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At least 721 records · Page 40Linked to original sources

PubMed2000

Self-reported visual dysfunction in multiple sclerosis: results from the 25-Item National Eye Institute Visual Function Questionnaire (VFQ-25).

Visual impairment is one of the most common clinical manifestations of Multiple Sclerosis (MS), and is strongly related to overall health-related quality of life (HRQOL) in MS and other disorders. However, the assessment of vision-specific HRQOL in patients with MS has been limited. The purpose of this study was to examine self-reported visual dysfunction in a clinically heterogeneous MS cohort using the 25-Item National Eye Institute Visual Function Questionnaire (VFQ-25). The VFQ-25 was administered by telephone interview to a subset of participants in a follow-up study to a phase III trial of interferon beta-1a for relapsing-remitting MS. Mean VFQ-25 composite scores and selected sub-scale scores were significantly lower (worse) among patients in our MS cohort (n=35) compared with a published reference group of patients with no history of chronic eye disease (n= 118). These differences were observed despite a relatively younger age and tighter distribution of binocular visual acuities in the MS cohort Patients with MS in this study thus demonstrated a greater degree of self-reported visual dysfunction, as measured by the VFQ-25, compared with an eye disease-free reference group. The VFQ-25 is a potentially useful measure of vision-specific HRQOL in patients with MS.

Adult↗

PubMed2004

Controlling visually induced self-motion perception: effect of overlapping dynamic visual noise.

The effect of overlapping dynamic visual noise on visually induced self-motion perception (vection) by upward or downward optical flow was tested. The dynamic visual noise consisted of rapidly refreshed sparse random dots. Binocular disparity of the overlapping noise plane was varied. The results showed that when the noise was presented on the flow plane or on a plane farther than the flow plane, vection was totally impaired. This demonstrates that dynamic visual noise is functionally equivalent to static patterns in the vection suppression effect. A possibility of dynamic visual noise as a vection suppressor in an application on a 3-D display is discussed in relation to simulator sickness.

Humans↗

PubMedDate not supplied

[Visual motor and visual defects in spina bifida].

Among the numerous problems that Spina Bifida (SB) patients are faced with, impairments to the visual apparatus are often considered late and are not covered extensively in the literature. At the Pediatric Department of the University of Padua, an assessment of the visual function of 59 SB patients between 5 months and 26 years of age (29 male and 30 female) has been carried out by means of an ophthalmologic protocol As far as the alteration of the exstrinsic ocular mobility is concerned, 44% (26/59) of our patients revealed a manifest squint and only 3% (two patients) suffered from a latent squint. The most frequent type is a convergent squint (80%). The assessment of visual acuity made through Optotype was good in 82% of the cases (unlike what is commonly reported in the literature) and mild in 18%. None of the patients manifested hypovision. Refraction defects were present in 59% (34/59) of the patients. Regular ophthalmologic evaluations from birth or from diagnosis allow ophthalmologic treatments that are tailored to children suffering from SB and also enable them to reach and maintain a good visual standard and to observe the subtle symptoms of endocranial hypertension sooner. An early discovery and correct treatment of visual problems improves cognitive and motive performance as well as the autonomy of SB patients.

Adolescent↗

PubMed1990

[Examination by densitometer on visualization of non-ionic contrast medium (iohexol) in excretory urography. 2. Changes in visualization by DIP].

Changes in the visualization of non-ionic contrast medium (Omnipaque 300) in the urography by DIP were monitored for the normal sided urinary tract in patients with urolithiasis using a densitometer. In addition, changes of the visualization in relation to the dose of contrast medium used was examined and compared with that of ionic contrast medium (60% Urografin). The optimum photographing time was 15 minutes in the upper urinary tract (nephrogram, calyx, pelvis, upper ureter) and 20 minutes in the lower urinary tract (lower ureter, urinary bladder). Visualization of high usefulness appeared to be obtainable for the imaging diagnosis by DIP in subjects with normal renal function even when the photographing was completed 20 minutes after infusion of contrast medium. In relation to the doses of contrast medium used, no difference was observed in the variation pattern but a better imaging was obtained in the 100 ml group than 50 ml group with a significant difference (P less than 0.01) in the 15-20 minute images of the calyx and pelvis of the kidney and urinary bladder in particular, this suggested the high usefulness of 100 ml dosing for the imaging diagnosis. In the visualization of ionic contrast medium, some difference was observed in the variation pattern and the visualization was better in Ominpaque 300 groups than in 60% Urografin group with a significant difference (P less than 0.01) in the 15-20 minute images of the calyx and pelvis of the kidney and urinary bladder. This suggested the high usefulness of non-ionic contrast medium.

Absorptiometry, Photon↗

PubMed1981

The guidance of saccadic eye movements to perceptually mislocalized visual an non-visual targets.

The present experiment examined whether saccadic eye movements to visual targets are dependent on the perceived directions of the targets or on their retinally specified directions. Perceptual mislocalizations of visual targets were induced by having the target light attached to a subject's stationary hand while his biceps or triceps muscle was vibrated. Such vibration leads to apparent extension or flexion of the subject's restrained forearm and perceived visual motion of the stationary target light (6-8). Subjects always made accurate saccadic eye movements to a visual target, even when the target was perceptually mislocalized by as much as 20 degrees. By contrast, when subjects made saccadic eye movements to a nonvisual target, the location of their hand in the dark, they always looked to the perceived direction of the target even though it did not necessarily correspond to the true direction. These findings indicate that a distinction is maintained between "reflexive aspects" of oculomotor control related to foveation and the computation of perceived visual direction.

Adult↗

PubMed1982

Visual hypoemotionality as a symptom of visual-limbic disconnection in man.

In a patient with bilateral occipitotemporal hematomas secondary to head trauma, profound prosopagnosia, topographical memory disturbance, and a modality-specific inability to become emotionally aroused by visual cues developed. Data from neurological, neuropsychological, and psychophysiological assessment of the patient's deficits were interpreted as indicating a visual-limbic disconnection syndrome. The patient's symptoms were related to findings of emotional changes and visual impairment in macaques with bitemporal ablations and/or complete visual-temporal disconnection.

Acoustic Stimulation↗

PubMed2000

Does the visual system of the flying fox resemble that of primates? The distribution of calcium-binding proteins in the primary visual pathway of Pteropus poliocephalus.

It has been proposed that flying foxes and echolocating bats evolved independently from early mammalian ancestors in such a way that flying foxes form one of the suborders most closely related to primates. A major piece of evidence offered in support of a flying fox-primate link is the highly developed visual system of flying foxes, which is theorized to be primate-like in several different ways. Because the calcium-binding proteins parvalbumin (PV) and calbindin (CB) show distinct and consistent distributions in the primate visual system, the distribution of these same proteins was examined in the flying fox (Pteropus poliocephalus) visual system. Standard immunocytochemical techniques reveal that PV labeling within the lateral geniculate nucleus (LGN) of the flying fox is sparse, with clearly labeled cells located only within layer 1, adjacent to the optic tract. CB labeling in the LGN is profuse, with cells labeled in all layers throughout the nucleus. Double labeling reveals that all PV+ cells also contain CB, and that these cells are among the largest in the LGN. In primary visual cortex (V1) PV and CB label different classes of non-pyramidal neurons. PV+ cells are found in all cortical layers, although labeled cells are found only rarely in layer I. CB+ cells are found primarily in layers II and III. The density of PV+ neuropil correlates with the density of cytochrome oxidase staining; however, no CO+ or PV+ or CB+ patches or blobs are found in V1. These results show that the distribution of calcium-binding proteins in the flying fox LGN is unlike that found in primates, in which antibodies for PV and CB label specific separate populations of relay cells that exist in different layers. Indeed, the pattern of calcium-binding protein distribution in the flying fox LGN is different from that reported in any other terrestrial mammal. Within V1 no PV+ patches, CO blobs, or patchy distribution of CB+ neuropil that might reveal interblobs characteristic of primate V1 are found; however, PV and CB are found in separate populations of non-pyramidal neurons. The types of V1 cells labeled with antibodies to PV and CB in all mammals examined including the flying fox suggest that the similarities in the cellular distribution of these proteins in cortex reflect the fact that this feature is common to all mammals.

Animals↗

PubMed1981

Development alterations in binocular competitive interactions and visual acuity in visually deprived cats.

The purpose of the present study was to determine the effects of developmental alterations in binocular competitive interactions between the eyes on visual acuity. Comparisons were made between animals which were monocularly deprived (MD) of patterned visual input, binocularly lid-sutured cats (BD), and animals which had the lids of one eye sutured closed and the other eye removed prior to natural eye opening (MDE). Thus, each group differed in the degree of competitive imbalance between the eyes during postnatal development. Threshold visual acuity for high contrast, squarewave gratings was measured in a jumping stand. Mean visual acuities for each group using a single deprived eye were: group MD, 0.65 cycles/deg; group BD, 3.2 cycles/deg; group MED, 3.72 cycles/deg. These results indicated that the greater the competitive disadvantage an eye is placed at during development, the greater the acuity (sensory) deficits. Further, comparisons made between MD and MDE animals indicated that the acuity deficits using effects of deprivation per se.

Animals↗

PubMed1981

[Correlation of infarctions of the visual cortex with homonymous visual field defects. A computer tomographic study (author's transl)].

Computed tomography (CT) is a simple and non-invasive method of demonstrating infarctions of the visual cortex. Seventy-eight CT-proven infarctions were correlated with the visual field defects. This correlation between cortical infarctions and visual field defects is difficult to achieve by angiography because of the variations in the vascular supply. CT, on the other hand, provides a far better correlation, showing the functional-anatomical structure of the visual cortex by projection in three planes (transverse, sagittal, coronar). CT, however, can not replace angiography in cases where arteriovenous malformations are suspected.

Acute Disease↗

PubMed2001

[Electrical stimulation of the visual system. From empirical approach to visual prostheses].

The investigation of the influence of electrical stimulation on the visual system can be sub-divided into empirical, diagnostic and therapeutic phases of development. The first electrical stimulations of the visual system in animals dating back to the eighteenth century represent empirical approaches well before knowledge on the principles of bioelectrical nerve activity was available. Despite this lack of understanding, attempts were made at that time to treat blind people by electrical stimulation. More than 100 years later, with the advancement of technology and knowledge on nerve function, attempts were made to establish various methods of electrical stimulation for the diagnosis of different diseases of the visual system. For more than 30 years attempts to develop electrical devices have been made to by-pass defects of the visual system and to restore basic orientation. Presently nine different groups world-wide are focusing on retinal, optic or cortical implants. A short review on the historical use of electrical stimulation and new therapeutical attempts are given in this paper.

Action Potentials↗

PubMed1987

Attention to central and peripheral visual space in a movement detection task. III. Separate effects of auditory deprivation and acquisition of a visual language.

We employed event-related brain potentials (ERPs) and measures of signal detectability to compare attention to peripheral and central visual stimuli in normal hearing subjects who were born to deaf parents (HD Ss) and whose first language was American Sign Language (ASL). The results were compared with those obtained from normal hearing Ss and congenitally deaf Ss in the same paradigm. Task performance and ERPs during attention to the foveal region were similar in the 3 groups. In contrast, with attention to the peripheral stimuli the deaf Ss displayed attention effects over the occipital regions of both hemispheres that were several times larger than those in the hearing and the HD Ss. However, both HD and deaf Ss displayed lateral asymmetries in behavior and ERPs that were opposite in direction to those of the hearing Ss. Whereas hearing Ss detected the direction of target motion better when it occurred in the left visual field, deaf and HD Ss performed better for right visual field targets. Consistent with these results, the amplitude of the attention-related increases in the ERPs were larger from temporal and parietal regions of the right than the left hemisphere in hearing Ss, but were larger from the left than the right hemisphere in both the HD and the deaf Ss. These results suggest that auditory deprivation and the acquisition of a visual language have marked and different effects on the development of cortical specializations in humans.

Adolescent↗

PubMed1994

The topography of visual evoked response properties across the visual field.

Visual evoked potentials (VEPs) to luminance and pattern reversal stimulation were derived for a large number of small areas throughout the central visual field. In one study, the field was tested with a stimulus array consisting of 64 equal-area patches. Local response components were extracted by independent m-sequence modulation of the patches. Field topographies were compared between and within subjects using different electrode placements. The subject-dependent local variability observed in response characteristics is attributed to contributions from two or more cortical representations of the visual field and to inter-subject variations in gross cortical anatomy. The second study used luminance modulation of 56 patches across a 15 degrees field, scaled to activate approximately equal cortical areas in area V1. This produced many robust signals at all eccentricities. Bipolar and double differential ("1-dimensional Laplacian") signals were compared. The double differencing reduced contributions from distant or distributed sources, enhancing nearby current source activity, and greatly improved S/N for many stimulus locations. The high-resolution visual field maps demonstrated that clinical field testing using the VEP is not feasible because of effects of cortical convolutions on responses. However, the vast improvement in data quality and quantity make it a useful tool for VEP source localization and identification.

Brain↗

PubMed1994

The development of visual acuity in the peripheral visual field of human infants: binocular and monocular measurements.

We measured binocular and monocular grating acuity in the peripheral visual field of infants, using a modified preferential looking procedure. Both binocular and monocular peripheral acuity increased between 2 and 11 months of age, but had not reached adult levels at the end of the first year of life. Binocular acuity was always higher than monocular acuity. At all ages tested, acuity was higher in the temporal than in the nasal visual field. We conclude that, in spite of the relative morphological maturity of the peripheral retina, visual acuity develops in the peripheral visual field.

Adult↗

PubMed1991

Naloxone effects on the visual evoked potentials recorded from the main and accessory visual pathways of the cat.

1. The effects produced by repetitive i.v. administration of naloxone (1, 2 or 4 mg/kg) on the visual evoked potentials (VEPs) recorded along the main and accessory visual pathways were investigated in a modified "encéphale isolé" cat preparation. 2. Naloxone provoked a progressive amplitude enhancement and latency reduction of some components, depending on the structure analyzed, the dose used and the number of administrations applied. Electroretinogram (ERG) and N1-P1 VEP components of optic chiasm (OCh), lateral geniculate body (LGB) and visual cortex (VC) did not present significant changes. 3. Late-latency components (more than 200 msec) appeared in the VEPs of LGB and VC, mainly when 4 mg/kg were used. 4. Our results suggest that endogenous opioids have a modulatory role in the processing of sensory information at different levels of the visual system.

Animals↗

PubMed2004

Sensitivity and specificity of the 76-suprathreshold visual field test to detect eyes with visual field defect by Humphrey threshold testing in a population-based setting: the Thessaloniki eye study.

PURPOSE: To evaluate the screening performance of the 76-Suprathreshold (76-STHR) visual field test to detect eyes with visual field defect (VFD) as measured by Humphrey threshold testing in a population-based setting. DESIGN: Cross-sectional study. METHODS: All 88 subjects who agreed to participate in the pilot phase of the Thessaloniki Eye Study were included. Participants underwent a 76-STHR visual field test followed by a 30-full threshold (30-2 FTHR) test (Humphrey field analyzer). One eye/subject was randomly selected and included in the analysis. Sensitivity and specificity rates of the 76-STHR to detect eyes with VFD by the 30 to 2 FTHR test were calculated. RESULTS: When eyes with borderline results in the 30 to 2 FTHR test were classified as having a VFD, sensitivity rates of the 76-STHR to detect eyes with VFD by the 30 to 2 FTHR were 85.2%, 77.8%, and 74.1%, whereas specificity rates were 70%, 78%, and 86%, depending on the cutoff used for the 76-STHR. CONCLUSIONS: The 76-STHR test showed high sensitivity and low false-negative results at the "at least one point missed" cutoff level criterion to detect eyes with visual field defect by Humphrey threshold testing in a population-based setting. This criterion should be used when screening in a population-based study setting. By contrast, the 76-STHR would not be the appropriate screening test in a primary care setting with limited resources.

Aged↗

PubMed2005

The visual basis of category effects in object identification: evidence from the visual hemifield paradigm.

The basis for the category specific living things advantage in object recognition (i.e., faster and more accurate identification of living compared to nonliving things) was investigated in two experiments. It was hypothesised that the global shape of living things on average provides more information about their basic level identity than the global shape of nonliving things. In two experiments subjects performed name-picture or picture-name verification tasks, in which blurred or clear images of living and nonliving things were presented in either the right or the left visual hemifield. With blurred images, recognition performance was worst for nonliving things presented to the right visual field/left hemisphere, indicating that the lack of visual detail in the stimulus combined with a left hemisphere bias toward processing high frequency visual elements proved detrimental for processing nonliving stimuli in this condition. In addition, an overall living things advantage was observed in both experiments. This advantage was considerably larger with blurred images than with clear. These results are compatible with the global shape hypothesis and converge with evidence using other paradigms.

Adult↗

PubMed2005

Multifocal visual evoked potentials--a method study of responses from small sectors of the visual field.

OBJECTIVE: A method study of the mfVEP technique to establish a standardised way to identify stable response components from small areas in all parts of the visual field and a test-retest reliability study. METHODS: MfVEP was recorded from 26 healthy volunteers. RESULTS: Two response components could be clearly identified. The latencies corresponded to those of the traditional VEP response (N75 and P100). The visual field was divided into 12 sectors. A characteristic pattern was obtained. Component I was mainly negative in the upper sectors and positive in the lower sectors. Component II was positive in the upper sectors and negative in the lower ones. Most of the sectors with missing responses were the ones adjacent to the horizontal meridian, corresponding to the phase reversals. In a test-retest reliability study, the amplitude and latency measurements of the second test were plotted against those of the first test. Correlation coefficients between 0.84 and 0.93 were obtained. CONCLUSIONS: The mfVEP allows a reliable quantification of two response components from small parts of the visual field. SIGNIFICANCE: This paper suggests that mfVEP could be a valuable supplement to the traditional VEP for exploring restricted parts of the visual pathways.

Adult↗

PubMed2000

Functional plasticity in extrastriate visual cortex following neonatal visual cortex damage and monocular enucleation.

Neonatal lesions of primary visual cortex (areas 17, 18 and 19; VC) in cats lead to significant changes in the organization of visual pathways, including severe retrograde degeneration of retinal ganglion cells of the X/beta class. Cells in posteromedial lateral suprasylvian (PMLS) cortex display plasticity in that they develop normal receptive-field properties despite these changes, but they do not acquire the response properties of striate neurons that were damaged (e.g., high spatial-frequency tuning, low contrast threshold). One possibility is that the loss of X-pathway information, which is thought to underlie striate cortical properties in normal animals, precludes the acquisition of these responses by cells in remaining brain areas following neonatal VC damage. Previously, we have shown that monocular enucleation at the time of VC lesion prevents the X-/beta-cell loss in the remaining eye. The purpose of the present study was to determine whether this sparing of retinal X-cells leads to the development of striate-like response properties in PMLS cortex. We recorded the responses of PMLS neurons to visual stimuli to assess spatial-frequency tuning, spatial resolution, and contrast threshold. Results indicated that some PMLS cells in animals with a neonatal VC lesion and monocular enucleation displayed a preference for higher spatial frequencies, had higher spatial resolution, and had lower contrast thresholds than PMLS cells in cats with VC lesion alone. Taken together, these results suggest that preserving X-pathway input during this critical period leads to the addition of some X-like properties to PMLS visual responses.

Animals↗