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At least 271 records · Page 15Linked to original sources
PubMed2001

Sensory eye dominance.

BACKGROUND: Sensory eye dominance is revealed in tasks like the Red Lens test and binocular rivalry. To understand its neural basis, we used a new protocol based on binocular rivalry to quantify its consequent interocular imbalance. Then we investigated whether the extent or sign of interocular imbalance is correlated with the difference in monocular contrast responses at threshold and suprathreshold and with the observer's motor eye dominance. METHODS: To evaluate sensory eye dominance, the stimulus intensity in each eye during rivalry was adjusted to achieve equal predominance. The difference in stimulus intensity constitutes the interocular imbalance. Standard procedures were used to measure monocular spatial contrast sensitivity, suprathreshold brightness judgment, and motor eye dominance. RESULTS: There was no positive correlation between interocular imbalance (sensory eye dominance) and motor eye dominance. No systematic correlation was found between interocular imbalance and monocular contrast sensitivities at 1 and 3 cycles/degree. Correlation coefficient between interocular imbalance and monocular suprathreshold brightness judgment was close to significant, suggesting that a difference in monocular brightness percept might (in part) account for interocular imbalance. But this explanation is only partial, since the difference in the monocular brightness percept was too small to account for the interocular imbalance. CONCLUSIONS: Interocular imbalance is a sensory eye dominance that cannot be equated with motor eye dominance. It manifests largely as a binocular phenomenon, which bears little relationship with the monocular neural mechanisms of contrast detection and brightness perception.

Adult↗
PubMed2002

Dissociation between location and shape in visual space.

There are often large perceptual distortions of shapes lying on the ground plane, even in well-lit environments. These distortions occur under conditions for which the perception of location i saccurate. Four hypotheses are considered for reconciling these seemingly paradoxical results, after which 2 experiments are reported that lend further support to 1 of them--that perception of shapeand perception of location are sometimes dissociable. The 2 experiments show that whereas perception of location does not depend on whether viewing is monocular or binocular (when other distance cues are abundant), perception of shape becomes more veridical when viewing is binocular. This means that perception of shape is not fully constrained by the perceived locations of the vertices that define the shape.

Adolescent↗
PubMed1992

[Results of early treatment of congenital strabismus].

The authors analyse the results obtained after very early treatment of Esotropia in 38 children. These children were divided into 4 groups according to their age at the time of treatment. At the age of 30 months, they studied binocular vision, manifest latent nystagmus (NML) and dissociated vertical deviation (DVD). In groups 1 and 2, treatment was instituted before the age of 6 weeks (13 children) no DVD was noted, only one NML and 11 children have binocular vision. In groups 3 and 4, treatment was instituted after the age of 3 months (25 children) 4 cases of DVD and 10 of NML are noted, and only 9 children have binocular vision. In case of congenital esotropia, the authors recommend treatment before 2 months old to obtain a possibility of binocular vision and to decrease the risk of NML and DVD.

Eyeglasses↗
PubMed1992

[Binocular coordination during reading].

Is there an effect on binocular coordination during reading of oculomotor imbalance (heterophoria, strabismus and inadequate convergence) and of functional lateral characteristics (eye preference and perceptually privileged visual laterality)? Recordings of the binocular eye-movements of ten-year-old children show that oculomotor imbalances occur most often among children whose left visual perceptual channel is privileged, and that these subjects can present optomotor dissociation and manifest lack of motor coordination. Close binocular motor coordination is far from being the norm in reading. The faster reader displays saccades of differing spatial amplitude and the slower reader an oculomotor hyperactivity, especially during fixations. The recording of binocular movements in reading appears to be an excellent means of diagnosing difficulties related to visual laterality and to problems associated with oculomotor imbalance.

Child↗
PubMed2003

[Invariants of spatial summation for S (short wavelength) cone vision].

Spatial summation in the human visual system was studied as a function of retinal eccentricity upon selective stimulation of the short-wavelength sensitive cones. The area of complete spatial summation (Ricco's area) was found to increase with retinal eccentricity while the threshold of stimuli equal in size with Ricco's area remained constant. Comparisons with known morphology of the small bistratified retinal ganglion cells, the only cells known to be excited by S-one ON stimulation, showed that Ricco's area included 2-4 such cells and is up to 1.5 times larger than the dendritic field of a single cell. These relationships were relatively constant within the eccentricity range tested (5-20 deg along the temporal horizontal meridian) and might be the source of threshold invariance of stimuli matching Ricco's area.

Adult↗
PubMed1992

Botulinum alignment for congenital esotropia.

This is the first report of a group of patients with congenital esotropia examined for motor and sensory evidence of binocularity a minimum of 3 years after alignment by botulinum. Evidence for binocularity was clearly present in approximately one half of the patients. Lag time to satisfactory alignment was at least 1 month (average, 5 months) following the initial botulinum injection. The results must be considered preliminary. However, when these results are compared with those of patients with congenital esotropia aligned by incisional surgery by age 2 years and examined with the same testing devices by this same investigator, botulinum alignment appears to be less effective than surgical alignment in establishing evidence for binocularity (P < 0.005).

Botulinum Toxins↗
PubMed1992

Treatment of esotropia with anomalous correspondence: a case report.

Management of anomalous correspondence in esotropia has been a controversial topic until recently. This case report presents a sequential treatment regimen which resulted in a successful binocular result for the patient. The implementation of overcorrecting prism, vision therapy/orthoptics, and extraocular muscle surgery is covered in the discussion of management strategies.

Child↗
PubMed1992

Psychophysical experiments and a neural network model of binocular rivalry.

The alternation process in binocular rivalry was examined by psychophysical experiments. The stimulus strength to the central part of the visual field in one eye was varied while the stimulus strength in the other eye remained constant. The data obtained by the experiments indicate that the variations in stimulus strength alter the mean dominance duration, variance and predominance, and the frequency histogram of the dominance duration almost fits to the gamma distribution. To explain these results, a model which consists of neural elements receiving impulse trains with stochastic fluctuations is proposed and the experimental results are simulated on a computer using the model. Although the present model is restricted to explain only the rivalry between two lines which have different orientations, we could obtain agreement between the simulation results and the experimental results by giving appropriate values for some parameters of the model.

Humans↗
PubMed2005

[Effects of short-term VDT usage on visual functions].

OBJECTIVE: To evaluate the effects of short-term VDT usage on visual functions. METHODS: Visual function of the video display terminal (VDT) operators before and after 1 hour VDT usage were assessed. These included refraction, amplitude of accommodation, near point of convergence, AC/A, phorias, fusional convergence and divergence, tear film break time (BUT) and aberrations. And the same situation was compared was the non-VDT usage. RESULTS: In comparison with pre-VDT use, amplitude of accommodation, BUT were significantly decreased (P < 0.05), near point of convergence, near lateral exophoria were significantly increased after VDT use (P < 0.05). Total, high order, 4th and 5th order aberrations were significantly greater after VDT use (P < 0.05). CONCLUSIONS: Short-term VDT work does have a significantly greater temporarily effect on visual function, tear film quality and visual quality.

Adolescent↗
PubMed2006

[The dependence of the range of fusion on some selected functions of the visual system. Part I: Study on convergent and divergent fusion].

After examined 132 patients, the authors selected 90 patients with correct visual acuity of both eyes, correct range of eyeballs' mobility, parallel setting of the eyeballs, no difference in refraction between both eyes and with muscular balance. These 90 patients were divided into 3 groups: children between 8 and 10 years old, teenagers between 11 and 20 years old and adult people between 21 and 40. All the groups were subject to the main examination of the study carried out by means of prism bar and synoptophore for each of the eye separately. The results were compared in order to define the difference in the range of fusion between both eyes. The study involved an examination of horizontal range of convergent and divergent synoptophoric fusion as well as that of free space for near and for far. A statistically significant difference between both eyes was observed in range of synoptophoric, for near and for far convergent fusion. The difference was confirmed in an average of 35.6% of patients for convergent fusion for near, in 34.4% of patients for convergent fusion for far, and in 65.6% of patients for synoptophoric convergent fusion. The mean difference between the eyes in the range of fusion was: 4.6 degrees for convergent fusion for near, 3.9 degrees for convergent fusion for far and 6.4 degrees for synoptophoric convergent fusion. No significant differences between both eyeballs were detected in the range of divergent fusion. The authors suggested calling the phenomenon connected with the difference between both eyeballs in convergent fusion the following term: "visual unevenness of the range of convergent fusion".

Adolescent↗
PubMed2006

[The dependence of the range of fusion on some selected functions of the visual system. Part II: Accommodation and dominance].

This present study is the continuation of Part I of the research into the range of fusion in which the difference between both eyeballs as far as convergent fusion is concerned was described. The phenomenon was called "visual unevenness of the range of convergent fusion". This part of the study is devoted to the analysis of the relationship between the unevenness of the fusion, ocular dominance and accommodation. A lower range of convergent fusion was observed in the dominant eye with the higher accommodation, In contrast, a higher range of fusion was observed in the not dominant eye with lower accommodation. The authors think that the phenomenon of ocular unevenness of the range of convergent fusion does not depend on the peripheral part of visual organ. In fact, it does seem to point out to a cortical process. The authors suggest that quantitative tests on amplitude of fusion should be carried out first on the first eye and then on the other. The results obtained from both eyes should be compared with each other.

Accommodation, Ocular↗
PubMed1991

Distance and near readings of associated heterophoria taken on 500 patients.

Distance and near readings of associated heterophoria were taken, using standard Mallett units, on 500 patients passing consecutively through an optometric practice and any symptoms, connected with distance and near vision, were noted. Complete sets of results were obtained on 383 people. Distance readings, either in size or direction, did not appear related to symptoms and such readings did not appear helpful in patient management. For near vision a fair degree of association existed between readings of associated phoria and symptoms and it was possible in the under 40 years and 40-59 years age groups to express clinically useful rules regarding the relationship. Over 60 years of age such a relationship was complicated by the fact that high degrees of exophoria readings existed in both symptomatic and asymptomatic patients and it is suggested that this may be related to the quality of binocular vision.

Adolescent↗
PubMed1991

[Reversion of eye position after surgical correction of exotropia].

The authors analysed the reversion of eye position in 62 postoperative patients of concomitant exotropia. The results indicated the presence of a correlation with the preoperative condition of binocular vision, the type of strabismus, and the age of patient. The authors opened that the amplitude of surgical correction should depend on these factors, and prudence should be exercised in recommending surgical intervention for mild intermittent exotropia in children.

Adolescent↗
PubMed1991

[Binocular vision of concomitant esotropia after surgical correction].

Binocular vision of grade I or better was restored to 51.5% of 312 cases of concomitant esotropia after surgical correction. Cases of acquired, partially accommodative, and small-angle esotropia had better chances of restoration than did cases of congenital, non-accommodative, and large-angle esotropia (P less than 0.01), as were younger patients (less than 12 years) with satisfactory surgical correction than older patients with less satisfactory surgical correction. Factors that affected restoration of binocular single vision were discussed.

Adolescent↗
PubMed1990

[Use of Pulfrich's phenomenon in ophthalmological diagnosis].

The Pulfrich effect is a simply observable visual stereo phenomenon arising when the visual latency for one eye is longer than for the another. In the paper the review of the literature devoted to the application of this phenomenon for the ophthalmological diagnosis is presented. The authors come to the conclusion that the Pulfrich effect can be successfully used in clinical practice as an indicator of many ophthalmological disorders especially of optic neuritis.

Functional Laterality↗
PubMed1990

Monovision.

Monovision has been a controversial contact lens correction modality for over 30 years. This paper addresses the major issues and concerns and considers them in the light of patient safety, visual efficiency and practitioner liability.

Adaptation, Ocular↗
PubMed1990

[Dyslexia-- a peculiar form of heterophoria?].

The authors discuss the problem of legasthenia--a particular impediment in the learning of fluent reading and orthographic writing. One connects it with a form of heterophoria in which the eyes--because of an inacurate and changeable function of binocular vision are unable to exert precise saccadic movements enabling a binocular or precisely unimacular reading. A childish art of following with the eyes from one detail to the other during the learning of reading must be transformed into minute fixation movements in conditions of a permanent excitation of convergence and accommodation to which the child is not accustomed. This leads sometimes to a false positioning of the eyes and in the consequence to a spatial disorganization in the succeeding set of letters. Therapeutical results show that as well legasthenia as its complications in the general behaviour of the child are receding together with the improvement of the sensorimotor functions of the eye.

Child↗