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At least 307 records · Page 17Linked to original sources
PubMed1999

Loss of visual acuity due to eye injuries among 6292 school children in the Sultanate of Oman.

PURPOSE: In 1992-94 a nation-wide survey in primary schools in the Sultanate of Oman for ocular disorders was conducted. This report focuses on the prevalence of visual acuity loss after injury. METHODS AND MATERIAL: A random selection of 6,292 children from Grades 1 and 6 from all primary schools in the country provided the research sample. Children who failed the visual acuity screening test received a complete "on the spot" eye examination by the pediatric ophthalmologist. RESULTS: 12 children were found to have monocular low vision (VA <0.3 to amaurosis) caused by injury. Total prevalence for loss of vision in one eye was 0.19%, with 0.15% in 6-year-olds and 0.25% in 12-year-olds Traumatic cataracts were noted in 4 children, 3 of these were in need of surgery. One child had aphakia after trauma surgery and needed a secondary lens implant. CONCLUSION: Altogether the prevalence of traumatic monocular visual damage in our study was 0.19%. Next to amblyopia, injury is the main reason for monocular loss of vision in childhood, however, both are preventable. Information about trauma prevention and the need for adequate ophthalmic care should be emphasized. Regular and repeated screening of visual acuity in children is essential.

Age Distribution↗
PubMed1976

Rapid changes in cerebral blood flow and initial visual experience in the developing chick.

A single eye of young chicks was sewed shut for various times. Regions contralateral to and primarily or secondarily innervated by the sutured eye had a reduced rate of cerebral blood flow in comparison to the corresponding ipsilateral regions. However, upon reopening the sutured eye after 2 days, these contralateral regions (optic lobes and cerebral hemispheres) exhibited a rapid increase in cerebral blood flow to a level significantly above that in control ipsilateral areas. The duration of this effect was considerably prolonged in chicks that were monocularly sutured immediately after hatching without prior exposure to light. Chicks that had 1 week of normal vision before monocular suture did not show this overcompensatory effect. If the period of monocular suture was extended to 7 days before restoration of vision to the occluded eye, the overcompensatory vascular effect was delayed. The maximal effect was apparent only upon the 1st exposure of an eye to major visual input. A possible relation exists between this rapid increase in regional blood flow and the period when visual imprinting could normally be expected to be maximal.

Age Factors↗
PubMed1986

Binocular vs. monocular task performance.

Functional advantages of binocularity were investigated by having 13 subjects perform a group of occupational-type tasks under monocular and binocular conditions. Significant binocular advantages ranging from 29.5% (pointers in straws) to 3.7% (reading speed) were measured. Tasks with many disparity cues showed the greatest binocular advantage. This shows that patients with normal binocular vision use binocular cues, most likely stereopsis, to enhance performance. In a second experiment, three subjects with normal binocular vision underwent monocular occlusion for 5 days to investigate whether monocular skills improved to compensate for the loss of binocular vision. During that period binocular performance was consistently better than monocular performance, and both monocular and binocular performance improved, even though the subjects were only gaining monocular experience. Although the 5 day occlusion period does not simulate the long-term denial of normal binocularity that strabismics or monocular patients experience, it shows that binocular superiority remains after short-term loss of binocularity.

Functional Laterality↗
PubMed1999

Monocular involuntary eyelid closure.

OBJECTIVES: Monocular blepharospasm (MBLS) is precipitated by ipsilateral ocular pathology and becomes bilateral over time. Two patients are reported with monocular visual disturbance exhibiting monocular involuntary eyelid closure (MIEC), resembling MBLS. MATERIAL AND METHODS: A 31-year-old female with hyperthyroidism developed monocular polyopia with left eye vision on binocular fixation followed by ipsilateral visual extinction. Monocular vision was otherwise normal. A 57-year-old male with renal failure developed monocular blindness secondary to retinal hemorrhage. RESULTS: The first patient had anisocoria and proptosis. Brain magnetic resonance (MR) was normal. The second patient had involuntary movements of the left eye. Head computerized tomography (CT) was normal. Both patients exhibited MIEC of the eye with visual impairment that could be overcome voluntarily, but reappeared upon distraction. Neither of the two developed BLS in long-term follow-up. CONCLUSION: MIEC represents a complication of ipsilateral ocular pathology in the absence of other involuntary movements, apraxia of eyelid opening, or blepharospasm (BLS). MIEC needs to be distinguished from MBLS, since not all MBLS becomes bilateral.

Adult↗
PubMed1986

[Pelvi-trainer, a training device in operative pelviscopy for teaching endoscopic ligation and suture technics].

Unlike in laparotomy, the art of pelviscopic surgery cannot be learned through assisting. For this reason, a training dummy, called a Pelvi-Trainer, has been developed. With this device, all surgical measures occurring in abdominal surgery can be simulated, such as adhesiolysis, internal ligature, internal sutures, resection, adnexectomy, enucleation of myomas, etc. The Pelvi-Trainer, designed for a three-stage plan, allows one to become gradually acquainted with the field of endoscopic surgery, and to make the transition from binocular vision to perfect three-dimensional control over intra-abdominal surgery under monocular endoscopic vision.

Endoscopes↗
PubMed1998

Corneal aberrations, monocular diplopia, and ghost images: analysis using corneal topographical data.

Corneal irregularities can create conditions in which monocular diplopia, "ghost images," and multiple images of various types occur, thus degrading vision. For these secondary images to occur, corneal irregularities must create areas which form: (1) images which are displaced from the primary image; (2) sufficiently focused images; and (3) images which have sufficient contrast to be noticed in the presence of the primary image. Criteria necessary to satisfy these three conditions using measurable data are developed. The concept of a differential deflection field is introduced, and a method to create this field using corneal topography data is developed. It is shown how to use differential deflection field data to assess if conditions necessary for creating secondary images will occur in cases of corneal distortion.

Algorithms↗
PubMedDate not supplied

Application of pattern reversal visual evoked potentials (PVEPS) in transient monocular blindness (resp. amaurosis fugax).

UNLABELLED: We investigated 11 patients (63.1 +/- 10.9 y) after recovery (median: 3 days) from amaurosis fugax of 12.1 +/- 12.0 min duration with the method of pattern reversal visual evoked potentials (PVEPs) derived from Oz to Fz (Cz ground) after randomized monocular stimulation. SELECTION CRITERIA: clear-cut cases with no hemispheric symptomatology, normal vision and normal cranial CT. The parameters were measured without knowing the affected eye and compared with age matched controls (n = 32). N80 latencies of the affected eyes were significantly prolonged (3.2 +/- 1.9 ms; p < .025) in comparison with the not affected eyes. The controls did not show such interocular difference. P100 latency behaved similarly but less prominently so (2.0 +/- 2.3 ms; p < .05; controls: p > .05). N80/P100 amplitude was reduced in 82% after stimulation of the affected side without reaching statistical significance. The 5 patients showing angiographically ipsilateral very tight stenosis of carotid artery (> 95%) behaved more prominently so in all 3 parameters. The findings indicate a damage of nerval tissue responsible for visual perception or a hemodynamic insufficiency under stimulus condition in affected eyes outlasting the clinical symptomatology for a certain period of time.

Aged↗
PubMed1995

Monocular visual loss after closed head trauma: immediate resolution associated with spinal manipulation.

OBJECTIVE: To discuss the case of a patient who demonstrated that spinal injuries may cause both cortical and ocular visual loss that was ameliorated by manipulative care. CLINICAL FEATURES: The patient suffered separate incidents of binocular and monocular loss of vision. A female child, aged 9 yr, presented with bilateral concentric narrowing of the visual fields that returned to normal immediately after spinal treatment. Approximately 1 yr later, she returned with monocular loss of vision after she was struck on the head by a ball. INTERVENTION AND OUTCOME: The child was treated by spinal manipulation under anesthesia; the vision was found to be normal on awakening from the anesthesia. Both visual recoveries were authenticated by an independent ophthalmic specialist. CONCLUSIONS: This case history adds to the other recorded occasions in which vision is noted to improve when the spine is manipulated. Discussion is directed to the basic pathogenesis: is her condition a form of psychoneurosis, is it a variant of migraine, or could it be a combination of both conditions?

Child↗
PubMed1981

The effects of early visual experience on the cat's visual cortex and their possible explanation by Hebb synapses.

1. Kittens were dark-reared until 4-6 weeks old, and then for another 4-7 weeks with various combinations of cylindrical lenses, monocular occlusion, and normal vision. 2. Single unit recordings from 816 neurones of the visual cortex (area 17) were obtained after the end of exposure. Clear-cut effects on the distributions of the neurones' ocular dominance and orientation preference were found yielding close correlations with the rearing conditions. 3. It was confirmed that most cortical neurones prefer vertical stimulus orientations when experience is restricted to vertical contours in both eyes. It was further confirmed that, if the experienced orientations are different in the two eyes, each eye dominates over those neurones whose orientation preference corresponds to the orientation this eye has experienced. 4. When one eye is covered while the other sees only contours of one orientation, the ocular dominance distribution of cortical neurones shows a bias towards the open eye. Neurones dominated by this eye prefer orientations corresponding to the experienced range. Neurones preferring other orientations are shared between both eyes. 5. When vision is unimpaired in one eye and restricted to vertical contours in the other, binocularity is common among neurones preferring vertical orientations. Neurones with orientation preferences off the vertical are mainly monocular and dominated by the eye with unrestricted vision. 6. When normal monocular vision of one eye precedes restricted monocular vision of the other eye, only a few binocular units are encountered. Reversal of the initial effects of monocular experience is found only in neurones preferring the orientation that has been experienced by the newly opened eye. The other neurones remain dominated by the originally open eye. Thus, complementary distributions of orientation preferences are found for the two eyes. 7. A good correlation was found between the amount of orientational experience as determined by the number of orientations exposed and the number of normally tuned neurones. Conversely, the number of neurones responding to all orientations decreases with increasing amount of experience.

Animals↗
PubMed1989

McCollough aftereffects in strabismus and amblyopia.

In strabismic people, the functioning of the deviating eye is impaired. This impairment is binocular in origin since it depends on stimulation of the straight eye; sensitivity and acuity of the deviating eye are usually better when the straight eye is patched than when both eyes are viewing. We investigated interactions between the eyes in strabismic people by using the McCollough color aftereffect as an exploratory procedure. Both normal and strabismic people adapted to black and colored bars and then examined black and white test bars. They reported colors in the achromatic test bars that were complementary to the adapting colors; this is the McCollough aftereffect. Both a monocular McCollough effect and a binocular McCollough effect were induced in people having normal vision. Strabismic people did not show a binocular McCollough effect. Aftereffect strengths were the same in each eye of normal people but were stronger in the impaired eye of strabismic people. A speculation is offered as to why the "non-seeing" eye of strabismic people "sees" the aftereffect better.

Adaptation, Ocular↗
PubMed2005

A noisy zygoma fracture--complication of carotid-cavernous sinus fistula: total recovery of monocular blindness and frozen-eye after endoarterial coil embolization.

A case of a patient with a zygoma fracture in combination with a carotid-cavernous sinus fistula--an arterio-venous fistula between the internal carotid artery and the cavernous sinus--is presented. The most frequent cause is trauma, but the carotid-cavernous sinus fistula itself may have been the cause of trauma. The patient showed complete loss of ocular motility and total monocular blindness. Treatment of the fistula with endoarterial coil embolization was followed by improvement of vision and ocular motility, until finally complete recovery of ocular functions, which is exceptional. In this case, careful analysis of the MRA's showed that the CCSF most likely developed in the posttraumatic phase.

Accidental Falls↗
PubMed1992

Vergence errors: some hitherto unreported aspects of fixation disparity.

Measurement of the monocular components of fixation disparity indicated a higher prevalence of asymmetric contributions to the total deviation than previously reported. Furthermore, the exact proportion varied from moment to moment. Two of six subjects showed significant changes in fixation disparity over a period of 1 week. For all six subjects the changes in fixation deviation of one eye were virtually independent of those changes occurring in the other eye. In other words, these monocular variances were uncorrelated. Settings of the monocular components of binocular fixation disparity were accomplished at an accuracy close to that achieved by using a monocular vernier technique. The remaining differences appeared to be due to occasional instabilities during binocular viewing. The usual method of clinical measurement in which only one element is moved is not always equivalent to that determined by summing the two monocular components. The principal process measured by subjective fixation disparity appears to be either oculomotor or localized directional shifts of a monocular nature.

Convergence, Ocular↗
PubMed2004

Motion repulsion is monocular.

Motion repulsion is the illusory enlargement of the angle between objects moving in two different directions of motion. Previous work suggests that motion repulsion occurs under dichoptic conditions, and therefore is binocular. In reference repulsion the direction of motion is misperceived even if only a single direction of motion is presented. In an experiment I show that repulsion under dichoptic conditions is correlated with reference repulsion, but not with binocular motion repulsion. This suggests that motion repulsion proper, which occurs over and beyond reference repulsion, does not occur under dichoptic conditions, implying that motion repulsion is monocular.

Humans↗