PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Visual function”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed1984

Developmental aspects in the assessment of visual function in young children.

The developmental aspects in the assessment of visual acuity in the preverbal child have been reviewed. Several investigative techniques indicate that visual acuity of infants increases significantly between birth and age 6 months. Transient oculomotor deviation in infancy must be differentiated from pathologic ocular conditions. Changes in refraction of the developing eye that occur normally and as a result of an ocular disorder must be recognized and managed early in the infant's life.

Age Factors↗
PubMed1992

Isoluminant stimuli may not expose the full contribution of color to visual functioning: spatial contrast sensitivity measurements indicate interaction between color and luminance processing.

Visual performance is greatly impaired when tested with heterochromatic isoluminant stimuli. It is thus concluded that the chromatic system contribution to many visual tasks is limited. We suggest that unless color and luminance are shown to be processed independently, such experiments do not demonstrate shortcomings of the chromatic system but rather the inadequacy of using isoluminant stimuli for isolating that system. We hypothesize that color vision has evolved not only to encode color per se but also to enhance luminance-based visual processing, so that for color information to be fully effective, luminance as well as chromatic variations should be present in the stimulus. The hypothesis was tested by studying the contribution of color to spatial vision. The human contrast sensitivity function (CSF) was studied using luminance, isoluminance (color) and combined luminance/color sinusoidal gratings. It is found that luminance contrast sensitivity is enhanced when luminance contrast is accompanied by color contrast and vice versa. The nature of the interaction is best described by an additive single analyzer model. Color opponent cells which respond to both chromatic and achromatic stimuli may be identified as the analyzer.

Color Perception↗
PubMed1992

Structural modeling of functional visual pathways mapped with 2-deoxyglucose: effects of patterned light and footshock.

This paper describes the first application of structural modeling to the visual system. Structural modeling, or path analysis, is a mathematical method that allows for the quantification of the functional strengths of anatomical connections between the structures that form a neural system. The objective was to demonstrate how structural modeling can be used to determine the functional interrelationships between brain structures that form the visual system and how these interrelationships change under different conditions. Data were obtained from measures of 2-deoxyglucose uptake in the visual system of rats presented with either patterned light or darkness. The effects of arousing footshock on visual system operations were also investigated. Models based on the anatomical connections and the interregional correlations between metabolic activity data were used to determine path coefficients representing the magnitude of the influence of each directional path. Statistical evaluation of the models revealed that the dominant positive influences on visual system activity in the darkness were the tectocortical subsystem and the descending connections from secondary visual cortex. In the patterned light model, the total influence of the geniculocortical subsystem was higher than in the dark, and the tectocortical pathways showed both a reduction and a shift in the direction of effects. The models also revealed that the effects of footshock-induced arousal on visual system operations depended upon the visual environment and on extra-visual influences. The footshock led to an increase in the interaction of the two main subsystems at the level of connections between primary visual cortex and the lateral posterior nucleus, and a descending negative influence from the secondary visual cortex became dominant. The models are discussed in the context of conventional analyses to show how structural modeling allows for the determination of much more information about the functional interactions within the visual system of subjects under different experimental conditions.

Animals↗
PubMed1989

Assessment of visual function in suspected ocular malingering.

Three new techniques are presented for assessing visual acuity in the presence of suspected malingering. The first technique is based on the preferential looking method commonly used to test acuity in infants. The second uses polarising filters to present stimuli briefly to both eyes or to each eye alone, without the patient's being aware of which eye is tested. The third presents the stimuli on a computer monitor and separates the ray paths of the two eyes by means of special spectacles that obscure vision in one eye for fractions of a second while a stimulus is presented.

Humans↗
PubMed1996

[Visual function of automobile drivers during the workday].

Peculiarities of drivers' work require visual strain. The studies prove considerable changes in accommodation (value of absolute and resources of relative accommodation), muscular balance, visual performance in correction test, that prove visual fatigue of automobile drivers, especially aged 20 to 30.

Accommodation, Ocular↗
PubMed1994

Lead-induced alterations in rod-mediated visual functions and cGMP metabolism: new insights.

Long-term scotopic (rod-mediated) visual deficits following developmental lead exposure occur in monkeys and hooded rats. This report describes and summarizes previous ERG and biochemical findings, presents new biochemical data aimed at determining the mechanism of inhibition of lead on rod cGMP-PDE, presents an integratory framework for understanding the ERG and cGMP results and speculates on the implications of the present data. A- and b-wave voltage-log intensity and latency-log intensity functions, generated from single-flash ERGs in fully dark-adapted rats, revealed that low and moderate level lead exposure caused decreases in absolute sensitivity and amplitude, and increases in latency. Rod- and cone-mediated flicker fusion frequency measures revealed selective rod deficits in temporal resolution. In addition, the slope of the increment threshold function was decreased, but only at scotopic adapting backgrounds, and dark adaptation was delayed. Prior exposure to lead produced a dose-response inhibition of retinal cGMP-phosphodiesterase (PDE) resulting in an increase in cGMP in dark-adapted and light-adapted states and an increase in the calcium content of rods. In vitro experiments with adult rat retinas incubated with 10(-9) to 10(-4) M Pb2+ revealed a concentration-dependent inhibition of cGMP-PDE which suggested that Pb2+ directly inhibited the rod cGMP-PDE. This was confirmed in experiments conducted with isolated, purified, trypsin-activated bovine rod cGMP-specific PDE exposed to 5 x 10(-8) to 10(-4) M Pb2+. The cGMP data are entirely consistent with the observed ERG changes. The ERG data is relevant to low level pediatric lead poisoning since rat rods are similar to human rods. Finally, since a lesion in the gene that codes for a cAMP-PDE leads to defective learning and memory in the Drosophila dunce flies, it is possible that lead-induced alterations in cyclic nucleotide phosphodiesterases contribute to the long-term CNS deficits produced by developmental lead exposure.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMedDate not supplied

[Compensation for disruptions of visual function in the dog after partial exclusion of the neocortex].

The recovery of visual disturbances provoked by partial neocortical deafferentation was studied in dogs with two sets of visual patterns: figures and differently oriented lines. The disturbances were more prominent, when the dogs had to solve the most complex visual tasks (6 stimuli showed to a dog simultaneously). There was a distinct recovery of figure recognition in the process of compensation, i. e. in 4--6 months after the neocortical deafferentation. On the contrary, recognition of oriented lines did not improve. Probably the differences between the two sorts of recognition mentioned above may be explained by various changes of their mechanisms' properties in the process of compensation.

Adaptation, Physiological↗
PubMed1990

Visual function and reading disability: an optometric viewpoint.

Recent research has identified a low-level transient visual system deficit in patients with reading disability. This deficit has been shown to have consequences on higher level perceptual and cognitive functions, including reading. This new information provides optometrists with a theoretical framework to expand the understanding of the relationship between vision and reading. In this paper, traditional concepts are described and an extensive literature review is provided. The impact of these processing deficits on reading performance is discussed based on metacontrast masking and foveal-parafoveal sequential attention models of reading. Clinical implications of transient system function in other clinical entities are also provided.

Attention↗
PubMed1986

The effects of behavioral vision training on multiple aspects of visual functioning in myopic adults.

Twenty myopic adults were randomly assigned to either a behavioral visual acuity training program or to a no-treatment control group in order to assess changes in several aspects of visual behavior. Measures were obtained both pre- and posttraining for a number of variables. These included recognition and resolution visual acuity, contrast sensitivity, perceived clarity and confidence of responses, and stimulus duration. Results indicated that training subjects significantly improved on all three measures of visual acuity: recognition acuity, resolution acuity, and contrast sensitivity. Improvements in acuity were associated with significant improvements in the perceived clarity of the stimuli but not in the confidence of the subject's response. These data expand our knowledge concerning the effectiveness of behavioral training programs in improving visual acuity in myopia. The potential utility of such programs is discussed.

Behavior Therapy↗
PubMedDate not supplied

Can my child see? The evaluation of visual function in children.

Careful evaluation of all parameters of ocular function are required to delineate the cause of lack of visual responses in children. Any visual fixation, no matter how fleeting, is a sign of intact visual pathways. If no sign of ocular pathology can be found on the routine exam of the visually inattentive child, electrophysiologic testing may be necessary to confirm the presence of abnormality of the visual pathways. In the child with a generalized CNS disorder, the lack of visual response may be due to his inability to respond to visual information (perceptual blindness) rather than to organic pathology in the occipital cortex (cortical blindness).

Age Factors↗
PubMed1993

[Possibility of detecting visual functional disturbance in rats by the open-field test].

In order to determine whether visual disturbance in small rodents is detectable by means of the open-field test, the ambulation scores of enucleated and intact rats in an open-field were measured. In a 30-min test of Slc:Wistar/ST rats, there were significant differences in ambulation scores between enucleated and intact rats in the first 10-min. In addition, the effects of observation times (09:00-11:00, 13:00-15:00 and 17:00-19:00 hr) and strains on the open-field test were studied using a 10-min test. Regardless of observation times, ambulation scores of enucleated rats of the Slc:Wistar/ST and F344/N Slc strains were significantly elevated as compared with those of intact rats from both strains. When tested during the 13:00-15:00 hr period, there were significant differences in the Slc:SD rats. These findings indicate that the changes in ambulation are due to visual disturbance. However, significant ambulatory changes in F344/N Slc rats were documented at the three different observation times. Based on these results, Slc:Wistar/ST rats appear to be suitable for detecting visual disturbance by the open-field test.

Animals↗