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Results for “Eye Movement Measurements”

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At least 289 records · Page 16Linked to original sources
PubMed1991

Interrelations between measures of visual acuity and parameters of eye movement in congenital nystagmus.

The authors assessed relationships between visual acuity and the amplitude, frequency, intensity, and duration of foveation periods in a retrospective study of 32 patients. Twenty-four patients had congenital idiopathic nystagmus, and eight patients had nystagmus and albinism. Visual acuity was determined for Landolt ring optotypes and, as the extrapolated high-frequency cutoff of the contrast sensitivity function, for horizontal and vertical gratings. No significant correlation existed between acuity and any measured eye movement parameter; however, optotype acuity was related to the magnitude of astigmatic refractive correction, both in patients with idiopathic nystagmus and in albinos. In a subgroup of patients with idiopathic nystagmus whose astigmatic refractive error was -1.50 D or less, nystagmus intensity (amplitude x frequency) correlated significantly with acuity for optotypes (r = 0.71), but not for gratings. Although resolution for vertical gratings was correlated with astigmatic refractive correction, the ratio of resolution for gratings parallel and orthogonal to the meridian of nystagmus was not. Thus, the belief that poorer acuity in patients with substantial astigmatism is attributable to an optically induced meridional amblyopia is supported only partly by these results. The authors concluded that among patients with congenital nystagmus, the influence of eye motion on visual acuity is not readily predicted either from the parameters of nystagmus that they evaluated or from the comparison of resolution for horizontal and vertical gratings.

Albinism, Ocular↗
PubMed1997

Precise measurement of individual rapid eye movements in REM sleep of humans.

An automated analyzer for individual eye movements (EMs) has been developed that enables precise analyses of their incidence. Three new parameters for each EM are obtained: EM magnitude, the angle and speed of eyeball rotation, and the energy of each EM. All rapid eye movement (REM) sleep EMs from 40 nights of polysomnography for 20 healthy young men were analyzed. The mean frequency of eye movement (EM frequency) was 15.9 per minute. Compared to conventionally analyzed rapid eye movement (REM) density, EM frequency was more sensitive to differences among sleep cycles, nights, and individuals. The mean EM rotation was 6.27 +/- 0.021 degrees, the mean speed of rotation was 58.73 +/- 0.18 degrees/second, and mean energy was 525.85 +/- 3.82 degrees2/second. The distribution of changes in these new parameters differed from conventional measures across REM episodes. The conventional measures, REM episode duration, and REM density increased progressively in successive REM episodes in an ascent-to-right pattern. However, the new parameters peaked in the second, followed by relatively low values, producing an inverted V pattern. This discrepancy could indicate physiological mechanisms of EM that are not revealed in conventional measures of REM sleep intensity.

Adult↗
PubMed1999

Whipple's disease mimicking progressive supranuclear palsy: the diagnostic value of eye movement recording.

Treatable causes of parkinsonian syndromes are rare; Whipple's disease is one of them. A patient is described who presented with a parkinsonian syndrome and abnormal vertical gaze. Measurement of eye movements showed marked slowing of upward saccades, moderate slowing of downward saccades, a full range of voluntary vertical eye movements, curved trajectories of oblique saccades, and absence of square wave jerks. These features, atypical of progressive supranuclear palsy, suggested the diagnosis of Whipple's disease, which was subsequently confirmed by polymerase chain reaction analysis of intestinal biopsy material. Precise measurement of the dynamic properties of saccadic eye movements in parkinsonian patients may provide a means of identifying treatable disorders.

Biopsy↗
PubMed1997

Eye fixations, speech rate and bilingual digit span: numeral reading indexes fluency not word length.

The present study examined whether the reading of language-neutral stimuli, as numerals are, at maximal speed by bilinguals indexes processes related to fluency rather than differences in articulation time between languages. We tested two groups of bilinguals that spoke the same languages (Finnish and Swedish) but whose mother tongues were different and obtained measures of Arabic numeral processing by monitoring eye movements. These measures were contrasted with articulation and numeral reading estimates of word length. The results indicated that Finnish- and Swedish-dominant bilinguals had shorter gaze durations and shorter reading times in their respective dominant languages, whereas both groups articulated digits faster in Swedish than Finnish. The Swedish-dominant group had a larger digit span in Swedish, whereas digit span was marginally greater in Finnish than Swedish for the Finnish-dominant group. The finding that numeral reading was influenced by cognitive loads independent of articulation, thus, moderated the view that bilingual digit span effects are mediated exclusively by variation in word length between languages.

Finland↗
PubMedDate not supplied

Cervico-ocular reflex in the normal adult.

(1) The cervico-ocular reflex (COR) in humans was measured while the subjects (n = 10) stood on a rotatable platform in a dark room with the head fixed by a stationary biteplate. Eye movements were measured in response to active and passive rotations about a vertical axis. (2) The COR gain (i.e., horizontal eye movement/amplitude of body rotation) was as great as 22% at low frequency of body rotation (0.025 Hz). With increasing frequency (e.g., at 0.4 Hz) the gain decreased to about 2%. (3) The phase angle of the eye movement ranged generally between -80 and -240 degrees with an average response around -180 degrees. (4) During active rotation, the COR response was similar to the responses measured during passive body rotation. (5) The principal conclusion drawn is that in normal adult humans the COR does not aid in stabilization of the image on the retina during passive or active body rotations. A theoretical function for the COR is presented and discussed.

Adult↗
PubMed1989

Extraretinal information about eye position during involuntary eye movement: optokinetic afternystagmus.

Despite importance for theories of perception, controversy exists as to whether information is available to the perceptual system about involuntary as well as voluntary eye movements. We measured the perceived direction of targets flashed briefly in an otherwise dark field during the primary phase of optokinetic afternystagmus (OKAN), an involuntary eye movement that persists in darkness following optokinetic stimulation. Perceived direction was measured by unseen pointing in one experiment and by pointing made under visual control in a second experiment. Pointing was essentially veridical in both experiments, indicating that accurate extra-retinal information about eye position (presumably, as efference copy) exists for OKAN. Illusory motion of visual targets, which can occur during involuntary oculomotor responses, therefore cannot be attributed to a lack of efference-copy signals for such eye movements.

Attention↗
PubMed1987

Combined measure of smooth pursuit eye movements and ventricle-brain ratio in schizophrenic disorders.

Smooth pursuit eye movements (SPEM) were examined in 67 schizophrenic patients and 101 control subjects. Our study confirms that eye tracking in schizophrenic patients is impaired compared to that in controls. The similar pattern of distribution of SPEM abnormalities in Italian patients as in ethnically different populations strengthens the hypothesis that these abnormalities may be a biological marker for schizophrenia. We also examined the relationship between SPEM abnormalities and the ventricle-brain ratio (VBR), which is also considered useful for differentiating schizophrenic subgroups. Our preliminary results indicate that there is an inverse correlation between abnormal SPEM performance and ventricular enlargement, suggesting that these abnormalities mark distinct subgroups of patients.

Adolescent↗
PubMed1996

Rapid eye movements density as a measure of sleep need: REM density decreases linearly with the reduction of prior sleep duration.

In the recovery nights from total and partial sleep deprivation there is a reduction of oculomotor activity during paradoxical sleep as compared to baseline nights. Aims of the present within-subjects study are to contribute in understanding the nature of the relationship between REM density and sleep need and to evaluate whether an inverse relationship exists between REM density and slow wave sleep (SWS) amount. Six healthy subjects were studied for 7 consecutive weeks with standard polysomnographic recordings. Variations in REM density were assessed in the recovery nights following a gradual sleep restriction, obtained by postponing the sleep onset time while maintaining the final awakening time constant. Results indicate that sleep curtailment decreases REM density in the ensuing recovery nights; the decrease is linearly related to the amount of sleep curtailment. The decrease in REM density parallels an increase in SWS, while no corresponding variation was found neither in the duration of paradoxical sleep nor in the latency of any other sleep stage. These results suggest that REM density could be used as a measure of sleep need.

Adult↗
PubMed2000

The influence of repetitive eye movements on vergence performance.

We measured the peak velocity of convergence eye movement responses in four normal subjects before and after a large number of either repetitive vergence or repetitive saccadic eye movements. A 20% decrease in the mean value of peak velocity was observed in vergence responses after 100 repetitive step vergence eye movements. However, 100 cycles of slow sinusoidal vergence tracking did not induce any notable change in vergence dynamics. Five hundred repetitive saccadic eye movements also caused an approximately 20% decrease in peak velocity. The reduction in peak velocity was related to the number of repetitions for both vergence and saccadic fatiguing stimuli. The frequency of occurrence of double-vergences was also used as an index to monitor the influence of repetitive eye movements on convergence performance. Results showed that repetitive step convergence movements could double, or even triple, the frequency of the occurrence of double-vergence responses, while slow sinusoidal vergence tracking or repetitive saccades had no influence on the frequency of response doubles.

Convergence, Ocular↗
PubMed1992

Encoding of text, manual movement planning, and eye-hand coordination during copytyping.

Typing span and coordination of word viewing times with word typing times in copytyping were examined. In Experiment 1, typists copied passages of text while their eye movements were measured. Viewing location was determined during each eye fixation and was used to control the amount of usable visual information. Viewing constraints decreased interword saccade size when fewer than 7 character spaces of text were visible to the right of fixation and increased interkeypress times when fewer than 3 character spaces of text were visible. The eye-hand span amounted to 2.8 character spaces. Experiment 2 revealed increases in word typing times and word viewing times as biomechanic typing difficulty increased and word frequency decreased. These findings are consistent with a model of eye-hand coordination that postulates that eye-hand coordination involves central and peripheral processes.

Attention↗
PubMed2003

Dodge-ing the issue: Dodge, Javal, Hering, and the measurement of saccades in eye-movement research.

Dodge, in 1916, suggested that the French term 'saccade' should be used for describing the rapid movements of the eyes that occur while reading. Previously he had referred to these as type I movements. Javal had used the term 'saccade' in 1879, when describing experiments conducted in his laboratory by Lamare. Accordingly, Javal has been rightly credited with assigning the term to rapid eye movements. In English these rapid rotations had been called jerks, and they had been observed and measured before Lamare's studies of reading. Rapid sweeps of the eyes occur as one phase of nystagmus; they were observed by Wells in 1792 who used an afterimage technique, and they were illustrated by Crum Brown in 1878. Afterimages were used in nineteenth-century research on eye movements and eye position; they were also employed by Hering in 1879, to ascertain how the eyes moved during reading. In the previous year, Javal had employed afterimages in his investigations of reading, but this was to demonstrate that the eyes moved horizontally rather than vertically. Hering's and Lamare's auditory method established the discontinuous nature of eye movements during reading, and the photographic methods introduced by Dodge and others in the early twentieth century enabled their characteristics to be determined with greater accuracy.

Biomedical Research↗
PubMed1996

Fluoxetine-induced sleep disturbance in depressed patients.

Abnormal polysomnographic (PSG) features, most notably increased electromyographic (EMG) tone and eye movements during non-REM sleep have been observed during sleep in fluoxetine-treated depressed patients. However, the relationship between these PSG features and sleep disruption is unclear. Nine depressed patients treated with 10 to 80 mg of fluoxetine and six unmedicated, depressed patients were studied polysomnographically on two consecutive nights during which sleep parameters, transient arousals, and eye movements were measured. The fluoxetine group experienced a lower-average sleep efficiency index (SEI) and significantly more eye movements and arousals during non-REM sleep than the control group. Eye movement and arousal counts were significantly correlated. In addition, clinically significant periodic limb movement disorder (PLMD) was observed in 44% of the fluoxetine-treated group versus none of the control group. We conclude that a higher incidence of PLMD and frequent transient arousals associated with eye movements may be responsible in part for the complaint of insomnia made by patients treated with fluoxetine.

Adult↗