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At least 1,369 records · Page 76Linked to original sources
PubMed1993

Evaluation of numerical displays of visual field data by human observers--the definition of scotomas and clusters by human interpreters.

Numerical printouts of 23 visual field examinations performed with glaucoma program G1 were analyzed by 3 perimetrists. The task consisted of defining the existence of clusters or scotomas. Considerable discrepancy with regard to the existence or the size of clusters and/or scotomas was found among the three perimetrists. The median difference in number of clusters as compared for each pair of interpreters was found to differ from zero at a significance level of 5% (Wilcoxon's signed-rank nonparametric test). These findings suggest that the interpretation of a visual field status by human observers will always remain subjective and to a large extent contradictory. This situation calls for the implementation of interpretative computer software to supplement the currently available algorithms.

Adult↗
PubMed1990

Rod visual fields in cone-rod degeneration. Comparisons to retinitis pigmentosa.

Dark-adapted visual fields to short- and long-wavelength stimuli were obtained from 20 patients with cone-rod degeneration, 20 patients with retinitis pigmentosa, and ten normal subjects. Patients were selected because they retained rod electroretinographic (ERG) function over a sufficient range for the Naka-Rushton analysis of retinal illuminance versus amplitude functions. Patients with cone-rod degeneration retained a relatively normal field topography although overall sensitivity was reduced. The mean sensitivity loss was consistent with a small elevation in ERG semisaturation constant and minimally delayed rod b-wave implicit times. Rod visual fields from patients with retinitis pigmentosa retaining rod ERG function were consistent with log sensitivity profiles reported previously for type 2 patients. Sensitivity loss was greatest in midperipheral regions, with most patients showing least loss in the far periphery. Disproportionate loss in the midperiphery is consistent with a large elevation in the ERG semisaturation constant and prolonged rod b-wave implicit times.

Adolescent↗
PubMed1989

[Graphic and numerical presentation of visual field findings].

This article reviews the various ways in which visual field defects can be represented and the advantages and disadvantages of the most commonly used methods. In addition, the G1 analysis program, which will soon be available, is briefly described.

Computer Graphics↗
PubMed1978

Visual-field displacements in human beings evoked by accoustical transients.

Sixty-two of 133 subjects reported visual-field displacements when they were exposed to intense (125 dB SPL) repetitive audiofrequency transients. This phenomenon was investigated in three experiments. Frequency (100-5000 Hz) was varied in experiment I; repetition rate (0.5/s--6.0/s) was varied in experiment II; acoustical transient onset/offset time (0.2--25 ms) was examined in experiment III. The results of these three experiments indicated that the largest proportion of displacement reports and the largest perceived motion magnitudes followed stimulation in the 500- to 1000-Hz frequency range at repetition rates of about 1/s. Response differences as a function of onset/offset time were erratic. The pattern of results obtained in this study, in conjunction with the results of previous investigations of acoustical vestibular stimulation, suggests that the visual-field displacments resulted from stimulation of the receptors of the vestibular system. These experiments may account for discrepancies in reports of infrasound-evoked eye movements. Finally, it is suggested that intense sound exposure may damage the vestibular receptors with or without concomitant damage to the auditory portion of the membranous labyrinth.

Acoustic Stimulation↗
PubMed1982

Visual field deficits in cats reared with unequal alternating monocular exposure.

Thirty-four kittens reared by allowing each eye patterned visual input, but on alternate days and for unequal periods of time (unequal alternating monocular exposure (AME)), were tested for their ability to orient to targets at different positions in visual space. In all unequal AME cats, the visual field of the more experienced eye (MEE) was normal, while that of the less experienced eye (LEE) was restricted. In contrast, in 14 cats reared with equal AME, the fields of both eyes were equal and of normal size. The field deficits observed in the unequal AME cats must therefore be due to the imbalance in stimulation and thus result from a competitive interaction between the afferents from the MEE and the LEE. The field deficits observed in the unequal AME cats differed from those observed in two monocularly deprived (MD) cats. Neither of the MD cats ever responded to targets presented in the region of normal binocular overlap when tested with the deprived eye (DE). The unequal AME cats all showed a nasal field loss in the LEE, but responded normally to targets throughout the temporal portion of the binocular visual field. When the imbalance in stimulation was large (8 to 1) or moderate (8 to 4), there was an abrupt drop in responsiveness (from 100% to zero) as the position of the target was changed from temporal to nasal. When the imbalance was slight (8 to 7), the drop in responsiveness was more gradual and occurred within the nasal field. Our results demonstrate that (1) the paradigm of unequal AME is a useful one for studying binocular competition quantitatively, (2) even the slightest imbalance in stimulation of the two eyes can affect the outcome of the competitive interaction, and (3) the pathways serving binocular vision are not uniformly affected by binocular competition: the ipsilateral pathway is more sensitive than the contralateral pathway.

Animals↗
PubMed2004

Orientation discrimination across the visual field: matching perceived contrast near threshold.

Performance can often be made equal across the visual field by scaling peripherally presented stimuli according to F=1+E/E2 where E2 is the eccentricity at which stimulus size must double to maintain foveal performance levels. Previous studies suggest that E2 for orientation discrimination is in the range of 1.5 degrees -2 degrees when stimuli are presented at contrasts well above detection threshold. Recent psychophysical and physiological evidence suggests spatial reorganization of receptive fields at near-threshold contrasts. Such contrast-dependent changes in receptive field structure might alter the amount of size scaling necessary to equate task performance across the visual field. To examine this question we measured orientation discrimination thresholds for a range of stimulus sizes and eccentricities (0 degrees -15 degrees ). We used the same procedure previously employed except that stimuli were presented at near-threshold contrasts. We controlled for the effects of perceptual contrast on thresholds through a matching procedure. A standard line of 3 degrees in length presented at fixation was set to 2 just noticeable differences above detection threshold. The perceived contrast of all other stimuli was adjusted by the subject to match this one. Orientation discrimination thresholds were then obtained at these matching contrasts for all stimulus sizes and eccentricities. E2 values of 3.42 degrees and 3.50 degrees were recovered for two subjects; these values were about a factor of two larger than E2 values previously found for this task when stimuli were presented at higher physical contrasts.

Contrast Sensitivity↗
PubMed2002

Treatment with taurine, diltiazem, and vitamin E retards the progressive visual field reduction in retinitis pigmentosa: a 3-year follow-up study.

The purpose of this study to assess the effect of the formula taurine/diltiazem/vitamin E on the progression of visual field loss in retinitis pigmentosa. A double blind, placebo controlled study in 62 patients: visual field threshold values were obtained in a Humphrey Field Analyzer from center (30 degrees) and periphery (30-60 degrees), every 4 months during 3-year follow-up. Data were analyzed by univariate regression, with slopes obtained from the best fit lines. Based on slope values, three groups of patients were identified as those showing negative, positive, or zero slope: > or = 1 to < or = +1. In controls (32 patients), at central area, the distribution in negative, zero, or positive slope was, respectively, 16 (50%), 11 (35%), and 5 (15%). In the treated group (30 patients) this distribution was 6 (20%) negative, 17 (53%) zero, and 7 (23%) positive slope. In periphery, 16 control patients were distributed as 11 (69%) negative, 4 (25%) zero, and 1 (6%) positive slope. In the treated group (17 patients), the distribution was opposite: 1 (6%) negative, 7 (41%) zero, and 9 (53%) positive slope. Nineteen patients receiving treatment up to 6 years showed similar distribution by slope values. Eight out of 9 patients switched from placebo (2 years) to treatment (2-3 years), showed improving changes in their slope values. A beneficial effect of the treatment decreasing the rate of visual field loss was observed, likely through a protective action from free radical reactions in affected photoreceptors.

Adolescent↗
PubMed1999

The oblique effect with colour defined motion throughout the visual field.

We assessed the extent of the oblique effect (OE) and the meridional orientation effect (MOE) for a chromatic motion task using red/green gratings throughout an 80 degrees visual field. Four different stimulus orientations were tested. Generally, sensitivity to chromatic motion decreased with increasing eccentricity regardless of the visual field meridian. Also, sensitivity was highest for horizontal or vertical gratings, thus supporting the presence of an OE rather than of a MOE. The strength of the OE varied between subjects, but was present from the fovea to 20 degrees of eccentricity. At 40 degrees of eccentricity, chromatic motion was always perceived but the grating orientation did not consistently influence chromatic motion sensitivity. The present study confirmed our previous results on chromatic motion sensitivity and isoluminance ratios throughout the visual field. In addition, our data show that the chromatic system can exhibit OEs at lower spatial frequencies than is observed for the achromatic system.

Analysis of Variance↗
PubMed1998

How good are we at assessing driving visual fields in diabetics?

PURPOSE/BACKGROUND: Following laser panretinal photocoagulation (PRP) for proliferative diabetic retinopathy, patients are at risk of failing the UK driving visual field test due to loss of peripheral field. Although a definition of the minimum field requirement exists, differences in its interpretation may influence whether fields pass or fail. Currently it is not known how fields are interpreted in practice nor to what extent this affects failure rates. METHODS: Uniocular and binocular Esterman visual fields from 60 diabetic patients following PRP were examined both by the chairman of the Visual Standards Sub-Committee of the Royal College of Ophthalmologists and separately by four consultant ophthalmologists. The results were analysed (1) to assess the extent of agreement and (2) to identify, from the chairman's results, the field deficits that are still compatible with passing. RESULTS: Agreement was generally good for binocular fields but was only moderate for uniocular fields. In up to 15% of binocular fields and 43% of uniocular fields the chairman's decision was different from that of the consultants. Several key aspects of the field that influence a pass/fail decision are identified. CONCLUSIONS: Substantial differences in the assessment of driving visual fields following RPR currently exist between consultants and the chairman of the Visual Standards Sub-Committee. Using the information presented here to guide assessment it is now possible to reduce this variation.

Automobile Driver Examination↗
PubMed1984

The qualitative comparative analysis of the visual field using computer assisted, semi-automated and manual instrumentation: I. Scoring system.

Previous methods for the qualitative evaluation of visual field instruments are subject to certain limitations. A system is proposed to overcome these deficiencies. It has been developed from experiences of a clinical study involving 5 different visual field instruments. The method uses 4 levels of analysis and permits separate appraisals of diagnostic potential and detailed inter-instrument comparative evaluation.

Computers↗
PubMedDate not supplied

Screening for visual field abnormalities with automated perimetry.

Recent studies indicate that automated perimetry can serve as an effective method of screening for visual field abnormalities associated with ophthalmologic and neurologic disorders. The techniques have been successfully applied to the private practitioner's office for screening of patients and to mass visual field screening of the general population. This paper describes the principles underlying automated perimetric screening, evaluates the capabilities and limitations of such techniques, and provides some general guidelines for using automated perimetric screening procedures.

Adolescent↗
PubMed1993

The visual acuity for the lateral visual field of the pigeon (Columba livia).

Previous studies on pigeons indicated that the visual acuity for the frontal visual field was much higher than that for the lateral one. Suspecting that the poor values for the lateral field were due to suboptimal testing conditions, we determined the lateral field acuity in eight head-fixed pigeons with high-contrast square-wave gratings. An instrumental conditioning task with water as reinforcer and mandibulation as an operant was used. Subjects achieved a mean acuity value of 12.6 c/deg. The results show that the acuity of the lateral visual field is only slightly lower than that of the frontal field. These data provide a psychophysical basis for ecological observations that pigeons and most other birds gaze laterally when scrutinizing small and distant objects.

Animals↗
PubMed1986

The interpretation of the differential threshold in the central visual field.

Computer assisted perimetry has revolutionised the investigation of the visual field. Experience of central field assessment with the Octopus Automated Perimeter shows that sensitivity recorded with target size 3 across all age groups can frequently be greater than the published normative values. Use of the latter values can therefore provide a serious underestimation of field loss. Inter-individual variation in sensitivity is found within and between age groups. The limitations associated with the use of the measurement error to define abnormality and the additional problems of hypernormal thresholds and resolution of the blind spot are discussed. It is suggested that methods should be developed to evaluate sensitivity on an intra-individual basis.

Adolescent↗
PubMedDate not supplied

Little correlation of the pattern electroretinogram (PERG) and visual field measures in early glaucoma.

Pattern-electroretinograms (PERG) to checkerboard reversal at 16/s. 0.8 degrees and 15 degrees check size and visual fields (Octopus G1) were retrospectively analyzed in 40 eyes of 30 patients with early glaucoma. The mean visual field defect was calculated separately for the central 26 degrees x 34 degrees covered by the PERG stimulus (MDc) and the more peripheral area (MDp) surrounding the stimulus. Deeper field loss was correlated with a reduced pattern electroretinogram amplitude (p < 0.01 for both MDp and MDc), indicating that the pattern electroretinogram deteriorates as glaucoma advances. If the analysis was confined to those 18 eyes (16 patients) that had no field defect within the area covered by the PERG stimulus (normal MDc but abnormal MDp), 13 of these had an abnormal PERG amplitude (p < 0.001). The results suggest that the PERG can reveal impairment of ganglion cell function that is not detected by conventional perimetry.

Adult↗
PubMed2004

Decreased visual field sensitivity measured 1 day, then 1 week, after migraine.

PURPOSE: To determine whether perimetric performance is worse the day after a migraine than prior interictal measurements, and if so, to determine whether differences have resolved by 1 week after migraine. METHODS: Twenty-two nonheadache control subjects (aged 18-45 years) and 22 migraineurs (aged 18-45 years: 10 migraine with visual aura, 12 migraine without aura) participated. Standard automated perimetry (SAP) and temporal modulation perimetry (TMP) were measured by perimeter (model M-700; Medmont, Pty Ltd., Camberwell, Victoria, Australia). Control subjects attended two test visits: baseline and retest. Migraineurs attended three times: baseline (>or=4 days after migraine), the day after the offset of the next migraine, and 7 days later. Groups were compared using the global indices of the perimeter: Average Defect (AD) and Pattern Defect (PD), in addition to point-wise comparisons. RESULTS: Group migraineur TMP performance was significantly worse the day after a migraine, showing decreased general sensitivity and increased localized loss. Performance measured 7 days later was not significantly different from that measured the day after a migraine. Group migraineur SAP performance was not significantly worse after migraine; however, a subgroup of six eyes from five patients had 10 or more visual field locations with decreases in sensitivity greater than control test-retest 95% confidence limits. CONCLUSIONS: Decreased visual field performance was present after migraine, as well as greater test-retest variability in the migraine group compared with control subjects. As migraineurs constitute 10% to 15% of the general population, the presence of this subgroup of patients with periodic prolonged decreased visual field sensitivity after migraine has implications for differential clinical diagnosis, and for clinical research using perimetry.

Adolescent↗
PubMed1999

Visual field differences in spatial frequency discrimination.

Subjects discriminated between sine-wave gratings that differed by either +/-0.125 octaves (small difference) or +/-1.0 octaves (large difference). Baseline stimuli consisted of either 1.0 or 4.0 cycles per degree gratings. A left visual field advantage was obtained for the small difference in frequency, with no visual field advantages for the large difference in frequency. Similarly, moderate support for right versus left visual field advantages in processing high versus low spatial frequencies was found, although these interactions were not statistically significant. The results are discussed in light of Kosslyn's (1987) categorical and coordinate framework.

Cognition↗
PubMed1998

Visual field defects in optic neuritis and anterior ischemic optic neuropathy: distinctive features.

BACKGROUND: We analyzed the value of visual-field defects in the differential diagnosis of optic neuritis (ON) and non-arteritic anterior ischemic optic neuropathy (AION). METHODS: Ninety-nine consecutive patients with acute-onset optic neuropathy formed the basis for this study. Compressive and vasculitic neuropathies were excluded. Eighty-six patients fulfilled the criteria for either ON (50 patients): < or = 35 years, normal disk, recovery of visual function, or AION (36 patients): > or = 60 years, swelling of the disk, no recovery of visual function. Without knowledge of other clinical data, visual fields obtained by Gold-mann perimetry were classified into five types of defects (forced choice). With the correct diagnosis at hand, fields were reviewed for characteristic features. RESULTS: Forced-choice classification into defect types [%]: Central scotoma ON 68, AION 18; superior altitudinal defect ON 13 AION 7; inferior altitudinal defect ON 8, AION 52; peripheral defect ON 1, AION 5; diffuse defect ON 10, AION 18. Search for pathognomonic defects: a scotoma centered on the fixation point with a sloping border occurred exclusively in ON (25 of 50 patients). An inferior altitudinal defect with a sharp border along the horizontal meridian, particularly in the nasal periphery, occurred only in AION (10 of 36 patients). A steep centrocecal scotoma occurred in 3 of the 36 AION cases and not at all in the ON cases. Scotomas in the center breaking through to the periphery, superior altitudinal defects (with a sloping border along the horizontal meridian) and diffuse depressions verging on blindness occurred in both ON and AION. CONCLUSION: A sctoma centered on the fixation point with a sloping border is highly characteristic of ON, while an inferior altitudinal defect with a sharp border along the horizontal meridian, particularly in the nasal periphery, is highly characteristic of AION. To identify these diagnostic criteria, it can be necessary to examine full fields. With restriction of perimetry to 30 degrees a large central scotoma can be mistaken for a diffuse defect and the border in the nasal periphery can be missed.

Acute Disease↗
PubMed1982

The Friedmann Visual Field Analyser Mark II--technical evaluation and clinical results.

The perimetric concept and the technical construction of the Friedmann Visual Field Analyser Mark II (VFA Mk II) were evaluated. This instrument for multiple stimulus static campimetry of the central 25 degrees is the successor of the Friedmann VFA Mk I. The number of stimuli is increased (99 vs. 47) and the console is improved. The positions of the presented stimuli are indicated on a LED-monitor. The mechanical and electrical construction of the VFA Mk II appeared to be good. 106 eyes of patients and normal subjects were tested and we conclude that the larger number of stimuli, though improving the chance of detecting small defects, complicates the manual registration and the interpretation of clinical results and prolongs the test, especially in the case of visual fields with substantial defects.

Glaucoma↗