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PubMed1992

On the relation between visual spatial attention and visual field asymmetries.

In the typical visual laterality experiment, words and letters are more rapidly and accurately identified in the right visual field than in the left. However, while such studies usually control fixation, the deployment of visual attention is rarely restricted. The present studies investigated the influence of visual attention on the visual field asymmetries normally observed in single-letter identification and lexical decision tasks. Attention was controlled using a peripheral cue that provided advance knowledge of the location of the forthcoming stimulus. The time period between the onset of the cue and the onset of the stimulus (Stimulus Onset Asynchrony--SOA) was varied, such that the time available for attention to focus upon the location was controlled. At short SOAs a right visual field advantage for identifying single letters and for making lexical decisions was apparent. However, at longer SOAs letters and words presented in the two visual fields were identified equally well. It is concluded that visual field advantages arise from an interaction of attentional and structural factors and that the attentional component in visual field asymmetries must be controlled in order to approximate more closely a true assessment of the relative functional capabilities of the right and left cerebral hemispheres.

Attention↗
PubMed1997

Color search and visual field segregation.

Visual search for targets that combine color and shape features that are shared by distracting items can be conducted spatially in parallel. Experimental results show that parallel search for color/shape conjunctions is possible when the shapes chosen let observers segregate the spatially interspersed items into figure and ground and when, within the figure, the target differs from other items by a distinguishing color feature. Results of experiments that manipulate stimulus color suggest that adaptive mechanisms of color discrimination are used to detect targets within such a figure.

Color Perception↗
PubMed1988

Effects of lateral displacement of the visual field on the development of visual-motor abilities in cats.

In this study, we test the flexibility of the cat's visual system by examining the visual-motor effects of both moderate and extreme lateral displacement of the visual field. While being reared with masks that provided either 0, 15, or 30 diopters lateral displacement of the visual field, 23 kittens received 3 tests of visual-motor abilities: a visual cliff task, a visual guiding task, and a five-alley choice task. No significant differences were found among the 0, 15, or 30 diopter displacement groups for any of the 3 tasks for either the total number of days to reach criterion performance, for the development of performance over time during the early days of testing, or for the development over time to criterion performance. After reaching criterion, kittens readapted to transposed conditions of displacement. The group changed 30 diopters did significantly worse than the group changed 15 diopters, both in error scores and in time to criterion performance. The present results with kittens are compared to those of other investigators and suggestions are made for future research.

Aging↗
PubMed1984

[Quantitation of the visual field].

With kinetic perimetry, the visual field chart had the appearance of a geographical map. Since the isopters were not geometric, their surfaces were barely measurable. However, with recent three dimensional computerised (or semi-computerised) perimetry quantitative evaluation of the print-out may easily be done. The visual acuity is expressed by a fraction or ratio. In a similar way our deficit ratio gives a percentage score of visual field volume defects. Using the Peritest, it is very easy to establish the field's deficit ratio. All the defects are classified and have a score. Scores are then added up to establish the deficit ratio. (The same procedure may be used with other perimeters like the Visual Field Analyser). Why express field loss as a deficit ratio? In the natural history of a Primary Open Angle Glaucoma (i.e. a disease of the visual field), the comparison between consecutive visual fields may be difficult. Instead of looking at a collection of print outs, it is easier to look at the numbers of the deficit ratio to appreciate if there is evolution of the disease. In discussions with the patient, it sounds better if the ophthalmologist speaks of a "percentage" of visual field loss: the patient may understand his own situation more easily. Each point is tested twice at each examination to give an idea of patient response fluctuation. Before finding progression of the disease, it is necessary to know the range of an individual's variation in answers. The principle of all sciences is to measure what is measurable, and to render measurable that which is not.

Computers↗
PubMed1988

Cluster analysis in visual field quantification.

The central visual fields of 2165 normal and 106 glaucoma eyes were measured using a threshold related suprathreshold strategy. The effects of altering the cluster radius in normals and glaucoma eyes sheds light on the nature of defects in these two groups. It is estimated that approximately 13% of normals have clusters; the great majority of these individuals have one cluster of two defects. Most clusters in normals are formed artefactually due to angioscotoma and/or physiological variations in the blind spot position. Clusters due to other factors occur rarely. Clusters are found with equal frequencies in the superior and inferior fields in normal eyes, but with a greater frequency in the superior field in glaucoma eyes. The use of clusters in quantification is both sensitive and specific. Using results from this large sample and looking at other visual field properties, it is possible to devise weighted probability indices to score visual fields.

Adult↗
PubMed1983

The working threshold approach to Friedmann visual field analyser screening.

Central visual field screening of 2223 eyes without field defects was conducted with the Friedmann Visual Field Analyser Mark II. There was wide variation in the filter setting at which all stimuli were seen and in the working threshold relative to the recommended age filter. The ability to see all stimuli at settings higher than the age filter was found in 803 eyes (36.1%). The difference between mean working threshold and the age filter ranged from 0.22 to 0.40 log units, being greatest in middle age groups. The performance of the screener in correctly identifying normal eyes was thus improved with the working threshold approach, as the criterion for depression of sensitivity was an individually determined threshold.

Adolescent↗
PubMedDate not supplied

Identification of progressive glaucomatous visual field loss.

In normal individuals, visual field measures are not perfectly repeatable and individual test locations exhibit both short- and long-term sensitivity variations. This physiologic variability is greatly increased in glaucoma and confounds detection of real progressive loss in visual function. Distinguishing progressive glaucomatous visual field loss from test variability therefore represents a complex task. Procedures used for detection of glaucomatous visual field progression may be broadly grouped into four categories: 1) clinical judgment, which consists of simple subjective observation of sequential visual field test results; 2) defect classification systems, whereby specific criteria are used to stratify field loss by discrete score and define progression as score change over time, such as the Advanced Glaucoma Intervention Study scoring system; 3) trend analyses, which follow test parameters sequentially over time to determine the magnitude and significance of patterns within the data, for example linear regression; and 4) event analyses, which identify single events of significant change relative to a reference examination. All of these methods demonstrate distinct benefits and drawbacks, making each useful in specific circumstances, although no single method appears universally ideal. At the present time the best method of detection of progression may be to rely upon confirmation of change at successive examinations and also by correlation of visual field changes with other clinical observations. Alternative analysis methods may become available in the near future to help identify cases of progressive loss.

Confounding Factors, Epidemiologic↗
PubMed1992

The four-meter confrontation visual field test.

The 4-m confrontation visual field test has been successfully used at the Mayo Clinic for many years in addition to the standard 0.5-m confrontation visual field test. The 4-m confrontation visual field test is a test of macular function and can identify small central or paracentral scotomas that the examiner may not find when the patient is tested only at 0.5 m. Also, macular sparing in homonymous hemianopias and quadrantanopias may be identified with the 4-m confrontation visual field test. We recommend use of this confrontation visual field test, in addition to the standard 0.5-m confrontation visual field test, on appropriately selected patients to obtain the most information possible by confrontation visual field tests.

Hemianopsia↗
PubMed1988

Neuroretinal rim area and visual field in glaucoma.

The correlation between visual field and neuroretinal rim area of the optic disc was studied in 70 eyes of 44 patients with suspected or definite glaucoma. Visual field analysis was performed by automated perimetry with the Octopus 2000R, using the program G1; the neuroretinal rim area of the disc was measured by the "Optic Nerve Head Analyzer." All eyes with a glaucomatous loss within the central sector of the visual field showed a significantly reduced neuroretinal rim area in the corresponding, i.e., the temporal quadrant of the disc. The reverse conclusion, however, was not valid: If there is a significantly reduced neuroretinal rim area in the temporal quadrant of the optic disc, one cannot predict the presence or absence of visual field loss. Actually, both high and low values are found in the neuroretinal rim area even if no visual field loss is detectable by the Octopus G1 program. There are two clinical consequences based on this result: (1) follow-up examinations of the disc structure that show increasing loss of the neuroretinal rim area may establish the diagnosis of glaucoma even at a stage where no visual field loss can be detected. Therefore, analysis of the disc structure may be more sensitive than analysis of the visual field, especially in patients who only show elevated intraocular pressure and no other signs of glaucoma. (2) If there is already a definite visual field loss due to glaucoma, the effect of antiglaucomatous therapy should be monitored by visual field analysis rather than by analysis of the optic nerve head.

Evaluation Studies as Topic↗
PubMed1996

[Noise field screening. Results of a television field study for detection of visual field defects].

White noise field campimetry is able to transform usually negative scotomas immediately into perceivable visual field defects. As this method needs a monitor, the obvious solution was to evaluate the suitability of the noise field stimulus broadcasted to home TV sets. Therefore, in cooperation with the "Süddeutscher Rundfunk" (SDR) as well as several health insurance companies ("AOK Baden-Württemberg" and other "RVO-Kassen"), approximately 300,000 viewers were invited to take this test after receiving brief information and instruction. There were 531 calls for questionnaires to document the subjects' findings and the results of a subsequent ophthalmological examination. In most cases this clarified the perceived noise field defect. Out of 127 evaluable questionnaires, 78 cases did not show any relevant ophthalmological pathology; this held true especially for lesions of the visual pathway. However, in 49 persons the ophthalmologists detected pathological findings; in 20 of these, the scotomas were previously unknown to the physicians. Glaucomatous optic neuropathy and macular degeneration were most frequently diagnosed as causing the white noise field defects. Finally, some preliminary estimates of the costs and benefit of this study are presented.

Adolescent↗
PubMed1989

[The Bebié curve (cumulative defect curve) for differentiating local and diffuse visual field defects].

Damage to the visual field can be diffuse as well as local. In the absence of local defects, diffuse damage can easily be recognized with the help of the visual field indices. In the presence of scotomas, diffuse damage in the remaining part of the visual field which is better or "normal" is more difficult to recognize and quantify. Bebié et al. have published a new method of assessing the visual field in relation to normal values. They present the results with a cumulative defect curve, a method which we have called the "Bebié curve". This method allows an easy recognition of diffuse as well as local damage. In our study we evaluate the clinical application of the Bebíe curve in different diseases and for the follow-up of the visual field.

Computer Graphics↗
PubMed1981

Confrontation visual field techniques in the detection of anterior visual pathway lesions.

The accuracy of a variety of finger and color confrontation tests in identifying chiasmal and optic nerve visual field defects was assessed in patients whose field defects had been established beforehand by a conventional achromatic kinetic technique on the Goldmann perimeter. Kinetic and static finger confrontation methods identified an average of 42% of the 28 chiasmal hemianopic defects. False negatives included eyes with hemianopias complete to the largest (V4e) Goldmann isopter. False positives (average, 15%) occurred in eyes containing nerve fiber bundle defects with borders that fell near the vertical fixational meridian. Kinetic and static color confrontation techniques were 78.6% sensitive to hemianopias. Accuracy did not differ significantly whether the red target was presented kinetically or statically against the tangent screen, projected on the Autoplot screen, or held in the examiner's hand without attention to background. False positives (average, 23%) were slightly greater than with finger confrontation methods and occurred not only in eyes with nerve fiber bundle defects but also in eyes with no defects in reference visual fields. Finger confrontation identified 11% or fewer of optic nerve field defects, while some color techniques detected as many as 31 1/3%. There were no false positives.

Hemianopsia↗
PubMed1991

Fresnel prisms for field enhancement of patients with constricted or hemianopic visual fields.

The concept of visual field enhancement is to increase the effect of the patient's habitual scanning skills by displacing peripheral images toward the residual field and mid-line. This reduces the extent of ocular and head rotation by patients with severely restricted and hemianopic visual fields. High power fresnel press-on prisms are used to effect the image displacement. This paper describes a technique that we believe to be less empirical and more reproducible than previously described in the literature.

Eyeglasses↗
PubMed1994

Pressure increase following primary laser trabeculoplasty. Effect on the visual field.

Possible damaging effects on the visual field of postlaser pressure elevations the first 24 h following primary laser trabeculoplasty were investigated in 61 patients with exfoliative or open-angle glaucoma. The intraocular pressure was monitored the first 24 h after treatment. Treatment with pressure reducing agents was started if the intraocular pressure was > or = 50 mmHg. The visual field was plotted before and 1, 3, and 6 months after laser treatment with the C-30-2 program on a Humphrey visual field analyzer. Peak pressures > or = 50 mmHg occurred with 15 (25%) patients. There was no relationship between visual field changes at 1 month and pressure increase, peak pressure, prelaser pressure, prelaser visual field indices, the use of timolol postlaser, or the pressure decrease or pressure level 1 month after laser treatment. From 1 to 6 months after laser trabeculoplasty the visual field parameters remained stable. Postlaser pressure spikes do not seem to damage the visual field providing they are detected and treated.

Aged↗
PubMed2002

Visual field asymmetries and allocation of attention in visual scenes.

Single items such as objects, letters or words are often presented in the right or left visual field to examine hemispheric differences in cognitive processing. However, in everyday life, such items appear within a visual context or scene that affects how they are represented and selected for attention. Here we examine processing asymmetries for a visual target within a frame of other elements (scene). We are especially interested in whether the allocation of visual attention affects the asymmetries, and in whether attention-related asymmetries occur in scenes oriented out of alignment with the viewer. In Experiment 1, visual field asymmetries were affected by the validity of a spatial precue in an upright frame. In Experiment 2, the same pattern of asymmetries occurred within frames rotated 90 degrees on the screen. In Experiment 3, additional sources of the spatial asymmetries were explored. We conclude that several left/right processing asymmetries, including some associated with the deployment of spatial attention, can be organized within scenes, in the absence of differential direct access to the two hemispheres.

Adolescent↗
PubMed2004

Association of binocular lower visual field impairment, impaired simultaneous perception, disordered visually guided motion and inaccurate saccades in children with cerebral visual dysfunction-a retrospective observational study.

The principal pathways serving higher visual function comprise the dorsal stream and the ventral stream. The dorsal stream runs between the occipital lobes and the parietal lobes and subserves the ability to process the whole visual scene and carry out visually guided movement. The ventral stream runs between the occipital lobes and temporal lobe tissue and primarily subserves visual recognition and memory. These tissues are susceptible to dysfunction in children with brain damage. We report a series of 40 children in whom damage to the brain has led to a common symptom complex affecting vision. Lower visual field loss was frequently elicited. This was associated with impaired ability to make accurate visually guided movement (particularly of the lower limbs) accompanied by impaired simultaneous perception, and in some cases, with inaccurate saccades and in others, impaired perception of movement. These features are consistent with parietal/dorsal stream dysfunction. Difficulty recognising faces and problems with route finding (which are ventral stream functions) were also present in a number of the children. These visual difficulties can be manifest in the presence of normal visual acuity. Recognition of these problems leads to understanding of the child's visual difficulties and facilitates adaptation of curriculum delivery at school.

Adolescent↗