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At least 1,405 records · Page 78Linked to original sources
PubMed1991

Contralateral visual field representation in area 17 of the cerebral cortex of the agouti: a comparison between the cortical magnification factor and retinal ganglion cell distribution.

The cortical representation of the contralateral visual field in area 17 of the agouti's brain was studied by multiunit recording. The borders of area 17 were determined by electrophysiological, cytoarchitectonic and myeloarchitectonic criteria. The results were plotted in flat, bidimensional representations of the cerebral cortex to minimize perspective distortions. The V1 map, a first order topological transformation of the visual field, shows a magnified representation of the horizontal meridian that corresponds to a retinal specialization, the visual streak. The visual field representation has asymmetries that are not directly related to the topography of the retinal ganglion cell density. Whereas the ganglion cell density shows a plateau along the visual streak, the areal cortical magnification factor is higher in the region that corresponds to the intersection of the horizontal and vertical meridians. This suggests functional specializations that are not obvious when one considers the distribution of the whole ganglion cell population but which might be related to the distribution of specific ganglion cell classes.

Animals↗
PubMed1985

[Studies with the computer-guided perimeter "Peritest" on the effect of Cosaldon A+E on glaucomatous visual field defects].

Investigations on 114 glaucoma patients with the computerized perimeter 'Peritest' showed that treatment with Cosaldon A + E resulted in a decrease or elimination of visual field defects. Favourable results were also obtained with statistical significance for severe visual field defects of defect class greater than or equal to 2.0 log U. Treatment time was generally 4-5 months. During the first 6-10 weeks of treatment strong fluctuations were observed regarding individual sensitivity of light perception as well as number of defect positions.

Adult↗
PubMed1979

Oculographic automatic perimetry in glaucoma visual field screening: a clinical study--preliminary results in glaucoma patients.

An automatic method for visual field screening using oculographic potentials have been evaluated on 12 eyes of 65 glaucoma patients. The oculographic perimeter records, plotting the central 22 degrees of the visual field, have been compared with Armaly's manual selective perimetry performed by the Goldman Perimeter. In spite of different testing standards of both methods, equivalent pathological field defects were demonstrated in 72% of the eyes following the first examination. Successive plottings with the automatic method improved the results considerably. The method has proved to be a reliable objective automatic test. Further development is suggested through which the procedure might be useful for glaucoma screening in the future.

Adolescent↗
PubMed1994

Longterm effect of topical beta-blockers on intraocular pressure and visual field sensitivity in ocular hypertension and chronic open-angle glaucoma.

In a prospective, randomized study, nineteen patients with ocular hypertension (n = 14) or chronic open-angle glaucoma (n = 5) were treated with either betaxolol 0.5% or timolol 0.5% in both eyes twice daily. Visual field sensitivity and intraocular pressure were assessed with the Octopus perimeter (program G1) and applanation tonometry, respectively, at 3, 6, 12, 24, 36, and 48 months during treatment. Four of the nineteen patients (two timolol-treated and two betaxolol-treated) were lost to follow-up after the 36-month examination. Whereas both drugs reduced the intraocular pressure, the decrease in the timolol-treated group was statistically more pronounced than in the betaxolol-treated group at month 3, 6, and 48 (p < 0.03). In both treatment groups, the visual field mean sensitivity (MS) index decreased slightly during the first six months of treatment, but remained so only in the timolol-treated group at all subsequent examinations. In the betaxolol-treated group, there was a statistically significant increase in MS at the 12, 24, 36, and 48 month visits (p < 0.01). These findings suggest that factors other than IOP alone may determine visual field outcome.

Administration, Topical↗
PubMed2001

Near-field visual acuity in Japanese jungle crows (Corvus macrorhynchos).

The near-field visual acuity of three Japanese jungle crows (Corvus macrorhynchos) was determined by means of operant conditioning. The task was discrimination of grating stimuli, and the threshold was measured by up-and-down method between sessions. To keep observing distance constant, a photo sensor was used and the head position was behaviorally fixed. The average visual acuity was 8.4 cycles/degree. When compared with other birds, this result is better than that of pigeons, and worse than that of predators.

Animals↗
PubMed1990

Visual field differences in the magnitude of the Oppel-Kundt illusion vary with processing time.

Three experiments were performed to investigate hemispheric differences in susceptibility to the Oppel-Kundt illusion presented tachistoscopically to the two visual hemifields. Experiment 1 used a successive comparison mode, in which 16 undergraduate students indicated whether the second of two successive extents looked shorter or longer than the first. Experiment 2 (20 under-graduates) and Experiment 3 (1 commissurotomy patient) required judgments of two extents presented simultaneously. The first experiment found no significant visual field differences, although females were more susceptible than males. In the second experiment, the illusion magnitude was greater in the left visual field, and in the third experiment, it was greater in the right visual field. Post hoc analyses resolve the conflicting results and show that in all three experiments, the susceptibility of the right hemisphere declined more than that of the left hemisphere during illusion processing. An interpretation is offered in terms of two parallel processes, one that is fast, uses feature extraction, and is performed more effectively in the left hemisphere, and one that is slow, uses visuospatial analysis to compute distances between parts of the illusion figure, and is performed more effectively in the right hemisphere.

Adolescent↗
PubMed2003

Patterns of glaucomatous visual field defects in an older population: the Blue Mountains Eye Study.

This report aims to describe the frequency of different patterns of visual field loss in open-angle glaucoma (OAG). The Blue Mountains Eye Study examined 3654 persons (aged 49+) during 1992-1994. Humphrey supra-threshold visual fields were performed in 88.9%. Those classified as glaucoma suspects had 30-2 full-threshold fields (9.2%). Of OAG cases (n = 108) with field tests in both eyes (n = 97), unilateral defects were present in 49 (50.5%) and bilateral in 48 (49.5%). Advanced field loss was found in 16 (15.4%) subjects and in 22 (10.9%) eyes, with bilateral loss present in 6 (6.2%) cases. Of all eyes of OAG cases (n = 201), 49 (24.4%) had no defects, 52 (25.9%) upper, 61 (30.3%) lower, and 17 (8.5%) had combined upper and lower loss. Of the upper and lower cases (n = 113), the types of defects included nasal step (36), arcuate (26), nasal plus arcuate (26), and hemispherical defects (25). Of subjects with fields in at least one eye (n = 104), there was a similar proportion in the worse eye of upper defects (28.8%), lower (31.7%), and combined upper and lower (24.0%). Undiagnosed OAG was more frequent in unilateral (65.3%) than bilateral (34.7%) cases (P = 0.003). This study reports the pattern of typical glaucomatous field loss in an older Australian population.

Aged↗
PubMed1994

Effectiveness of unsupervised oculokinetic perimetry for detecting glaucomatous visual field defects.

Oculokinetic perimetry (OKP) is a simple, inexpensive technique which was introduced primarily to promote more widespread use of visual field screening for glaucoma. The effectiveness of unsupervised OKP screening was evaluated using 145 non-glaucomatous patients and 64 patients with previously undiagnosed primary open angle glaucoma. Glaucoma cases were validated by the extended 132 point program on the Henson CFS2000 instrument. Both sample populations were representative of patients presenting for primary vision care. The effectiveness of the 26 point OKP test was compared with the 26 point Henson screening program. The results suggest that, in contrast to the Henson screening test (sensitivity = 85.1%, specificity = 93.8%), unsupervised OKP screening (sensitivity = 25.0%, specificity = 93.6%) has limited effectiveness for detecting glaucomatous visual field defects.

Adult↗
PubMed1986

Fully automated screening procedure for early detection of visual field defects.

A major problem in mass screening for glaucoma is the substantial time required to detect areas of depressed visual sensitivity, scotoma. We have developed a novel instrument for testing rapidly and automatically the sensitivity of the visual field. The patient views a large CRT screen on which up to four luminous points are presented in a prearranged pattern. The patient's vocal response is a number from zero to four, the number of stimulus points that he has observed, which is recognized by the controller and recorded. A series of 90 such patterns is presented sequentially, giving a 288 points visual field test, at the conclusion of which a hard copy probabilistic map of the retinal location of scotoma is drawn. The examination procedure is much faster than that using conventional 'automatic' tests and its results are almost identical with those from two commercial instruments with which our experimental 'perimeter' has been compared. Initial clinical trials are very encouraging.

Glaucoma↗
PubMed2006

Resolution of complex motion detectors in the central and peripheral visual field.

We examine how local direction signals are combined to compute the focus of radial motion (FRM) in random dot patterns and examine how this process changes across the visual field. Equivalent noise analysis showed that a loss in FRM accuracy was largely attributable to an increase in local motion detector noise with little or no change in efficiency across the visual field. The minimum separation for discriminating the foci of two overlapping optic flow patterns increased in the periphery faster than predicted from the resolution for a single FRM. This behavior requires that observers average numerous local velocities to estimate the FRM, which enables resistance to internal and external noise and endows the system with the property of position invariance. However, such pooling limits the precision with which multiple looming objects can be discriminated, especially in the peripheral visual field.

Differential Threshold↗
PubMed1991

Stress induced reversal of a lexical divided visual-field asymmetry accompanied by retarded electrodermal habituation.

An interplay of structural and dynamic process cerebral asymmetries was investigated with medical students in a within subject design. Structural asymmetries were investigated with a divided visual-field lexical task and dynamic asymmetries through the influence of anxiety induced by examination stress and compared with a less stressful occasion. The validity of the stressful life event was substantiated by measures of non-specific electrodermal responses and a frustration-tension subscale from an anxiety questionnaire. The order of testing was counterbalanced. Under stress there was a shift in hemispheric balance such that a right visual-field advantage gave way to a left visual-field advantage. Variations in hemispheric processing were more pronounced in the right hemisphere in which performance was enhanced under stress.

Adult↗
PubMed1993

Visual fields with protective eyewear.

Sports-related eye injuries are quite common, yet the number of athletes who utilize protective eyewear is extremely low. The purpose of this study was to determine if there is a significant visual field loss associated with wearing eye protection. One of the authors was subjected to standard kinetic visual field testing with and without eye goggles. No significant difference was revealed. Physicians, physical therapists, and trainers should promote the use of protective eyewear and reassure athletes that they will not lose visual field.

Athletic Injuries↗
PubMed1994

[Visual field defects in normal tension glaucoma and primary open angle glaucoma. Comparison in the late stage of disease].

To compare the visual field defects in the late stage of disease between normal-tension glaucoma (NTG) and primary open angle glaucoma (POAG), measurements taken with the 30-2 and 10-2 threshold program of the Humphrey Visual Field Analyzer were analysed by statistical methods including logistic discriminant analysis. Thirty-four eyes of 34 NTG cases and 63 eyes of 63 POAG cases whose mean deviation (MD) given by STATPAC was equal to or less than -15 dB were included and there was no significant difference in MD, refraction, or age between the two groups. The analyses demonstrated that the upper arcuate area was significantly more depressed in POAG and the inferior Bjerrum area was significantly more depressed in NTG eyes. It was also shown that the lower papillo-macular area was less affected in NTG than in POAG eyes.

Discriminant Analysis↗
PubMed1999

Visual fields in Short-toed Eagles, Circaetus gallicus (Accipitridae), and the function of binocularity in birds.

Visual fields were determined in alert restrained birds using an ophthalmoscopic reflex technique. The region of binocular overlap is relatively small: maximum width of 20 degrees occurs approximately 15 degrees below the horizontal, and the field extends vertically through 80 degrees with the bill tip placed close to the centre. Monocular field width in the horizontal plane is 139 degrees, and the field is asymmetric about the optic axis. The cyclopean field extends through 260 degrees, and the blind area above and behind the head reaches maximum width of 100 degrees close to the horizontal. At the frontal margins of the monocular field the retinal and optical fields do not coincide; the retinal field margin lies approximately 10 degrees inside the optical margin. This gives rise to an apparent binocular field that is twice the width of the functional binocular field. Interspecific comparisons show that the binocular field of Short-toed Eagles is similar in shape and size to those of bird species that differ markedly in phylogeny, ecology, foraging technique, and eye size. This suggests that these relatively narrow binocular fields are a convergent feature of birds whose foraging is guided by visual cues irrespective of whether items are taken directly in the bill or in the feet, as in eagles, and irrespective of the size and shape of the monocular and cyclopean visual fields. It is argued that binocular vision in birds results from the requirement for each monocular field to extend contralaterally to embody a portion of the optical flow field which is radially symmetrical about the direction of travel. This is in contrast to functional explanations of binocularity, such as those concerned with stereopsis, which present it as a means of extracting higher order information through the combination of two monocular images of the same portion of a scene.

Animals↗
PubMedDate not supplied

Sensitivity to full-field visual movement compatible with head rotation: variations among axes of rotation.

Movement detection thresholds for full-field visual motion about various axes were measured in three subjects using a two-alternative forced-choice staircase method. Thresholds for 1-s exposures to rotation about different rotation axes varied significantly over the range 0.139 +/- 0.05 deg/s to 0.463 +/- 0.166 deg/s. The highest thresholds were found in response to rotation about axes closely aligned to the line of sight. Variations among the thresholds for different axes could not be explained by different movement patterns in the fovea or variations in motion sensitivity with eccentricity. The variations can be well simulated by a three-channel model for coding the axis and velocity of full-field visual motion. A three-channel visual coding system would be well suited for extracting information about self-rotation from a complex pattern of retinal image motion containing components due to both rotation and translation. A three-channel visual motion system would also be readily compatible with vestibular information concerning self-rotation arising from the semicircular canals.

Adult↗
PubMed1998

Is the rod visual field temporally homogeneous?

Cone vision has been shown to be temporally inhomogeneous across the visual field. In the periphery, contrast sensitivity is lower for low temporal frequencies and higher for high temporal frequencies. Here we ask a similar question for rod vision at mesopic luminances. Isolation is obtained by testing a well documented rod monochromat. We show that the rod visual field exhibits only a modest degree of temporal inhomogeneity.

Color Vision Defects↗
PubMed1989

Contrast sensitivity versus static visual field testing during experimental elevation of intraocular pressure.

Contrast sensitivity testing has been recommended as a more sensitive indicator of early visual loss than visual field testing. Using gravity inversion to induce an intraocular pressure rise, we performed contrast sensitivity testing on each eye of 10 normal subjects in the upright and inverted positions. Contrast sensitivity results were not altered in the head-down position, even though in 5 of the 10 subjects (7 of 20 eyes), visual field alterations on static perimetry were elicited during inversion. In both of these evaluations, the subject's results in the upright position served as the control, freeing us from reliance upon age-matched populations. We conclude that precise measurement of static thresholds with automated perimetry is more sensitive than routine contrast sensitivity testing in detecting visual dysfunction related to transient acute elevations of intraocular pressure.

Adult↗
PubMedDate not supplied

Automatic perimetry and visual P300: differences between upper and lower visual fields stimulation in healthy subjects.

Human visual-evoked potentials (VEPs) from upper and lower hemifield stimulation are thought to reflect the anatomical and functional differences between the hemiretinas and corresponding visual pathways. Conflicting results have, however, been reported in topographic studies on the putative cortical generators. We have estimated by automatic perimetry (Octopus 2000R, Program 32) and compared the sensitivity thresholds of lower and upper hemifields of the retina in 12 healthy subjects with no history or evidence of visual or neurological diseases. A visual P3 that is linked to cognitive function was recorded in an odd-ball paradigm with presentation of high-contrast checkerboards at two different spatial frequencies at 20 degrees eccentricity in each hemifield. VEP and P3 were recorded at O1 and O2 and at Cz according to the 10/20 international system. Lower sensitivity thresholds were found, and higher VEP and event-related potential (ERP) amplitude values were obtained when stimulating the lower, compared with the upper, visual hemifield. The results are consistent with previous findings and anatomical and physiological evidence in animals and man. Interactions between perceptive process in the visual system and higher cognitive functions are a possible explanation for this finding.

Adult↗