Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Eye Movement Measurements”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1985

Measuring eye movements with a search coil: non-linear filter allows simultaneous recording of horizontal and vertical eye position by means of the phase modulation method.

Measuring eye position from the phase angle of the signal induced by a rotating magnetic field in a search coil presents a number of advantages. So far, however, existing schemes using this principle either record eye position in one dimension only or require two search coils. We describe here a simple analog circuit which singles out a signal of given frequency from a frequency composite without changing the signal's phase. This makes it feasible to measure horizontal and vertical eye position with a single search coil by using two orthogonal rotating fields of different frequency.

Electronics↗
PubMed1989

Conspicuity in realistic scenes: an eye-movement measure.

An experiment is described to measure the distracting effects of advertisements on the conspicuity of routing signs in realistic scenes. Slides of railway station scenes were shown in which subjects had to search for a target word used in a routing sign present in the scene. Eye movements were recorded to determine search time and number of fixations during search time. Both search time and number of fixations increased systematically with the number of advertisements in two of the three experimental scenes. The distribution of fixations over the scenes is discussed.

Journal Article↗
PubMed1999

A method for measuring eye movements using Hall-effect devices.

A system for precise recording of eye position and movements in laboratory animals, by means of Hall-effect devices, is described. The system, useful in neurophysiological and neurobehavioral studies, allows the analysis of saccadic eye movements, optokinetic- and vestibular-induced nystagmus, slow tracking movements, eye vergences, and so forth. This small, light-weight, and inexpensive system uses a set of Hall-effect devices and associated electronics to sense variations in the position of high-power magnets fixed in the eye sclera or in scleral contact lenses. The output of the Hall-effect devices is amplified by operational amplifiers, collected through an A/D converter, and analyzed in a PC computer by specific software.

Animals↗
PubMedDate not supplied

Measuring eye movements during locomotion: filtering techniques for obtaining velocity signals from a video-based eye monitor.

Video-based eye-tracking systems are especially suited to studying eye movements during naturally occurring activities such as locomotion, but eye velocity records suffer from broad band noise that is not amenable to conventional filtering methods. We evaluated the effectiveness of combined median and moving-average filters by comparing prefiltered and postfiltered records made synchronously with a video eye-tracker and the magnetic search coil technique, which is relatively noise free. Root-mean-square noise was reduced by half, without distorting the eye velocity signal. To illustrate the practical use of this technique, we studied normal subjects and patients with deficient labyrinthine function and compared their ability to hold gaze on a visual target that moved with their heads (cancellation of the vestibulo-ocular reflex). Patients and normal subjects performed similarly during active head rotation but, during locomotion, patients held their eyes more steadily on the visual target than did subjects.

Adult↗
PubMedDate not supplied

Does fatigue exist in a quantitative measurement of eye movements?

The measurement system for quantitative analysis of eye movements and distribution of eye fixation points was developed through the study. Experiments on physiological fatigue characteristics of eye movements were studied using the system. The subjects involved in the study were six young males. No significant change was quantitatively found in saccadic eye movements during and/or after five hours of rapid eye tracking tasks. The saccadic velocity of two subjects were found in binocular decreased temporarily. The maximum velocity of eye movements obtained in the present experiment was ascertained in order to produce a scale for various visual work as an ergonomic index.

Asthenopia↗
PubMed1998

Clinical use of three-dimensional video measurements of eye movements.

Noninvasive measurements of three-dimensional eye position can be accurately achieved with video methods. A case study showing the potential clinical benefit of these enhanced measurements is presented along with some thoughts about technological advances, essential for clinical application, that are likely to occur in the next several years.

Aged↗
PubMed2005

A new method for accurate and fast measurement of 3D eye movements.

Videooculography (VOG) is an eye movement measurement method used in the objective evaluation of vestibulo-ocular reflexes (VOR). An important requirement of VOG is to accurately estimate pupil center and ocular torsion, irrespective of drooping eyelids, eyelashes, corneal reflection, and blinking. Finding the accurate center of the pupil is particularly important in three-dimensional VOG, since otherwise, significant errors can occur in measuring torsional eye movement. A fast algorithm was proposed to accurately ascertain the pupil center, in spite of the complicating factors mentioned above. In this study, real-time three-dimensional VOG, which can measure horizontal, vertical, and torsional eye movements and calculate the pupil radius, was implemented using the proposed method. When the pupil radius was determined, the vertical position was measured within an error margin of less than 3%, even though only 10% of the pupil was visible. The time required to measure both three-dimensional eye movements and the pupil radius was less than 16 ms. Thus, eye movements can be measured in real-time. The resolutions of horizontal, vertical, and torsional eye movement were 0.2 degrees, 0.2 degrees, and 0.1 degrees, respectively, with maximum ranges of +/- 35 degrees, +/- 25 degrees, and +/- 18 degrees.

Algorithms↗
PubMed1984

Voluntary selection of the target for smooth eye movement in the presence of superimposed, full-field stationary and moving stimuli.

Prior work has shown that smooth eye movements in the presence of both stationary and moving stimuli are determined, at least in part, by the voluntary selection of either the stationary or the moving stimulus as the target for smooth eye movements. The effectiveness of voluntary selection in eliminating the influence of the stimuli not selected (i.e. backgrounds) on smooth eye movement is not known because prior studies used targets and backgrounds with different physical characteristics. Thus, effects of voluntary selection were confounded with the relative strength of target and background as stimuli for smooth eye movements. We measured eye movements (resolution 1') of two highly-experienced eye movement subjects with a target and background with the same physical characteristics: two, identical, full-field, superimposed patterns of randomly-positioned dots (1 dot/deg2 or 8 dots/deg2). One field was stationary and the other moved at 70.2 minarc/sec. The effect of the moving background on smooth eye movements when the stationary field was the target, and the effect of the stationary background on smooth eye movements when the moving field was the target was negligible (0-4% for one subject; 0-2% for the other). The influence of the background on smooth eye movements was affected by a six-fold reduction in the intensity of either the target or background, but effects of such intensity changes were small and different for each subject. Taken together, these results show that the effectiveness of voluntary selection in eliminating the influence of background stimuli on smooth eye movements can be virtually complete. Any observed influence of the background--however small--can be attributed to voluntary factors (e.g. subjects' failure to apply sufficient effort or attention) rather than to the operation of an involuntary mechanism that automatically integrates velocity information from target and background. The attention and effort required to ensure that voluntary selection is perfect may impair the accuracy of psychophysical judgments made about the background.

Attention↗
PubMed2004

Three-dimensional analysis of dentist's eye movements.

We measured the eye movements of a dentist while a pediatric patient walked toward a dental chair. Bilateral eye movements were measured and analyzed three-dimensionally based on the angle of convergence. The frequency of fixation points registered in each test ranged from 2 to 11, with an average of 6.6. No significant differences were observed when the experiments were grouped according to the age of the observed child. In 13 out of 74 experiments, the calculated distances between the observer and the fixation points corresponded to the actual distances. According to the patterns of where the fixation points occurred, 13 experiments had an "inside-outside" pattern and 61 had an "outside-only" pattern. None of the experiments had an "inside-only" pattern. The "outside-only" group was further subclassified into 50 "behind-only" patterns, 5 "in front-only" patterns, and 6 "in-front-and-behind" patterns. As far as depth perception is concerned, the angle of convergence determined by the eye movements would rarely correspond to the actual distance between the observer and the fixation point.

Accommodation, Ocular↗
PubMed2006

Use of an electromagnetic eye movement monitor for easy measurement of arm movements.

This paper proposes a new technique for measuring arm movements, which is an adaptation of the electromagnetic method for measuring eye movements. Two small coils of wire are mounted onto the subject's elbow, moving rigidly with the humerus, and two more coils are mounted onto the subject's wrist, moving rigidly with the radius-ulna. The subject is placed inside three alternating magnetic fields at different frequencies in the X, Y, and Z directions. As the arm moves, the voltages induced into the coils vary with angle. For each coil, the voltages are de-modulated to give three dc voltages giving the vector direction of that coil's axis. Corrections for the nonuniformity of the magnetic fields are computed. The method works unambiguously for all possible arm movements within the physiological ranges of the joints. Measurement of finger angles is just as easily done. The five angles describing arm movements can be measured at millisecond intervals with noise as small as 2 arcsec rms and drift of about 1 arcmin over a day, i.e., the electronics is more stable than the attachment of the coils to the arm.

Algorithms↗
PubMed2005

Comparing the accuracy of video-oculography and the scleral search coil system in human eye movement analysis.

The measurement of eye movements in three dimensions is an important tool to investigate the human vestibular and oculomotor system. The primary methods for three dimensional eye movement measurement are the scleral search coil system (SSCS) and video-oculography (VOG). In the present study, we compare the accuracy of VOG with that of SSCS using an artificial eye. We then analyzed the Y (pitch) and Z (yaw) component of human eye movements during saccades, smooth pursuit and optokinetic nystagmus, and the X (roll) component of human eye movement during the torsional vestibulo-ocular reflex induced by rotation in normal subjects, using simultaneous VOG and SSCS measures. The coefficients of the linear relationship between the angle of a simulated eyeball and the angle measured by both VOG and SSCS was almost unity with y-intercepts close to zero for torsional (X), vertical (Y) and horizontal (Z) movements, indicating that the in vitro accuracy of VOG was similar to that of SSCS. The average difference between VOG and SSCS was 0.56 degrees , 0.78 degrees and 0.18 degrees for the X, Y and Z components of human eye movements, respectively. Both the in vitro and in vivo comparisons demonstrate that VOG has accuracy comparable to SSCS, and is a reliable method for measurement of three dimensions (3D) human eye movements.

Adult↗
PubMed2006

Saccades in presymptomatic and early stages of Huntington disease.

OBJECTIVE: To evaluate quantitative measures of eye movements as possible biomarkers in prediagnostic and early stages of Huntington disease (HD). METHODS: The study sample (n = 215) included individuals both at risk and recently diagnosed with HD. All participants completed a uniform clinical evaluation which included administration of the Unified Huntington's Disease Rating Scale (UHDRS) by a movement disorder neurologist and molecular testing to determine HD gene status. A high resolution, video-based eye tracking system was employed to quantify measures of eye movement (error rates, latencies, SD of latencies, velocities, and accuracies) during a computerized battery of saccadic and steady fixation tasks. RESULTS: Prediagnostic HD gene carriers and individuals with early HD demonstrated three types of significant abnormalities while performing memory guided and anti-saccade tasks: increased error rate, increased saccade latency, and increased variability of saccade latency. The eye movement abnormalities increased with advancing motor signs of HD. CONCLUSIONS: Abnormalities in eye movement measures are a sensitive biomarker in the prediagnostic and early stages of Huntington disease (HD). These measures may be more sensitive to prediagnostic changes in HD than the currently employed neurologic motor assessment.

Eye Movements↗