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PubMed1988

[Estimation of the required bandwidth of a DC amplifier for measurement of eye saccades].

Saccadic eye movements are analysed with DC-amplifiers when electrodes are used. The present investigation on measuring the velocity of eye movement gives an estimation for the required bandwidth, because the upper frequency has a decisive influence on the result. Theoretically there would be no error of measurement if no filters were used. But there are two reasons for filtering. One is that the Shannon-Theorem asks for a limited frequency in order to digitize the signal on a computer later on. The other is an increasing of disturbance in the signal by an extended top frequency. It takes no trouble to solve the first problem by changing the sampling-rate of the computer. The second problem asks for a compromise. Error in measurement will increase by reducing the top frequency, but also disturbances in the signal will be reduced. The value in question of this investigation is the velocity of eye movement, i.e. the maximum gradient in the signal and that could be the gradient of a disturbance-spike. The present estimation shows that an amplifier with two RC-Filters and a Butterworth-Filter second order with a resulting top frequency at 20 Hz (3 dB-limit) offers a good compromise.

Amplifiers, Electronic↗
PubMed1982

Cerebellar control of fixation eye movements.

Human subjects normally have miniature eye movements during tasks that require steady visual fixation. These eye movements were compared in 12 control subjects and 4 patients with degenerative cerebellar disorders. Slow drifts, small fixation saccades, square waves, saccadic oscillations, flutter, and vertical nystagmus occurred in both control subjects and patients. In the patients, however, fixation eye movements were enlarged and square waves and saccadic oscillations were more frequent. It appears that some forms of pathologic fixation instability are due to defective cerebellar control of fixation eye movements, and that precise measurements of these eye movements may quantitate disorders of cerebellar function.

Adolescent↗
PubMed2004

Effects of extraocular muscle surgery on 15 patients with oculo-cutaneous albinism (OCA) and infantile nystagmus syndrome (INS).

PURPOSE: The purpose of this report is to characterize the clinical and electrophysiological effects of extraocular muscle surgery in 15 patients with oculo-cutaneous albinism (OCA) and infantile nystagmus syndrome (INS). Our hypothesis is that surgery on the extraocular muscles of patients with OCA and INS changes their nystagmus and their visual function. DESIGN: Interventional, prospective, cohort, noncomparative case series. METHODS: All 15 patients had surgery on all four virgin horizontal recti; three for strabismus alone, three for nystagmus alone, five for an eccentric gaze null zone alone, and four for an eccentric gaze null zone plus strabismus. All patients have been followed for at least six months. All 15 patients had the subjective outcome measure of pre- and postoperative binocular best optically corrected acuity (BBOCA). Objective outcome measures included anomalous head posture (AHP) in nine patients, eye movement recording measures of expanded nystagmus acuity function (NAFX) in 10 patients, null zone position (NUZP) and null zone width (NUZW) in 10 patients, and foveation time (FOV) in nine patients. RESULTS: The results are summarized as follows; BBOCA increased 0.1 LogMar or greater in 14 of 15 patients. In those operated on for an AHP with or without associated strabismus the AHP improved significantly (P < .01 for all). The NAFX, NUZP, NUZW, and FOV measured from eye movement recordings showed persistent, significant increases in all patients (P < .01 for all). CONCLUSIONS: This report adds to the evidence that surgery on the extraocular muscles in patients with INS has independent neurologic and visual results.

Adolescent↗
PubMed1993

Eye-movement rhythmicity and reading comprehension.

The purpose of these two studies was to examine the rhythmical patterns displayed by subjects with and without reading disabilities while they were reading (Study 1), and to vary rhythmicity through priming and observe the effects on parsing ability using eye-movement and comprehension measures (Study 2). Rhythmicity during silent reading was operationalized by transcribing eye-movement measures into pitch, rhythm, and rests. In Study 1, 17 subjects with reading disabilities and 15 control subjects (M age = 15, male = 60%) parsed 20 flawed and control sentences. In Study 2, 35 control subjects (M age = 21, male = 43%) parsed 9 phrases from familiar songs under one of three rhythm-priming conditions. Results (Study 1) indicated significant differences in rhythm patterns. Subjects with reading disabilities exhibited rhythm variability, unpredictability, and lethargic tempos. In Study 2, significant differences across priming conditions were found, with primed subjects exhibiting improved parsing and comprehension. Rhythm may be an organizational substrate for syntax.

Adolescent↗
PubMed2004

Convergence eye movements evoked by microstimulation of the rostral superior colliculus in the cat.

Results of our previous studies suggest that the circumscribed area in the rostral superior colliculus (SC) of the cat is involved in the control of accommodation. Accommodation is closely linked with vergence eye movements. In this study, we investigated whether or not vergence eye movements are evoked by microstimulation of the rostral SC in the cat. In addition, we studied the effect of chemical inhibition of the rostral SC on visually guided vergence eye movements. This study was conducted on three cats, weighing 2.5-3.5 kg. The animals were trained to carry out visually guided saccade and convergence tasks. Eye movements were measured using search coils placed on both eyes. We recorded eye movements evoked by microstimulation of the rostral SC in the alert cats. Muscimol was injected into the rostral SC, and the effect of SC inactivation on visually guided vergence eye movements was investigated. Convergence eye movements were evoked by low-current stimulation (< 30 microA) of a circumscribed area in the intermediate layers of the rostral SC on one side. Spontaneous saccades were interrupted by the stimulation of the low-threshold area for evoking convergence. Visually guided convergence eye movements were severely diminished by the injection of muscimol into the low-threshold area for evoking convergence of the SC. The rostral SC is related to the control of vergence eye movements as well as accommodation. The rostral SC may be involved in the functional linkage between accommodation, convergence and visual fixation.

Action Potentials↗
PubMed1991

Measuring three dimensions of eye movement in dynamic situations by means of videooculography.

A primary function of the vestibular system is the stabilisation of the eye during head movement. Consequently, evaluation of reflex eye movements represents an essential means to both clinical diagnosis and researching of the vestibular function. Movements in the eye can be resolved into three orthogonal components, i.e. horizontal, vertical and torsional. As an improvement on most current techniques, which provide only measurement of the horizontal and vertical components, videooculography (VOG) facilitates non-invasive measurement of all three of the defined components. To date, only the scleral coil technique, which involves the semi-invasive placement of coil rings onto the bulbi, yields a continuous measure of eye torsion. Employment of suitable solid-state devices permit the integration of a compact, high resolution video recording system. In the basic configuration, eye movements can be observed and simultaneously recorded for later analysis or documentation. The video images of the eye are obtained by means of a miniaturised CCD video sensor mounted on a light-occluding mask. Image processing of the acquired video images determines horizontal and vertical coordinates of eye position online. Ocular torsion, as reflected by the rotation of the natural iris, is measured for each video frame. The VOG algorithm has been implemented on a PC based workstation, which permits online observation, recording and evaluation of eye movements. In addition, the technique has found clinical application as a portable eye-movement observation and recording system, allowing bedside examination and recording of transient symptoms. Preliminary results from various studies, including the objective evaluation of positional nystagmus (BPPN), are presented.

Eye Movements↗
PubMed2005

Cyclotorsional eye movements during a simulated PRK procedure.

PURPOSE: Eye alignment is a serious concern when performing corneal surface ablation. Although several excimer lasers monitor horizontal and vertical movements, little is known about the potential impact of cyclotorsional movements. Dynamic cyclotorsions have been measured on 10 emmetropic subjects during a simulated PRK treatment. METHODS: Cyclotorsional eye movements were measured using a 3D videoculographic system (SMI) in 10 emmetropic subjects in upright and supine position. The subjects were wearing an eyelid speculum and were asked to fixate on a 1 degrees red spot. The fixation target was either in focus or optically degraded by electronic filters. Data were collected at the University Eye Clinic, Torino, Italy, and the different setting measurements were compared using Student's t-test for paired data. RESULTS: Cyclotorsions were significantly higher when subjects were fixating an optically degraded stimulus (upright: P=0.04; supine: P=0.0002). The cyclotorsional movements ranged from -13 to 17 degrees. A significant difference in eye orientation was present when changing from the upright to the supine position (P=0.03). Even when correcting for this positional error, significantly higher cyclotorsional movements were detected in the supine position (in focus: P=0.0043; optically degraded: P=0.0008). The torsional range was from -14.85 to 14.55 degrees. CONCLUSIONS: The high range of cyclotorsional eye movements during a simulated PRK procedure suggests that 3D tracking could improve surface ablation results when treating high astigmatism or when wavefront guided.

Adult↗
PubMed1990

Behavior of accessory abducens and abducens motoneurons during eye retraction and rotation in the alert cat.

1. The activity of both accessory abducens (Acc Abd) and abducens (Abd) motoneurons (Mns) was recorded in the alert cat during eye retraction and rotational eye movements. Cats were fitted with two scleral coils, one measured rotational eye movements directly and the other retraction by distinguishing the translational component. 2. Acc Abd and Abd Mns were identified following antidromic activation from electrical stimulation of the ipsilateral VIth nerve. 3. In response to corneal air puffs, bursts of spikes were produced in all (n = 30) Acc Abd Mns. The burst began 7.2 +/- 1.2 (SD) ms after onset of the air puff and 8.9 +/- 1.9 ms before eye retraction. 4. Acc Abd Mns were silent throughout all types of rotational eye movements, and tonic activity was not observed during intervals without air-puff stimulation. 5. In contrast, all (n = 50) identified Abd Mns exhibited a burst and/or pause in activity preceding and during horizontal saccades as well as a tonic activity proportional to eye position. 6. Only 10% of Abd Mns fired a weak burst of spikes in response to air-puff stimulation. 7. We conclude that Acc Abd Mns are exclusively involved in eye retraction in the cat and that only a few Abd Mns have an eye-retraction signal added to their eye position and velocity signals. Thus any rotational eye-movement response described in retractor bulbi muscle must result from innervation by Mns located in the Abd and/or the oculomotor nuclei. 8. The organization of the prenuclear circuitry and species variation are discussed in view of the nictiating membrane extension response measured in associative learning.

Abducens Nerve↗
PubMed1980

Lateral eye movement and handedness as measures of functional brain asymmetry in learning disability.

Evidence is presented which suggests that learning disability is related to lateral asymmetry. Significant differences were found in lateral eye movement and handedness between a learning disabled group and a control group of normal learners. Left lateral eye movement and right handedness was the predominant pattern exhibited in learning disability. These results support Day's notion that left lateral eye movement is associated with educational difficulties. They also provide evidence concerning Orton's hypothesis that mixed cerebral dominance characterizes the learning disabled.

Child↗
PubMed1980

Eye movements and choice times in mirror image pattern discrimination.

This paper studied mirror image and nonmirror image pattern discrimination by measuring adults' eye movements as they responded to spatially simple or spatially complex stimulus pairs. Two measures were derived from the eye movement data; the average position of the subject's gaze as a function of time (scanpath), and the distribution of eye positions sampled over the patterns (dwell distribution). The data show that spatial complexity has a qualitative influence on the processing of mirror and nonmirror patterns, that spatially complex pairs tend to be scanned from left-to-right, and that peripheral features are not usually directly fixated. The data also bear on theories of symmetry perception, and indicate that symmetry is not always perceived in a holistic fashion.

Choice Behavior↗
PubMed1987

Comparison of smooth pursuit and combined eye-head tracking in human subjects with deficient labyrinthine function.

The effects of deficient labyrinthine function on smooth visual tracking with the eyes and head were investigated in ten patients with bilateral peripheral vestibular disease. Ten normal subjects served as controls. In the patients active, combined eye-head tracking (EHT) was significantly better than smooth pursuit (SP) with the eyes alone with a target frequency of 1.0 Hz. Normal subjects pursued equally well with SP and with active EHT. The gain of compensatory eye movements during active head rotation in darkness was also measured. Compensatory eye movements in labyrinthine-deficient patients (attributable to residual vestibulo-ocular reflex (VOR), cervico-ocular reflex (COR) and pre-programmed eye movements) were always less than in normal subjects. These data were used to examine current hypotheses that postulate central cancellation of the VOR (or compensatory eye movements) during EHT. A model that proposes summation of an internal smooth pursuit command and VOR/compensatory eye movements accounted for the findings in normal subjects and labyrinthine-deficient patients. In seven labyrinthine-deficient patients and nine normal subjects, passive EHT was measured during en bloc rotation while they viewed a head-fixed target. With a target frequency of 1.0 Hz, both subjects and patients showed significantly better tracking during passive EHT than during SP. Normal subjects also showed superior tracking during passive EHT compared with active EHT. These findings support the notion that during passive EHT, parametric gain changes contribute to modulation of the VOR.

Adult↗
PubMed1992

Eye movements during motion after-effect.

Using the magnetic search coil technique, we measured torsional eye movements in four male subjects during and after rotation of a visual display around the line of sight. During rotation of the display, subjects developed a torsional nystagmus with slow-phases in the direction of target rotation that had a typical gain of less than 0.01. Upon cessation of display motion, subjects experienced a motion after-effect (MAE) in the direction opposite prior target rotation, which persisted for greater than 15 sec. During this MAE, slow-phase eye movements of low velocity were in the same direction as the MAE, but did not persist as long as perceptual effects. In separate experiments, horizontal eye movements were recorded during horizontal stimulus motion; during MAE, no eye movements occurred due to stronger fixation mechanisms. We conclude that MAE is not caused by retinal slip of images, but MAE and the accompanying eye movements might be produced by shared or similar mechanisms.

Adult↗
PubMed2002

Gabapentin attenuates superior oblique myokymia.

PURPOSE: To investigate therapeutic effects of oral gabapentin therapy on superior oblique myokymia. DESIGN: Observational case series with measurement of visual acuity and eye movements before, during, and after therapy. METHODS: Two adult patients with superior oblique myokymia, refractory to other therapies, were treated with gabapentin orally after informed consent was obtained. Eye movements were measured using the magnetic search coil technique. RESULTS: Superior oblique myokymia completely resolved after starting gabapentin. CONCLUSION: Gabapentin may be an effective treatment for superior oblique myokymia; a double-blind study seems justified.

Acetates↗
PubMed1984

Vergence eye movements and visual suppression.

Visual sensitivity was measured during vergence eye movements in order to determine whether a suppression of vision similar to that associated with saccades is also present during vergence. Suppression was evaluated psychophysically by determining sensitivity to briefly presented, full-field decrements of light in a Ganzfeld. Subjects were rougly 0.5 log unit less sensitive when stimuli were presented at the beginning of a 2-3 deg convergent or divergent eye movement, than during steady fixation. Thus, the concept of saccadic suppression must be broadened to include visual suppression that also accompanies nonsaccadic eye movements. These results support the hypothesis that vision is affected by signals that accompany initiation of oculomotor activity.

Electrooculography↗
PubMed2005

Direct visualisation of gaze and hypometric saccades in cerebellar patients during visually guided stepping.

Four patients suffering from primary cerebellar degeneration and healthy matched controls undertook a test of functional mobility that demanded precise foot placement at each step. Vertical and horizontal eye movements were measured (using a head mounted eye tracking system) together with footfall patterns. Healthy subjects stepped accurately onto all targets and produced a clear pattern of saccadic eye movements, fixating each target in the sequence just prior to footlift. Still video frames, showing direction of gaze while walking, provide direct visual confirmation that these saccades serve to transfer gaze between successive targets in the walkway sequence. The planning of the saccade to the next target probably provides the locomotor control system with information useful for planning the corresponding (and shortly following) step. Cerebellar patients showed characteristic locomotor and oculomotor deficits. Dysmetric saccades to fixate footfall targets were seen in 39% of steps. Analysis confirms that these multi-saccadic eye movements include an initial hypometric saccade, which undershoots the target, followed by one or more additional saccades in the same direction. Direct visualisation of gaze at the end of a saccadic sequence confirms that these additional saccades are indeed corrective resulting in a foveal image of the footfall target.

Cerebellar Diseases↗
PubMed2003

Errors of binocular fixation are common in normal subjects during natural conditions.

PURPOSE: To investigate the accuracy of fixation after symmetrical vergence eye movements along the midline during natural full-field viewing conditions using a video method of eye position measurement. METHODS: The accuracy of binocular fixation after symmetrical vergence eye movements during natural conditions was measured on 29 young adults using a precise head-mounted video eye movement measuring system. All subjects had normal binocular vision and good visual acuity. Measurements were taken for both near and far fixation after vergence changes of 5 degrees, 10 degrees, and 15 degrees using three rates of change, approximately 0.25, 0.5, and 1 Hz. RESULTS: The amplitude of the vergence movement tended to be hypometric, resulting in underconvergence for near fixations, and overconvergence for distance fixation. For far fixations, most errors (82%) were from -120 to +120 min arc, and for near, most errors (85%) were from -30 to +120 min arc. For far fixations, there was a significant effect of the size of vergence change (F1,28 = 61.8; p < 0.001), the rate of change (F1,28 = 7.08; p = 0.013), and the interaction between these two factors (F1,28 = 7.17; p = 0.012) on resulting errors, with the eyes showing greater overconvergence on the target for the larger and faster fixation changes. For near fixations, there was a significant effect (F1,28 = 15.9; p < 0.001) for the angle of change with the faster vergence changes producing relatively more convergence, thus reducing the mean vergence error. No subject reported diplopia during any conditions despite our measures showing vergence errors of up to 5 degrees. CONCLUSIONS: Vergence errors of up to +/-2 degrees, without diplopia, were common in subjects with normal binocular single vision. Errors of 5 degrees were rare but present. In all, the largest number of errors occurred as a failure of divergence for far fixations, consistent with previous studies that have suggested differences in the neural control of pathways for convergence and divergence, or possibly caused by differences in the anatomical properties of the medial and lateral rectus muscles and their associated fascia. The absence of diplopia during the period of fixation could only be partly associated with the visual suppression associated with vergence eye movements that has been reported by others because it was still present after the vergence movement was completed. The natural viewing conditions in this study that included a full visual field and multiple disparities may have contributed to this effect.

Adolescent↗
PubMed1995

A syntactic analysis method for eye movements of vestibulo-ocular reflex.

In this study a computer method is described which is designed to recognize these eye movements originating from vestibulo-ocular reflex signals. The corresponding head movement signal measured concurrently with eye movements serves as the stimulation signal which is utilized in the pattern recognition process and in the computation of gain and phase shift parameters. The recognition method is syntactic with a formal grammar and language applied to terminal symbols into which the measured signals are transformed in a preprocessing phase of the method after filtering. After preliminary tests in an otoneurological laboratory the method seems to function correctly and accurately, and has been taken into use for eye movement investigations of patients suffering from otoneurological diseases.

Eye Movements↗
PubMed1992

Accommodation on downward gaze.

A study was conducted with the purpose of examining the possible effects of vertical and horizontal eye movements upon accommodation. A special Badal stimulator was made which was vertically rotatable around the center of an eye. The stimulator was attached to the Three-Dimensional Optometer III (TDOIII), which could measure accommodation, eye movement, and pupil diameter simultaneously. The reliability of the TDOIII measurements of accommodation was checked by comparing with a stigmatoscope measurement. Three young males served as subjects. A small but definite near accommodation was measured dynamically in association with vertical eye movement. We believe this to be the first report of this finding. The amount of near accommodation with downgaze showed a tendency to decrease when the target was brought near.

Accommodation, Ocular↗