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At least 613 records · Page 34Linked to original sources
PubMed1976

Simple formed hallucinations confined to the area of a specific visual field defect.

Thirteen patients with transient or permanent homonymous visual field defects experienced formed hallucinations localized to the affected part of the visual field. The lesion was occipital in 8 instances (infarction 7, porencephalic cyst 1), parietooccipital in 3 (infarction 2, angioma 1) and probably parietal in 2 (epilepsy 1, encephalitis 1). The disorder involved the right hemisphere in 9 cases, the left hemisphere in 3 cases and both hemispheres sequentially in one patient. Hallucinations were accompanied by palinopsia in 2 cases, metamorphopsia in one case and constriction of one pupil in another case. This particular type of hallucination is considered as an irritative phenomenon of the visual association cortex which can be symptomatic of a parieto-occipital lesion and does not necessarily implicate the temporal lobes. Distinctive features about the visions were that they consisted of people, animals or objects. There was no auditory accompaniment and any action that took place was stereotyped and did not tell a story. In most cases, the hallucinations were not clearly related to any visual memory. It is suggested that the visual association cortex amy be responsible for the organization of visual percepts into broad categories of which people, animals and objects are representative. The occurrence of such hallucinations with a visual field defect suggests that the cells of the association cortex are more likely to discharge spontaneously once they are deprived of their normal afferent inflow from the calcarine cortex.

Adolescent↗
PubMed2006

Influence of differences of visual acuity in various visual field conditions on spectral characteristics of the center of pressure sway.

This study examined the influence of visual acuity and visual field on the spectral characteristics of the center of pressure during standing. 17 men and 20 women participated in High and Low visual acuity groups. Both groups underwent center of pressure measurements under three visual field conditions: No vision: subjects were given no visual information, Central vision: they were given only central visual field information, and Full vision: they were given full visual information. To assess the spectral characteristics of center of pressure, mean power frequency and frequency of maximal power were calculated from medial-lateral and anterior-posterior center of pressure directions. The Friedman test and Scheffé pairwise comparison tests showed that frequency of maximal power was higher in the No vision than in the Central and Full vision conditions in the High visual acuity group. In conclusion, people with high visual acuity are more susceptible to visual field conditions than those with low visual acuity. It is suggested that postural control characteristics differ with visual acuity or resolution in the central visual field.

Adult↗
PubMed1999

Progressive visual field defects from experimental glaucoma: measurements with white and colored stimuli.

PURPOSE: Our purpose was to study the effects of using monochromatic test stimuli to measure the relative rate of progression of visual field defects caused by experimental glaucoma. METHODS: Visual field measurements were obtained by static perimetry from trained macaque monkeys with laser-induced, unilateral glaucoma. The visual field defects were assessed by perimetric (global) indices derived from comparisons of experimental visual fields to the expected normal fields of monkeys. Three types of perimetry stimuli were used, the conventional white Goldmann III and two monochromatic (460 and 620 nm) Goldmann V test stimuli. The relationships between field defects with white and monochromatic stimuli were investigated by linear regression of the Z-scores for the perimetric indices. RESULTS: The correlations between the mean deviation global indices for chromatic vs. white stimuli were high (r > 0.9) and linear throughout the period of progression of field defects. The slopes of the regression lines typically were greater than unity, indicating that statistical significance was higher for visual field defects measured with chromatic stimuli than with white light stimuli. The higher significance level for defects measured with chromatic stimuli was not explained by a difference in visual thresholds, because the thresholds with chromatic and white light were highly correlated across the full range of visual field defects, from initial-onset to end-state. This result also suggests that the early detection of glaucomatous visual defects with monochromatic stimuli does not reflect a selective loss of retinal ganglion cells. CONCLUSIONS: Although these experiments do not suggest an alternative neural mechanism for the clinical utility of perimetry with chromatic light for the early detection of glaucoma, it is very likely that the combinations of neural and/or analytical factors that explain the utility of perimetry with chromatic stimuli will also provide an explanation for the higher sensitivities in identifying early glaucoma reported for other prototype stimuli.

Animals↗
PubMed2003

[Unawareness for homonymous visual field defect].

BACKGROUND: There was no report which dealt with the relationship between emotional state, degree of defective visual search, severity of hemianopic dyslexia, the episode when the patient became aware of the defect, and unawareness of visual loss in homonymous hemifield. OBJECTIVE: To investigate the relationship between degree of awareness and those factors that might be responsible for the unawareness, including the aspects listed above. METHODS: Four patients with visual field defects caused by a brain lesion after a stroke was investigated. Self rating of emotional state, search performance for an object among many placed on a table, and for text reading, as well as visual field, visual positive phenomena, and hemispatial neglect were evaluated. Degree of unawareness for field loss was evaluated by modified version of the method of Bisiach et al. (1985). In addition, the episodes when the patient became aware of the defect were asked. RESULT: In accordance with the previous studies, we found no relationship between the degree of awareness of field defect and anatomic lesions, co-existence of hemispatial neglect, or the degree of awareness of hemiplegia. However, the patient with neglect was unaware of their troubles in vision at all, whereas the patients without neglect were aware of the troubles but misinterpreted them as problems of the eyes including acuity. In accordance with previous studies, co-existence of visual hallucinations or illusions seemed to be associated with awareness of visual field defect. No relationship was found between the degree of awareness of field defect and emotional state, degree of field loss, degree of defective visual search, or severity of hemianopic dyslexia. Their responses to the inquiry about the degree of awareness of field defect were not consistent. Thus, the awareness of the field defect seemed to be difficult to be kept firmly in their mind. On the other hand, the patients could remember the episode when they became aware of the defect for the first time, being able to specify time, place, and situation. CONCLUSION: Levine (1990) suggested that the sensory loss in this sort of patients was never phenomenally immediate but instead must be discovered by observation and inference. Non-specificity of the lesion, qualitative difference in awareness between the patient with and without hemispatial neglect, association of positive visual phenomena and awareness, fluctuation of awareness, and dependence of awareness on personal experiences found in our patients, can be explained with this 'discovery' hypothesis.

Aged↗
PubMed1980

Central visual field contributions to the visual-evoked response.

Visual evoked responses (VER) were recorded from bipolar electrodes placed transversely across the occipital region. A series of apertures were used to block the stimulation of the foveal area. The transverse distribution of the C2 component of the VER corresponds to a radial dipole source, and this is consistent with a foveal origin in the visual cortex. A clinical test for the presence of intact foveal projection, when opaque media preclude more conventional tests, could employ the VER.

Computers↗
PubMed1992

Age and visual field differences in computing visual-spatial relations.

Age and brain hemispheric differences in visual-spatial performance were investigated using 2 versions of categorical and coordinate (metric) spatial relations tasks. Thirty-two young adults (M = 19.2 years) and 32 older adults (M = 68.8 years) participated. An overall age-related decrement in computing visual-spatial relations was obtained for lateralized presentations and when items were presented centrally. In contrast to some previous findings, there was no evidence to suggest differential aging of the right hemisphere in computing visual-spatial relations.

Adult↗
PubMed1991

High frequency of asymptomatic visual field defects in subjects with transient ischaemic attacks or minor strokes.

The hypothesis that asymptomatic visual field defects can be found in patients with carotid transient ischaemic attacks (TIA) or minor strokes was tested. Twenty-two consecutive male patients with TIA and 18 patients with minor strokes from the carotid artery territory were examined by perimetry, cerebral computerised tomography and regional cerebral blood flow. Asymptomatic visual field defects were found in many TIA and minor stroke patients, 29% (5/17) and 57% (8/14), respectively (NS). Eighty-five per cent (11/13) of the scotomas were solely or predominantly located in the upper part of the visual field (P = 0.008 for absolute defects and P = 0.03 for relative defects). We conclude that both carotid territory TIA and minor stroke patients have a high frequency of asymptomatic visual field defects, predominantly located in the upper part of the visual field.

Adult↗
PubMed2000

Stages of improvement in visual fields after pituitary tumor resection.

PURPOSE: To use static threshold perimetry to examine the stages of improvement and the potential for late improvement of visual fields after surgical resection of pituitary adenomas causing visual loss from compression of the anterior visual pathways. METHODS: Retrospective review of charts of patients with pituitary tumors and abnormal static threshold perimetry before or soon after treatment who had subsequent visual fields. Quantification of the visual field mean deviation overall, superotemporally, and inferotemporally was performed and compared between visits. Postoperative visits were considered in five time periods: visit 1 (surgery to 1 week), visit 2 (1 month to 4 months), visit 3 (6 months to 1 year), visit 4 (2 years), and visit 5 (3 or more years). RESULTS: Sixty-two patients were included (33 men and 29 women; mean age 54 years [SD +/- 15 years; range, 22 to 83 years]). At visit 1, the relative improvement of the overall mean deviation for the right eye was 30.8% (P =.01) and for the left eye was 13.7% (P =.3067). At visit 2, the relative improvement of the overall mean deviation for the right eye was 30. 4% (P =.0142) and for the left eye was 32.6% (P =.0092). At visits 1 and 2, the inferotemporal quadrants were the quadrants with greatest improvement (visit 1, right eye, 37.8% [P =.0082]; visit 2, left eye, 30.8% [P =.0074]). At visits 3, 4, and 5, an overall trend toward mild improvement was observed with statistical significance only for the inferotemporal quadrant of the left eye from visit 2 to visit 3, which improved 19.7% (P =.0270). CONCLUSION: The pattern of recovery of visual function after decompression of the anterior visual pathways suggests at least three phases of improvement. The early fast phase (surgery to 1 week) of improvement may lead to normalization of visual fields in some individuals. The early slow phase (1 month to 4 months) is the period of most notable improvement. A late phase (6 months to 3 years) of mild improvement does not appear significant overall but may be marked in some individuals. Each of these phases may have one or more mechanisms underlying the observed improvement.

Adenoma↗
PubMed1999

Recovery of visual field function in the optic neuritis treatment trial.

PURPOSE: To assess the pattern of recovery of the visual field of patients with optic neuritis and to determine whether all affected portions of the visual field recover similarly or certain portions of the visual field have greater recovery. METHODS: We reviewed the Humphrey Visual Field (Allergan-Humphrey Inc, San Leandro, California) data from the initial and 6-month examination for the involved and fellow eyes of patients enrolled in the Optic Neuritis Treatment Trial (ONTT). The average threshold for each patient was calculated for the entire tested field and for locations within concentric rings having a radius 3, 9, 15, 21, and 27 degrees from fixation. The absolute amount of improvement and percentage improvement in average threshold between entry and the 6-month follow-up examination were determined for each patient. These measurements were compared within the concentric rings to assess patterns of recovery. RESULTS: Patients with localized defects recovered 86%+/-20% of their initial defect in average threshold, whereas those having diffuse defects recovered an average of 85%+/-23%. The area about fixation had the greatest relative recovery of threshold (87%+/-21% at 3 degrees); the relative recovery decreased with increasing eccentricity from fixation (P<.01). CONCLUSIONS: Patients with optic neuritis have a marked return of visual field function that does not appear to differ between patients with diffuse or localized field defects. The reduced redundancy of axons in the periphery of the field compared with near fixation may be responsible for the greater relative recovery of threshold near fixation.

Fixation, Ocular↗
PubMed1990

The influence of intraocular pressure on visual field damage in patients with normal-tension and high-tension glaucoma.

There have been several reports to suggest that the type of visual field damage in open-angle glaucoma is influenced by intraocular pressure (IOP). This study was undertaken to determine the extent to which patients with normal-tension (NTG) and high-tension glaucoma (HTG) could be differentiated on the basis of some features of their visual fields. The results from 40 pairs of NTG and HTG patients were matched closely for the extent of visual field damage, pupil size, and visual acuity. Using this pooled material, the authors increased the IOP difference between the two groups in either direction, ie, by either progressively lowering the highest recorded IOP allowed for inclusion in the NTG group or by progressively increasing that required for inclusion in the HTG group. They compared the normal areas of the patients' visual fields by using simple visual field indices designed to quantify the undisturbed field. Using receiver operating characteristics (ROC) analysis, they showed that changing the inclusion criterion in the NTG group resulted in no better separation between the groups. However, when the inclusion criterion was changed in the HTG group, the two groups tended to become more separable. In this case, the degree of separation appeared to be related to the difference in the highest recorded IOP between the two groups although the separation was not complete. These findings show that pressure has a greater influence on the type of visual field damage at the higher end of the IOP spectrum encountered in open-angle glaucoma and suggest that there is no common single pathophysiologic mechanism in this disease.

Cluster Analysis↗
PubMed2002

Prediction of clinical response to transcranial magnetic stimulation for depression by baseline lateral visual-field stimulation.

OBJECTIVE: We examined whether baseline-affective responses to lateral visual-field stimulation could predict clinical responses to left, prefrontal, transcranial, magnetic stimulation (TMS) in patients who are depressed. BACKGROUND: Schiffer et al have reported that left and right lateral visual-field stimulation can often evoke different (positive versus negative) psychologic responses in a given patient. Some had improvements while looking to the left and others while looking to the right. METHODS: We asked 37 patients who were severely depressed and resistant to treatment (26 women, 11 men) to report changes in affective state in response to two pairs of goggles, each allowing vision out of either the left or right visual field. We then evaluated whether these responses predicted clinical responses to TMS as measured by the percent decrease in the Hamilton Depression Rating Scale (HDRS.4%) scores between baseline and 4 weeks (2 weeks after a 2-week course of daily TMS). RESULTS: The 20 patients who felt more improvement with right than left lateral visual-field stimulation with 45-second baseline goggle trials had a 42% (+/- SD 22.2) reduction in HSDR.4%. The 15 patients who felt more improvement looking to the left than to the right had an 11% (+/- SD 28.4) decrease in HSDR.4%. Seventy-five percent of the 20 patients in the first group had a decrease in HSDR.4% more than 20%, and 80% of the 15 in the second group had a decrease in this score of less than 20%. A two-tailed Fisher exact test showed a significant difference between the two groups (p = 0.002). CONCLUSION: Baseline affective responses to lateral visual-field stimulation predicted clinical responses to left, frontal TMS in depressed patients.

Adult↗
PubMed1999

Scoring systems for measuring progression of visual field loss in clinical trials of glaucoma treatment.

OBJECTIVES: To compare the statistical properties of two visual field scoring systems used by clinical trials of glaucoma treatments with a view to their performance as longitudinal measures of visual field progression. DESIGN: Cohort study comparing the scoring systems used by the Advanced Glaucoma Intervention Study (AGIS) and the Collaborative Initial Glaucoma Treatment Study (CIGTS) using pairs of visual fields (C-30-2 of the Humphrey Analyzer) spaced 1 year apart. PARTICIPANTS: Sixty-seven eyes of 56 subjects with glaucomatous visual field loss from a natural history study of glaucoma were examined. METHODS: Because both scoring systems are scaled so that they range from 0 to 20, the AGIS and CIGTS scores were compared by scatterplot, Pearson correlation, and the mean difference between scores. The difference between pairs of scores 1 year apart was used to compare the temporal variability of each scoring system. The proportion of subjects whose visual field "deteriorated" in 1 year by the amount specified for unconfirmed progression in each clinical trial was calculated. MAIN OUTCOME MEASURES: Mean difference in scores 1 year apart and the variance of these differences were measured. RESULTS: The median scores for the first of the two fields was 5.2 (interquartile range [IQR] = 9.8) for CIGTS and 5.0 (IQR = 7.0) for AGIS. The CIGTS scores were slightly larger than AGIS scores by an average of 0.5 (P = 0.06). The mean CIGTS score of the baseline fields was 0.06 (standard deviation = 3.8) higher than the mean of the second fields and 0.12 (standard deviation = 2.8) higher for AGIS. Fifteen percent of eyes had CIGTS scores that deteriorated by three or more (the cutoff for unconfirmed progression) over 1 year, while 7.5% of eyes had AGIS scores that deteriorated by four or more (the AGIS cutoff for unconfirmed progression) over the same period. Twenty-one percent improved by CIGTS criteria, while 12% improved by AGIS criteria. CONCLUSIONS: CIGTS scores are systematically slightly higher than AGIS scores. The CIGTS scoring system has higher temporal variability than the AGIS system. The CIGTS criterion for unconfirmed progression over a 1-year period is likely to lead to higher estimated rates of progression than the AGIS criteria. This is mostly because of the difference in the definition of progression between the two study criteria.

Clinical Trials as Topic↗
PubMed2002

Spatial attention in agenesis of the corpus callosum: shifting attention between visual fields.

The role of the corpus callosum in spatially selective visual attention is uncertain. Research using commissurotomy and callosotomy patients has attempted to determine if the corpus callosum plays a role in reorienting attention between visual fields, as if spatial attention is unitary or divisible between the cerebral hemispheres. Reorienting of selective visuospatial attention within versus between visual fields was tested in 10 individuals with agenesis of the corpus callosum (ACC) and nine matched controls. Spatially focused attention to the most likely location of target appearance was created using both peripheral sensory cues and central symbolic cues in separate tests. Results demonstrated that individuals with ACC have significantly greater difficulty reorienting attention to an invalidly cued target stimulus occurring in the opposite visual field. However, this effect did not interact with the type of cueing (sensory or symbolic). Individuals with ACC did not differ from controls either with respect to the laterality of within-field reorientation of attention, or with respect to the most efficient direction of between-field shifting of attention. Since congenital absence of the corpus callosum significantly reduces efficiency in the reorienting of attention between visual fields, spatial attention cannot be completely unified based on a subcortical mechanism and the mobilization of attentional resources within each hemisphere must depend on callosal processes.

Adult↗
PubMed2001

Upper/lower visual field asymmetry on a spatial relocation memory task.

The purpose of this study was to investigate whether the lower visual field advantage reported on a number of visual tasks depends on the activity of neural systems which process information from different spaces. To this end, a double dissociation logic was followed by observing the effects of visual and spatial interference on a relocation memory task performed by 80 volunteers. Results showed that participants were better at relocating stimuli presented in the lower than in the upper visual field. Moreover, a concurrent spatial task, but not a concurrent visual task, disrupted the visual field vertical asymmetry. Those findings confirm that the vertical asymmetry of visual field depends on the spatial processing of incoming stimuli.

Adult↗
PubMed2001

The effect of flicker rate on measured visual field extent in very young children.

PURPOSE: To investigate the effect of flicker rate on measured visual field extent in toddlers. METHODS: A total of 270 full-term children (90 each at 11-, 17-, and 30-months of age) and 36 adults were tested binocularly with an LED static perimetry procedure using a black double-arc perimeter. Each subject was tested with one of three flicker rates: 0, 3, or 10 Hz. The median farthest location seen and an interpolated estimate of the location at which 50% of the subjects detected the peripheral stimulus were calculated for each age group for each flicker rate. RESULTS: For 11-, 17-, and 30-month-old subjects, but not adults, flickering stimuli produced a larger measured visual field extent than nonflickering stimuli. For the 10-Hz stimuli, measured visual field extent in children did not differ from that of adults. CONCLUSIONS: In infants and young children, binocular measured visual field extent is enhanced by peripheral stimulus flicker. Maturity of the measured visual field depends on the stimulus parameters used during testing.

Adult↗
PubMed2003

Neural networks to identify glaucomatous visual field progression.

PURPOSE: To describe a method to determine progression of glaucoma based on visual field thresholds. DESIGN: Observational retrospective longitudinal cohort study. METHODS: A back propagation neural network with three hidden layers was developed with commercial software. Visual field data from 80 patients who participated in the Advanced Glaucoma Intervention Study (AGIS) were used. Glaucomatous visual field progression was defined as a change of 4 or more units in the AGIS score, confirmed by at least two sequential subsequent tests. Inputs to the neural network consisted of threshold measurements from 55 visual field locations from the baseline examination and each follow-up examination. The data set was randomized so the sequence of examinations would not influence the training or testing of the neural network. Two thirds of the randomized data were used for training and the remaining one third for testing. RESULTS: The mean age of 80 patients enrolled in AGIS at initial examination was 67.4 (+/- 7.3 standard deviation [SD]) years. The average follow-up period was 7.2 (+/-2.3 SD) years and the mean duration between examinations was 0.46 (+/- 0.39 SD) years. The neural network estimated the probability of progression for each baseline and follow-up comparison with an average sensitivity of 86% and specificity of 88%. The area under the receiver operating characteristic (ROC) curve was 0.92, with a sensitivity of 86% at the 80% specificity level and a sensitivity of 91% at the 90% specificity level. CONCLUSIONS: From analysis of AGIS data, progression of glaucoma could be detected from visual field thresholds with a neural network.

Aged↗