the superior nasal orbit. Diagnosis was established by observing the cysticercus cyst with scolex on imaging (ultrasound B scan, magnetic resonance imaging, and/or computed tomography). Oral albendazole (15 mg/kg) and oral prednisolone (1mg/kg) were given for 4 weeks, and the patients were followed up for 1 year. Clinical recovery with improvement of ocular motility and regression of imaging features was noted in all patients. CONCLUSIONS: Acquired Brown syndrome secondary to superior oblique muscle cysticercosis is a rare entity. Awareness of this condition, which leads to early diagnosis and institution of prompt medical treatment, results in a successful clinical outcome.

Adolescent↗
PubMed1992

Gaze and eye movement disorders.

Cortical areas were explored with regard to saccade control: the lateral intraparietal (LIP) area is involved in the spatial aspects of sensorimotor processing; the supplementary motor area in goal-directed gaze control; and from lesion studies; the posterior parietal cortex in triggering visually guided saccades. Different studies have suggested that the spatial-to-temporal transformation takes place in the superior colliculus (SC) and the cerebellum. When the vestibulo-ocular reflex (VOR) produces inadequate eye movements, other supplementary mechanisms (e.g. non-visual, saccade) may play a role in correcting gaze. A classification of central vestibular disorders of the brainstem and VOR has been proposed, as manifested in any one of the three major planes of action (yaw, pitch and role).

Cerebral Cortex↗
PubMed2003

[Asthenopic complaints and ocular convergence at the computer workstation: new test procedures for practice and research].

BACKGROUND: The present paper summarizes a series of ergonomic studies on the relation between asthenopic complaints and binocular vision at the computer workstation. In particular, the paper reports on measurements of the accuracy of ocular convergence during fixation of central fusion stimuli (i. e. fixation disparity) as a function of viewing distance. METHODS: Different versions of subjective tests for fixation disparity (using dichoptic nonius lines) are presented, including a computer-controlled procedure (the eye-test PC). RESULTS: These new tests suggest that non-presbyopic subjects with normal binocular vision may suffer from asthenopic complaints if they have - in near vision - an exo fixation disparity larger than average. CONCLUSION: In these cases, the stress exercised on the convergence system can be reduced by using a longer viewing distance at the workplace.

Accommodation, Ocular↗
PubMed1994

[Computer-assisted measurement of ocular misalignment in infants and young children using the digital Purkinje reflection pattern procedure].

A digital image recording and processing system is presented that allows a quick diagnosis of microstrabismus in non-cooperative children. It is thus particularly suited for screening purposes. METHOD: The Purkinje Reflection Pattern Evaluation (RPE) method is used: three small flashes are used to produce the desired Purkinje images. Two horizontal rows of the three 1st Purkinje images (anterior corneal reflections) and of the three 4th Purkinje images (posterior crystalline lens reflections) stemming from the three light sources form the characteristic Purkinje image reflection pattern. Each eye's position is calculated from the shift between the upper and lower rows of reflections by means of two simple formulae. From the angles obtained in binocular fixation and monocular fixation the manifest angle of strabismus corresponding to the angle measured in the simultaneous prism-and-cover test is computed. The measurement is performed at a fixation distance of 50 cm under natural viewing conditions. To obtain a picture one only has to get the child's attention for a short moment. The primary position is triggered with the fixation light, which is operated by a switch. APPARATUS: The digital image recording is done with a hand-held device comprising two miniaturized video cameras, three photo flashes and a fixation light that is operated manually. An IBM-compatible PC equipped with a hard disk and two frame grabbers was adapted for the storage and processing of the pictures. The pictures are evaluated interactively in a few minutes on the workstation's monitor immediately after the measurement. To this end specially designed menu-driven software was implemented. RESULTS: Examples of the measuring procedure and clinical results in infants with microtropic highlight the potential of the system as a screening apparatus and for the exact measurement of small and large squint angles. Usually even 1-year-old children can cooperate well enough to get good-quality pictures in binocular fixation. The new digital system allows easy and rapid application of the Purkinje Reflection Pattern Evaluation method since the time-consuming photographic film processing and evaluation are no longer necessary. For the first time small angles of strabismus under 5 degrees (10 PD) can be measured with a precision of less than 1 degree (2 PD) under clinical conditions in non-cooperative children.

Adult↗