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At least 685 records · Page 38Linked to original sources
PubMed1999

Enhancement of the vestibulo-ocular reflex by prior eye movements.

We investigated the effect of visually mediated eye movements made before velocity-step horizontal head rotations in eleven normal human subjects. When subjects viewed a stationary target before and during head rotation, gaze velocity was initially perturbed by approximately 20% of head velocity; gaze velocity subsequently declined to zero within approximately 300 ms of the stimulus onset. We used a curve-fitting procedure to estimate the dynamic course of the gain throughout the compensatory response to head rotation. This analysis indicated that the median initial gain of compensatory eye movements (mainly because of the vestibulo-ocular reflex, VOR) was 0. 8 and subsequently increased to 1.0 after a median interval of 320 ms. When subjects attempted to fixate the remembered location of the target in darkness, the initial perturbation of gaze was similar to during fixation of a visible target (median initial VOR gain 0.8); however, the period during which the gain increased toward 1.0 was >10 times longer than that during visual fixation. When subjects performed horizontal smooth-pursuit eye movements that ended (i.e., 0 gaze velocity) just before the head rotation, the gaze velocity perturbation at the onset of head rotation was absent or small. The initial gain of the VOR had been significantly increased by the prior pursuit movements for all subjects (P < 0.05; mean increase of 11%). In four subjects, we determined that horizontal saccades and smooth tracking of a head-fixed target (VOR cancellation with eye stationary in the orbit) also increased the initial VOR gain (by a mean of 13%) during subsequent head rotations. However, after vertical saccades or smooth pursuit, the initial gaze perturbation caused by a horizontal head rotation was similar to that which occurred after fixation of a stationary target. We conclude that the initial gain of the VOR during a sudden horizontal head rotation is increased by prior horizontal, but not vertical, visually mediated gaze shifts. We postulate that this "priming" effect of a prior gaze shift on the gain of the VOR occurs at the level of the velocity inputs to the neural integrator subserving horizontal eye movements, where gaze-shifting commands and vestibular signals converge.

Adult↗
PubMed1975

[Legal questions in ophthalmology after head injuries (author's transl)].

After a short review of the literature the reduction of earning capacity on the common labour market in cases of decrease of fusion, convergence and accommodation caused by head injuries is discussed and percentual values are proposed. Hereby not only the single reduction of one of these functions but also combined occurrence is allowed for and values for the total reduction of earning capacity are considered.

Accommodation, Ocular↗
PubMed1986

Clinical neurophysiology of dementia.

The role of EEG in the study of the dementias is to help in the differential diagnosis of the multiple causes of this syndrome. EEG is useful in differentiating early on between treatable and as of now untreatable forms of dementia. Space-occupying lesions that give rise to dementia are reliably detected by EEG. Infectious, toxic, and metabolic processes are associated with early and severe electroencephalographic abnormalities. The "slow virus" infections show characteristic electrical patterns that reliably distinguish them from the cortical or subcortical dementias. Finally, the EEG may contribute to distinguishing between Alzheimer's disease and MID, two commonly occurring forms of dementia. The paucity of substantial early EEG abnormalities in Alzheimer's disease, although helping to differentiate it from other dementias, leaves us without a currently available physiologic test that provides positive evidence for this condition. Recent studies of EPs, however, suggest that some intermediate latency VEP components may be delayed in patients with Alzheimer's disease when compared with normal subjects. This is encouraging, as latencies in VEPs are more reliable and less variable than amplitude that has previously been reported as "abnormal" in some early Alzheimer patients. Long latency ERPs and CNV also show early abnormalities in Alzheimer's disease. Tests of eye movements such as ERPs are psychophysiologic tests requiring some degree of patient cooperation. Performance on tests of ocular smooth pursuit correlate highly with severity of the dementia syndrome in Alzheimer's disease. In contrast, smooth pursuit testing is usually normal in elderly patients with pseudodementia of depression, suggesting this test may be of some value in differentiating these two clinical disorders. Some evidence exists that smooth pursuit eye movements are also normal, at least in the early and middle stages, in Pick's disease, again suggesting that eye movement testing may prove to have some utility in differentiating this form of dementia from Alzheimer's disease. Ocular scanpaths are abnormal in dementia. They typically are poorly organized and at times perseveratory. In addition, the average durations of eye fixations during directed visual search are altered in dementia as compared with normals. The average eye fixation durations are longer with Alzheimer's disease and briefer in patients with frontal lobe tumors as compared with elderly normal controls. These group differences suggest differing scanning strategies for these two forms of dementia.(ABSTRACT TRUNCATED AT 400 WORDS)

Alzheimer Disease↗
PubMed1978

Effectiveness of optometric vision therapy.

One hundred consecutive optometric vision therapy patients' records were evaluated to determine what changes occurred in the visual processing system. An ordinal visual performance scale was utilized to rate visual functioning on a one hundred point scale. The scale divides the visual processing system into 10 functions of 10 points each. Each of the 10 functions improved at the .001 level of significance as a consequence of the binocular vision therapy treatment program.

Accommodation, Ocular↗
PubMedDate not supplied

Effect of labyrinthine dysfunction upon head oscillation and gaze during stepping and running.

Head oscillations and eye movements when stepping and running were studied in normal subjects and in patients with labyrinthine dysfunctions. In normal subjects, whereas linear head oscillations in the horizontal plane were very limited during both stepping and running, a marked increase in the vertical linear displacement induced pitching motions of the head during running. Patients with unilateral and bilateral lesions complaining of oscillopsia manifested lateral and diffuse oscillations, respectively, in the horizontal plane during stepping. The ratio of eye amplitude to head amplitude in the vertical plane showed larger values in subjects with labyrinthine lesions than in normals. The present results suggested that oscillopsia during upright locomotion is closely related to linear head oscillations with irregular and high-frequency components, in addition to dysfunction of the vestibulo-ocular reflex.

Adult↗
PubMed1987

A direct test of Listing's law--II. Human ocular torsion measured under dynamic conditions.

Ocular torsion was recorded with a scleral search coil technique in five normal subjects. The dynamic aspects of torsion were investigated during monocular fixation, blinking, smooth pursuit and saccades. Torsion near the primary position showed considerable short-term (SD about 0.25 deg) and a much larger long-term fluctuation (SD about 2.3 deg). During saccades between diagonally opposite tertiary positions torsion transiently reached values approximating those in the sustained primary position. During smooth pursuit across the primary position, the minimal values of torsion varied with the direction and the trajectory of pursuit, in violation of Donder's law. Changes in torsion associated with horizontal and vertical saccades and during the aftermath of blinks often had a sluggish, exponential time course. During eye movements around a circular or square trajectory torsion showed hysteresis. During clockwise pursuit the right eye showed relative intorsion compared to counterclockwise pursuit. It is proposed that central nervous control of torsion is usually imprecise, and that the eye follows Listing's and Donder's laws only approximately.

Blinking↗
PubMedDate not supplied

A review of age changes in perceptual information processing ability with regard to driving.

Age related changes in the sensory modalities of hearing and vision, along with changes in the information processing abilities of selective attention, perceptual style, and perceptual-motor reaction time, were reviewed in the context of driving behavior. Literature reported, indicated age related changes in these abilities have relevance for the understanding of the driving behavior of the older adult.

Accommodation, Ocular↗
PubMed1978

Disturbances of ocular movements and blinking in schizophrenia.

Neurological examination and electroencephalograms and electro-oculograms, recorded by telemetry, from unmedicated patients with acute and chronic schizophrenia demonstrate a number of abnormalities of extraocular movement including staring, abnormal blink rate, absent glabellar reflex, and increase in horizontal eye movements. As potential clues to the pathophysiology of schizophrenia, these disturbances are analysed in relation to anatomical substrate and dopamine modulation of ocular movement, rapid eye movement sleep, and the neurological disorders in which similar disturbances of ocular movement occur.

Adolescent↗
PubMed1989

Response properties of normal observers and patients during automated perimetry.

Automated perimetry was performed on both eyes of 54 normal subjects, 36 patients with ocular hypertension and normal visual fields, and 20 patients with early glaucomatous visual field loss to evaluate false-positive errors, false-negative errors, fixation losses, consistency of double determinations, and testing time. For all subject groups and response measures, large interindividual variation was found. No meaningful age-related changes were obtained for false-negative errors, false-positive errors, fixation losses, or consistency of double determinations. Contrary to earlier reports, we found a low number of normal subjects and patients exceeding the 33% false-positive and false-negative limits established for the Humphrey Field Analyzer. A large number of normal subjects and patients, however, exceeded the 20% limits for fixation losses.

Adult↗