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At least 109 records · Page 6Linked to original sources
PubMed2006

Visual fields and eye movements in a harbor seal (Phoca vitulina).

The boundaries of the visual fields of a harbor seal were measured using static perimetry. In the seal lying on a plane surface (fixation point "0 degrees" straight ahead at eye-level), the visual field with fixed eyes extended over 208 degrees horizontally and reached from -12 degrees to +69 degrees vertically. The binocular visual field amounted to 67 degrees. Eye movements of 12 degrees (+/-2) degrees to both sides and 64 degrees upwards could be induced. In the seal performing eye movements, a visual field of 210 degrees in the horizontal plane and 121 degrees to the dorsal side was determined. From the measured eye movements, a visual field of 232 degrees in the horizontal plane appears possible.

Animals↗
PubMed1993

Saccadic eye movements as a measure of the effect of low vision rehabilitation on reading rate.

We assessed saccadic eye movements and reading capabilities in individuals with macular disease by a masked clinical study to determine whether changes in saccadic frequency were correlated to changes in reading rates or number of errors for a reading task. We used a measure of eye movement characteristics in the form of a saccadic frequency score (SFS). Twelve subjects with macular disease were tested before and after an intense 6-week inpatient vision rehabilitation program. The mean age was 70.9 years (63 to 77 years). Mean visual acuity was 10/100 (10/40 to 10/200). Mean reading rates at entry and discharge were 8.5 words/min and 20.9 words/min, respectively (p = 0.02). SFS improved from 2.709 to 2.022 (p = 0.07). Reading errors improved from 5.60 to 4.00 (p = 0.03). Reading rates and SFS's were highly inversely correlated both pre- and post-treatment (Pearson r = -0.892 and -0.896, respectively). SFS and the number of reading errors were highly correlated with both pre- and post-treatment as well (Pearson r = 0.782 and 0.601, respectively). Interestingly the data appeared to cluster into two groups, one showing improvement and the other showing none. Cluster analysis revealed a strong association among reading rate, saccade scores, and reading errors. Membership in the two clusters is consistent pre- and post-rehabilitation in all but one case. Clustering is most evident for reading rate and reading errors and less so for saccade scores.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1998

Plausibility and argument structure in sentence comprehension.

In two experiments, we investigated how reading time was affected by the plausibility of the prepositional phrase in subject-verb-noun-phrase-prepositional-phrase sentences, and the status of the prepositional phrase as argument versus adjunct of the verb. Highly plausible prepositional phrases were read faster than less plausible ones, and argument prepositional phrases were read faster than adjuncts. These effects appeared both in a self-paced reading experiment and in an experiment that measured eye movements during normal reading. The effects of plausibility were substantially larger and longer lasting than the effects of argument status, but both appeared very early in the reading of the prepositional phrase. The implications of these effects for models of parsing and sentence interpretation are discussed.

Cognition↗
PubMed2000

Digital measurement of torsional eye movement due to postural change and its effect on reading performance.

PURPOSE: Posture induced torsional eye movements have rarely been investigated. The current study made use of digital imaging technology to measure the cycloduction resulting from postural change. The effect of cycloduction on reading performance was also investigated. METHODS: Thirty subjects were recruited and pictures of the right eye were captured using a digital camera at three postures, i.e. sitting, 90 degrees tilted to the right and 90 degrees tilted to the left. With the identification of a conjunctival landmark, torsional eye movement was measured. The subjects were then required to read a custom designed near chart while in those three postures, the reading card being rotated 90 degrees clockwise or 90 degrees anti-clockwise, to match with the tilting of the head. The reproducibility of the torsional eye movement and reading performance measure was determined in 12 of those 30 subjects. RESULTS: Incycloduction was induced when tilting to the right and excycloduction when tilting to the left. This method was found to be reproducible with the 95% confidence limits of 0.80 degrees between visits. The mean incycloduction induced was 6.50 degrees (SD 1.51 degrees ) and 6.41 degrees (SD 1.46 degrees ) for excycloduction. No significant difference in amount was demonstrated (paired t-test: t = 0.624, P = 0.538). No significant difference was found in the reading scores at various postures (Repeated measures ANOVA: df = 2, F = 1.881, P = 0.162). CONCLUSIONS: The results presented here demonstrate that we have developed an objective and instantaneous method with good precision, which could be applied in other studies that require the measurement of torsional eye movements. The induced cycloduction did not affect the reading performance.

Adolescent↗
PubMed1977

Bilateral lesions of the medial longitudinal fasciculus in monkeys: effects on the horizontal and vertical components of voluntary and vestibular induced eye movements.

Bilateral transections across the brainstem interrupted the medial longitudinal fasciculus (MLF) in three monkeys trained to make eye movements while subjected to horizontal or vertical angular accelerations. Eye movements measured before and after the lesion revealed deficits in both voluntary and vestibular compensatory eye movements; the deficits differed in the horizontal and vertical directions. Vertical saccades in both directions were normal but eccentric positions of fixation could not be maintained; a drift toward the midline followed by a corrective saccade produced vertical fixation nystagmus. Furthermore, the vertical vestibulo-ocular reflex (VOR) was abolished and vertical smooth pursuit was impaired. Along the horizontal meridian, adduction across the midline could not be achieved during either saccades, smooth pursuit, or the VOR. Temporal saccades were normal whereas nasal saccades were considerably slowed. If the eye was not required to cross the midline, the phase shift during the VOR was within 15 deg of normal in each eye. The gain of the VOR was reduced to about 0.4 immediately after the lesion, but recovered within one month. These findings suggest that the MLF transmits quite different kinds of information to horizontal and vertical oculomotoneurons and that deficits in vertical eye movements may be a sensitive indicator of anterior internuclear ophthalmoplegia.

Animals↗
PubMed1995

Accommodation-convergence relationships and age.

PURPOSE: The objective of this study was to determine if there are differences in accommodative-convergence/accommodation (AC/A) and convergence-accommodation/convergence (CA/C) ratios in subjects with increasing age. The authors aimed to relate the findings to the present theories of the development of presbyopia. METHODS: Using a Canon AutoRef R-1 to measure accommodation and an IRIS eye movement monitor to measure eye movements, the authors determined objective AC/A and CA/C ratios for 23 subjects between 17 and 42 years of age with normal binocular vision. Changes in accommodation and convergence responses were stimulated by lenses (-1.00 DS and -2.00 DS) and prisms (4 and 8 prism diopters), respectively. Measures were made at two visits on consecutive days. RESULTS: A moderate linear relationship was found between AC/A ratio and age (P < .002), and a strong linear relationship was found between CA/C ratio and age (P < .0001). The decrease in CA/C ratio with age was due to a decreased accommodative response to prisms (P = .0001). Measurements were reliable, with 95% confidence intervals at +/- 1.28 delta/D and +/- 0.02 D/delta for AC/A and CA/C ratios, respectively. A reciprocal relationship existed between the AC/A and CA/C ratios. CONCLUSION: The AC/A ratio increases, and the CA/C ratio decreases, in persons between 20 and 40 years of age. This may be because increasing ciliary muscle contraction is required to produce a given change in accommodation with increasing age or because of changes in the adaptability of the tonic accommodation and vergence systems with age.

Accommodation, Ocular↗
PubMed1991

Stereo-thresholds: simultaneity, target proximity and eye movements.

Stereo-thresholds are much higher when adjacent targets are presented without temporal overlap than when they are shown simultaneously. Sequentially presented adjacent targets also evoke small involuntary eye movements toward the newly presented target. Neither of these phenomena is evident with widely separated targets; for sequential presentation of targets 10 degrees apart, stereo-thresholds are only slightly higher (a factor of about 1.5) than for simultaneous presentation; and stable fixation can be maintained. If the differing influence of simultaneity on stereoacuity for adjacent and for widely separated targets arises because adjacent alternating targets evoke eye movements, that effect is apparently not mediated exclusively by displacement of retinal images due to the measured eye movements. It could, however, be due to a general long-term instability of fixation associated with repetitive small involuntary eye movements.

Adolescent↗
PubMed1999

3D eye movements--basics and clinical applications.

The eye muscles in humans are arranged such that they allow rotations of the globe about any axis in three-dimensional space. Only 3D analysis techniques will suffice to describe the sometimes complex dependencies between the elicited eye movements and the stimulation conditions. With the recent availability of modern 3D eye movement measurement techniques and the further development of appropriate mathematical descriptions, we are now able to study eye movements in all three degrees of freedom. This article describes the basic mathematical tools for 3D eye movement analysis like rotation vectors, reference frames, coordinate systems, and the concept of Listing's law. In a second part some clinical applications are presented. The close coupling between the vestibular and the oculomotor system suggests that by observing spontaneous and elicited eye movements in the case of an acute unilateral vestibular pathology we might be able to find out which parts of the vestibular system (that is, which of the semicircular canals or which of the otoliths) are affected. The rationale of such an analysis is based on the observation that electrical stimulation of single semicircular canal afferents in animals induces eye movements that lie roughly in the plane of the canal. It is, therefore, possible to deduce which canals cause the eye movements observed when only some parts of the vestibular system are defective. Thus, the analysis of 3D movements not only provides an improved understanding of how the brain organizes movement in 3D space, but also has the potential to significantly improve our diagnostic capabilities.

Electronystagmography↗
PubMed1986

Saccadic eye movements as a measure of residual effects: temazepam compared with other hypnotics.

Eye movements are classified into two categories: quickly running saccades and smooth pursuit movements. Saccades are fast conjugate eye movements with a preprogrammed direction, amplitude, and speed course; their purpose is to register new objects in the visual field. The duration and velocity of saccadic eye movements are very much dependent on vigilance. Comparisons were made with a number of psychometric tests [d 2 Durchstreichtest (cross out test), Viennese determination apparatus, and flicker fusion frequency] and the velocity of fast eye movements. The results of three separate investigations are presented. Standardization was undertaken in 100 healthy volunteers, 50 male and 50 female subjects aged between 20 and more than 50 years were included. In an open parallel group study, comparisons were made between various hypnotics with different half-lives (temazepam, flunitrazepam, flurazepam, and phenobarbital). There were 10 healthy volunteers in each group, and medication was taken as a single night-time dose for 7 nights. In a double-blind study, temazepam (20 mg/day) was tested against flunitrazepam (2 mg/day). Dosing lasted 7 days. A marked impairment of the saccadic eye movements was observed with flunitrazepam but not with temazepam. Of all the benzodiazepines tested, only temazepam had no influence on the parameters of the saccade test. These results can be explained by temazepam's short half-life and also by the fact that no active metabolites are formed.

Adult↗
PubMed1990

Video-oculographic measurement of 3-dimensional eye rotations.

An effective and relatively calibration-free method for the measurement of 3-dimensional eye rotations is described. The experimental method consists of recording with a video camera the positions of distinct globe markers provided by a tight-fitting, soft contact lens before and after an eye rotation. The mathematical analysis represents the eye rotation by a rotation vector (rotation axis and angle) and three, spherical Euler angles. The method is linear over the entire range of natural eye rotation, the resolution limited only by the video set-up used. Due to its easy applicability, the system is well suited for various eye movement measurements in clinical or research environments.

Eye Movements↗
PubMed2002

Analysis of substitution test performance using eye movement and video data.

Substitution tests continue to enjoy widespread popularity in applied neuropsychology. Though highly sensitive, these tests lack specificity, and substitution test decrements are often reported in terms that bear little relation to cognitive or other psychological theory. Objectives were to quantify, using eye movement/video analysis, subitem performance elements for the Wechsler Adult Intelligence Scale-Revised (WAIS-R) Digit Symbol Test (DST); to assess the relative contribution of each of these to standard WAIS-R DST performance in a group; and to assess whether wearing the eye-movement measuring equipment interfered with test performance.

Adult↗
PubMed1994

An illusion of velocity in motion perception.

We report a phenomenon that seems to have potential to elucidate a role of eye movement in motion perception. When tracking a target controlled by a triangular wave, the viewer perceives movement of the target like a ball bouncing in between two walls. We measured eye movement with electrooculograms (EOGs) when the subject was tracking a target controlled by a triangular wave. Eye movement after passing the turning point and rapidly returning to the target with saccadic movement and then smoothly tracking the target was recorded for all 4 adults. It was considered that extraretinal information on eye position during saccade may mainly contribute to this illusion.

Acceleration↗
PubMedDate not supplied

Disconjugate eye movements during electronstagmographic testing in patients with known central nervous system lesions.

A tacit assumption underlying current ENG testing is that the eyes move conjugately. However, considering the intricate neuroanotomical pathways within the ocular motor system in addition to the elaborate vestibulo-ocular connections, we think it reasonable that disconjugate eye movements may result with certain CNS lesions. Recently we have employed independent eye movement measuring techniques in order to assess the movement of each eye separately during our ENG valuations. The preliminary work has revealed that disconjugate eye movements occurred even with extra-axial lesions which spared the medial longitudinal fasciculus. These data may be valuable for the neurotologist with regard to differential diagnosis and prescription of a treatment plan for the patient. The eye movement patterns of patients with confirmed CNS lesions and other interesting findings are presented.

Adult↗
PubMed1990

Measurement of eye rotations in three dimensions and the retinal stimulus projection using scanning laser ophthalmoscopy.

A transformation algorithm is introduced to specify eye rotations in three dimensions from two-dimensional translations of ocular fundus landmarks dynamically monitored by means of the novel Scanning Laser Ophthalmoscope (SLO). The rotation parameters are expressed as Y-X-Z Euler angles and in terms of the rotation axis and one rotation angle. Additionally, the angular distance of the retinal stimulus projection can be evaluated relative to the fovea. By simultaneously operating as eye movement measurement device, fundus camera, and visual target projector, the SLO opens a variety of new applications for the combined analysis of eye movements and the underlying 'retinal events' in vision and oculomotor research.

Algorithms↗
PubMed1990

Eye movement indices of mental workload.

Four investigations were carried out to assess the feasibility of using eye movement measures as indices of mental workload. In the first experiment, saccadic extent was measured during free viewing while subjects performed low, moderate and high complexity, auditory tone counting as the workload tasks. The range of saccadic extent decreased significantly as tone counting complexity (workload) was increased. In the second experiment the range of spontaneous saccades was measured under three levels of counting complexity with a visual task that did not require fixation or tracking. The results indicated that the extent of saccadic eye movements was significantly restricted as counting complexity increased. In the third experiment, the effects of practice were examined and decreased saccadic range under high tone counting complexity was observed even when significant increases in performance occurred with practice. Finally, in experiment 4, the first experiment was repeated with additional optokinetic stimulation and the saccadic range was again observed to decrease with tone counting complexity. The results indicated that the extent of spontaneous and elicited eye movements was significantly restricted as counting complexity increased. We conclude that this measure may provide a valuable index of mental workload.

Adult↗
PubMed1992

[Real-time measurement of torsional eye movements by video-based technique].

The authors developed a real-time measurement system to analyze torsional eye movements using video-based technique with two small dots on a soft contact lens as the targets. The lens, saturated with physiological saline solution, was made to adhere to the eye by dropping distilled water on it, according to Edelman's method. It was demonstrated that the clear image of the lens marker was sufficient to extract torsional eye information without using complex image processing technique and that the lens attached firmly to the eye during recordings. An engineering work station (Hewlett Packard Inc, HP9000/350) was used for hardware implementation, which required only 15 milliseconds to process one frame of a video image and the torsional angle was able to record and display in real-time rate. The accuracy (precision error) of this measurement, evaluated by simultaneous recordings with dyed dots on the conjunctiva and an error propagation analysis, was better than delta = 0.08 degrees.

Contact Lenses↗
PubMed1981

Fusional response to extrafoveal stimulation.

Horizontal and vertical fusional responses to extrafoveal stimulation were examined. An objective binocular eye movement measuring technique was utilized to position an artificial, stabilized scotoma over the central 10 degrees diameter area of one eye. The responses contained both a motor and nonmotor, or sensory, component. The monocular eye movements were asymmetrical.

Eye Movements↗
PubMed2001

Improving the homogeneity of the magnetic field in the magnetic search coil technique.

The magnetic search coil technique is used to obtain accurate eye-movement measurements. For the data analysis it must be assumed that the magnetic field does not change over time (apart from the required modulation). To comply with this assumption either no translational movements of the eye coil(s) are allowed or the magnetic field has to be perfectly homogeneous. Both are normally not the case, i.e., measurement errors occur. These errors can be minimized by keeping the magnetic field as homogeneous as possible. Larger field coils are typically chosen to achieve this aim. However, sometimes the experimental setup imposes limitations on the size of the configuration. We present a method for improving the homogeneity of the magnetic field by adding supplementary field coils without changing the size of the configuration.

Equipment Design↗