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At least 883 records · Page 49Linked to original sources

PubMed1976

Assessment of visual field impairment by objective technique.

An objective psychophysical technique for investigating visual fields by averaged scalp potentials evoked by pattern gratings of alternating contrast and by sinusoidally modulated flicerking light is applied to a child with a right homonomous hemianopsia. This technique illustrates a value, in obtaining clinical data on visual fields in situations were subjective perimetry is difficult to administer or where conservating diagnostic methods do not yield evidence of pathology.

Child↗

PubMed1996

Relationship between optic nerve head parameters of Heidelberg Retina Tomograph and visual field defects in primary open-angle glaucoma.

To investigate the correlation between optic nerve head configuration and visual field defects, optic nerve head analysis using confocal scanning laser tomography (Heidelberg Retina Tomograph, HRT) and automated static threshold perimetry using a Humphrey Field Analyzer (program C30-2) were performed on 81 eyes of 44 primary open-angle glaucoma (POAG) patients. The optic nerve head parameters-rim area, rim volume, mean retinal nerve fiber layer thickness, height variation contour, and third moment in contour were measured by HRT and were analyzed for correlation with visual field indices-mean deviation, and corrected pattern standard deviation. All optic nerve head parameters except HVC correlated significantly with the visual field indices; the highest correlation was between rim area and mean deviation (r = 0.6172, p < 0.00001). The rim area of the superior and inferior quadrants correlated significantly with the visual field defects in corresponding sectors. Structural optic disc measurements by HRT correlated significantly with functional optic nerve head damage in POAG.

Female↗

PubMed1994

Compromises in the visual field with the M43 aviation mask.

This study evaluated peripheral vision through the M43 protective mask currently worn by aviators in the AH-64 Apache helicopter. A Humphrey Visual Field Analyzer was used to measure the sensitivity of a subject's visual field with and without the mask. The results were analyzed using Dicon's Fieldview software. The monocular visual field was reduced for each eye when wearing the mask, especially superiorly and nasally. The overall size of the visual field was not reduced when both eyes were open; however, the quality of the visual field was reduced. The area of binocular vision (central binocular vision fusion field subserving stereopsis) was restricted to the central 30 degrees.

Adult↗

PubMed1994

High-resolution perimetry of the central visual field.

The Octopus Program M1 was designed for the detection/follow-up of central or paracentral visual field defects in patients with neurological disorders or with macular or perimacular diseases. Within the central 25 degrees visual field, 59 test locations provide a resolution of < or = 1.4 degrees. The differential light sensitivity is measured with 'Octopus normal strategy', i.e. a 4/2/1 staircase procedure. The Program M2X has 81 test locations in the central 10 degrees, giving even higher resolution (< or = 0.7 degrees) of the central visual field. Both programs have 2 phases, the second being a re-test. Program M2X's phases are divided into 4 stages and allow interruption anytime.

Adult↗

PubMed2004

Neural attractor network for application in visual field data classification.

The purpose was to introduce a novel method for computer-based classification of visual field data derived from perimetric examination, that may act as a 'counsellor', providing an independent 'second opinion' to the diagnosing physician. The classification system consists of a Hopfield-type neural attractor network that obtains its input data from perimetric examination results. An iterative relaxation process determines the states of the neurons dynamically. Therefore, even 'noisy' perimetric output, e.g., early stages of a disease, may eventually be classified correctly according to the predefined idealized visual field defect (scotoma) patterns, stored as attractors of the network, that are found with diseases of the eye, optic nerve and the central nervous system. Preliminary tests of the classification system on real visual field data derived from perimetric examinations have shown a classification success of over 80%. Some of the main advantages of the Hopfield-attractor-network-based approach over feed-forward type neural networks are: (1) network architecture is defined by the classification problem; (2) no training is required to determine the neural coupling strengths; (3) assignment of an auto-diagnosis confidence level is possible by means of an overlap parameter and the Hamming distance. In conclusion, the novel method for computer-based classification of visual field data, presented here, furnishes a valuable first overview and an independent 'second opinion' in judging perimetric examination results, pointing towards a final diagnosis by a physician. It should not be considered a substitute for the diagnosing physician. Thanks to the worldwide accessibility of the Internet, the classification system offers a promising perspective towards modern computer-assisted diagnosis in both medicine and tele-medicine, for example and in particular, with respect to non-ophthalmic clinics or in communities where perimetric expertise is not readily available.

Diagnosis, Computer-Assisted↗

PubMed2005

Optic-flow and egocentric-direction strategies in walking: central vs peripheral visual field.

The impact of a central or peripheral visual field loss on the vision strategy used to guide walking was determined by measuring walking paths of visually impaired participants. An immersive virtual environment was used to dissociate the expected paths of the optic-flow and egocentric-direction strategies by offsetting the walker's point of view from the actual direction of walking. Environments consisted of a goal within a forest, the goal alone, or the forest alone following a brief presentation of the goal. The first two environments allowed an evaluation of the visual information used in a goal-directed task whereas the third environment investigated the information used in a memory-guided task. Participants had either a central (CFL) or peripheral visual field loss (PFL) or were fully sighted (FS). Results showed that, for the goal-directed task, the CFL group was less influenced by optic flow than was an age-matched FS group. Optic flow decreased heading error by only 1.3 degrees (16%) in the CFL group compared to 3.6 degrees (42%) in the FS group. The PFL group showed an optic-flow influence (2.4 degrees or 26%) comparable to an older, age-matched FS group (2.9 degrees or 31%). For the memory-guided task, all but the PFL group had heading errors comparable to those obtained in the goal-alone scene, demonstrating the ability to use an egocentric-direction strategy with a stored representation of either the goal's position or an offset relative to a landmark instead of a visible goal. The paths of the PFL group veered significantly from the predicted paths of both the optic-flow and egocentric-direction strategies. The findings of this study suggest that central vision is important for using optic flow to guide walking, whereas peripheral vision is important for establishing and/or updating an accurate representation of spatial structure for navigation.

Adult↗

PubMed1998

Intraocular pressure and visual field defects.

During a five-year study period, therapeutic levels of intraocular pressure (IOP) and visual field defects were assessed in 108 patients with open-angle glaucoma. In a group of 53 glaucoma patients with non-progressive visual field changes (mean age 65.2 +/- 6.3 years), the IOP level was 15.8 +/- 2.6 mm Hg, whereas in a group of 58 patients with progressive visual field changes (mean age 68.7 +/- 8.3 years) the IOP level was 19.9 +/- 2.9 mm Hg. Study results suggested that preservation of the visual field in glaucoma patients requires therapeutic IOP levels of < 16 mm Hg.

Disease Progression↗

PubMed1978

Indirect, across-the-midline retinotectal projections and representation of ipsilateral visual field in superior colliculus of the cat.

1. In agreement with previous work, we have found that the ipsilateral visual field is represented in an extensive rostral portion--from one-third to one-half--of the superior colliculus (SC) of the cat. This representation is binocular. The SC representation of the ipsilateral visual field can be mediated both directly, by crossed retinotectal connections originating from temporal hemiretina, and indirectly, by across-the-midline connections relaying visual information from one-half of the brain to contralateral SC. 2. In order to study the indirect, across-the-midline visual input to the SC, we have recorded responses of SC neurons to visual stimuli presented to either the ipsilateral or the contralateral eye of cats with a midsagittal splitting of the optic chiasm. Units driven by the ipsilateral eye, presumably through the direct retinotectal input and/or corticotectal connections from ipsilateral visual cortex, were found throughout the SC, except at its caudal pole, which normally receives fibers from the extreme periphery of the contralateral nasal hemiretina. Units driven by the contralateral eye, undoubtedly through an indirect across-the-midline connection, were found only in the anterior portion of the SC, in which is normally represented the ipsilateral visual field. Receptive fields in both ipsilateral and contralateral eye had properties typical of SC receptive fields in cats with intact optic pathways. 3. All units having a receptive field in the contralateral eye had also a receptive field in the ipsilateral eye; for each of these units, the receptive fields in both eyes invariably abutted the vertical meridian of the visual field. The receptive field in one eye had about the same elevation relative to the horizontal meridian and the same vertical extension as the receptive field in the other eye; the two receptive fields of each binocular unit matched each other at the vertical meridian and formed a combined receptive field straddling the vertical midline of the horopter...

Animals↗

PubMed1984

The short-term effect of laser trabeculoplasty on the glaucomatous visual field. A prospective study using computerized perimetry.

Several earlier studies have shown improvement of glaucomatous visual fields after pressure reduction achieved by acetazolamide or filtering surgery, while other studies have given conflicting results. In the present study laser trabeculoplasty was used to reduce the IOP in 42 eyes with glaucomatous visual field defects. Although good pressure reduction was achieved, no general regression of field defects was observed. The changes of the visual field were not correlated to the degree of pressure reduction. The results do not support the hypothesis that glaucomatous field defects are reversible when the IOP is reduced.

Adult↗

PubMed2003

Visual field information in the face perception of chimpanzees (Pan troglodytes).

Evidence for a visual field advantage (VFA) in the face perception of chimpanzees was investigated using a modification of a free-vision task. Four of six chimpanzee subjects previously trained on a computer joystick match-to-sample paradigm were able to distinguish between images of neutral face chimeras consisting of two left sides (LL) or right sides (RR) of the face. While an individual's ability to make this distinction would be unlikely to determine their suitability for the VFA tests, it was important to establish that distinctive information was available in test images. Data were then recorded on their choice of the LL vs. RR chimera as a match to the true, neutral image; a bias for one of these options would indicate an hemispatial visual field advantage. Results suggest that chimpanzees, unlike humans, do not exhibit a left visual field advantage. These results have important implications for studies on laterality and asymmetry in facial signals and their perception in primates.

Animals↗

PubMed2006

[Optic nerve drusen and deep visual fields defects].

PURPOSE: Optic nerve drusen needs to be included in the differential diagnosis of pseudopapilledema. As the identification of this entity by funduscopy may be difficult, ultrasonography has thus become the gold standard for its diagnosis. Severe optic nerve drusen has been correlated with a reduction of the nerve fiber layer measured by optic coherence tomography and with the presence of serious visual field defects. To demonstrate the relationship between extensive optic nerve drusen and visual field defects. METHOD: A prospective observational study of the visual fields of a series of 5 patients with severe optic nerve drusen diagnosed by ultrasonography. RESULTS: Visual field defects of widely differing severity, from inferior nasal quadrant to severe hemivisual field defects, were described in each patient studied. CONCLUSIONS: Visual field defects of diverse severity are common in patients with deep optic nerve drusen. For that reason ultrasonography and/or optical coherence tomography is highly recommended where such visual field defects exist.

Adult↗

PubMed2002

Sex differences in functional brain activation during a lexical visual field task.

Functional MRI was used to investigate sex differences in brain activation during a paradigm similar to a lexical-decision task. Six males and 6 females performed two runs of the lexical visual field task (i.e., deciding which visual field a word compared with a pseudoword was presented to). A sex difference was noted behaviorally: The reaction time data showed males had a marginal right visual field advantage and women a left visual field advantage. Imaging results showed that men had a strongly left-lateralized pattern of activation, e.g., inferior frontal and fusiform gyrus, while women showed a more symmetrical pattern in language related areas with greater right-frontal and right-middle-temporal activation. The data show evidence of task-specific sex differences in the cerebral organization of language processing.

Adult↗

PubMed1995

Pattern of visual field defects in normal-tension and high-tension glaucoma.

There are probably two major types of causative factors in open-angle glaucoma: pressure-dependent and pressure-independent. If clinical features such as the pattern of visual field defects differ between normal-tension and high-tension glaucoma, the differences may provide an insight for discriminating between the pressure-dependent and the pressure-independent damage in open-angle glaucoma. This article gives a brief review of the most recent studies including reports wherein progression or pattern of visual field defects in normal-tension and high-tension glaucoma or primary open-angle glaucoma are addressed. Further deterioration of the visual field in 5 years is expected in about 50% of eyes with normal-tension glaucoma in which intraocular pressure is one of the contributing factors. This figure may be greater than that seen in eyes with primary open-angle glaucoma where intraocular pressure is controlled with surgery in the middle teens. When eyes with normal-tension glaucoma and high-tension glaucoma or primary open-angle glaucoma were matched for extent of overall visual field loss, many studies noted a difference in the pattern of visual field defects between the two groups. Visual field defects in normal-tension glaucoma are relatively more localized and closer to fixation, especially in the nasal superior quadrant and may be more predominant in the lower hemifield. Results of other psychophysical tests also appear to support the above findings.

Glaucoma, Open-Angle↗

PubMed1996

Visual field defects due to spectacle frames: their prediction and relationship to UK driving standards.

One male and one female subject wore a selection of ten current spectacle frames in random order. Monocular visual fields were assessed using an Aimark perimeter in accordance with UK Driver and Vehicle Licensing Authority (DVLA) guidelines. Of the ten frames, seven plastic frames produced an absolute scotoma intruding into a 120 degrees x 40 degrees 'letterbox' area acting as a driving visual field template. Three metal frames gave a relative scotoma; however, our apparatus was too insensitive to plot these scotomata. Relevant frame and patient parameters were measured and entered into a computer program which enabled theoretical visual field defects due to a spectacle frame to be calculated. Good agreement is shown to be possible between actual and computed visual field defects. Spectacle frames can and frequently do cause visual field defects which may affect a driver's fitness to drive. Our data also show that a frame which allows an adequate field of vision at night could cause a marked visual field defect during daylight hours. A model and rule-of-thumb are given to determine the size of these potential defects and suggestions are given to minimise or eliminate them.

Adult↗

PubMed1994

Visual fields at different stages of diabetic retinopathy.

Available studies on visual field disturbances in diabetic retinopathy have shown conflicting results, obtained with different and often non-comparable techniques. We have studied visual fields at different stages of diabetic retinopathy with modern sensitive computerized technique taking precautions to limit disturbing effects of random field variation and lack of perimetric experience. Sixty-three diabetic patients, insulin-dependent and non-insulin dependent, were each subject to three test sessions using the 30-2 full threshold program of the Humphrey perimeter. Retinopathy levels ranged from 10 to 65 in the ETDRS Final scale. In eyes without retinopathy or with very mild and mild disease (levels 10-35) mean deviation values exceeding the p < 5% level occurred in only 4% of eyes in trained sessions, and the number of test points with significantly reduced sensitivity did not exceed that expected in normal eyes. In moderate and moderately severe diabetic retinopathy (level 43-47) and in severe non-proliferative and proliferative retinopathy (levels 53-65) there was clear evidence of field loss, however, with significantly reduced mean deviation values in 44% of the eyes and 6.5% of tested points showing reproducible loss of sensitivity. Thus, there was no evidence of field loss in eyes with mild disease, but clear field defects in eyes with more advanced disease. Significantly reduced sensitivity was often correlated with retinal non-perfusion and there was seen a tendency towards more correlation in the midperiphery than paracentrally.

Adult↗

PubMed1978

[The effect of lens opacities on the visual field (author's transl)].

The stray light effect on the visual field was quantitatively studied in normal subjects under experimental conditions. Stray light comparable to that caused by lens opacities was produced by means of selective occluders or diascleral illumination. The results derived from this model were compared with the statistical evaluation of the visual fields of 123 eyes with glaucoma followed for a minimum of 10 years. As expected lens opacities resulted in a concentric constriction of the peripheral fields and a loss of the inner isopters. The light difference sensitivity as determined by static perimetry was generally reduced preferentially in the central fields. These calculations provide a measure to anticipate the degree of lens opacifications from a depressed visual without knowledge of the visual acuity.

Adult↗

PubMed2006

Relationship between asymmetric central corneal thickness and glaucomatous visual field loss within the same patient.

PURPOSE: Considering that thinner central corneal thickness (CCT) has been identified as a significant glaucoma risk factor, this study was designed to determine whether patients with glaucoma with asymmetric CCT demonstrate greater visual field loss in their thinner CCT eye compared with their thicker CCT eye. METHODS: Patient logs were used to retrospectively identify patients with primary open-angle glaucoma (POAG) and patients with normal-tension glaucoma (NTG) with CCT asymmetry of 10 microm or greater. Severity of glaucoma was determined using Advanced Glaucoma Intervention Study (AGIS) visual field scoring criteria. After statistical analysis was used to compare all thinner CCT eyes vs. corresponding thicker CCT eyes, subjects with worse visual field loss in the thinner CCT eye were compared with subjects with worse visual field loss in the thicker CCT eye. Subanalysis was then completed using only subjects with CCT asymmetry of 15 microm or greater. RESULTS: In the 52 subjects who met all criteria for study inclusion, mean AGIS score was significantly higher in the thinner CCT eyes compared with the thicker CCT eyes. Subjects with higher AGIS score in their thinner CCT eye outnumbered subjects with higher AGIS score in their thicker CCT eye, with the differences approaching statistical significance in the full sample (p = 0.06) and achieving significance when analysis was limited to subjects with CCT asymmetry of 15 microm or greater (p = 0.001). Multivariate logistic regression analysis identified thinner CCT as the primary risk factor associated with higher AGIS score in subjects with CCT asymmetry of 15 microm or greater. CONCLUSION: These results correspond to prior reports implicating CCT as an independent risk factor for glaucomatous visual field loss. When significant CCT asymmetry is present in patients with glaucoma, the thinner CCT eye is at greater risk for more advanced visual field loss. The underlying nature of this increased risk is unknown, but further study into structural vulnerabilities associated with thinner CCT seems justified.

Aged↗

PubMed1991

Effects of monocular deprivation on the visual fields of squirrel monkeys.

Five squirrel monkeys were monocularly deprived at birth for 3 years. Visual field testing for the deprived eye revealed no responses to visual stimuli at any position, including the monocular segment. These results are similar to those obtained in macaque monkeys after long-term neonatal monocular deprivation and indicate that lack of patterned visual input to an eye during development in primates can produce functional blindness throughout the visual field. Because the monocular segment of the visual field was not spared, binocular competition cannot be the only mechanism underlying this loss. Instead, lack of patterned visual input probably causes improper neuronal connections during development in all segments of the visual cortex resulting in complete loss of form vision.

Animals↗