Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “VISION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,639 records · Page 91Linked to original sources
PubMed2004

Shape perception in human vision: specialized detectors for concentric spatial structures?

It has been suggested that second-order shape integration mechanisms in human spatial vision (e.g. the neurons at V2 and V4 cortical areas) may contain specialized detectors for concentric shapes [Vision Res. 37 (1997) 2325; Vision Res. 38 (1998) 2933]. We tested this notion using psychophysical techniques in which the observers' task was to detect orientation noise (randomly oriented dot pairs) in concentric and linear Glass patterns. Our results showed that the detection of orientation noise was easier in concentric Glass patterns, thus supporting the notion of specialized detectors.

Analysis of Variance↗
PubMed2005

Cross-modal activation of visual cortex during depth perception using auditory substitution of vision.

Previous neuroimaging studies identified multimodal brain areas in the visual cortex that are specialized for processing specific information, such as visual-haptic object recognition. Here, we test whether visual brain areas are involved in depth perception when auditory substitution of vision is used. Nine sighted volunteers were trained blindfolded to use a prosthesis substituting vision with audition both to recognize two-dimensional figures and to estimate distance of an object in a real three-dimensional environment. Using positron emission tomography, regional cerebral blood flow was assessed while the prosthesis was used to explore virtual 3D images; subjects focused either on 2D features (target search) or on depth (target distance comparison). Activation foci were found in visual association areas during both the target search task, which recruited the occipito-parietal cortex, and the depth perception task, which recruited occipito-parietal and occipito-temporal areas. This indicates that some brain areas of the visual cortex are relatively multimodal and may be recruited for depth processing via a sense other than vision.

Acoustic Stimulation↗
PubMed2005

Treatment and vision-related quality of life in the early manifest glaucoma trial.

PURPOSE: To evaluate the effect of treatment, visual function, and other factors on vision-targeted health-related quality of life (HRQOL) of patients with early glaucoma. DESIGN: Randomized clinical trial. PARTICIPANTS: Two hundred fifty-five patients with newly detected open-angle glaucoma and repeatable early visual field (VF) defects, 50 to 80 years old (66% female). METHODS: Patients were randomized to receive either betaxolol plus laser trabeculoplasty in eligible eye(s) or no initial treatment and had ophthalmologic examinations every 3 months. A Swedish translation of the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25) was self-administered at 2 follow-up visits (3 and 6 years after randomization). MAIN OUTCOME: Multiple linear regression analyses determined the effect of treatment and other factors on (1) VFQ-25 composite scores at the first administration and (2) change in scores between administrations. RESULTS: Two hundred thirty-three patients had 1 NEI VFQ-25 administration and 167 patients had 2 administrations. Internal consistency reliability was high for the composite VFQ-25 score (Cronbach alpha = 0.88) and satisfactory (alpha> or =0.76) for most subscale scores. At the first administration, the composite score was high (88.8+/-11.7). Mean subscale scores were also generally high (98.0-58.3) and were similar for each study group when analyzed separately. Most lower subscale scores were modestly but significantly related to worse visual acuity (VA) or mean deviation (MD) (better eye, r = 0.15-0.35). Composite scores were similar for treated and untreated patients. Lower composite scores were associated with low VA in the better eye (worse than 0.70) and worse perimetric MD (<4.16 decibels) and nuclear lens opacities (Lens Opacities Classification System II grade > or = 2), but not with age, gender, VF progression, intraocular pressure, cardiovascular disease, or hypertension. Between VFQ-25 administrations, larger decreases in the composite score were associated with larger decreases in VA (P<0.05), female gender (P = 0.001), and older age at first administration (P = 0.006). Treatment (assigned at randomization or later in the study) was not associated with change in HRQOL. CONCLUSIONS: Results suggest that absence or delay of treatment did not influence vision-targeted HRQOL in these newly diagnosed glaucoma patients. However, visual function affected vision-targeted quality of life up to 6 years after Early Manifest Glaucoma Trial enrollment.

Aged↗
PubMed2004

Subacute sclerosing panencephalitis: a cause of acute vision loss.

A 4-year-old male presented with only acute vision loss. His neurologic examination, funduscopic examination, and pupils were normal. Cranial magnetic resonance imaging revealed abnormal hyperintense, bilaterally symmetric lesions (on T(2)-weighted and fluid-attenuated inversion recovery, images) in bilateral optic radiations, pulvinar region in the thalami, crus posterior of internal capsules, periventricular white matter, and unilaterally left anterior pons. Elevated measles antibody titers in the cerebrospinal fluid confirmed the diagnosis of subacute sclerosing panencephalitis. Vision loss improved and cranial magnetic resonance imaging findings regressed,but myoclonic jerks and deterioration began 7 months later. The diagnosis of subacute sclerosing panencephalitis should be considered in cases with acute vision loss resulting from cortical blindness even when classical findings of the central nervous system do not exist.

Acute Disease↗
PubMed2004

Intracranial metastatic prostate carcinoma presenting as intermittent double vision.

We describe a prostate cancer patient whose initial symptom was intermittent double vision. Intracranial magnetic resonance imaging demonstrated a pituitary mass extending to the cavernous sinus, which caused the double vision. After hormonal therapy for prostate cancer, the pituitary mass disappeared, and double vision was completely resolved without local therapy for the brain. In the 19 months of follow-up after hormone treatment, the prostate cancer remained stable, and the patient remained neurologically intact.

Adenocarcinoma↗
PubMed2005

Learning to identify contrast-defined letters in peripheral vision.

Performance for identifying luminance-defined letters in peripheral vision improves with training. The purpose of the present study was to examine whether performance for identifying contrast-defined letters also improves with training in peripheral vision, and whether any improvement transfers to luminance-defined letters. Eight observers were trained to identify contrast-defined letters presented singly at 10 degrees eccentricity in the inferior visual field. Before and after training, we measured observers' thresholds for identifying luminance-defined and contrast-defined letters, embedded within a field of white luminance noise (maximum luminance contrast=0, 0.25, and 0.5), at the same eccentric location. Each training session consisted of 10 blocks (100 trials per block) of identifying contrast-defined letters at a background noise contrast of 0.5. Letters (x-height=4.2 degrees) were the 26 lowercase letters of the Times-Roman alphabet. Luminance-defined letters were generated by introducing a luminance difference between the stimulus letter and its mid-gray background. The background noise covered both the letter and its background. Contrast-defined letters were generated by introducing a differential noise contrast between the group of pixels that made up the stimulus letter and the group of pixels that made up the background. Following training, observers showed a significant reduction in threshold for identifying contrast-defined letters (p<0.0001). Averaged across observers and background noise contrasts, the reduction was 25.8%, with the greatest reduction (32%) occurring at the trained background noise contrast. There was virtually no transfer of improvement to luminance-defined letters, or to an untrained letter size (2 x original), or an untrained retinal location (10 degrees superior field). In contrast, learning transferred completely to the untrained contralateral eye. Our results show that training improves performance for identifying contrast-defined letters in peripheral vision. This perceptual learning effect seems to be stimulus-specific, as it shows no transfer to the identification of luminance-defined letters. The complete interocular transfer, and the retinotopic (retinal location) and size specificity of the learning effect are consistent with the properties of neurons in early visual area V2.

Adult↗
PubMed2006

Visual training improves underwater vision in children.

Children in a tribe of sea-gypsies from South-East Asia have been found to have superior underwater vision compared to European children. In this study, we show that the improved underwater vision of these Moken children is not due to better contrast sensitivity in general. We also show that European children can achieve the same underwater acuity as the Moken children. After 1 month of underwater training (11 sessions) followed by 4 months with no underwater activities, European children showed improved underwater vision and distinct bursts of pupil constriction. When tested 8 months after the last training session in an outdoor pool in bright sunlight-comparable to light environments in South-East Asia-the children had attained the same underwater acuity as the sea-gypsy children. The achieved performance can be explained by the combined effect of pupil constriction and strong accommodation.

Accommodation, Ocular↗
PubMed1997

Severe vision loss and neovascular glaucoma complicating superior ophthalmic vein approach to carotid-cavernous sinus fistula.

PURPOSE: To report a patient with unilateral vision loss and neovascular glaucoma after attempted superior ophthalmic vein embolization in the treatment of a carotid-cavernous sinus fistula. METHODS: A 69-year-old man with a history of a left dural carotid-cavernous sinus fistula underwent attempted treatment with superior ophthalmic vein embolization. The procedure was unsuccessful, and the left superior ophthalmic vein was ligated. RESULTS: Uncontrolled left proptosis and intraocular pressure necessitated urgent orbital decompression with severe vision loss and neovascular glaucoma. CONCLUSION: Superior ophthalmic vein embolization in the management of carotid-cavernous fistula may be associated with vision-threatening complications.

Aged↗
PubMed2001

Contribution of vision and cutaneous sensation to the control of centre of mass (COM) during gait termination.

This study employed manipulation of sensory inputs (vision and plantar-surface cutaneous sensation) during gait termination to elicit insight into the roles played by these sensory systems in the control of gait termination. Attenuation of cutaneous sensation was achieved through hypothermic anesthesia. Visual information was occluded using special glasses. The subjects were asked to walk along an 8 m walkway and during randomly selected trials (25% of trials) to terminate their gait in a predetermined area. The centre of mass (COM) was obtained in order to provide an indication of the efficiency and stability during termination when sensory inputs were manipulated. Lack of visual information delayed the initiation of the slowing down of the COM forward progression and increased the step length of the last step of termination. Additionally, lack of vision resulted in the COM moving closer to the base of support (BOS) during double support and more variability, in the COM, when attempting to achieve a final stable position. Insensitivity of the plantar-surface mechanoreceptors led to a longer second step and a more variable foot placement of the first step, and increased the loading rate during the final two steps of termination. Additionally when vision and cutaneous information were absent the resolution of the final stable position was not as effectively controlled. The results demonstrated that visual information about self-motion and object-motion and sensation from the plantar surface of the foot play phase-specific roles in the control of COM during gait termination.

Adult↗
PubMed2001

Visual indexes, preconceptual objects, and situated vision.

This paper argues that a theory of situated vision, suited for the dual purposes of object recognition and the control of action, will have to provide something more than a system that constructs a conceptual representation from visual stimuli: it will also need to provide a special kind of direct (preconceptual, unmediated) connection between elements of a visual representation and certain elements in the world. Like natural language demonstratives (such as 'this' or 'that') this direct connection allows entities to be referred to without being categorized or conceptualized. Several reasons are given for why we need such a preconceptual mechanism which individuates and keeps track of several individual objects in the world. One is that early vision must pick out and compute the relation among several individual objects while ignoring their properties. Another is that incrementally computing and updating representations of a dynamic scene requires keeping track of token individuals despite changes in their properties or locations. It is then noted that a mechanism meeting these requirements has already been proposed in order to account for a number of disparate empirical phenomena, including subitizing, search-subset selection and multiple object tracking (Pylyshyn et al., Canadian Journal of Experimental Psychology 48(2) (1994) 260). This mechanism, called a visual index or FINST, is briefly discussed and it is argued that viewing it as performing a demonstrative or preconceptual reference function has far-reaching implications not only for a theory of situated vision, but also for suggesting a new way to look at why the primitive individuation of visual objects, or proto-objects, is so central in computing visual representations. Indexing visual objects is also, according to this view, the primary means for grounding visual concepts and is a potentially fruitful way to look at the problem of visual integration across time and across saccades, as well as to explain how infants' numerical capacity might arise.

Cognitive Science↗
PubMed2000

The temporal properties of first- and second-order vision.

Vision is sensitive to first-order modulations of luminance and second-order modulations of image contrast. There is now a body of evidence that the two types of modulation are detected by separate mechanisms. Some previous experiments on motion detection have suggested that the second-order system is quite sluggish compared to the first-order system. Here we derive temporal properties of first- and second-order vision at threshold from studies of temporal integration and two-pulse summation. Three types of modulation were tested: luminance gratings alone, luminance modulations added to dynamic visual noise, and contrast modulations of dynamic noise. Data from the two-pulse summation experiment were used to derive impulse response functions for the three types of stimulus. These were then used to predict performance in the temporal integration experiment. Temporal frequency response functions were obtained as the Fourier transform of impulse responses derived from data averaged across two observers. The response to noise-free luminance gratings of 2 c/deg was bi-phasic and transient in the time domain, and bandpass in the frequency domain. The addition of dynamic noise caused the response to become mono-phasic, sustained and low-pass. The response to contrast modulated noise (second-order) was also mono-phasic, sustained and low-pass, with only a slightly longer integration time than in the first-order case. The ultimate roll-off at high frequencies was about the same as for the first-order case. We conclude that second-order vision may not be as sluggish as previously thought.

Contrast Sensitivity↗
PubMed1998

Colour vision in gyrate atrophy.

A follow-up study of colour vision in two patients with gyrate atrophy was performed. Gyrate atrophy was diagnosed in the first patient at the age of 17 years. Her colour vision was first tested at the age of 25 years; at the follow-up examination 7 years later, she correctly interpreted the Standard Pseudoisochromatic Plates part 2, however, with one mistake due to lens opacity. In the Farnsworth-Munsell 100 hue test and in the Color Vision Meter 712 (CVM) anomaloscope, the results were within normal ranges. In the second patient, gyrate atrophy was diagnosed at the age of 4 years. At the ages of 4 and 5 years, he correctly interpreted the Ishihara, AO H-R-R, and Lanthony Tritan Album plates as well as the City University test. At the ages of 6, 7, and 8 years, he correctly interpreted the plate tests, the Farnsworth Panel D 15, and Lanthony's Desaturated Panel. The CVM anomaloscope results were normal.

Adult↗
PubMed2003

Historical contingency in the evolution of primate color vision.

Primates are unique among eutherian mammals for possessing three types of retinal cone. Curiously, catarrhines, platyrrhines, and strepsirhines share this anatomy to different extents, and no hypothesis has hitherto accounted for this variability. Here we propose that the historical biogeography of figs and arborescent palms accounts for the global variation in primate color vision. Specifically, we suggest that primates invaded Paleogene forests characterized by figs and palms, the fruits of which played a keystone function. Primates not only relied on such resources, but also provided high-quality seed dispersal. In turn, figs and palms lost or simply did not evolve conspicuous coloration, as this conferred little advantage for attracting mammals. We suggest that the abundance and coloration of figs and palms offered a selective advantage to foraging groups with mixed capabilities for chromatic distinction. Climatic cooling at the end of the Eocene and into the Neogene resulted in widespread regional extinction or decimation of palms and (probably) figs. In regions where figs and palms became scarce, we suggest primates evolved routine trichromatic vision in order to exploit proteinaceous young leaves as a replacement resource. A survey of the hue and biogeography of extant figs and palms provides some empirical support. Where these resources are infrequent, primates are routinely trichromatic and consume young leaves during seasonal periods of fruit dearth. These results imply a link between the differential evolution of primate color vision and climatic changes during the Eocene-Oligocene transition.

Animals↗
PubMed2000

Phylogenetic analysis and experimental approaches to study color vision in vertebrates.

To elucidate the molecular mechanisms of vertebrate color vision, it is essential to establish associations between amino acid substitutions and the directions of lambda max shifts of visual pigments. In this way, we can identify critical amino acid changes that may be responsible for lambda max shifts of visual pigments. In this process, we may consider only highly conserved residues, simply because the evolutionary conservation often implies functional importance. Using such an "evolutionary model" as a convenient tool in designing mutagenesis experiments, we can test specific hypotheses on the molecular mechanisms that are responsible for color vision in vertebrates. Virtually any vertebrate opsin cDNA can be expressed in COS cells, reconstituted with 11-cis-retinal, and the lambda max values of the regenerated pigments can be measured rather easily. By constructing mutant pigments with desired amino acid changes and conducting the in vitro assay and comparing their lambda max values with those of corresponding wild-type pigments, we can elucidate the molecular mechanisms of lambda max shifts--and color vision--of vertebrates rigorously.

Amino Acid Sequence↗
PubMed2002

Color vision and occupational chemical exposures. II. Visual functions in non-exposed subjects.

This paper presents data on visual functions (visual acuity, contrast sensitivity, and several tests of color vision), in a group of 199 non-exposed healthy subjects with an even distribution over the age range 18-65 years, and sex. Although subjects with obvious congenital color vision deficiencies were removed from the analyses (four males), females were superior to males on several of the color vision tests applied. Age influenced visual acuity and contrast sensitivity, while color discrimination was less affected. Correlations between functions of the right and the left eye in the individual subjects were rather low, ranging from 0.40 to 0.73. Correlations between visual acuity and contrast sensitivity on the one hand and color discrimination ability on the other hand were still lower (r < 0.20). These low correlations between functions in the two eyes support the need for testing each eye separately.

Adolescent↗
PubMed2002

Color vision perception in the capuchin monkey (Cebus apella): a re-evaluation of procedures using Munsell papers.

In previous experiments based on color vision discrimination of Munsell chips, Pessoa et al. (Behav Brain Res 1997;89:285-8) presented evidence of trichromatic color vision in capuchin monkeys. However, the possibility of subjects using brightness cues was not eliminated. The purpose of the present study was to reassess the color perception in Cebus apella in a similar behavioral paradigm, but using a range of brightness values at each tested hue. We now report that male capuchins show a dichromatic behavior. The results are discussed in terms of the hypothesis of male dichromatism in the New World monkey, the biological role of color vision and cognitive abilities of capuchin monkeys.

Adult↗
PubMed1999

Prospects for trichromatic color vision in male Cebus monkeys.

Polymorphic color vision is characteristic of many species of New World monkey. A fundamental feature of the polymorphism is that male monkeys are routinely dichromatic. A recent paper describes an experiment in which Cebus monkeys were required to discriminate between pairs of Munsell color chips (Pessoa VF, Tavares MCH, Aguiar L, Gomes UR, Tomaz C. Color vision discrimination in the capuchin monkey Cebus apella: evidence for trichromaticity. Behav Brain Res 1997;89:285-288). The results were interpreted as demonstrating trichromatic color vision in male Cebus monkeys. An examination of the literature on Cebus. monkey photopigments and results from a replication of the discrimination experiment conducted with dichromatic human subjects cast doubt on this claim.

Animals↗
PubMed1998

Vision and vestibular adaptation.

This article summarizes six recent degree-of-freedom studies of visual-vestibular interaction during natural activities and relates the findings to canal-otolith interactions evaluated during eccentric axis rotations. Magnetic search coils were used to measure angular eye and head movements of young and elderly subjects. A flux gate magnetometer was used to measure three-dimensional head translation. Three activities were studied: standing quietly, walking in place, and running in place. Each activity was evaluated with three viewing conditions: a visible target viewed normally, a remembered target in darkness, and a visible target viewed with x2 binocular telescopic spectacles. Canal-otolith interaction was assessed with passive, whole-body, transient, and steady-state rotations in pitch and yaw at multiple frequencies about axes that were either oculocentric or eccentric to the eyes. For each rotational axis, subjects regarded visible and remembered targets located at various distances. Horizontal and vertical angular vestibulo-ocular reflexes were demonstrable in all subjects during standing, walking, and running. When only angular gains were considered, gains in both darkness and during normal vision were less than 1.0 and were generally lower in elderly than in young subjects. Magnified vision with x2 telescopic spectacles produced only small gain increases as compared with normal vision. During walking and running all subjects exhibited significant mediolateral and dorsoventral head translations that were antiphase locked to yaw and pitch head movements, respectively. These head translations and rotations have mutually compensating effects on gaze in a target plane for typical viewing distances and allow angular vestibulo-ocular reflex gains of less than 1.0 to be optimal for gaze stabilization during natural activities. During passive, whole-body eccentric pitch and yaw head rotations, vestibulo-ocular reflex gain was modulated as appropriate to stabilize gaze on targets at the distances used. This modulation was evident within the first 80 msec of onset of head movement, too early to be caused by immediate visual tracking. Modeling suggests a linear interaction between canal signals and otolith signals scaled by the inverse of target distance. Vestibulo-ocular reflex performance appears to be adapted to stabilize gaze during translational and rotational perturbations that occur during natural activities, as is appropriate for relevant target distances. Although immediate visual tracking contributes little to gaze stabilization during natural activities, visual requirements determine the performance of vestibulo-ocular reflexes arising from both canals and otoliths.

Adaptation, Physiological↗