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PubMed1988

Visual field differences in the processing of numerical stimuli.

Twenty-four right-handed subjects received random presentations of the numbers 1-6 in the form of words, digits, and dot patterns, to the left and right visual fields. Accuracy and reaction time were recorded for an odd-even judgment requiring a manual response. A significant stimulus type of visual field interaction was obtained, with words showing a left-hemisphere advantage and digits and dot patterns showing a right-hemisphere advantage. This pattern supports Coltheart's (1980, Deep dyslexia: A right hemisphere hypothesis, In M. Coltheart, K. Patterson, & J.C. Marshall (Eds.), Deep dyslexia, London: Routledge & Kegan Paul) right hemisphere reading hypothesis, which suggests that the left hemisphere's general advantage in processing linguistic material may be specific to stimuli which involve phonological processing. When phonological processing is not possible (e.g., for arabic digits and other ideographic orthographies), the right hemisphere may have an advantage because of its superior visuospatial processing capabilities.

Cerebral Cortex↗
PubMed1985

Refractive sectors in the visual field of the pigeon eye.

Scheiner's principle has been used in electroretinographic optometry to refract the photoreceptor plane in different regions of the visual field of the pigeon eye. Along the horizon and in the upper visual field the eye is emmetropic, or nearly so. Below the horizon the eye becomes progressively more myopic at more negative elevations, refractive state falling to -5D at -90 deg. Lower field myopia is not an artifact of oblique astigmatism, nor of an aberration symmetrical about the optical axis. It is suggested that lower field myopia is a biological adaptation suited to keep the photoreceptors in the upper retina conjugate with the ground. Refractive state below the horizon can be fitted with a sine function by varying a parameter H (eye-ground height). The value of H agrees well with directly measured eye-ground height.

Animals↗
PubMed2002

Normal readers have an upper visual field advantage in change detection.

The ability to detect change has not been well studied in children.A research paradigm was used involving search for a change made to one of four letter targets, presented twice, with a gap of 250 ms.Sixty-one schoolchildren, aged 7.3 - 12.9 years,participated in the study. The duration of the first presentation was such that each child was detecting change at a rate of 71% correct. The mean duration was 0.91 s (SD = 0.58 s),with older children not significantly faster in detecting change. In the second phase, using the duration established in the first phase, the effect of cue condition on detection was studied. An upper visual field advantage for change detection was clearly evident for un-cued trials. The most likely explanation derives from the masking produced by the reappearance of the four targets, which interferes with the process of change detection. The greater dorsal pathway representation of the lower visual field implies greater masking there, yielding better change detection in the upper visual field.

Child↗
PubMed2003

[A 65-year-old woman with progressive loss of vision and visual field defects].

We report a 65-year-old Japanese lady who suffered from progressive loss of vision and visual field defect. She was well until her 61 years of the age in November of 1999, when she was found to have bitemporal hemianopsia. A small enhancing mass lesion was found in the chiasmatic region. She was treated with steroid and she noted marked improvement in her visual field defects. In August of 2000, she noted disturbance of gait. Cranial MRI revealed a mass in the right midbrain extending into the hypothalamic and thalamic regions. She was again treated with steroid with marked improvement. However, in November of 2001, she started to show somnolence and diabetes insipidus. She was treated with steroid, nasal desmopressin, and insulin for her steroid induced diabetes mellitus. Cranial CT scan showed a large enhancing lesion involving the entire midbrain, hypothalamus, and the thalamic regions. She developed respiratory arrest on July 15, 2001 and was pronounced dead. She was discussed in a neurological CPC and the chief discussant arrived at the conclusion that the patient had a primary malignant lymphoma of the brain. Clinical diagnosis in the early stage of her disease was neurosarcoidosis. Post-mortem examination revealed a mass continuously involving the pons, midbrain, hypothalamus, thalamus, and the putamen. The optic chiasm was enlarged. By histologic examination, the mass consisted of dense medium sized tumor cells. Immunohistologic observation revealed that the tumor cells were B-cell type malignant lymphoma. No tumor cells were found in the systemic organs.

Brain↗
PubMed1998

Automated visual field examination in children aged 5-8 years. Part I: Experimental validation of a testing procedure.

In 106 children aged 5-8 years, we determined how much training was needed to stabilize the response strategy prior to actual visual field assessment and we evaluated the reliability and acceptable duration of automated static perimetry (Octopus 2000R). A specially designed familiarization procedure was used to train the children to: (1) gaze at the center of the visual field while paying attention to light stimuli projected onto the periphery and (2) press the buzzer only when light stimuli were perceived. The subsequent examination phase consisted of 15 successive identical blocks of 27 trials (12 stimulus trials, 12 false-positive catch-trials, and three false-negative catch-trials), and was stopped before the end if signs of fatigue appeared. Age had a marked influence both on endurance (the number of blocks performed increased significantly) and on response reliability (false-positive responses decreased between 5- and 6-year-olds). The increase in false-negative responses toward the end indicates that examination is no longer reliable, and should be stopped. We concluded that most children as young as five can undergo examination by automated static perimetry. Changes regarding learning, stimulus intensity and testing procedure are suggested in order to adapt the examination to age, level of vigilance and health condition of the children.

Age Factors↗
PubMed2006

Corneal thickness and visual field damage in glaucoma patients.

PURPOSE: To verify whether there was a significant correlation between central corneal thickness (CCT) and visual field damage in patients with primary open angle glaucoma (POAG). METHODS: A total of 99 eyes with POAG were consecutively recruited. Patients were classified as glaucomatous based on visual field and optic nerve head damage. All underwent applanation tonometry, Humphrey perimetry, and measurement of CCT with ultrasonic pachymetry. Based on CCT value, the sample was split at the mode in two groups (group 1<535 microm, n=49; group 2>or=535 microm, n=50). RESULTS: Entire cohort: mean CCT 554 microm+/-45.03; mean deviation (MD) -6.68 dB+/-7.32; pattern standard deviation (PSD) 5.33+/-3.75; intraocular pressure (IOP) 17.91+/-4.16 mmHg with treatment. Group 1: CCT was 504.8 microm+/-30.8; MD -9.01 dB+/-8.72; PSD 6.38+/-3.99; IOP 18.02 mmHg+/-4.66. Group 2: mean CCT 574.6 microm+/-35.03; MD -4.39 dB+/-4.70; PSD 4.25+/-3.19; IOP 17.79 mmHg+/-3.57. A significant difference was found between the two groups for both MD and PSD. Linear regression analysis showed a significant correlation between CCT and PSD (P<0.001). CONCLUSIONS: Our data show that patients with a thinner cornea had a worse MD and PSD. As a thinner CCT causes an underestimation of the true IOP, there may be a delay in the diagnosis of POAG or an inadequate estimate of the clinical course despite apparently desirable IOP applanation readings.

Adult↗
PubMed1982

Detection of moving stimuli in the binocular and nasal visual fields by infants three and four months old.

A technique of monocular eye patching was used to measure the response of infants three and four months old to nasally and temporally placed stimuli at various eccentricities in the visual field. The results indicated a field of field of binocular overlap of approximately 60 deg in infants three months old and 80 deg in infants four months old. These figures compare with visual field widths obtained under binocular viewing conditions of at least 140 deg in infants three months old and of at least 150 deg in infants four months old.

Child Development↗
PubMed1983

Visual fields described by contrast sensitivity, by acuity, and by relative sensitivity to different orientations.

Sinewave grating contrast sensitivity was measured as a function of eccentricity and azimuthal angle for four orientations of gratings whose spatial frequencies ranged from 2 to 20 c/deg. Visual fields for cutoff spatial frequency were also mapped. Log contrast sensitivity fell off approximately linearly with eccentricity for all azimuths. Orientational differences in contrast sensitivity varied irregularly over the visual field and, though small for central vision, could reach as high as 25 dB in localized patches at eccentricities greater than about 12 degrees.

Adult↗
PubMed1993

An examination of the effects of axis foreshortening, monocular depth cues, and visual field on object identification.

Four experiments are reported on the identification of line drawings of common objects. In each experiment, performance on "unconventional" views of the objects, in which the major axis of the object was foreshortened, was compared to performance on more "conventional" views without appreciable foreshortening. In each experiment, except Experiment 2, where performance on the two views was experimentally equated, the foreshortened views were more difficult to identify than were the conventional views. Experiments 1 and 2 showed that if the foreshortened views were presented on a background with strong monocular depth cues, object identification was improved. This result suggests that part of the difficulty in identifying objects depicted from such a view stems from an improper depth interpretation of the object depictions. Experiments 3 and 4 examined visual field differences in the identification of the two types of object view. Results reported in the neuropsychological literature have shown that people with right-hemisphere damage have particular difficulty with the identification of unconventional views of objects that foreshorten major axes. Accordingly, it was expected that there would be a left visual field advantage for the foreshortened views. Neither experiment yielded any visual field effects consistent with this expectation. Possible reasons for the lack of a field effect are discussed.

Cues↗
PubMed2003

Visual field defects in pediatric patients on vigabatrin monotherapy.

UNLABELLED: Vigabatrin (GVG) is an effective antiepileptic drug used for treating partial seizures in adults and children. Over the last years, an increasing number of articles have been published reporting visual field defects (VFD) associated with GVG therapy in adults. To date, however, only an small number of pediatric patients have been reported. This paper is a retrospective review of clinical review to evaluate the prevalence and features of VFD in pediatric patients on GVG monotherapy. METHODS: Fifteen children, on GVG therapy in the Department of Child Neurology, underwent visual field examination by static threshold automated perimetry using the Humphrey Field Analyzer Program 30-2. The age of these patients ranged from 6 to 18 years (12.4 +/- 3.6 years), 10 of them being male and five female. RESULTS: Three patients (20%) on GVG monotherapy showed VFD. These consisted in localised, bilateral, and relatively symmetrical, nasal field loss, with relative preservation of the temporal field within the central 30 degree area.

Adolescent↗
PubMed1986

[Features of responses of the neurons of the caudate nucleus to various localizations of a photic stimulus in the visual field of the alert cat].

The responses of caudate neurons to restricted light stimuli differently located in the visual field were studied during natural fixation of the gaze on the visual target in awake cats. 71% of visually responsive neurons were sensitive to changing of stimulus location. It indicates that some neurons (17%) had restricted receptive fields in the centre of the gaze, other neurons (17%) had decreasing sensitivity to stimuli removed from the centre of the field and 37% of responsive neurons received information of different quality from different parts of the visual field. It is suggested that caudate nucleus neurons participate in the analysis of visual sensory information.

Animals↗
PubMed1992

Contrast dependence of the oscillatory motion threshold across the visual field.

Observer sensitivity to oscillatory step displacements of sine-wave gratings was investigated at various loci in the visual field (0-30 degrees) as a function of contrast. Detection thresholds at 10 Hz and high grating contrasts were approximately 11-15 arcsec in the fovea and 37-47 arcsec at 30 degrees eccentricity. At any given contrast, threshold displacement increases linearly with eccentricity. The data provide evidence against an interpretation based on cortical magnification, because the slope and the scale-free x intercept of the eccentricity function vary strongly with contrast. While foveal thresholds for high-contrast gratings are in the range of the hyperacuities, the oscillatory motion threshold falls off an order of magnitude more slowly than the traditional hyperacuities. Rather than conceiving of the oscillatory motion threshold as a spatial acuity limited by cortical magnification, we suggest an alternative approach that is based on a form of contrast discrimination. Oscillatory motion can be decomposed into the sum of a modulating counterphase grating and a static masking grating, both of which are in spatial quadrature (i.e., 90 degrees out of phase). At low grating contrast, oscillatory motion can be detected when the counterphase component exceeds a constant contrast value. Above a critical contrast value of the static component Cscrit, threshold rises as a power function of contrast with a slope near 1.0. The critical contrast value Cscrit increases linearly with eccentricity, indicating that oscillating gratings observed with the peripheral visual field are less easily masked compared with foveally fixated gratings.

Contrast Sensitivity↗
PubMed1999

Comparing significance and magnitude of glaucomatous visual field defects using the SITA and Full Threshold strategies.

PURPOSE: To evaluate and compare visual field test results as presented by the Statpac interpretation tools in tests obtained with the new short SITA Standard and the even shorter SITA Fast strategies to the traditional Humphrey Full Threshold strategy. SUBJECTS AND METHODS: One eye of each of 44 glaucoma patients was examined four times with each of the Humphrey SITA Standard, SITA Fast, and Full Threshold strategies. Another 21 eyes of 21 normal subjects had one eye examined once with each of the three strategies. RESULTS: Average light sensitivity was highest with the shortest SITA Fast strategy and lowest with the longest Full Threshold strategy. Magnitude of field loss as defined by the Statpac Mean Deviation (MD) did not differ between the three strategies. In the glaucoma patients, both SITA strategies showed larger number of significantly depressed points in Statpac probability maps than the Full Threshold strategy. In the normal subjects SITA Standard showed more significantly depressed points, close to the statistically expected number, at the lowest probability level (p<5%) than both Full Threshold and SITA Fast. At higher probability levels (p<1%) SITA Standard and Full Threshold showed similar numbers of significantly depressed points. CONCLUSION: Both SITA Standard and SITA Fast identified at least as much significant glaucomatous field loss as the Full Threshold using the Statpac interpretation tools.

Adult↗
PubMed1987

Interference and priming within and across visual fields in a lexical decision task.

A lower-case target word or non-word was laterally presented by itself or simultaneously with an upper-case distractor word in the same or in the opposite visual field. The distractor words were either semantically associated or unrelated to the target. Subjects performed a lexical decision task on the target. Two kinds of selection within and across visual fields were investigated. Selection of an external target relevant for the response (filtering) and selection of an internal target by automatic priming. No lateral asymmetry was found for automatic priming. Filtering was equally efficient within hemispheres, but strongly asymmetrical across hemispheres. Unrelated distractor words presented to the right hemisphere interfered less with target processing in the left hemisphere than vice versa. Thus, all distractor words received equivalent semantic processing; those presented to the right hemisphere, however, were least costly to exclude from task-relevant processing in the left hemisphere.

Adolescent↗
PubMed1995

Visual field loss after pars plana vitrectomy with air/fluid exchange.

PURPOSE: To report the postoperative finding of a dense, permanent, peripheral temporal visual field defect in the treated eyes of three patients who underwent pars plana vitrectomy with air/fluid exchange. METHODS: The patient's charts were reviewed. RESULTS: Visual field loss after pars plana vitrectomy and air/fluid exchange occurs and may be caused by mechanical trauma to the optic nerve head. CONCLUSION: Great caution is advised when aspirating directly over the optic nerve with any extrusion instrument.

Adult↗