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At least 109 records · Page 6Linked to original sources
PubMed1992

Primary hypothyroidism with pituitary enlargement and a visual field abnormality.

A 23 year old man presented with classical hypothyroidism of 9 years duration. This was associated with pituitary enlargement, documented on magnetic resonance imaging (MRI), and abnormal half-field visual evoked responses (VERs). Following the initiation of thyroxine therapy the pituitary enlargement and the VER abnormalities resolved. The final diagnosis was of primary hypothyroidism with secondary pituitary hyperplasia.

Adult↗
PubMed1986

The influence of visual field disorders on visual identification tasks.

Visual identification of shapes, figures, objects and faces was tested in a group of 26 patients with homonymous field defects due to unilateral "posterior" brain damage. In addition, a search test was used for evaluation of the effect of visual field loss on visual information acquisition. Of the patients, 5 performed entirely normally, i.e. errorless and within age-matched time limits, in all tests. The majority of patients (n = 15) also performed correctly but required significantly more time than normals. In contrast, 6 patients showed a rather specific impairment in visual identification tasks. It is argued that visual field loss per se does not impair visual identification but may affect visual search and, thus, information acquisition. Visual identification may be impaired, however, if brain damage involves the inferotemporal cortex.

Adult↗
PubMed1979

Static vs dynamic visual field evaluation; with emphasis on the utility of the Friedmann Visual Field Analyzer.

This paper contrasts static and dynamic perimetry, highlighting the advantages and disadvantages of each. A type of static perimetry, the Friedmann Visual Field Analyzer, is discussed in some detail. A clinical study, comparing the sensitivity of the Friedmann Visual Field Analyzer and B&L Autoplot in detecting field defects in known glaucoma patients, is presented. The results of this study support the notion that static fields (utilizing the FVFA) are significantly more sensitive than dynamic fields (utilizing the B&L Autoplot) in detecting field defects in known glaucoma patients.

Diagnostic Errors↗
PubMed1991

Visual field asymmetries in pattern discrimination: a sign of asymmetry in cortical visual field representation?

A visual field asymmetry is described relative to the discrimination of mirror symmetric bars with ramp-like luminance profiles. Along the vertical meridian the discrimination is better performed for patterns oriented parallel to the meridian than for patterns oriented orthogonally at all eccentricities tested (2-8 deg). Along the horizontal meridian, the preference for radially oriented stimuli is present at 2 deg from the fovea, but vanishes at larger eccentricities. The meridional asymmetry thus revealed psychophysically may reflect asymmetries in the representation of the vertical and horizontal meridians in the human visual cortex.

Discrimination, Psychological↗
PubMed1993

[The central visual field defects in low-tension glaucoma. A comparison of the central visual field defects in low-tension glaucoma with those in primary open angle glaucoma].

To discover if there is difference in central visual field damage between low-tension glaucoma (LTG) and primary open angle glaucoma (POAG) eyes, the data obtained with the 10-2 threshold program of the Humphrey visual field analyzer were analysed using logistic discriminant analysis. One hundred and four LTG eyes from 65 case (maximum IOP < or = 21 mmHg) and 48 POAG eyes from 34 cases (maximum IOP > or = 25 mmHg) with early to moderately advanced visual field damage were included. There was no significant difference in mean deviation (MD, STATPAC), refraction, or age between the 2 groups. The analysis demonstrated that an arcuate area in the upper central 5-10 degrees of the visual field was significantly more depressed in LTG than in POAG eyes.

Aged↗
PubMed2005

Spatial attention triggered by eye gaze enhances and speeds up visual processing in upper and lower visual fields beyond early striate visual processing.

OBJECTIVE: The detection of a lateralized visual target is faster when preceded by a face gazing to the location of this stimulus. Here we aimed to clarify the time-course of the visual processing modulated by these reflexive shifts of attention. METHODS: ERPs were measured on 16 subjects performing a speeded location task on a circular checkerboard. The checkerboard target appeared either on the left or right of the upper or lower visual field, and was preceded by a central face orienting its gaze obliquely to one of the four possible corner locations for the target to appear. RESULTS: Congruently cued targets were located faster than incongruently cued targets and were associated with larger and earlier occipital P1 (approximately 110 ms) and occipito-parieto-temporal N1 (approximately 150 ms) components. However, no such attentional modulations were found on the earlier C1 visual component, best observed with a negative polarity for upper visual field stimulations, and thought to originate largely from primary visual cortex. CONCLUSIONS AND SIGNIFICANCE: These results show that reflexive shifts of attention following oblique eye gaze to upper and lower visual fields increase and speed up the processing of visual information beyond the feedforward flow of information in primary visual cortex.

Adult↗
PubMed1988

Representation of the visual field in the second visual area in the Cebus monkey.

The representation of the visual field in the second visual area (V2) was reconstructed from multiunit visual responses and anatomical tracers. Receptive field plotting was performed during multiple recording sessions in seven Cebus apella monkeys under N2O/O2 and immobilized with pancuronium bromide. V2 forms a continuous belt of variable width around striate cortex (V1) except at the most anterior portion of the calcarine sulcus. In each hemisphere V2 contains a visuotopic representation of the contralateral visual hemifield. The representation of the vertical meridian is adjacent to that of V1 and forms the posterior border of V2. The representation of the fovea of V2 is adjacent to that of V1. The representation of the horizontal meridian (HM) is continuous with that of V1; then it splits to form the anterior border of V2, both dorsally and ventrally. The lower quadrant of the visual field is represented dorsally and the upper quadrant ventrally. The visual topography of V2 is coarser than that of V1. In V2, receptive fields corresponding to recording sites separated by a cortical distance of up to 4 mm may represent the same portion of the visual field. In three additional animals, combined injections of fluorescent tracers along the HM representation in V1 yielded two projection sites at the anterior border of V2. The split of the HM representation is estimated to occur at an eccentricity below 1 degree. Quantitative analysis showed that in V2 the representation of the central visual field is magnified relative to that of the periphery. The cortical magnification factor is greater along the isopolar dimension than along the isoeccentric one. Receptive field size in V2 increases with increasing eccentricity. In sections stained for myelin by the Heidenhein-Wöelcke method V2 can be distinguished from the surrounding cortex for most of its extent.

Animals↗
PubMed2005

Visual fields correlate better than visual acuity to severity of diabetic retinopathy.

AIMS/HYPOTHESIS: We compared the outcomes of perimetric and visual acuity tests in patients with diabetic retinopathy. METHODS: We examined 59 diabetic patients with different degrees of retinopathy using stereo fundus photography in accordance with the Early Treatment of Diabetic Retinopathy Study (ETDRS) and fluorescein angiography. Conventional white-on-white perimetry (WWP) and short wavelength automated perimetry (SWAP) were performed and analysed with reference to normal values. Visual acuity was measured with ETDRS charts. RESULTS: Regression analysis revealed that visual acuity was significantly associated with increasing severity of retinopathy according to the ETDRS scale when visual acuity was estimated by counting logarithm of minimum angle of resolution (LogMar) scores, but not when visual acuity was measured by the conventional reading of the smallest line that could be seen. Visual acuity decreased by 0.02 LogMar per ETDRS step (p=0.03). The degree of visual field loss was significantly associated with increasing severity of retinopathy according to the ETDRS scale, perimetric sensitivity decreasing by 0.44 dB per ETDRS step (p=0.0001) using WWP, and by 0.40 dB per ETDRS step (p=0.04) with SWAP. The size of the area of the foveal avascular zone and adjacent perifoveal intercapillary areas (PIAs) also affected the central visual field as obtained both by WWP (-2.6 dB/mm2, p=0.03), and by SWAP (-7.9 dB/mm2, p=0.002), but did not affect visual acuity. The regression model fit for peripheral retinopathy according to the ETDRS scale was better using WWP than SWAP or visual acuity, while SWAP testing was superior to both WWP and visual acuity when measuring effects caused by enlarged foveal avascular zones and PIAs. CONCLUSIONS/INTERPRETATION: Perimetry can provide more useful information than visual acuity on functional loss in diabetic retinopathy, particularly when the perifoveal capillary network is damaged.

Adult↗
PubMed2003

Visual field representations and locations of visual areas V1/2/3 in human visual cortex.

The position, surface area and visual field representation of human visual areas V1, V2 and V3 were measured using fMRI in 7 subjects (14 hemispheres). Cortical visual field maps of the central 12 deg were measured using rotating wedge and expanding ring stimuli. The boundaries between areas were identified using an automated procedure to fit an atlas of the expected visual field map to the data. All position and surface area measurements were made along the boundary between white matter and gray matter. The representation of the central 2 deg of visual field in areas V1, V2, V3 and hV4 spans about 2100 mm2 and is centered on the lateral-ventral aspect of the occipital lobes at Talairach coordinates -29, -78, -11 and 25, -80, -9. The mean area between the 2-deg and 12-deg eccentricities for the primary visual areas was: V1: 1470 mm2; V2: 1115 mm2; and V3: 819 mm2. The sizes of areas V1, V2 and V3 varied by about a factor of 2.5 across individuals; the sizes of V1 and V2 are significantly correlated within individuals, but there is a very low correlation between V1 and V3. These in vivo measurements of normal human retinotopic visual areas can be used as a reference for comparison to unusual cases involving developmental plasticity, recovery from injury, identifying homology with animal models, or analyzing the computational resources available within the visual pathways.

Brain Mapping↗
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↗
PubMed1992

Computer-assisted interpretation of visual fields in glaucoma.

Visual field abnormality is an important diagnostic sign in glaucoma. Therefore, the presence or absence of visual field loss most often strongly influences diagnostic and therapeutic decisions in glaucoma management. Interpretation of visual field results is often difficult, however. Physiological variability of perimetric sensitivity values contributes to these difficulties. It has been our aim to develop improved computer-assisted methods for the recognition of early glaucomatous field loss. Our approach has therefore been to design techniques that are highly sensitive to small but significant departures from normality. We have investigated normal physiological variability in perimetric results and combined the obtained knowledge with pathophysiological models which are sensitive to the spatial patterns of field loss commonly seen in glaucoma. Thus, we have devised probability scores in order to take the complex physiological variability into account, and developed a hemifield analysis and an arcuate cluster analysis based on the normal anatomy of the retinal nerve fibre layer. A fundamental approach in the collection of normative data and the selection of glaucoma cases used in this project has been to select subjects using non-perimetric criteria (except for the removal of large field defects). Our objective here was to reduce bias from pre-conceived ideas of visual fields. This approach was used for (1) empirical studies on physiological variability, (2) development of analysis methods, and (3) evaluation of such methods. Glaucoma patients were selected based on evaluations of optic disc appearance. Normal subjects were never eliminated on the basis of perimetric results alone. The new methods developed in these studies have significantly improved discrimination between normal and glaucomatous field results, as compared with previously available techniques. Our results indicated that the usage of probability scores was the main source of this improvement, and that the location of observed field abnormalities and spatial modelling were other important factors. Candidate methods which did not properly combine spatial and normative analyses resulted in false positive defects in the mid-periphery and/or underestimated paracentral glaucomatous field defects. Similar approaches based on classification of visual field results in terms of significances, and on recognition of specific spatial patterns of field loss could be used for other groups of diseases having visual field abnormality as an important diagnostic sign.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMedDate not supplied

Visual field indices for the nasal step: different calculation procedures and their correlation with the clinical classification of visual field defects.

We calculated normal values for the normal population of the Octopus G1 program (n = 836) and values for defective fields due to glaucoma and other diseases (n = 147) to determine indices for a nasal step in the interpretation of glaucomatous visual fields. We used different calculation procedures and correlated the results with the clinical evaluation of the visual field. All indices tested were able to detect and quantify nasal steps in defective fields and to separate them from normal findings (area under curve of Receiver Operating Characteristic curves 0.963 to 0.999). Indices calculated excluding sensitivity values of positions with the greatest distance from the horizontal meridian or weighting of sensitivity values according to their closeness to the horizontal meridian showed the best results (auc = 0.999). We can thus conclude that the calculation of an index for nasal step is a simple and effective adjunct to any interpretation system for visual fields.

Diagnosis, Computer-Assisted↗