Lack of generalized constriction of affected visual field in glaucoma patients with visual field defects in one eye.
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[The papilla and visual field in glaucoma. Relation between planimetrically determined papilla and visual field changes].
From 126 patients with ocular hypertension and/or primary open-angle glaucoma, those (n = 18) who had an untreated intraocular pressure of at least 25 mm Hg or a cup/disk ratio of at least 0.8 were selected for this study. The course of the disease was followed by means of photos of the disk and visual field examinations performed with an automated perimeter. The area of the neuroretinal rim was measured planimetrically. The mean period of observation was 3.7 years, in the course of which the size of neuroretinal rim became decreased in 10 patients, merely fluctuated in 6 patients, and increased in 2 patients. No definite correlation between the course of the visual fields and that of changes in the neuroretinal rim could be demonstrated at either the first or the last examination. Nonetheless, when the visual field changes were juxtaposed to those in the neuroretinal rim, a tendency to a decrease in rim area and an increase in visual field losses was noted. However, numerous exemplary cases showed that one cannot necessarily predict visual field losses from the size of the rim and vice versa. Comparison of estimated rim areas with those determined planimetrically obviously verifies that planimetry provides more accurate results.
Aged↗
Confrontation visual field loss as a function of decibel sensitivity loss on automated static perimetry. Implications on the accuracy of confrontation visual field testing.
PURPOSE: To evaluate the accuracy of confrontation visual field testing with regard to the density of the visual field defect and its location in the peripheral visual field. METHODS: A prospective comparison of confrontation visual field testing with full-threshold Humphrey automated static perimetry C24-2 or C30-2 was conducted at a university eye center over a 3-month period. Seventy-two patients with a variety of neurologic and ophthalmologic conditions underwent confrontation visual field testing and automated perimetry as a part of their evaluation. One visual field from each patient was analyzed for this study. RESULTS: Confrontation visual field testing yielded an overall sensitivity for detecting an abnormal visual field (full-field analysis) of 63%, when sensitivity of confrontation testing rested on the detection of just one abnormal quadrant. The sensitivity of confrontation testing varied depending on the type of visual field loss present: 51% for arcuate scotomas, 67% for visual field constriction, 78% for altitudinal scotomas, and 90% for hemianopias. The sensitivity of detecting abnormal visual field quadrants, rather than the full-field analysis, was, however, poor at 38%. The sensitivity of confrontation testing was lower for superior quadrant defects and higher for inferior quadrant defects. The estimated probability of detecting an abnormal visual field quadrant occurring at a -26-decibel sensitivity loss from age-matched healthy patients for superior quadrant defects and a -19-decibel sensitivity loss for inferior quadrant defects was 50%. The increased sensitivity noted for visual field defects and for inferior quadrant defects appears to be related, in part, to the density of the visual field loss present. CONCLUSION: Confrontation visual field testing is relatively insensitive unless a moderate to dense defect is present, and as such is a poor screening test. However, when visual field defects are identified with confrontation visual field testing, the defects often are real as per the high specificity (97%) and high positive predictive value (96%).
Adult↗
Visual loss in pseudotumor cerebri. Incidence and defects related to visual field strategy.
Visual field examinations were performed serially on 20 patients with pseudotumor cerebri using a modified Armaly-Drance visual field strategy with a Goldmann perimeter as well as an automated perimeter (Octopus). Visual loss was found in 75% of eyes using the manual strategy and in 77.5% of eyes with automated threshold perimetry. This incidence of visual loss is 50% greater than any previously reported series. All major defects detected were present with both types of perimetry. Both strategies were more sensitive for documenting visual loss than previously described strategies. Since therapy for pseudotumor cerebri is determined by the degree and progression of visual loss, a specific sensitive strategy, rather than routine screening perimetry, should be used for determination of visual loss.
Adult↗
Visual field defects and multifocal visual evoked potentials: evidence of a linear relationship.
OBJECTIVE: To determine the relationship between spatially localized multifocal visual evoked potentials (mfVEPs) and Humphrey visual fields (HVFs) in patients with unilateral field defects. METHODS: Humphrey visual fields and mfVEPs were obtained from 20 patients with unilateral field losses due to either ischemic optic neuropathy or glaucoma. Monocular mfVEPs were obtained for each eye. The amplitude of the mfVEP responses was calculated using root-mean-square and signal-noise ratio measures. Estimates of the HVF loss in the same regions of the field used for the mfVEP were obtained by interpolating the 24-2 HVF data. RESULTS: Monocular mfVEP amplitude decreased with HVF loss, although small mfVEP signals were not uniquely associated with poor fields. On average, the monocular mfVEP was indistinguishable from noise for field losses between -5 and -10 dB, and good monocular mfVEP amplitudes were never associated with extensive visual field loss. The interocular ratio of the mfVEP amplitudes correlated well with the difference between the HVF values of the 2 eyes, and this correlation improved with increased signal-noise ratio. CONCLUSIONS: The monocular and interocular results were consistent with a linear relationship between the amplitude of the signal portion of the mfVEP response and linear HVF loss. One way to produce this relationship would be if both the signal in the mfVEP and linear HVF loss were linearly related to the percentage of local ganglion cells lost. The clinical limitations of the mfVEP technique can be understood by taking the signal-noise ratio, and the linear model proposed herein, into consideration.
Adult↗
Plasticity in the adult visual cortex: implications for the diagnosis of visual field defects and visual rehabilitation.
It has recently been shown that, contrary to long-held beliefs, sensory and motor maps are not stable in the adult cerebral cortex. Alteration of input from the periphery results in changes in topography in the cortex, including the primary visual cortex. Mechanisms involved consist mainly of reshaping the receptive field of cortical cells and increasing the sensitivity of deprived cells in the visual cortex. Cortical plasticity allows the brain to adapt to background modifications or to damage of the nervous system. It also underlies learning and attention processes. Cortical changes occurring after focal visual differentiation modify visual perception by filling in visual field defects with information from the area surrounding the scotoma. This modification causes affected subjects to ignore or underestimate their defects. With visual field defects, cortical plasticity also causes distortion in spatial perception. Although the effects of cortical plasticity are prominent in neuro-ophthalmological daily practice, they are usually unrecognized or greatly underestimated. These effects cause delay in recognizing visual field defects, and hence in receiving therapy, while affecting the results of some procedures for testing the visual field. Affected individuals who are unaware of their defects may have increased difficulty in coping with activities in everyday life. Up to now, phenomena related to plasticity in the visual system have been investigated mainly by psychophysicists and neurophysiologists. It is essential to start considering the various effects of cortical reorganization in clinical practice. It is especially important to introduce into clinics the concept of dissociation between actual and perceived defects in the visual field, resulting from the filling-in process, and the need to measure it. This dissociation should also be demonstrated to the affected subjects.
Adult↗
Neurological visual fields.
Neurological visual field defects represent lesions to the visual pathway, some of which may be life-threatening. It is, therefore, crucial that optometrists understand how to diagnose these lesions, so they may know when, and to whom to refer the patient. The following cases illustrate the management of patients with lesions to the prechiasmal, chiasmal, and postchiasmal visual pathway.
Adenoma, Chromophobe↗
[The extent of visual field damage in chiasmal lesions--contribution to the selection of methods for visual field examination].
The authors analyse 200 visual fields (examine with automatic perimetry) of patients with the chiasmal syndrome. On the basis of their own results they recommend the use of quantitative perimetry for early diagnosis of visual field changes in the range of central visual field (0-30 degrees).
Brain Neoplasms↗
An AI approach to dynamic visual field testing.
Visual field test results are crucial to the accuracy and efficiency of diagnosing blinding diseases such as glaucoma. Herein, a method of integrating self-organizing neural networks and empirical heuristics is used to perform visual field tests via a dynamic test strategy, which can lead to a reduction in the number of trials in a perimetric test. Experiments performed using clinical test records show that we are able to reduce by 20% to 30% the number of trials per test without much adverse effect on the accuracy of the tests.
Algorithms↗
Evaluation of the Friedmann Visual Field Analyser Mark II. Part 2. Results from a population with induced visual field defects.
The Friedmann Visual Field Analyser Mark II is evaluated with a group of 301 normal eyes, 155 of which had an induced visual field defect. Measures of sensitivity and specificity are calculated from these data by criteria similar to those used by other researchers. The inadequacies of using pass/fail criteria in the clinical situation are discussed, and a solution is proposed in which each field response is scored and the score compared with those from normal and defective populations. An example is given of how this form of analysis could be incorporated into the clinical situation.
Evaluation Studies as Topic↗
Effect of peripheral visual field size upon visual search in children and adults.
Twenty observers in each of the age groups, three, four, five, and twenty-one years, were asked to identify pictures displayed through five different sizes of peephole. Recognition latency changes as a cube-root power function of aperture area. It was found that latency decreased as age and area increased. However, the exponent of the power function showed little age-related change. Effectiveness of the peripheral visual field size was discussed in terms of magnitude of the exponent.
Adult↗
[Visual field change and risk factors for progression of visual field damage in low tension glaucoma].
The authors carried out a prospective study in an attempt to determine the possible effect of intraocular pressure (IOP) and some clinical factors on the clinical course of low tension glaucoma (LTG). During the study period all the patients were followed without any antiglaucoma medication. The enrollment criteria for the study were reproducible, mild to moderate field loss as defined as a mean defect (MD) of greater than 2 dB and less than 10 dB or corrected loss variance (CLV) of greater than 7 dB revealed by the Octopus 201, G1 program. Forty-two consecutive patients (56 eyes) who fulfilled this criteria were enrolled. Baseline and follow-up examinations included applanation tonometry, perimetry with G1 program, blood pressure and pulse rate. When the MD increased by 4 dB or more on two consecutive perimetry examinations, the field defect was judged as "progressed". During the follow-up period (6-51 months, 25.1 +/- 12.5 months), the field defect progressed in 14 eyes of 12 patients. The life-table analysis (Kaplan-Meier) revealed that the rate of nonprogression of visual field defects was 55.5% at 48 months. The rate of nonprogression was significantly lower in 16 eyes with a mean IOP equal to or higher than 15 mmHg as opposed to 40 eyes with that lower than 15 mmHg (34.3% and 67.2% respectively, p less than 0.05). The results seem to indicate that IOP is likely to be responsible for the aggravation of visual fields in LTG. Canonical discriminant analysis revealed that the discriminant function containing four variables gives the best separation between the "progressed" and "nonprogressed" group (discriminant efficacy: 83.9%).
Adult↗
Computerized kinetic perimetry detects tubular visual fields in patients with functional visual loss.
PURPOSE: To report a novel test that uses computerized kinetic perimetry to detect tubular visual fields in patients with functional visual loss. DESIGN: Observational case series. METHODS: Ten patients who demonstrated generalized visual field constriction on prior examinations underwent testing combining computerized kinetic perimetry with a reversed Galilean telescope, used for optical visual field expansion. RESULTS: Six patients with physiologic visual field constriction demonstrated expansion of their visual fields with the use of the reversed telescope. Four patients with functional visual loss responded to the reversed telescope by demonstrating tubular visual fields, with responses equal to or smaller than their demonstrated visual fields delineated without the telescope. CONCLUSIONS: This test uses a computerized kinetic examination to reduce the subjective nature of tangent screen testing for tubular visual fields and to provide a computerized recording of visual fields. This method is a novel and easy-to-use technique to demonstrate functional visual loss.
Computing Methodologies↗
Function of the corpus callosum in the representation of the visual field in cat visual cortex.
Interposed between areas 17 and 18 of cat cerebral cortex is an architectonically distinct zone that represents a substantial portion of the ipsilateral visual field. The extent of this representation was assessed following severance of the corpus callosum by recording the activities of neurons and plotting their receptive fields. The results show that, even after the hemispheres are disconnected, the transition zone still contains a representation of part of the ipsilateral visual hemifield, albeit a reduced one. The extent of this representation is contracted towards the midline so that just one-half to one-third of the azimuths mapped in intact cats can be plotted. As in the intact cat, the width of the region represented is not equal at all elevations, for it extends to only -1.4 deg near the visual axis whereas it extends to -6.6 deg at an elevation of -20 deg. The retention of this representation after the transition zone neurons have been disconnected from the opposite hemisphere indicates that other pathways make a functional contribution to the representation of the ipsilateral field in this region of cortex.
Animals↗
[Study of the visual fields by comparing visual perception].
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Humans↗
Why word length only matters in the left visual field.
During visual word recognition, string length affects performance when stimuli are presented to the left visual field (LVF), but not when they are presented to the right visual field (RVF). Using a lexical-decision experiment, we investigated an account of this phenomenon based on the SERIOL model of letter-position encoding. Bottom-up activation patterns were adjusted via positional manipulations of letter contrast. This manipulation eliminated the LVF length effect by facilitating responses to longer words, thereby demonstrating that a length effect is not an inherent property of right-hemisphere processing. In contrast, the same manipulation slowed responses to longer words in the RVF, creating a length effect. These results show that hemisphere-specific activation patterns are the source of the asymmetry of the length effect.
Adolescent↗
Evaluation of the Friedmann Visual Field Analyser.
Visual fields were assessed in 320 eyes of 169 patients, using the Friedmann Visual Field Analyzer (F.V.F.A.) and the Oculus perimeter. The F.V.F.A. was found to be a rapid indicator of both the presence, the location and the density of scotomata. Because some defects were missed by the F.V.F.A. it should be used in combination with some other technique to search for early defects, particularly in the Bjerrum region. Since the F.V.F.A. can be used easily by a technician, the physician's efforts can be utilized to best advantage in exploring those regions likely to contain abnormalities.
Aged↗
The visual evoked response to word stimuli in the visual fields.
The visual evoked response (VER) has been considered an objective indicator of visual and perceptual processing, although as yet there is no clear evidence of a relationship between visual recognition and electrophysiological activity. The present study was performed to determine whether VER's can provide indications of differences in responses to word stimuli presented in different parts of the visual field. Additionally, evidence was sought as to whether the left and right hemispheres process visual information symmetrically. In 20 adult subjects with normal binocular vision, VER's were recorded simultaneously from left and right hemispheres in response to the repeated presentation of a three-letter word in each of 7 visual field locations. VER's of any subject in response to one stimulus site were consistent and repeatable; intersubject variation was large. For subject comparison, amplitude of VER was the measured response. No significant or consistent amplitude characteristics were identified that related to recognition of the stimulus. From comparison of responses to the different field locations, central stimulation (at 0 degrees) evoked the largest peak-to-trough amplitude (X=8.21 uV+/- 2.56). Amplitudes tended to be larger at 4 degrees than at 2 degrees from center; left field stimulation tended to give larger amplitudes than right field; however, these trends were larger than from the left, this difference was not valid since 11 subjects had larger right hemisphere responses, whereas 9 had larger amplitudes from the left hemisphere. Thus, the study suggests that the VER reflects some net electrical activity from the recording sites that may be traced to an external sensory stimulus and shows that this activity is symmetrical for each hemisphere.
Adult↗