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At least 559 records · Page 31Linked to original sources
PubMed2003

Automated detection of ocular alignment with binocular retinal birefringence scanning.

We previously developed a retinal birefingence scanning (RBS) device to detect eye fixation. The purpose of this study was to determine whether a new binocular RBS (BRBS) instrument can detect simultaneous fixation of both eyes. Control (nonmyopic and myopic) and strabismic subjects were studied by use of BRBS at a fixation distance of 45 cm. Binocularity (the percentage of measurements with bilateral fixation) was determined from the BRBS output. All nonstrabismic subjects with good quality signals had binocularity >75%. Binocularity averaged 5% in four subjects with strabismus (range of 0-20%). BRBS may potentially be used to screen individuals for abnormal eye alignment.

Automation↗
PubMed1989

Induction of illusory limb movement as a means of studying sensorimotor interactions in the eye-arm system.

In the present study, illusory movements were used as a means of investigating certain sensorimotor interactions: it was proposed to describe the effects produced on the oculomotor system when muscular proprioceptive afferents in the arm were artificially activated by tendon vibration. The gaze displacements induced by these vibratory stimuli were analyzed in terms of the instructions to subjects (i.e., 'simple fixation', allowing the possibility of ocular tracking, or 'obligatory fixation', not allowing any eye movements) and the points in space on which the subject's gaze was required to be fixed (on the hand or elsewhere). The results show that, whatever the experimental conditions applied, the oculomotor system always reacted to vibratory stimulation of proprioceptive afferents, even though no corresponding visual stimulus was present.

Afferent Pathways↗
PubMed1980

Functional analysis of vision in patients after retinal detachment repair.

A number of tests of vision were performed in patients after surgical repair of retinal detachment. The major tests performed were Snellen visual acuity, interferometric acuity, Stiles-Crawford function, and increment-threshold analysis. In two patients it was possible to evaluate all functions preoperatively. Althrough the sample it modest (ten eyes in nine patients), trends in visual recovery are identified and discussed.

Adaptation, Ocular↗
PubMed2004

EEG activity related to preparation and suppression of eye movements in three-dimensional space.

Eight normal subjects made visually guided eye movements to four LED targets placed at two different distances (20 and 70 cm) and on either side (+/-10 degrees ) at 70 cm. Four types of eye movements were elicited: pure saccades, convergence, divergence, and combined (divergent saccades). EEG activity was recorded from 62 electrodes and was aligned to stimulus onset. A negativity peaked after 140 ms and was modulated according to the location of the stimulus in space and the type of movement prepared, mainly in central and posterior cortex. For saccade targets, we confirmed a stimulus-related negativity in the posterior and central cortical area, contralateral to target direction. For convergence and divergence targets, this negativity was bilaterally distributed; convergence targets activated a rather extended cortical network in the central and posterior area, while divergence targets activated a more confined posterior area, spreading ventrally from the occipital cortex. Cortical activity for combined targets was lateralised contralaterally to stimulus direction but its topography resembled more closely that after the divergence stimulus. When observers suppressed the relevant eye movement to the stimulus, EEG activity was enhanced on the right hemisphere, showing the more pronounced effect on the right occipital-temporal and central-parietal electrode sites.

Adult↗
PubMed1982

Meridional variations in acuity and CSF's in monkeys (Macaca nemestrina) reared with externally applied astigmatism.

Infant macaque monkeys have been raised under such conditions that all visual experience was obtained while looking through a cylindrical lens. When tested at older ages, these monkeys were found to have meridional differences in acuity and contrast sensitivity. The direction of the differences were predictable on the basis of the defocus produced by the rearing condition. The data support the theory, previously suggested on the basis of clinical and correlational studies, that astigmatism is a major cause factor in the occurrence of meridional amblyopia.

Accommodation, Ocular↗
PubMed2004

Depth-of-focus of the human eye in the near retinal periphery.

Although the depth-of-focus in the foveal region has been well investigated, knowledge regarding the effect of retinal eccentricity on blur detection and sensitivity is limited. In the present study, the depth-of-focus at the fovea and in the near retinal periphery (0 degrees -8 degrees ) was assessed psychophysically in 7 human subjects using a 5 mm artificial pupil with accommodation paralyzed. The group mean total depth-of-focus progressively increased linearly from 0.89 D at the fovea to 3.51 D at a retinal eccentricity of 8 degrees at the rate of 0.29 D/degree, with response variability (S.E.M.) remaining relatively constant (+/-0.17 D). We speculate that the reduced detection and sensitivity to blur in the near periphery may be attributed to retinal topography, sharpness overconstancy, optical aberrations, and visual attention in peripheral vision.

Accommodation, Ocular↗
PubMed2006

The attenuation of perceived motion smear during combined eye and head movements.

The extent of perceived motion smear was compared for targets that underwent similar velocities of retinal image motion during the vestibulo-ocular reflex (VOR) in the dark, the visually enhanced VOR (VVOR), VOR suppression, and fixation. Compared to the extent of perceived motion smear during fixation, observers reported significantly less smear when the target moved either in the same direction or against the direction of the head movement during the VVOR and VOR. We also confirmed a previous finding that perceived smear is attenuated asymmetrically during VOR suppression, with attenuation occurring primarily for targets that move against the direction of the observer's head motion. The results support the hypothesis that the visual system employs extra-retinal signals that accompany eye and head movements to reduce the perception of motion smear for targets that move physically in the opposite direction of eye and/or head movements.

Eye Movements↗
PubMedDate not supplied

Characteristics and variability of vertical phoria adaptation in normal adults.

We evaluated the characteristics of phoria adaptation for vertically induced retinal disparity. An adaptive change in the fusion-free ocular alignment, phoria adaptation, was measured with a computer-aided mirror haploscope at 10, 30, and 60 minutes after the start of wearing of a 3-prism-diopter base up prism by 35 normal subjects ranging in age from 21 to 67 years (mean: 37 years). The relationships between phoria adaptation and the subjects' age, the vertical fusional amplitude, the amount of heterophoria, and the starting time of the examination were evaluated. All subjects showed phoria adaptation, with the mean (+/- SD) degree of 0.78 +/- 0.28 degree, 0.96 +/- 0.26 degree and 1.02 +/- 0.30 degrees at 10, 30, and 60 minutes, respectively, after wearing the prism. The repeatability (95% confidence interval) for the measurements was less than +/- 0.24 degree. There was a significant correlation between the vertical fusional amplitude and the gain of phoria adaptation (at 10 and 60 minutes, P < 0.05). The gain of phoria adaptation measured at 60 minutes showed a significant decrease with age (P < 0.01). The results indicate that the time course of phoria adaptation in the vertical direction is similar to that in the horizontal direction and its gain differs considerably among subjects.

Adaptation, Ocular↗