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At least 37 records · Page 2Linked to original sources
PubMed2001

Measuring everyday visual discrimination in visually impaired children with the Sonksen Picture Guide to Visual Function.

The Sonksen Picture Guide to Visual Function (SPGVF) assesses a person's ability to discriminate pictures of everyday objects. Sonksen added the SPGVF to tests of visual acuity, because real objects, miniatures, and pictures are the main learning medium for young children. In earlier studies correlations have been found between visual acuity and responses to the SPGVF. However, to date no studies have used visually impaired children. In the study reported here, the associations between performance on the SPGVF task, visual acuity and contrast sensitivity were investigated. Participants were 17 visually impaired and 29 children without disabilities, 4--6 years of age. The results showed that visual acuity was more important for picture recognition than contrast sensitivity. Contrast thresholds < 3.33% implied that not all SPGVF-pictures could be recognized. The visually impaired children in the current study showed shorter mean identification distances than the normally sighted children in the original Sonksen and Macrae study.

Child↗
PubMed2005

Evaluating the establishment and maintenance of visual-visual and gustatory-visual equivalence relations in adults with developmental disabilities.

Four adults with developmental disabilities were taught to make conditional discriminations between either pictures and their corresponding printed English and Spanish words, or tastes and their corresponding printed English and Spanish words. Participants required more training trials to master the visual-visual conditional discriminations than the gustatory-visual conditional discriminations, and 3 of the 4 participants performed with higher accuracy on visual equivalence class test trials than gustatory-visual equivalence class test trials. A follow-up equivalence test conducted 30 to 40 days later showed substantially greater stability over time for the gustatory-visual classes than for the visual classes, for all participants. That participants acquired gustatory-visual conditional discriminations, as well as equivalence classes based on those conditional discriminations, may have relevance for incorporating gustatory stimuli into mand training sessions, as well as for teaching individuals with sensory impairments in other modalities.

Adult↗
PubMed1994

The effect of panretinal laser photocoagulation on visual acuity, visual fields and on subjective visual impairment in preproliferative and early proliferative diabetic retinopathy.

The effect of panretinal laser scatter treatment on visual fields, visual acuity and subjective complaints was assessed in 11 patients with severe nonproliferative or early proliferative diabetic retinopathy. Patients were prospectively examined before and after panretinal treatment using automated static threshold perimetry with program 30-2 on the Humphrey perimeter, and they were interviewed. Visual field sensitivity was often depressed even before treatment with mean MD -4.3 (-1, -11.6) dB, but was significantly lower (p < 0.01, ANOVA) 2 weeks after treatment with mean MD -8.6 dB. Visual fields remained stable 4 months later. Treatment increased the number of eyes with visual fields as defined by abnormal MD values at the p < 0.05 level from 8 to 16 among the 17 treated. In spite of considerable impairment of visual fields after treatment, subjective problems were small and the visual field impairment seemed to have little influence on everyday life.

Adult↗
PubMed2003

Evaluating the visual experience: visual acuity and the visual analogue scale.

PURPOSE: To attempt a comparison of the visual experience [assessed using a visual analogue scale (VAS)] with visual acuity in a group of normally-sighted adult optometric patients. METHODS: A single-item 100 mm paper VAS was administered to a sequence of 142 normally-sighted pre-presbyopic patients. Each individual was invited to indicate their recent subjective distance visual experience between the extremes of 'dreadful' (0 mm) and 'perfect' (100 mm). Each patient's binocular visual acuity was then determined at 6 m using a high-contrast logMAR chart under usual consulting room conditions. RESULTS: A weak association was revealed between the subjective indication of recent visual experience and the actual level of binocular acuity recorded in this normally-sighted group of subjects. On the basis of group responses a statistically significant discontinuity in the scores recorded with the VAS was demonstrated between patients who attained a clinical acuity better or worse than 0.10 logMAR units (6/7.5). Patient gender, age, and whether spectacles were habitually worn for distance viewing, were each revealed to be not statistically significant features. CONCLUSIONS: For normally-sighted optometric patients the subjective criterion of visual satisfaction would appear to be only loosely associated with the contemporaneous record of clinical acuity.

Adult↗
PubMed1978

The retinotopic distribution of visual callosal projections in the suprasylvian visual areas compared to the classical visual areas (17, 18, 19) in the cat.

The distribution of the interhemispheric projection from area 17 and 18 was studied using the anterograde degeneration technique. Besides the classical visual areas (17, 18, 19), area 21 and several visual areas in the middle suprasylvian sulcus also received visual callosal input. In the four terminal areas of the middle suprasylvian sulcus the projection was found to be focused on representations of the ventrical meridian including the area centralis, as in the classical visual areas. An increase of the width of visual field represented in the zone of callosal terminations can be seen from area 17 through area 18 to area 19 and possibly this trend continues in the suprasylvian visual areas.

Animals↗
PubMed2005

Visual spatial and visual pattern working memory: neuropsychological evidence for a differential role of left and right dorsal visual brain.

According to neurophysiological, neuroimaging, and behavioural evidence, visual working memory (WM) can be separated into a "what" and a "where" component, reflecting the duality of visual processing. Whereas a wealth of empirical data suggests a right-sided fronto-parietal network critical for the maintenance of spatial information, the cortical structures underlying maintenance of object information have remained controversial. Although visual object processing depends on ventral, inferior temporal areas, recent neuroimaging results suggest that maintenance of visual object information involves a left-sided or bilateral fronto-parietal network. The aim of the present study is to further clarify the role of the left and right parietal lobes for pattern and spatial visual WM. Seven patients with left-sided, seven with right-sided parietal brain injury, and two age-matched healthy control groups performed a delayed-matching-to-sample task using either pattern (shape) or spatial (location) information or both. In addition, eight patients with left-sided injury sparing parietal areas were tested to further examine the specific role of the left parietal cortex in pattern WM. Left parietal injury resulted in pattern WM impairment, only, while right parietal injury was associated with pattern and spatial WM deficits. Non-parietal injury was not associated with comparable deficits. These results suggest that visual spatial WM depends critically on right parietal areas; in contrast, pattern WM depends on both, left and right parietal areas.

Adult↗
PubMedDate not supplied

Visual acuity measurements by swept spatial frequency visual-evoked-cortical potentials (VECPs): clinical application in children with various visual disorders.

Previous studies have indicated that visual acuities of normal infants can be estimated with good accuracy using swept spatial frequency visual-evoked-potentials (VECPs). In this report we describe acuity measurements obtained with this technique from 304 examinations performed on 135 children having various visual disorders. When possible, two or more different stimulation frequencies (8, 12, 15 or 24 contrast reversals/sec) were used in each patient, and three to eight sweep VECPs were obtained from each patient under each simulation and recording condition. High correlation coefficients (0.94 - 0.96) between the acuity estimated on each patient from either the single sweep giving the best visual acuity (BSS) or from vector averages (VeA) of the EEG data obtained from several sweeps confirmed previous findings in normal infants. We also found high correlation coefficients among BSS recorded at different temporal frequencies (0.79-0.97) and among comparisons of BSS or VeA acuity to optotype visual acuity (0.6-0.89). Children with clinically undetectable optokinetic responses showed lower visual acuity estimated by BSS than those who demonstrated optokinetic nystagmus. We conclude that the sweep VECP is a valid method, giving estimates of acuity which correlate well with optotype acuity and correspond well to other clinical findings, and that it can be useful in the clinical management of nonverbal patients.

Child↗
PubMed1986

The relationship between the Test for Visual Analysis Skills (TVAS) and standardized visual-motor tests in children with visual perception difficulty.

Two widely utilized tests for visual-motor integration are the Beery Test for Visual Motor Integration (VMI) and the Bender Visual-Motor Gestalt Test (Bender). Another test that appears to demonstrate good potential for the measurement of visual-motor performance is the Test for Visual Analysis Skills (TVAS). This study examines the difference in performance on these tests between a pediatric population derived from available standardized data, a concurrent normal clinical population and a referred population of children with visual perception difficulties. The results indicate that all three tests clearly differentiate between the normal and perceptually impaired groups. In addition, the three tests correlate with each other at a statistically significant level.

Adolescent↗
PubMed2003

Electrical activity in visual cortex associated with combined auditory and visual stimulation in temporal sequences known to be associated with a visual illusion.

When a subject views a visual stimulus paired with a brief click, a second click occurring approximately 80 ms later produces the hallucination of a second visual stimulus. We have used combinations of visual and sound stimuli to evoke cortical activity and have recorded the associated event-related potentials. We have recorded EPs in a conventional manner, and have calculated from multichannel recordings the Laplacian derivations to determine if the currents were generated in primary visual cortex. Clicks alone do not cause significant activity in V1, but if paired with pattern stimulation, modify the evoked potential. The timing of this extra activity almost certainly excludes "feed back" activation from higher centres, and can most simply be explained if sound-activated thalamo-cortical input can rapidly produce extra activity in 'primed' visual cortex. This finding has general implications for cortical function, for the generation of the hallucination and for 'blindsight'.

Auditory Perception↗
PubMed1999

Effects of low alcohol consumption on visual evoked potential, visual field and visual contrast sensitivity.

PURPOSE: We studied changes in the vision of 16 people after consumption of a small quantity of alcohol, at a blood alcohol level (BAL) of 0.57 g/kg. METHODS: We studied visual contrast sensitivity (VCS) using Vistech VCTS 6500, visual evoked potential (VEP) by checked pattern stimulations and the peripheral visual field (PVF) with a perimetric automatic Humphrey. We first carried out the tests on sober people and then on individuals with a BAL of 0.57 g/kg. RESULTS: Alcohol consumption caused no significant difference in performance for these 3 tests. However, at a BAL of 0.57 g/kg there was a decrease in cerebral function, as shown by an increase in the number of mistakes made in the Wisconsin Card Sorting Test. CONCLUSION: These results suggest that for a low blood alcohol level, visual performance is less affected by the visual changes than by alteration in brain functions.

Adult↗
PubMed2004

Functional and diffusion-weighted magnetic resonance imaging for visualization of the postthalamic visual fiber tracts and the visual cortex.

Diffusion-weighted magnetic resonance imaging (MRI) offers the possibility to study the course of the cerebral white matter tracts whereas functional MRI (fMRI) provides information about the specific functions of cortical areas. We evaluated the combination of fMRI and diffusion-weighted MRI to detect cortical visual areas with their corresponding visual fiber tracts in 15 healthy controls (age: 23 - 53 years, male : female = 8 : 7). We demonstrated activation within the primary visual cortex and white matter bundles connecting the lateral geniculate body and the striate cortex in all subjects investigated. Additional activation could be appreciated in some subjects within the lateral geniculate bodies (n = 2) and the motion-sensitive area V5 (n = 3). The combination of diffusion-weighted and functional imaging allows visualization of the origin, direction and functionality of large white matter tracts. This will prove helpful for imaging structural connectivity within the brain during functional imaging. Moreover, this technique might provide important information for neurosurgical patients presenting with space-occupying lesions close to the cortical and subcortical visual system since this technique can -- in contrast to diffusion tensor imaging -- easily be adopted into a neuronavigation system and can be performed on all MR scanners capable of diffusion-weighted imaging without specific post-processing programs.

Adult↗
PubMed1992

Mislocalizations of visual elevation and visual vertical induced by visual pitch: the great circle model.

The elevation visually perceived as eye level (VPEL) changes linearly with the pitch of an illuminated visual field. The magnitude of influence is only slightly less when the visual field contains only two dim vertical lines in darkness than when it is complexly structured and normally illuminated. Pitching a visual field consisting of only a single line in darkness produces an influence that is only slightly smaller than the 2-line stimulus. The slopes of the VPEL-vs.-pitch functions for the complex room, 2-line stimulus, and 1-line stimulus are +0.63, +0.56, and +0.52 respectively. Although VPEL is systematically influenced by the pitch of the 2-line stimulus, the orientation of a small line within a frontal plane that is visually perceived as vertical is unaffected. However, when the two lines are pitched by equal amounts in opposite directions, the offset of VPV from true vertical changes linearly with pitch magnitude but VPEL is unaffected. These results are identical to those obtained when the two vertical lines are rolled within the frontal plane, a result that depends on some identities between roll and pitch: roll of two parallel lines in the same direction influences VPV but not VPEL; roll of the two lines in opposite directions influences VPEL but not VPV. The interaction between stimulus conditions and discriminations demonstrates that separate mechanisms are in control of VPEL and of VPV. The slope of the VPEL-vs.-pitch function increases exponentially with line length for the 1-line stimulus (space constant = 15.1 degrees). Summation of influences on VPEL for two lines horizontally separated by 50.3 degrees is as great as for two coextensive lines. The above results are predicted from the Great Circle Model which assumes (1) central projection on a spherical approximation to an erect stationary eye; (2) the sign and magnitude of influence of each line on VPEL and on VPV are determined by the direction and magnitude of the separation between the upper pole of the spherical eye and the intersection of the great circle containing the line's image with the central vertical retinal meridian and with the midfrontal retinal meridian, respectively; (3) the influence of individual nonparallel lines is determined by a weighted average of the influences of individual sets of parallel lines; (4) a generalized version of the Great Circle Model is indicated in which extraretinal signals from head and eye are taken into account.

Curare↗
PubMed2000

Visual system in a diurnal marsupial, the numbat (Myrmecobius fasciatus): retinal organization, visual acuity and visual fields.

The visual system of the numbat (Myrmecobius fasciatus), a highly endangered diurnal marsupial, has been investigated both anatomically and behaviorally. The ganglion cell layer, examined in cresyl-violet stained wholemounts, contained 832,800 ganglion cells; the number of ganglion cells corresponded to optic axon counts. An area centralis was located in the mid-temporal retina, where cells formed a bilayer, but there was no evidence of a visual streak. Visual acuity, estimated from counts of peak ganglion cell density (8,100/mm(2)) and measurements of posterior nodal distance (7.84 mm), was found to be 6.3 cycles per degree. The value was similar to that of 5.2 cycles per degree estimated by behavioral tests. Sectioned material revealed the presence of numerous oil-droplets in a cone-dominated retina. A rich retinal vasculature of the end-artery type of paired arteries and veins formed beds in the ganglion cell and inner nuclear layers. Measurements of visual fields revealed a binocular overlap of 80 degrees in the horizontal plane, and a total field of view approaching 240 degrees of visual angle. Monitoring of pupillary responses with an infrared video camera showed that the numbat possesses a remarkably wide, static pupil. Our results are discussed in relation to the ecology of the species and its phylogeny.

Animals↗
PubMed1994

Intact visual imagery and impaired visual perception in a patient with visual agnosia.

Although it is now well accepted that visual mental imagery and visual perception share common underlying mechanisms, there are several reports in which they are dissociated. Evidence for the separability of these processes is provided by a patient, C.K., who has a profound visual object recognition deficit attributable to an impairment in grouping or segmenting visual images. Despite this perceptual deficit, C.K. was able to draw objects in considerable detail from memory, and his knowledge of the visual appearance of objects was preserved on a variety of mental imagery tasks. Together with previous cases, these findings confirm the double dissociation between object recognition and perception. Interestingly, C.K. could also recognize newly constructed objects in his internal imagery. To accommodate these results, we propose a model in which imagery and perception are strongly associated but are also functionally specialized.

Adult↗
PubMed2005

Visual memory testing in older adults with age-related visual decline: a measure of memory performance or visual functioning?

Although we know that vision is correlated with memory performance in older adults, the implications for this in terms of neuropsychological assessment have not been investigated. Relationships among age, visual acuity, and visual and verbal memory in 89 community dwelling volunteers aged 60 to 87 years were examined. Vision was tested using the Landolt C and visual and verbal memory were assessed via the Visual Reproduction (VR) and Word List (WL) subtests from the Wechsler Memory Scale, Third Edition (WMS-III; Wechsler, 1997), respectively. Significant correlations were observed between vision and the VR and WL tasks. Hierarchical multiple regression analyses revealed that vision significantly increased the R2 for VR and WL after controlling for age and education. The effect of vision was not specific to visual memory. We conclude that vision is correlated with general memory function in older adults, and is not modality specific.

Aged↗
PubMedDate not supplied

Visualization techniques (colposcopy, direct visual inspection, and spectroscopic and other visual methods). Summary of task force 7.

Visual screening techniques include both low-technology approaches, such as direct visual inspection (DVI), and high-technology approaches, such as those that utilize electrooptical detectors to identify cervical cancer precursors and invasive cervical cancer. Simple visual screening techniques, such as DVI, consist of washing the cervix with a solution of 5% acetic acid (e.g., vinegar) and then inspecting it using either the naked eye or with a low-power magnifying device to identify areas of acetowhitening, which frequently correspond to cervical squamous intraepithelial lesions (SILs). The simple visual screening methods are being evaluated as an alternative to cytology in low-resource settings where screening using cervical cytology is not feasible. Multiple studies have shown DVI to have sensitivity similar to that of cervical cytology for identifying women with high grade SIL but much lower specificity. The novel high-technology visual screening methods that utilize electrooptical sensors to identify cervical abnormalities are still in the developmental phases but offer considerable potential.

Acetic Acid↗
PubMed1999

Information from false statements concerning visual acuity and visual field in cases of psychogenic visual impairment.

BACKGROUND: If visual acuity (VA) and/or visual field (VF) is claimed to be worse than in reality, it can be difficult to estimate the actual VA/VF. This paper describes a method of proving malingering and of estimating the actual VA by statistical evaluation of the subjective responses to discrete visual stimuli. METHODS: VA is measured by using a Landolt or Snellen optotype with four possible directions. There are n (> or = 16) questions at each acuity level. Each direction of the optotype occurs with the same frequency. The sequence is not predictable. In testing the VF, the stimulus is presented in an unpredictable sequence but with the same frequency at each of four distinct locations outside the claimed field at the horizontal and the vertical meridian. The field is divided into four quadrants defined by the 45 degrees-225 degrees and 135 degrees-315 degrees meridians. The candidate is requested to search for the light. The target quadrant of the first eye movement is recorded. At each VA level, the distribution function of the binomial formula allows estimation of the probability Pc of < or = kc and > or = kc correct answers to n questions by mere accident. Regarding the VF, the direction of the first saccade at each stimulus presentation can be processed accordingly. RESULTS: If n = 32 and kc = 0,1,2, the chance P that this pattern is merely accidental is about 0.0001, 0.001, 0.007. Values of P < or = 0.01 strongly suggest that the answers were voluntarily wrong. Preference for the opposite direction can also point to psychogenic influence: If ko = 15,16,17,18, P is about 0.006, 0.002, 0.0006, 0.0002. CONCLUSION: Systematically false statements can yield valuable information about the actual visual functions.

Adult↗
PubMed1992

Central visual field, visual acuity, and sudden visual loss after glaucoma surgery.

The relationship between Snellen visual acuity and central visual field loss as determined by the Humphrey 10-degree test was examined in 96 glaucomatous eyes of 79 patients. The severity of the field defect was determined by the number of affected quadrants, defined as a sensitivity loss of at least 10 decibels from normal at the most central point of 1.4-degree eccentricity. The decrease in median acuity was gradual, one-half line per quadrant for one and two affected quadrants, and an additional one and one-half line to two lines for three and four quadrants. Loss of acuity was disproportionate when both temporal quadrants were affected. The major source of error was difficulty with fixation. One type, a prolonged fixation shift, was not related to short-term fixation losses. There was a significant correlation between acuity and foveal threshold over a wide range of both variables. Sudden visual loss from additional optic nerve damage was studied retrospectively in 96 eyes with advanced glaucoma and a central field defect. A frequency of 3% for any loss of visual acuity and a frequency of 1% for a loss to 20/200 or worse were noted. There were no apparent predictive factors.

Adult↗