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At least 19 recordsLinked to original sources
PubMed1975

Progressive changes in kitten striate cortex during monocular vision.

Following initial rearing in either total darkness or normal illumination, kittens at different ages were subjected to right-eye closure and various periods of vision through the left eye. After the period of monocular vision, single units in striate cortex were tested for visual responsiveness through each eye. A severe reduction in the proportion of units responsive to the deprived eye occurred over the first few days of monocular vision. Functional abnormalities were variably present after 1 day, marked after 2.5 and 3.5 days, and complete after 10 days. Monocular vision produced very much the same effect on ocular dominance of striate units, provided age and duration of suture were identical, regardless of whether kittens had received prior dark- or light-rearing.

Animals↗
PubMed1989

The microvascular system of the optic nerve in control and enucleated rats.

The microvascular system of the optic nerve of the rat was examined morphometrically to determine the effect of enucleation of one eye at birth on the microvascular development in the contralateral optic nerve. For this purpose, two groups of rats were used: three were unilaterally enucleated on the day of birth and studied on postnatal Day 28; three littermates were used as controls. Using plastic embedded semithin sections, we analyzed various parameters and compared the results statistically. The average diameter of microvessels up to 7.5 microns was found to be 4.7 +/- 0.2 micron in controls and 5.3 +/- 0.5 micron in experimental rats. The density of microvessels expressed as the mean number of sectioned capillaries per tissue area was 137 +/- 25/mm2 in the control group and 169 +/- 32/mm2 in the experimental group. The intravascular volume fraction percentage (Vv), which represents the volume fraction of the capillary network per unit of optic nerve volume (mm3/mm3%), was 0.06% in the controls and 0.10% in the enucleated rats. Total length of capillaries per unit of volume (Lv) averaged 1050 +/- 112 and 2235 +/- 195 mm/mm3 in control and experimental groups, respectively. The internal capillary surface area available for metabolic exchange expressed per volume unit (Sv) was 15.5 +/- 2.1 and 37.2 +/- 2.8 mm2/mm3 in control and experimental groups, respectively. These results, together with the lack of ultrastructural modifications in the vascular walls of microvessels, suggest that these rearrangements of the capillary system in the enucleated group could be triggered by an increase in the optic nerve metabolism resulting from monocular vision.

Animals↗
PubMed1992

Mobility of normal observers under conditions of reduced visual input.

The importance in mobility performance of the rate of presentation of visual information, binocular versus monocular vision, the use of multiple rather than single reference points, and local motion parallax was investigated in two experiments. In each experiment ten subjects walked a triangular mobility course in a totally darkened room; the only visible targets were light emitting diodes (LEDs), mounted on poles, at the apices of the triangle. The LEDs were mounted so that one or two could be used in a trial; if two were used the distance between them was varied horizontally (in experiment 1) and vertically (in experiment 2). The subjects walked around the course under a range of conditions, including two 'optimal trials' in full light. The LEDs were flashed for 1 ms at frequencies of 0.5, 1 and 5 Hz in experiment 1 and at 1 and 5 Hz in experiment 2. Mobility was measured with the use of an ultrasonic locator system which measured the subject's position on the course 10 times per second. The mean velocity of the subject in traversing the course was significantly reduced when the flash rate was slower, when the subject had one eye occluded, or when there was only one LED on the pole; when the spacing between the LEDs was varied, either vertically or horizontally performance was unaffected. These results imply that the frequency of updating of visual information is important in determining mobility performance, as are binocular cues, but that local motion parallax is not important. The number of LEDs on each pole had a significant effect on mobility performance an 'object' (two lights) gave more information than a point reference.

Adult↗
PubMed1992

Monocular acuity in the presence and absence of fusion.

Because little is known about monocular acuity during binocular fusion, acuity of the right eye was measured in binocularly normal subjects, with the fellow eye open or fully occluded. The target was flashed for 65 ms or presented sinusoidally for 1 s. Subjects had both eyes optimally focused, or the right eye defocused by +3.00 D. Monocular acuities were equivalent during fusion or occlusion when both eyes were optimally focused. Acuity of the defocused eye was reduced when the fellow eye was open compared to when it was occluded. Suppression of the blur, therefore, produced a measurable reduction in recognition thresholds. As monocular acuity was not measurably affected by the fellow eye when each eye was in focus, the finding that monocular vision is improved with the fellow eye occluded should be ascribed to something other than suppression or more sensitive spatial measures of the suppression should be obtained.

Humans↗
PubMed1991

Functional effects of bilateral form deprivation in monkeys.

Psychophysical methods were used to study the effects of binocular form deprivation, initiated at 1 month of age, on the visual sensitivities of young monkeys. All the monkeys reared with bilateral form deprivation for 7 weeks or longer had reduced spatial contrast sensitivity for both eyes. Although the contrast sensitivity deficits of the bilaterally form-deprived monkeys generally were larger for one eye than the other, the magnitudes of the deficits were small compared with those produced by similar periods of unilateral form deprivation. For other monocular vision functions investigated, temporal contrast sensitivity and increment-threshold spectral sensitivity, the data for the bilaterally form-deprived animals showed only minor variations from those of the control monkeys. However, none of the bilaterally form-deprived monkeys had binocular vision on either measures of binocular summation or stereodetection, even if the animal had normal monocular vision functions. Therefore, these results show that monocular sensory deficits caused by abnormal early visual experience as a result of bilateral form deprivation are much less severe than those caused by unilateral form deprivation. The differences in the severity of visual deficits may be attributed to the consequences of anomalous binocular competition associated with unilateral form deprivation that was minimized during bilateral form deprivation. Thus, these results illustrate that anomalous binocular competition is more detrimental to the developing visual system of infants than direct deprivation per se.

Amblyopia↗
PubMed1978

Is binocular vision always monocular?

Visual sensitivity of one eye was determined under binocular stimulus conditions yielding apparent fusion, stereopsis, monocular dominance, and monocular suppression. Marked losses in sensitivity accompanied monocular suppression but were not evident during stable singel vision. The results are inconsistent with the hypothesis that supression alone mediates binocular single vision.

Functional Laterality↗
PubMed1975

Optic organ and cervical proprioceptors in maintenance of body equilibrium.

Two experiments were made on the functional correlation between the optic organ and the cervical proprioceptors in maintenance of body equilibrium. Experiment I: The effects of weak and strong electric stimulation of the deep nuchal muscles on changes in optokinetic nystagmus and optokinetic after-nystagmus were examined in adult non-albino rabbits with binocular vision. Experiment II: Experiment I was repeated on rabbits with monocular vision giving optokinetic stimulation moving from the side of the blindfolded eye to that of the open eye and applying only weak electric stimulation to the neck muscles. The results obtained were as follows: (1) Experiment I: Weak electric stimulation of the deep nuchal muscles of rabbits with binocular vision tended to promote optokinetic nystagmus with either no significant change or decrease in optokinetic after-nystagmus. Strong electric stimulation had the opposite effects, i.e., it tended to inhibit optokinetic nystagmus and activate optokinetic after-nystagmus. It also produced abnormal optokinetic nystagmus, such as the inversion phenomenon of optokinetic nystagmus and "optokinetic nystagmus firing". (2) Experiment II: Weak electric stimulation of the deep nuchal muscles of rabbits with monocular vision had similar effects to those in experiment I, but promotion of optokinetic nystagmus was less obvious, while activation of optokinetic after-nystagmus was more marked. In addition, the inversion phenomenon of optokinetic nystagmus developed even on weak electric stimulation. From these results the following conclusions were drawn: (1) The cervical proprioceptors can function in two mechanisms causing promotion and break down of equilibrium of the optokinetic system. (2) The cervical proprioceptors, as an organ of equilibrium, can exert two different actions on the optokinetic eye reflexes, i.e., they can promote optokinetic nystagmus and inhibit optokinetic after-nystagmus.

Animals↗
PubMed1992

Correlations of memory and learning with vision in aged patients before and after a cataract operation.

The connection between memory and learning with vision was investigated by studying 100 cataract operation patients, aged 71 to 76 years, 25 of them being men and 75 women. The cataract operation restored sufficient acuity of vision for reading (minimum E-test value 0.40) to 79% of the subjects. Short-term memory was studied with series of numbers, homogenic and heterogenic inhibition, and long sentences. Learning was tested with paired-associate learning and word learning. Psychological symptoms were measured on the Brief Psychiatric Rating Scale and personality on the Mini-Mult MMPI. Memory and learning improved significantly when vision was normalized after the cataract operation. Poor memory and learning scores correlated with monocular vision before the operation and with defects in the field of vision, due to glaucoma and exceeding 20%, postsurgery. Monocular vision and defects in the visual field caused a continuous sense of abnormalness, which impaired old people's ability to concentrate on tasks of memory and learning. Cerebrovascular disturbances, beginning dementia, and moderate psychological symptoms obstructed memory and learning on both test rounds. Depression was the most important psychological symptom contributing to poor memory and learning scores after the cataract operation. The memory and learning defects mainly reflected disturbances in memorizing.

Aged↗
PubMed1989

[Monocular and binocular vision following lens implantation in traumatic cataract].

Lens implantation after surgery for traumatic cataract is a major help in rehabilitating the patient. Most such patients are still at work. Surgical problems result from injuries to the cornea, iris, lens, and vitreous body. If possible a posterior chamber lens should be implanted in the bag. In 35 patients, 24 posterior chamber lenses and 11 anterior chamber lenses were implanted. In 27 cases the traumatic cataract had been caused by perforating injury and in eight by contusion. In 28 patients there was a significant improvement in visual acuity by the day they were discharged. At short focus more than one-half of the patients had simultaneous vision with striated glasses, and two-fifths at long focus. Two-fifths of all patients attained stereoscopic vision at both short and long focus. The binocular functions were worse in most of the cases where the visual acuity of the injured eye was 0.4 or less.

Adult↗
PubMed1978

Monocular peripheral vision as a factor in flight safety.

The performance of static visual identification tasks and simulated operational flying tasks, by nine binocular pilots and nine adapted monocular pilots, was measured in a unique operational visual simulator. It was hypothesized that, with head free to move, and adapted monocular pilot would perform as well as a binocular pilot, while an unadapted monocular (simulated by covering an eye) would perform less well. Other hypotheses were advanced. The static primary central task required sequential identification of dial readings. The dynamic primary central task involved simulated aircraft landing operations. During each set of primary tasks, a set of secondary peripheral visual tasks was performed. Results of the primary tasks and times of execution of the secondary tasks were subjected to analysis of variance. Factors included head position (fixed or free), stimulus location in peripheral field, eye state (seeing eye, blind eye), and type of central task (static, dynamic). All hypotheses were validated.

Accident Prevention↗