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PubMed1990

[Dynamics of visual functions in the conditions of glow and sodium lighting. I. Visual acuity, accommodation, flicker fusion, visual field and heterophoria].

Investigations of the functions cited in the title were performed in 23 persons with a normal visual system in conditions of equal illumination, first the glow and the next day or later--the sodium one. All the tests were carried out three times in the morning hours evaluating in this way their dynamics as the time goes. The authors are analyzing the degree of the variability of the discussed functions in the time, as well as their behaviour in conditions of applied illumination. The results obtained suggest that in conditions of illumination by a high-pressure sodium lamp no negative characteristics of this source of light emerged. Deterioration of a small degree was observed only in the range of accommodation for near.

Accommodation, Ocular↗
PubMedDate not supplied

Effects of sighting and sensory dominance on monovision high and low contrast visual acuity.

We investigated the relationship between ocular dominance and monovision visual performance in 15 presbyopic subjects. Ocular dominance was determined using sighting (hole-in-the-card and mirror tests) and sensory (anisometropic blur suppression test) methods. Correcting the dominant sighting eye for a given viewing distance was found to be an unreliable method of optimizing blur suppression or binocular high/low contrast visual acuity at that distance. If there is any advantage to a particular strategy for selecting the distance monovision eye, it must be realized in vision performance areas other than visual acuity.

Adult↗
PubMed1990

[Effect of visual acuity degradation on stereoacuity].

53 subjects with normal binocular single vision and normal stereoacuity (SA) were performed the Titmus Stereo Test while degrading the visual acuity (VA) monocularly and binocularly with graded hazy films. The results showed that SA impairment with monocular decrement was more than with binocular symmetrical decrement at each VA level. The authors inferred that imbalance of VA between the two eyes in infants and children was harmful to the development of binocular vision, and that partial occlusion therapy would be more favorable for the binocular visual development of amblyopic children. Also, it was suggested to include SA in the criteria for cure of amblyopia.

Adolescent↗
PubMed1989

Analysis of a community vision screening program.

For 3 consecutive years a community vision screening program has been conducted on-site at the Walker Eye Clinic of the Indiana University (IU) School of Optometry. A group of 490 screened patients, including 86 who returned for comprehensive evaluation, was retrospectively studied for a variety of characteristics. It was determined that the typical participant was likely to be an adult female who learned of the screening program through the written media. She was likely to have had a previous vision examination but it probably took place 3 or more years earlier. She usually failed the vision screening for reasons of reduced visual acuity, a problem with binocularity or asthenopia. If she returned to the Walker Eye Clinic for a comprehensive examination, she was likely to do so within 5 months and would be found to have been accurately identified as being in need of vision care. The organization and implementation of this vision screening program are described, and its value as an educational tool for students of optometry and its technician program is discussed.

Adolescent↗
PubMed1989

Longitudinal study of acuity and stereopsis in infants with or at-risk for esotropia.

Grating acuity and stereopsis were measured longitudinally in five groups of infants: infantile esotropes, moderate hyperopes, high hyperopes, infants with a family history of strabismus or amblyopia and controls. Grating acuity was measured with a forced-choice preferential looking procedure. Stereopsis was assessed with a random-element stereogram. Testing was conducted when subjects were 3, 6, 9, 12, 18, 24, 30 and 36 months of age. No differences among groups in absolute acuity scores or interocular acuity differences were found until the infants reached 30 and 36 months of age. At these ages, treated infantile esotropes showed acuity scores that were, on average, 0.5 octave poorer than those of controls for both the eye showing the better acuity and the eye showing the worse acuity. Stereopsis testing indicated that few, if any, of the infantile esotropes showed stereopsis at any of the test ages. Over 30% of the high hyperopes developed strabismus by age 3 years, but none of the infants in the moderate hyperopia or family history groups developed strabismus.

Amblyopia↗
PubMed1995

Ingested ethanol and binocular rivalry.

PURPOSE: An early study claimed that ethanol ingestion can attenuate binocular rivalry and, in some cases, may produce the phenomenal fusion of normally rivalrous stimuli. The current study examined those claims in an experiment incorporating key controls that were lacking in the earlier study. METHODS: There were two conditions, one in which observers consumed ethanol and the other in which they consumed a placebo. Observers reported the course of binocular rivalry for several hours after drink consumption using two types of rivalry stimuli, one consisting of a continuously illuminated set of stimuli, the other consisting of dichoptic afterimages. RESULTS: Ingestion of ethanol resulted in a decrease in rivalry alternation rates, although there was no evidence of phenomenal fusion. Results were essentially identical for both stimulus types. CONCLUSION: It is suggested that this effect is not caused by ethanol-induced changes in oculomotor mechanisms but may be caused by ethanol-induced decreases in contrast sensitivity.

Adult↗
PubMed1993

Unilateral congenital ptosis: compensatory head posturing and amblyopia.

Patients with unilateral congenital ptosis often adopt chin elevation to maintain fusion. This compensatory head posturing has been considered a sign of fusion, thus indicating a low risk for amblyopia. To evaluate this sign, we reviewed the charts of 11 preverbal children with unilateral congenital ptosis who had straight eyes and appropriate compensatory head posturing to maintain binocular vision. Four additional patients with unilateral ptosis and no compensatory head posturing were tested for comparison. All patients had undergone an examination and had been tested by pattern Visual Evoked Potential (VEP) under chloral hydrate sedation. Five of the 11 patients with compensatory head posturing were found to be amblyopic, three moderately so and two severely affected. The four patients without compensatory head posturing were amblyopic. It is our hypothesis that compensatory head posturing allows peripheral fusion even when significant amblyopia is present. Additionally, the clinical sign of a compensatory head turn to maintain binocular vision does not rule out the presence of significant amblyopia.

Amblyopia↗
PubMed1995

A new protocol for the optometric management of patients with reading difficulties.

Research by Evans et al. (Ophthal. Physiol. Opt. 15, 481-487, 1995) has demonstrated a correlation between visual processing and ocular motor factors in people with specific reading difficulties (dyslexia). In addition, research by Wilkins et al. (Ophthal. Physiol. Opt. 14, 365-370, 1994) has shown that some people with dyslexia will benefit from a reduction of perceptual symptoms of discomfort and distortion if they use individually prescribed coloured filters. Three examples of the dyslexic patients who attend at the Institute of Optometry clearly demonstrate the importance of full investigation of ocular function, including the assessment of the effect of colour on visual perception. All three patients presented with similar symptoms of asthenopia when reading. Symptoms were alleviated for the first patient by use of orthoptic treatment of an exotropia with intermittent suppression. With the second patient, ocular motor functions were found to be within acceptable limits and relief of symptoms was obtained by the prescribing of lenses of a specific chromaticity. For the third patient, both orthoptic intervention and the use of specifically tinted lenses were necessary to relieve the visual difficulties that were being experienced. By taking advantage of recent research and developments in optometric instrumentation, it is possible for some of those with dyslexia to receive considerable benefit from optometric intervention.

Adolescent↗
PubMed1995

The 20-prism-dioptre base-out test: an indicator of peripheral binocularity.

OBJECTIVE: To assess the ability of the 20-prism-dioptre base-out test to detect the presence of peripheral fusion in children too young to undergo formal sensory testing. DESIGN: Case series. SETTING: Pediatric ophthalmology service at the Children's Hospital of Western Ontario, London. PATIENTS: Eighty orthophoric patients (mean age at presentation 19 months [range 4 to 50 months]) with a family history of strabismus or with a diagnosis of pseudostrabismus, blocked tear duct or chalazion, followed for an average of 36 (range 6 to 129) months, and 41 patients with surgically corrected infantile esotropia (mean age at testing with the 20-PD base-out test 21 months [range 9 to 50 months]), followed for an average of 53 (range 14 to 117) months. INTERVENTIONS: Twenty-PD base-out test and red-green Worth four-dot test at near (0.3 m). OUTCOME MEASURE: Presence of peripheral fusion. RESULTS: The 20-PD base-out test had a positive predictive value of 100% in detecting peripheral fusion in the orthophoric patients and 93% (95% confidence interval [CI] 82% to 100%) in the patients with surgically corrected infantile esotropia. CONCLUSIONS: Although the 20-PD base-out test had a negative predictive value of 21% (95% CI 0% to 43%), a positive response remains a useful indicator of peripheral binocular single vision in children too young to undergo more formal sensory testing.

Child, Preschool↗
PubMed1996

Temporal aspects of binocular slant perception.

We investigate temporal aspects of binocular slant perception in the presence and absence of a visual reference. Subjects judge slant induced by large-field stereograms of which one half-image is either horizontally scaled or sheared relative to the other half-image. Each stimulus is presented for different observation periods ranging from 0.1 to 19.2 sec. We quantitatively corroborate earlier findings that perceived slant develops significantly faster and to higher levels with visual reference than without it. In daily life, when we are active, there will not be much time for slant to develop. We find that if observation periods are brief (a few seconds or less) slant is poorly perceived if there is no visual reference. We conclude that the visual system is relatively insensitive to large-field horizontal scale and shear.

Adult↗
PubMed1997

Inter-ocular temporal asynchrony (IOTA): psychophysical measurement of inter-ocular asymmetry of visual latency.

Ocular pathology can be associated with inter-ocular asymmetry of conduction latency. We describe a relatively low-cost psychophysical method of quantifying this asymmetry of delay, an 'inter-ocular temporal asynchrony' (IOTA) system. Testing of 28 visually normal young adults gave IOTA results with a mean of 0.11 ms (SD +/- 2.4 ms). These results correspond to 95% confidence limits of -4.6 ms and +4.8 ms. Inter-ocular differences in retinal illumination, induced by using monocular neutral density filters in visually normal subjects, significantly affected IOTA in accord with an imposed perceptual delay in the 'filtered eye'. This demonstration that the IOTA technique is capable of detecting induced asymmetry of perceptual delay in visually normal subjects, along with the small measured confidence limits reported above, suggests that the apparatus should be capable of detecting inter-ocular asymmetries in response latencies with ocular disease, which have been previously measured by other techniques.

Adolescent↗
PubMed1996

Horror fusionis: a report of five patients.

BACKGROUND: Horror fusionis is an uncommon anomaly and is rarely reported in the literature. METHODS: Five adults with long-standing diplopia associated with horror fusionis were examined. RESULTS: All patients had strabismus since early childhood and had been treated at that time either with surgery, occlusion, and/or orthoptics/vision therapy. Prisms could not eliminate the diplopia. Graded occlusion was attempted with one patient but was not tolerated. Another patient with an asymmetrical dissociated vertical deviation could ignore the second image by fixating with the eye with the smaller deviation. Two patients reported the diplopia becoming less noticeable over the years. CONCLUSIONS: Because of its poor prognosis, the diplopia associated with horror fusionis must be differentiated from other types of diplopia occurring in adults with childhood onset strabismus.

Adult↗
PubMed1997

Effect of prolonged dissociation on the subjective measurement of near heterophoria.

Previous studies have demonstrated that vergence adaptation resulting from the prolonged decay of slow fusional vergence may prevent the accurate assessment of oculomotor deviations. Continuing changes in heterophoria have been reported after 27 days of monocular occlusion. However, since most slow fusional vergence will decay within the first few minutes of dissociation, a clinical assessment of both vergence adaptation and heterophoria could be made more rapidly. This report documents two investigations which examined changes in near horizontal heterophoria during 30 min and 180 min of continuous dissociation, respectively. Seven out of the 16 subjects exhibited significant changes in heterophoria during the 30 min dissociation period, with a mean increase in exophoria of 3.4 delta. The decay of slow fusional vergence took approximately 25 min to reach completion. Thus in the clinical setting, both the degree of vergence adaptation and a more accurate assessment of heterophoria may be obtained by maintaining dissociation for 25 min. Furthermore, the presence of vergence adaptation can be assessed after just 5 min of dissociation.

Adult↗
PubMed2002

Binocular vision: an orientation to disparity coding.

A new study has shown that neurons in the visual cortex are specialized to encode the larger range of horizontal - relative to vertical - disparities that occurs in central vision. These results challenge the established 'energy' model of disparity processing.

Animals↗