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At least 1,477 records · Page 82Linked to original sources
PubMed1991

Visual-field asymmetry in face recognition as a function of face discriminability and interstimulus interval.

Reaction times were measured for recognizing laterally presented faces as a function of two levels of face discriminability and three interstimulus-interval lengths between pairs of successively presented faces. Contrary to many face-recognition studies, no left visual-field/right-hemisphere advantage was observed for the recognition task. Instead, a right visual-field/left-hemisphere advantage occurred at the longest interstimulus interval (500 msec.) on trials on which faces were different and at the shortest interstimulus interval (5 msec.) on trials on which the faces were identical. It appears that visual-field asymmetries in face recognition may vary due to the characteristics of the stimuli and procedures used in face-recognition studies.

Brain↗
PubMed1991

Perceptual reference frames and visual field asymmetry for verbal processing.

Two experiments investigated the role of perceptual reference frames in producing visual field asymmetries for the recognition of consonant-vowel-consonant (CVC) nonsense syllables. In an upright stimulus display condition, both quantitative and qualitative visual field asymmetries replicated those obtained in earlier studies of CVC identification. When the stimulus displays were rotated 90 degrees clockwise or counterclockwise, there were no effects of presenting the CVC in relative LVF vs relative RVF stimulus locations. The contrast between results in the upright and rotated stimulus display conditions indicates that the LVF/RVF differences in the upright displays are attributable to the position of the CVC relative to the fovea, rather than relative to the perceptual reference frame. This finding is consistent with the interpretation that LVF/RVF differences in the upright condition are attributable to hemispheric differences in the processing of linguistic/phonetic information.

Adult↗
PubMed2005

Visual field asymmetries in selective attention: evidence from a modified search paradigm.

The present study investigated visual field differences in selective attention. Five stimuli were briefly presented and subjects were asked to identify a predefined target. The target/distractor physical similarity varied systematically (low, medium or high) in order to encourage attentional resolving. Right/left hemifield differences were examined in Experiment 1, temporal/nasal hemifield differences in Experiment 2, and upper/lower hemifield differences in Experiment 3. Visual field differences were found only in Experiment 1 suggesting a left/right hemispheric asymmetry in selective attention. These asymmetries appear with increasing stimuli similarity, and suggest that each hemisphere gets involved when attentional selection cannot be carried out without the mode of information processing that characterizes that hemisphere. The absence of other hemifield asymmetries is not in favor of neither a subcortical, nor a specific superior occipito-parietal involvement in attentional resolving and selectivity.

Adult↗
PubMed2004

Visual field changes after cataract extraction: the AGIS experience.

PURPOSE: To test the hypothesis that cataract extraction in glaucomatous eyes improves overall sensitivity of visual function without affecting the size or depth of glaucomatous scotomas. DESIGN: Experimental study with no control group. METHODS: One hundred fifty-eight eyes (of 140 patients) from the Advanced Glaucoma Intervention Study with at least two reliable visual fields within a year both before and after cataract surgery were included. Average mean deviation (MD), pattern standard deviation (PSD), and corrected pattern standard deviation (CPSD) were compared before and after cataract extraction. To evaluate changes in scotoma size, the number of abnormal points (P < .05) on the pattern deviation plot was compared before and after surgery. We described an index ("scotoma depth index") to investigate changes of scotoma depth after surgery. RESULTS: Mean values for MD, PSD, and CPSD were -13.2, 6.4, and 5.9 dB before and -11.9, 6.8, and 6.2 dB after cataract surgery (P < or = .001 for all comparisons). Mean (+/- SD) number of abnormal points on pattern deviation plot was 26.7 +/- 9.4 and 27.5 +/- 9.0 before and after cataract surgery, respectively (P = .02). Scotoma depth index did not change after cataract extraction (-19.3 vs -19.2 dB, P = .90). CONCLUSIONS: Cataract extraction caused generalized improvement of the visual field, which was most marked in eyes with less advanced glaucomatous damage. Although the enlargement of scotomas was statistically significant, it was not clinically meaningful. No improvement of sensitivity was observed in the deepest part of the scotomas.

Aged↗
PubMed1979

The role of the corpus callosum in the development of interocular eye alignment and the organization of the visual field in the cat.

In young cats, the posterior portion of the corpus callosum was sectioned 13--29 days after birth. The animal's eyes were photographed at weekly intervals for six months using the pupil-reflex method. From the corneal reflection evident in the photographs the degree of alignment for the optical axes of each cat was estimated (Sherman, 1972). The 17 experimental cats all showed a significant tendency toward permanent divergent strabismus, as compared to six normal cats. The limits of the visual field were determined for both groups of cats using a perimetry technique similar to that of Sprague and Meikle (1965) and Sherman (1973). With one eye open normal cats responsed from 90 degrees ipsilateral to 45 degrees past the vertical midline into the contralateral visual field. With either eye the experimental cats responsed from 90 degrees ipsilateral to approximately the vertical midline. The loss of visual responsiveness is within the contralateral region of the normally binocular zone. Three cats received the same operation at 9, 13, or 20 months old. Eye alignment and visual field perimetry were unaffected by the surgery. It is not known whether the observed abnormalities result from arrested development, or disruption of intrinsically determined ocular alignment.

Animals↗
PubMed1999

Relationship between parapapillary atrophy and visual field abnormality in primary open-angle glaucoma.

PURPOSE: To investigate the relationship of parapapillary atrophy measured by confocal scanning laser ophthalmoscopy to visual field sensitivity measured with standard automated perimetry and short-wavelength automated perimetry in patients with primary open-angle glaucoma. METHODS: Forty-seven eyes of 47 primary open-angle glaucoma patients with increased intraocular pressure (> or = 22 mm Hg) were enrolled. Optic nerve head topography and parapapillary atrophy (beta and alpha zones) were assessed by confocal scanning laser ophthalmoscopy. Mean deviation and corrected pattern SD were assessed with standard automated perimetry and short-wavelength automated perimetry. RESULTS: Beta and alpha zones were found in 23 (49%) and 47 (100%) eyes with primary open-angle glaucoma, respectively. The area of beta zone showed significant correlations with MD of standard automated perimetry, corrected pattern SD of standard automated perimetry, and corrected pattern SD of short-wavelength automated perimetry (Spearman r = -0.366, P = .012; r = 0.327, P = .025; and r = 0.436, P = .002, respectively). The area of alpha zone showed a significant correlation with mean deviation of standard automated perimetry (r = -0.378, P = .009). Mean MD of standard automated perimetry, mean corrected pattern SD of standard automated perimetry, and mean corrected pattern SD of short-wavelength automated perimetry were significantly worse in eyes with beta zone than in eyes without beta zone. CONCLUSIONS: Parapapillary atrophy measured by confocal scanning laser ophthalmoscopy, especially beta zone, is associated with glaucomatous visual field loss demonstrated by standard automated perimetry and short-wavelength automated perimetry.

Adult↗
PubMed1999

Effects of oral brovincamine on visual field damage in patients with normal-tension glaucoma with low-normal intraocular pressure.

PURPOSE: To prospectively study the effect of oral brovincamine, a relatively selective cerebral vasodilator, on further deterioration of visual field in patients with normal-tension glaucoma (NTG) with low-normal intraocular pressure (IOP). METHODS: Fifty-two patients with NTG (average age 57.7 years) with an IOP that was consistently less than 15 mmHg were randomly assigned to receive oral brovincamine (20 mg three times daily) or to an untreated control group. The groups were prospectively followed for 2 years with visual field examinations every 4 months, using the 30-2 Humphrey perimeter program. Changes in mean deviation (MD), corrected pattern standard deviation (CPSD), and total deviation (TD) at 74 test points were analyzed using regression analysis with linear mixed model. Data from one eye without media opacity of each subject were analyzed. RESULTS: There were no differences between groups in age; sex distribution; refraction; blood pressure; baseline IOP; MD, CPSD, or TD at each point. Changes in MD (standard error [SE]) during the study period were -0.778 (0.178) and -0.071 (0.195) dB/year in the control and brovincamine groups, respectively; change in the control group was significantly more negative than in the brovincamine group. Change in CPSD (SE) was 0.032 (0.015) and 0.004 (0.016) dB/year in the control and brovincamine groups, respectively. Change in the control group was significantly positive, but the intergroup difference was not significant. Change in TD was significantly negative at six test points in the control group, whereas no points showed a significant trend in the brovincamine group; the intergroup difference was significant. The average IOP was 13.2 mmHg and 13.1 mmHg in the control and brovincamine groups, respectively, and there was no significant intergroup difference. CONCLUSION: Oral brovincamine may retard further visual field deterioration in patients with NTG who have low-normal IOP.

Administration, Oral↗
PubMed1975

Bitemporal visual field defects in presumed multiple sclerosis.

Three patients with presumed multiple sclerosis had bitemporal hemianopia mimicking that caused by parasellar tumors; the visual loss was probably due to a plaque within the chiasm. The diagnosis of multiple sclerosis was made on the basis of a history of relapse and remission, signs and symptoms indicating involvement of different levels of the central nervous system, and normal neuroradiological studies. Extensive neuroradiological studies may be delayed or omitted in patients with established multiple sclerosis and nonprogressive bitemporal visual field defects if central visual acuity is not greatly reduced.

Adolescent↗
PubMed2004

Illusory motion reversal is caused by rivalry, not by perceptual snapshots of the visual field.

In stroboscopic conditions--such as motion pictures--rotating objects may appear to rotate in the reverse direction due to under-sampling (aliasing). A seemingly similar phenomenon occurs in constant sunlight, which has been taken as evidence that the visual system processes discrete "snapshots" of the outside world. But if snapshots are indeed taken of the visual field, then when a rotating drum appears to transiently reverse direction, its mirror image should always appeared to reverse direction simultaneously. Contrary to this hypothesis, we found that when observers watched a rotating drum and its mirror image, almost all illusory motion reversals occurred for only one image at a time. This result indicates that the motion reversal illusion cannot be explained by snapshots of the visual field. The same result is found when the two images are presented within one visual hemifield, further ruling out the possibility that discrete sampling of the visual field occurs separately in each hemisphere. The frequency distribution of illusory reversal durations approximates a gamma distribution, suggesting perceptual rivalry as a better explanation for illusory motion reversal. After adaptation of motion detectors coding for the correct direction, the activity of motion-sensitive neurons coding for motion in the reverse direction may intermittently become dominant and drive the perception of motion.

Humans↗
PubMed2004

Optic disc topography as measured by confocal scanning laser ophthalmoscopy and visual field loss in Japanese patients with primary open-angle or normal-tension glaucoma.

PURPOSE: To determine whether differences in the optic disc topography and those in the relation between the optic disc topography and visual field indices exist between Japanese patients with primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG). METHODS: The study included consecutive Japanese patients with POAG (n = 60) or NTG (n = 60). Using the Heidelberg Retina Tomograph (HRT), we measured disc area, cup area, cup-to-disc area ratio, rim area, cup volume, rim volume, cup shape measure, and height variation contour. Each HRT parameter was measured in the total optic disc and in its four 90 degree quadrants (superior, temporal, inferior, and nasal). The mean deviation for the entire field and the sum of the total deviation values corresponding to each optic disc quadrant were calculated using the Humphrey full-threshold 30-2 program. RESULTS: No significant differences were found between the POAG and NTG groups for any HRT parameter either globally or regionally. There were no significant differences between the two groups in the correlation coefficients between any HRT parameter and the corresponding visual field indices either globally or regionally. CONCLUSION: No significant differences were apparent between Japanese patients with POAG and NTG both in the optic disc parameters as measured by HRT and in the degree of correlation between HRT parameter and the corresponding visual field indices.

Female↗
PubMed1989

Behavioral control of visual field screening using a microcomputer.

A computer algorithm is described which automatically controls the presentation of visual field targets and analyzes the subject's responses. Data relating to the procedure's reliability and validity are reported along with experience using it with normal subjects on an IBM PC compatible. Suggestions are made for the further development of the microcomputer approach to visual field investigations.

Algorithms↗
PubMed1986

Hemifield pattern-reversal visual evoked potentials (VEPs) in retrochiasmal lesions with homonymous visual field defect.

This study was designed to examine the clinical significance and the reliability of hemifield pattern reversal VEPs in the assessment of homonymous visual field defects due to retrochiasmal lesions. 13 patients with traumatic, neoplastic or ischemic lesions of the cerebral parenchyma, and 18 normal subjects were studied. The results show that amplitude asymmetries over 4 microV (between responses evoked by right and left hemifield stimulation, recorded ipsilaterally to the stimulated hemifield) are clinically relevant for hemianopic visual field defect. Significant correlations were found between the VEP features and the site of the damage: lesions of the occipital cortex were generally found to cause more pronounced bioelectrical abnormalities than those due to lesions affecting the visual pathways, with cortical sparing.

Adolescent↗
PubMed1981

Visual field defects.

There are four classic types of visual field defects. Altitudinal field defects in which the defect is present above or below the horizontal midline are usually associated with ocular abnormalities. A central scotoma is characteristic of optic nerve disease of macular disease. A bitemporal hemianopia signifies optic chiasm disease and is most frequently associated with pituitary tumors. With homonymous hemianopia, the same portion of the field is absent in both eyes, and is found with lesions behind the chiasm.

Eye↗
PubMed1990

The influence of a social dose of alcohol on the central visual field.

The influence of a socially acceptable dose of alcohol (mean blood alcohol level approximately 90 minutes after ingestion 69.5 mg%; SE 6.20 mg%) on the central visual field as determined by automated static perimetry was investigated in 17 female subjects (17 eyes) trained in automated perimetry (mean age 22.5 years, SE 1.29 years). Central visual field examination was undertaken on the right eye with program 30-2 (stimulus size III) of the Humphrey Field Analyser 630, using a simple cross-over placebo design. Alcohol produced a small (1.0 dB) but statistically significant decrease in the mean deviation (P = 0.002) and small increases (0.6 dB) in the pattern and corrected pattern standard deviations (P = 0.003 and P = 0.046, respectively). The number of stimulus presentations increased by 6% (P = 0.006) and the number of false-negative responses also increased (P = 0.019), indicating impaired patient response. Attenuation of sensitivity as a result of alcohol increased with the increase in eccentricity (P = 0.046) independently of the meridian (P = 0.068) from a mean of 0.8 dB at 3 degrees eccentricity to 1.84 dB at 27 degrees.

Adult↗
PubMed1992

The effects of Kanji attributes on visual field differences: examination with lexical decision, naming and semantic classification tasks.

Using three experimental tasks (lexical decision, naming and semantic classification), the relative contribution of various Kanji attributes in left and right visual field recognition was examined. The results showed that first, factors contributing to the left visual field processing of Kanji differed depending on the level of processing; second, in an early stage of processing, perceptual attributes such as the number of strokes was a strong contributing factor; and third, in a later stage both perceptual- and imagery-related attributes contributed strongly to left visual field or right hemisphere processing.

Discrimination Learning↗
PubMed1982

Automated visual field screening in the flying Dutch population.

Results of automated perimetry (Fieldmaster 200, Synemed) in 1,000 subjects are described. In 17 subjects (1.7%) a serious field defect was found. In 9 subjects (0.9%) aspecific defects were found. Computer aided perimetry was found to give reliable results compared with kinetic perimetry. Since the visual field is of the utmost importance in aviation, while mass conventional visual field screening is not possible, it is suggested that use should be made of automated perimetry testing.

Adult↗
PubMed2005

Visual fields in flamingos: chick-feeding versus filter-feeding.

In birds, the position and extent of the region of binocular vision appears to be determined by feeding ecology. Of prime importance is the degree to which vision is used for the precise control of bill position when pecking or lunging at prey. In birds that do not require such precision (probe and filter-feeders), the bill falls outside the binocular field, which extends above and behind the head, thus providing comprehensive visual coverage. Flamingos Phoenicopteridae are highly specialised filter-feeders. They employ a unique technique that does not require accurate bill positioning in which the inverted head is placed between the feet. Feeding flamingos often walk forwards with the head pointing "backwards". Here we show that in Lesser Flamingos Phoeniconaias minor visual fields are in fact the same as those of birds that feed by precision pecking and that feeding flamingos are blind in the direction of their walking. We suggest that this is due to the requirement for accurate bill placement when flamingos feed their chicks with "crop-milk", and possibly when building their nest. We propose that chick-feeding may be the ultimate determinant of visual field topography in birds, not feeding ecology.

Animal Feed↗
PubMed1983

Identification of glaucomatous visual field defects from examination of monocular photographs of the optic disc.

A study was carried out of monocular disc photographs from 33 eyes for which the visual fields on both static profile and kinetic perimetry has been performed. Physical signs looked for at the optic disc included thinning of the neuroretinal rim, angulation of retinal vessels, extension of laminar dots, undercutting of the neuroretinal rim, and absence and pallor of the neuroretinal rim. These signs together proved more accurate than kinetic Goldmann perimetry in identifying the presence of glaucomatous visual field defect. Of these signs angulation of the retinal vessels was the one most consistently present.

Glaucoma↗