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At least 1,585 records · Page 88Linked to original sources
PubMed1997

The efficacy of vision therapy for convergence excess.

BACKGROUND: Convergence excess is a commonly encountered non-strabismic ocular motility disorder. There are, however, very few research data that evaluate the effect of vision therapy for this condition in a clinical population. METHODS: The records of 83 consecutive patients with convergence excess who were treated with vision therapy were reviewed to assess the impact of treatment on clinical findings and patient symptoms. RESULTS: Statistically and clinically significant changes in direct and indirect measures of negative fusional vergence were seen, with 84% of patients reporting a total elimination of initial symptoms. Larger increases in negative fusional vergence were found than those previously reported. This may be a result of the more extensive and better controlled in-office treatment used in this study. CONCLUSIONS: Vision therapy was successful in enhancing negative fusional vergence and eliminating symptoms in the vast majority of patients with convergence excess and should be considered an effective treatment for this condition.

Adolescent↗
PubMed1997

Vision, learning and dyslexia. A joint organizational policy statement of the American Academy of Optometry and the American Optometric Association.

1. Vision problems can and often do interfere with learning. 2. People at risk for learning-related vision problems should be evaluated by an optometrist who provides diagnostic and management services in this area. 3. The goal of optometric intervention is to improve visual function and alleviate associated signs and symptoms. 4. Prompt remediation of learning-related vision problems enhances the ability of children and adults to perform to their full potential. 5. People with learning problems require help from many disciplines to meet the learning challenges they face. Optometric involvement constitutes one aspect of the multidisciplinary management approach required to prepare the individual for lifelong learning.

Academies and Institutes↗
PubMed1997

Loss of vision alone may result in seesaw nystagmus.

A patient is described who developed seesaw nystagmus (SSN) associated with progressive severe vision loss due to cone-rod dystrophy. She was otherwise neurologically normal, and findings on magnetic resonance imaging of the brain were normal, including optic chiasm, meso-diencephalic junction, and brainstem. The literature is reviewed on neurologically normal patients with SSN and ocular vision loss, and the hypothesis is presented that SSN may become manifest as a result of vision loss alone, even in patients with chiasmal lesions, without disruption of central ocular motility pathways.

Adult↗
PubMed1997

Chalazion-induced hyperopia as a cause of decreased vision.

This article presents three cases of decreased vision due to acquired hyperopia, which were caused by a chalazion of the upper eyelid. Through manifest refraction and computerized corneal topographic analysis, acquired hyperopia associated with central corneal flattening was revealed. These findings were responsible for the blurred vision that was reversed by chalazion resolution or removal. Although not usually considered a risk factor for refractive disorders other than astigmatism, chalazia of the upper eyelid can present as a decrease in vision associated with reversible central corneal flattening and acquired hyperopia.

Aged↗
PubMed1997

Keeping an eye on vision: new tools to preserve sight and quality of life. A roundtable discussion, Part 2.

Research is pointing the way to new therapies for the eye diseases of aging. A gene that appears related to glaucoma has been identified, and a safe and effective inhibitor for aldose reductase is being sought for patients with diabetic retinopathy. Refinements in cataract surgery continue to improve the high success rate of this procedure. Physicians can educate their patients to participate in vision protection, through control of blood sugars, compliance with glaucoma medications, and the use of the Amsler grid by those at risk for macular degeneration. When vision cannot be corrected to the normal range, low vision rehabilitation offers magnification and new high-tech devices for optimizing independent patient function.

Age Factors↗
PubMed1997

Vision, learning, and dyslexia. A joint organizational policy statement. American Academy of Optometry. American Optometric Association.

1. Vision problems can and often do interfere with learning. 2. People at risk for learning-related vision problems should be evaluated by an optometrist who provides diagnostic and management services in this area. 3. The goal of optometric intervention is to improve visual function and alleviate associated signs and symptoms. 4. Prompt remediation of learning-related vision problems enhances the ability of children and adults to perform to their full potential. 5. People with learning problems require help from many disciplines to meet the learning challenges they face. Optometric involvement constitutes one aspect of the multi-disciplinary management approach required to prepare the individual for lifelong learning.

Academies and Institutes↗
PubMed1997

Vision screening in older adults on dialysis: do nephrology nurses have a role?

Undetected vision loss commonly occurs in older adults adding undue stress to those on dialysis. Poor vision is associated with increased risk of falls and decreased quality of life. Common visual impairments--presbyopia, cataracts, age-related macular degeneration, glaucoma, and diabetic retinopathy--often are detectable by visual acuity testing. Using various methods of visual acuity testing, nephrology nurses can perform vision testing quickly and inexpensively. Other nursing interventions also can improve eyesight.

Aged↗
PubMed1998

Sudden loss of vision.

BACKGROUND: Sudden loss of vision is an ophthalmological emergency. OBJECTIVE: This article explains how history and examination, particularly ophthalmoscopy, will greatly assist the general practitioner to diagnose the cause. DISCUSSION: Vision loss may be transient or prolonged. It is important to consider whether the eye is painful or comfortable, inflamed or not. An accurate diagnosis will direct the emergency management, which frequently determines the prognosis for vision.

Eye Diseases↗
PubMed1997

Positioning errors produced by persons with knee joint disease when vision is occluded.

This study examined the effect of occluding static vision on the ability of persons with knee joint disease and impaired position sense to actively reproduce knee angles in a one-legged standing position. The subjects, six women with knee joint disease, ages 54-75 years each performed a series of two knee repositioning tasks in the ranges of 20-40 degrees flexion on two different occasions, both with, and without visual feedback. On each occasion, the leg was marked with reflective markers and the resultant sagittal plane knee angles were photographed. Whilst the absolute differences between the criterion and the matching knee angles calculated from these records showed vision to have an effect on positioning accuracy (p = 0.04), there were no differences in mean absolute constant errors between the two experimental paradigms, indicating similar perceptual judgment in memory. However, variability in performance tended to be greater when vision was occluded (p = 0.08). These findings suggest that while visual sources of information may play a minor role in the knee positioning bias towards target overestimation apparent in this group, supplementary visual cues may help to promote more consistent positioning performance.

Aged↗
PubMed1997

Artificial vision workbench.

Machine vision is an important component of medical systems engineering. Inexpensive miniature solid state cameras are now available. This paper describes how these devices can be used as artificial retinas, to take snapshots and moving pictures in monochrome or color. Used in pairs, they produce a stereoscopic field of vision and enable depth perception. Macular and peripheral vision can be simulated electronically. This paper also presents the author's design of an artificial orbit for this synthetic eye. The orbit supports the eye, protects it, and provides attachment points for the ocular motion control system. Convergence and image fusion can be produced, and saccades simulated, along with the other ocular motions. The use of lenses, filters, irises and focusing mechanisms are also discussed. Typical camera-computer interfaces are described, including the use of "frame grabbers" and analog-to-digital image conversion. Software programs for eye positioning, image manipulation, feature extraction and object recognition are discussed, including the application of artificial neural networks.

Artificial Organs↗
PubMed1998

Structure determines function of the retina, a neural center. 4. The 'duplex' nature of vision.

Part 4 reveals how the differences in the quality of vision at high and low illumination are explained by synaptic interaction between the neurons in the outer plexiform layer changing with illumination. Analysis of data available in the literature revealed that rod vision is active over the entire range of light intensities generating visual responses. It is revealed that the input from the retina to brain centers involves information regarding a black and white image based on rod vision, which is improved with respect to spatial brightness contrast and darkness contrast by cone interference. Cones add color to the image, further increasing image contrast. The duplicity theory is shown to be based on erratic assumptions regarding how rods and cones function. The theory lacks an experimental basis and is not required to explain differences in the quality of the perceived images at high and low illumination.

Animals↗
PubMed1994

3-D vision and figure-ground separation by visual cortex.

A neural network theory of three-dimensional (3-D) vision, called FACADE theory, is described. The theory proposes a solution of the classical figure-ground problem for biological vision. It does so by suggesting how boundary representations and surface representations are formed within a boundary contour system (BCS) and a feature contour system (FCS). The BCS and FCS interact reciprocally to form 3-D boundary and surface representations that are mutually consistent. Their interactions generate 3-D percepts wherein occluding and occluded object parts are separated, completed, and grouped. The theory clarifies how preattentive processes of 3-D perception and figure-ground separation interact reciprocally with attentive processes of spatial localization, object recognition, and visual search. A new theory of stereopsis is proposed that predicts how cells sensitive to multiple spatial frequencies, disparities, and orientations are combined by context-sensitive filtering, competition, and cooperation to form coherent BCS boundary segmentations. Several factors contribute to figure-ground pop-out, including: boundary contrast between spatially contiguous boundaries, whether due to scenic differences in luminance, color, spatial frequency, or disparity; partially ordered interactions from larger spatial scales and disparities to smaller scales and disparities; and surface filling-in restricted to regions surrounded by a connected boundary. Phenomena such as 3-D pop-out from a 2-D picture, Da Vinci stereopsis, 3-D neon color spreading, completion of partially occluded objects, and figure-ground reversals are analyzed. The BCS and FCS subsystems model aspects of how the two parvocellular cortical processing streams that join the lateral geniculate nucleus to prestriate cortical area V4 interact to generate a multiplexed representation of Form-And-Color-And-DEpth, or FACADE, within area V4. Area V4 is suggested to support figure-ground separation and to interact with cortical mechanisms of spatial attention, attentive object learning, and visual search. Adaptive resonance theory (ART) mechanisms model aspects of how prestriate visual cortex interacts reciprocally with a visual object recognition system in inferotemporal (IT) cortex for purposes of attentive object learning and categorization. Object attention mechanisms of the What cortical processing stream through IT cortex are distinguished from spatial attention mechanisms of the Where cortical processing stream through parietal cortex. Parvocellular BCS and FCS signals interact with the model What stream. Parvocellular FCS and magnocellular motion BCS signals interact with the model Where stream.(ABSTRACT TRUNCATED AT 400 WORDS)

Depth Perception↗
PubMed2000

Monocular versus binocular visual acuity as measures of vision impairment and predictors of visual disability.

PURPOSE: To examine the relationship between monocular and binocular visual acuities as predictors of visual disability in a population-based sample of individuals 65 years of age and older. METHODS: Two thousand five hundred twenty community-dwelling residents of Salisbury, Maryland, between the ages of 65 and 84 years of age were recruited for the study. Corrected visual acuity was measured monocularly and binocularly using ETDRS charts. Reading speed, face discrimination, and self-reported difficulty with visual tasks were also determined. RESULTS: Binocular acuity is predicted with reasonable accuracy by acuity in the better eye alone, but not by the widely used American Medical Association (AMA) weighted-average algorithm. The AMA algorithm significantly underestimates binocular acuity when the interocular acuity difference exceeds one line. Monocular acuity and binocular acuity were significantly better predictors of reading speed than the AMA weighted score or a recently proposed Functional Vision Score (FVS). Monocular acuity in the better eye, binocular acuity, and the AMA and FVS algorithms were equally good predictors of self-reported vision disability. None of the acuity measures were good predictors of face recognition ability. CONCLUSIONS: The binocular acuities of older individuals can be inferred from measures of monocular acuity. There is little evidence for binocular inhibition when the monocular acuities in the two eyes are unequal, as opposed to the widely used AMA algorithm for computing binocular visual impairment. For tasks that are strongly associated with visual acuity, such as reading, this association can be captured from measures of monocular acuity and does not require separate assessment of binocular acuity.

Aged↗
PubMed1999

Motion parallax enables depth processing for action in a visual form agnosic when binocular vision is unavailable.

Visual-form agnosic patient DF, who has severe difficulties in using visual information about size, shape and orientation for perceptual report, can nevertheless--under normal viewing conditions--use the same information to accurately guide her hand movements. However, her performance of prehension tasks requiring the analysis of visual depth is severely disrupted when binocular vision is prevented. We have suggested that this deterioration in visuomotor control is due to an inability to use pictorial depth cues to compensate for the removal of binocular vision. In the current study we investigated whether DF was able to use motion parallax as an alternative to binocular cues. We asked her to grasp a square plaque slanted at different orientations in depth, under two monocular testing conditions. In one condition her head remained stationary on a chin rest, and in the other condition she made large lateral head movements just prior to each prehension movement. The results confirmed that DF is impaired in adjusting her hand orientation to the orientation of the target object when reaching monocularly with her head stationary. In contrast, when she made head movements, her manual performance was restored to almost normal levels. Our results are consistent with the idea that the processing of pictorial depth cues depends on the cortical ventral stream, which is known to be disrupted by DF's lesion. They further indicate that orientation in depth can be computed from motion parallax just as well as from binocular cues in the absence of a normally functioning ventral stream.

Adult↗
PubMed2002

Referral rates for a functional vision screening among a large cosmopolitan sample of Australian children.

The aim of this study was to investigate the incidence of functional vision problems in a large unselected cosmopolitan population of primary school-age children and to investigate whether constant clinical criteria for functional vision problems would be implemented by the practitioners involved in the screening. Refractive errors, near point of convergence, stereopsis, strabismus, heterophoria and accommodative facility were assessed for 2697 children (3-12 years) of varying racial backgrounds living in Australia. The spherical component of the refractive error ranged from -7.75 to +9.50 D (mean +0.54 D, +/-0.79) with a distribution skewed towards hypermetropia; astigmatism ranged from 0 to 4.25 D (mean -0.16 D, +/-0.35). There was a trend towards less hypermetropia and slightly more astigmatism with age. Mean near point of convergence was 5.4+/-2.9 cm, heterophoria at far and near was 0.12+/-1.58delta exophoria and 1.05+/-2.53delta exophoria, respectively, 0.55% of children exhibited vertical phoria at near >0.5delta, accommodative facility ranged from 0 to 24 cycles per minute (cpm) (mean 11.2 cpm, +/-3.7), stereopsis varied from 20 to 800 s (") of arc with 50% of children having 40" or better. The prevalence of strabismus was particularly low (0.3%). Twenty percent of the children were referred for further assessment based on criteria of one or more of: stereopsis >70", accommodative facility <8 cpm, near point of convergence (NPC) >9 cm, near exophoria >10delta or near esophoria >5delta, shift in eso or exophoria > or = 4delta between distance and near, astigmatism > or = 1 D, myopia more than -0.75 D, or hyperopia >+1.50 D. Post-hoc analysis of the record cards seeking the reason for further assessment indicates that referrals appear to have been based upon clinical intuition rather than on a set number of borderline or unsatisfactory results.

Accommodation, Ocular↗
PubMed2002

A test battery of child development for examining functional vision (ABCDEFV).

A battery of 22 tests is described, intended to give an integrated assessment of children's functional visual capacities between birth and four years of age. As well as sensory visual measures such as acuity, visual fields and stereopsis, the battery is intended to tap a range of perceptual, motor, spatial and cognitive aspects of visual function. Tests have been drawn from practice in ophthalmology and orthoptics, vision research, paediatric neurology, and developmental psychology to give an overall view of children's visual competences for guidance in diagnosis, further investigation, management and rehabilitation of children with developmental disorders. 'Core vision tests' require no motoric capacities beyond saccadic eye movements or linguistic skills and so assess basic visual capacities in children of any age. 'Additional tests' have age-specific requirements and are designed to pinpoint specific deficits in the perceptual, visuo-motor and spatio-cognitive domains. Normative data are reported on nine age groups between 0-6 weeks and 31-36 months, each including 32-43 typically developing children. Pass/fail criteria for each test are defined. These data allow the selection of a subset of tests for each age group which are passed by at least 85% of normally developing children, and so are appropriate for defining normal development. The normalized battery has been applied to a range of at-risk and clinical groups. Aspects of children's visual performance are discussed in relation to neurobiological models of visual development.

Child Development↗
PubMed1995

Vision in Alzheimer's disease.

In order to assess vision in Alzheimer's disease (AD) and related disorders, gerontologists must use tests that make minimal cognitive demands on the subject. Using such tests, we have found a pattern of deficits in color discrimination, stereoacuity, contrast sensitivity, and backward masking that differs from that seen in healthy elderly individuals. Impaired vision predicts deficient performance of subjects with AD on numerous tests of cognition, underscoring the importance of understanding visual changes in this population.

Aged↗
PubMed1981

Use of the Frostig Figure Ground in evaluation of adults with low vision.

The Frostig Figure Ground Test can be a valuable tool in the evaluation of adult low-vision patients. It is easily administered and can give valuable information about the patient's functioning. It provides an observable assessment of the individual sensory-perceptual capacities and has the further advantage of requiring the use of eye-hand coordination. Correlations of performance in this test with other data were analyzed for 79 low-vision patients. The test appears to provide some predictive information about the patient's reading performance, accounting for one-third of the variability of reading speed.

Eye Diseases↗