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At least 19 recordsLinked to original sources
PubMed1990

Clinical implications of parallel visual pathways.

Visual information travels from the retina to visual cortical areas along at least two parallel pathways. In this paper, anatomical and physiological evidence is presented to demonstrate the existence of, and trace these two pathways throughout the visual systems of the cat, primate, and human. Physiological and behavioral experiments are discussed which establish that these two pathways are differentially sensitive to stimuli that vary in spatial and temporal frequency. One pathway (M-pathway) is more sensitive to coarse visual form that is modulated or moving at fast rates, whereas the other pathway (P-pathway) is more sensitive to spatial detail that is stationary or moving at slow rates. This difference between the M- and P-pathways is related to some spatial and temporal effects observed in humans. Furthermore, evidence is presented that certain diseases selectively comprise the functioning of M- or P-pathways (i.e., glaucoma, Alzheimer's disease, and anisometropic amblyopia), and some of the spatial and temporal deficits observed in these patients are presented within the context of the dysfunction of the M- or P-pathway.

Animals↗
PubMed1992

Perceptual ambiguity and the short wavelength sensitive visual pathway.

Visual illusions and ambiguous figures are difficult to perceive when presented in a manner which stimulates only chromatic pathways. This perceptual limitation could indicate that these pathways are unable to mediate form perception, or it may reflect the relative visibility of the stimulus, regardless of the pathway utilized. To examine this issue, an ambiguous figure (illusory Necker cube) was presented to the short wavelength sensitive (S) cone pathway which is thought to convey only chromatic signals. Although few observers could recognize the cube when presented in isolation to S cones, the same reduction in recognition was found when the cube was detected by achromatic pathways at a level of visibility comparable to that conveyed by S cones. Our results indicate that for this object recognition task, visibility of the stimulus is the relevant variable, rather than the particular pathway traversed. Prior experience was also found to be important determinant of object recognition.

Color Perception↗
PubMed1986

Pattern disappearance visually evoked cortical potential in the diseases of visual pathway.

Visually evoked cortical potentials in response to pattern-appearance, -disappearance, and -reversal stimuli were studied in normal subjects and in patients suffering from optic neuritis. It was found in normal subjects that pattern disappearance VECPs were as reliable as the pattern reversal ones. On the other hand, the appearance response showed interindividual differences which made its evaluation rather difficult. The same was true in the records of the patients. Both the mean peak latencies of the disappearance responses and those of the pattern reversal ones were prolonged significantly in optic neuritis, compared with those obtained from normal subjects. We concluded that the peak latencies of the disappearance response could be more confidently used than those of the appearance response for diagnosing optic neuritis.

Adult↗
PubMed1985

The application of flash visual evoked potentials during operations on the anterior visual pathways.

Flash visual evoked potentials (F-VEP's) have been recorded in fifteen patients (thirty eyes) with anterior visual pathway compression lesions before, during and after the operation in relation to clinical visual testing. A grading system for the wide variety of abnormal F-VEP's has been established, based on changes in forty patients (eighty eyes). No significant correlation between change in F-VEP and visual acuity or visual field has been demonstrated. Intraoperative F-VEP's have been found to be sensitive to halothane and to surgical manipulation of the optic nerve and/or chiasm during dissection of the tumour. The technique is considered a useful means of identifying the optic pathway during operation and may assist in prevention of optic damage if the transphenoidal approach is used.

Adult↗
PubMed1976

Visual pathways, acuity dominance, and visual half-field asymmetry.

The effects of the visual pathways and acuity dominance on visual half-field (VHF) recall of verbal stimuli were investigated with 36 right-handed male undergraduates, with the use of the Hines-Satz short-term memory paradigm under monocular conditions. Scores for stimuli transmitted via the left temporal and right nasal pathways were significantly greater than those for stimuli transmitted via the left nasal and right temporal pathways. No other significant differences were found for either the pathways or acuity dominance variables. The results were hypothesized to reflect the primary influence of hemispheric asymmetry of function on the VHF recall task.

Adolescent↗
PubMed1991

[Disorders of the afferent visual pathway in HIV infection. 1. Optic nerve and 2. Visual pathways/visual cortex].

Up to now little involvement of the afferent visual pathway (optic nerve and optic radiation and visual cortex) in HIV infection has been apparent. These results are based on our prospective investigations of 538 HIV-infected individuals, among them 261 patients with full-blown AIDS carried out by the same examiner over a 6-year period (1984-1990). Diseases of the optic nerve were observed in 22/261 (8.4%) of Aids patients but in only 1/227 (0.4%) of patients with earlier stages of HIV infection. Optic neuritis was the most common disease (in 14/261 = 5.4% of Aids patients), for the most part occurring in the course of CMV (cytomegalovirus) retinitis. For this form the prognosis was primarily good under virustatic therapy with ganciclovir in contrast to primary CMC papillitis. Furthermore, a few cases of optic perineuritis, optic neuropathy in basal meningitis, ischemic optic neuropathy and papilloedema with increased intracranial pressure were observed, most of them caused by opportunistic infections of the central nervous system. In single cases the HIV might hypothetically have played a role in the etiology. Visual impairment of the patients varied from subtle disturbances to blindness. Often optic atrophy resulted. Homonymous hemianopsia was the principal sign in diseases of the visual pathway between the lateral geniculate body and the visual cortex (in 10/261 = 3.8% of Aids patients). This symptom resulted from cerebral toxoplasmosis in 7 cases, progressive multifocal leukoencepalopathy (PML) in 2 cases and primary intracerebral malignant lymphoma in 1 case. The visual fields and neuroradiological findings are demonstrated. In 3 cases the homonymous hemianopsia was the first clinical appearance of Aids. Involvement of the afferent visual pathway in HIV infection may be a cause of blindness or visual disturbances despite normal findings on examination of the eyes themselves.

Fluorescein Angiography↗
PubMed1989

Detection and recognition of visual field defects resulting from lesions involving the visual pathways.

A prospective study of visual field defects associated with lesions of the visual pathway was carried out using kinetic and suprathreshold static stimuli with a view to establishing the most effective screening method for these field defects. The 215 abnormal fields so obtained showed that all field defects due to lesions of the visual pathways are detectable within 30 degrees of fixation and that not only is central field testing mandatory in excluding such a field defect, but more peripheral field testing alone is ineffective. This study also revealed that when kinetic fields are charted, it is probably not worthwhile searching for scotomata other than within the most central part of the field. Furthermore, where outer and inner isopter depression is not coextensive, inner isopters are always depressed more than outer isopters when the field defect is due to a lesion of the visual pathway.

Central Nervous System Diseases↗
PubMed1988

Intracranial visual pathway gliomas in children with neurofibromatosis.

The association between neurofibromatosis and visual pathway gliomas is well documented. The introduction of computed tomography and magnetic resonance imaging has heralded a new era in the understanding of visual pathway gliomas. Both of these noninvasive neuroinvestigative techniques have demonstrated extensive abnormalities throughout the visual pathway in children with visual pathway gliomas, especially in those with neurofibromatosis. The clinical significance of these abnormal areas of brain, especially in asymptomatic patients, is unknown. In an attempt to clarify the incidence, natural history, and clinical course of patients with neurofibromatosis and visual pathway lesions, we reviewed our experience with 24 patients managed consecutively at Children's Hospital of Philadelphia over the past 12 years. The patients in this series were compared to 29 children with visual pathway gliomas without neurofibromatosis who were evaluated at our institution over the same period of time. Visual pathway gliomas in children with neurofibromatosis differ from those in children without neurofibromatosis. In general, lesions tended to be more extensive in patients with neurofibromatosis and the clinical course of these patients is more variable. Twelve of the 24 patients with neurofibromatosis in our series had symptoms of progressive disease at the time of diagnosis and underwent treatment with variable results. Twelve children with neurofibromatosis and visual pathway lesions had static lesions at the time of diagnosis and, to date, 3 have developed progressive disease. From our review we can make some recommendations concerning the management of children with neurofibromatosis and visual pathway gliomas, but many questions remain unanswered. Sequential follow-up of a large cohort of both asymptomatic and symptomatic children with neurofibromatosis and visual pathway lesions is needed to more definitively outline the best management approach for these patients.

Adolescent↗
PubMedDate not supplied

[Visual evoked potentials in cases of damage to visual pathways at different levels].

Visual potentials induced with a checker pattern were studied in a group of patients with damage to the visual pathways at different levels, and were compared with similar potentials in 10 adult subjects without diseases. A statistically significant prolongation of latency of the main deflections (N1, P max and N2) was observed in the group of 14 patients with optic nerve damage, while in 10 patients with lesions above the chiasma different, often normal responses were obtained. High-grade deformity of visual potentials was observed in 2 cases of visual agnosia. The study of visual evoked potentials may be in the opinion of the authors, useful in cases of damage to the optic nerve, retina and cortical visual centres.

Adult↗
PubMed1991

Efficacy and complications of radiotherapy of anterior visual pathway tumors.

A progressive disturbance in visual acuity or visual field, along with an unexplained optic nerve atrophy, suggests the possibility of a tumor. Tumors that frequently affect the anterior visual pathway include primary optic nerve sheath meningiomas, intracranial meningiomas, optic gliomas, pituitary tumors, and craniopharyngiomas. The location of these tumors sometimes prohibits a complete surgical excision that might jeopardize the visual system. Radiation therapy, however, can be beneficial in these cases. This article reviews the indications for radiotherapy of tumors that involve the anterior visual pathway, along with the possible complications. Cases that present the effect of radiation therapy and radiation damage are presented.

Adenoma↗
PubMed1989

A type II keratin is expressed in glial cells of the goldfish visual pathway.

The predominant intermediate filament proteins of the goldfish visual pathway consist of neuronal and non-neuronal isoelectric variants (58 kd). We have isolated a cDNA clone for the glial intermediate filament protein (ON3) from an optic nerve expression library. The predicted amino acid sequence of this clone reveals that it codes for a type II keratin representing the goldfish equivalent of mammalian keratin K8. K8 has been shown to be associated with embryogenesis and development. Unlike the mammalian visual system, the goldfish visual pathway displays a remarkable capacity for functional regeneration. The expression of K8, a protein not usually expressed in glial cells but shown to be associated with development, in the goldfish optic nerve may be involved with the processes of growth and regeneration in the goldfish visual pathway.

Amino Acid Sequence↗
PubMed1988

Management of pregeniculate anterior visual pathway gliomas.

Gliomas of the pregeniculate anterior visual pathways comprise about 5% of all intracranial tumors that occur in the first decade of life. Gliomas are the most common primary optic nerve tumor. Diagnosing a glioma of the anterior visual pathways is much easier since the advent of computerized tomography (CT) and magnetic resonance imaging (MRI); the continuing problem is appropriate management. Improved guidelines for management are suggested based on a review of the literature and the authors' experience. These guidelines include both the need to characterize accurately the location of the tumor and its clinical and radiologic progression, and the imperative to employ active intervention only when there is a specific therapeutic goal that can be used for measuring the success of the treatment.

Child↗
PubMed1987

Irradiation of meningiomas of the intracranial anterior visual pathway.

Twenty patients with progressive visual loss caused by intracranial meningiomas involving the anterior visual pathway were treated with irradiation alone (n = 4) or with irradiation combined with tumor excision (n = 16). Improvement in visual performance occurred in 13 patients; 2 patients experienced temporary improvement; and 5 others maintained stable visual function for up to 9.5 years (mean follow-up, 4.0 years). Radiotherapy seemed to have no effect in 2 patients. One patient experienced temporary improvement, but eventually died from spread of tumor. Only one definite complication of radiotherapy occurred and was related to excessive radiation dose (greater than 7,000 cGy). Irradiation in the range of 5,000 to 5,500 cGy was effective either alone or in combination with surgical excision. Serial assessment of visual acuity and fields allowed us to demonstrate and quantify improvement in our patients following radiotherapy; in contrast, follow-up computed tomographic studies rarely demonstrated reduced tumor size.

Combined Modality Therapy↗
PubMed1986

Aneurysmal compression of the anterior visual pathways.

Ten patients with aneurysmal compression of the anterior visual pathways had visual loss, unilateral in 4 and bilateral in 6. There was no typical clinical presentation. Visual loss was acute or gradual, acuity sometimes fluctuated, and visual field testing was highly variable. The aneurysms were supraclinoid (four patients), carotid-ophthalmic (two), anterior communicating-anterior cerebral (three), and intracavernous carotid (one). Nine patients had successful clipping of their aneurysm, and in one, ipsilateral common carotid ligation was performed. Postoperatively, visual acuity was improved in six cases, unchanged in three, and worse in one.

Adult↗
PubMed1989

Monoclonal antibodies differentiate neurofilament and glial filament proteins in the goldfish visual pathway: probes for monitoring neurite outgrowth from retinal explants.

The expression of the neurofilament proteins of the goldfish visual pathway reflects the degeneration and regeneration of the optic nerve after nerve crush. To monitor these processes, monoclonal antibodies (mAb) were generated to the intermediate filament proteins of this pathway. The predominant goldfish visual pathway intermediate filament proteins have a molecular weight of 58K and can be separated into 4 isoelectric variants, 2 of which are neuronal (ON1 and ON2) and 2 of which are non-neuronal (ON3 and ON4). The specificities of the mAbs were characterized biochemically and histologically. Immunoblot analysis demonstrated that 2 of the antibodies reacted specifically with the neurofilament proteins (ON1/ON2) and another antibody reacted specifically with the glial filament proteins (ON3/ON4) and with a 48K optic nerve protein of non-neuronal origin. Chymotrypsin digestion of the ON proteins and immunoblotting of the resulting fragments showed that the anti-ON1/ON2 mAbs were directed toward the variable domains of the filament proteins. In contrast, the anti-ON3/ON4 mAb was directed toward the 40K chymotrypsin-resistant region of the glial filament proteins containing the conserved intermediate filament core. When sections of optic nerve tissue were incubated with anti-ON1/ON2 or anti-ON3/ON4 mAbs, the staining resulted in either axonal or glial patterns, respectively. In retina, after optic nerve crush, anti-ON1/ON2 labeled retinal ganglion cells and Müller fibers. In contrast, prior to optic nerve crush, only Müller fibers were labeled. One of the neuronal-directed mAbs was used to decorate growing neurites from retinal explants; anti-ON1/ON2 reactivity appeared in a time-dependent manner that paralleled the expression of ON1/ON2 in vivo. Thus, the antibodies can differentiate these 2 types of goldfish intermediate filament proteins and can be used to monitor optic nerve regeneration in the goldfish visual pathway both in vivo and in vitro.

Animals↗
PubMed1987

Are flash-evoked visual potentials useful for intraoperative monitoring of visual pathway function?

Flash-evoked visual potentials (VEPs) recorded from the scalp were used in a series of 35 patients with tumors along the visual pathway: 3 orbital tumors, 25 perisellar tumors, 4 intraventricular tumors, and 3 occipital lesions. Preoperatively, various combinations of impaired visual fields and visual acuity were observed in over 90% of the patients. A postoperative decrease in visual function was observed in 3 cases. Of the 25 perisellar lesions, 13 were operated through a standard frontotemporal craniotomy and 12 were operated through a transnasal-transsphenoidal approach. VEPs were highly susceptible to volatile anesthetics, and there was a significant incidence of spontaneous latency increases and amplitude decreases in a large number of patients. There was an unacceptably high number of cases with significant VEP alteration occurring without concomitant visual function change. During trepanation or the transnasal approach, a reversible potential loss was observed in 11 patients, a profoundly altered wave form was seen in 8 cases, and a loss of single peaks was observed in 15 patients. During dissection of the tumor, a reversible potential loss or a potential with unidentifiable peaks was found in 25 cases; however, the VEPs recovered during closure or in the recovery room. There was no correlation between intraoperative VEP changes and the postoperative changes in visual function. In only 1 patient with an insignificant postoperative decrease in visual acuity from 0.4 to 0.3 was there a concomitant intraoperative potential loss. The major conclusion of our findings is that light-emitting diode flash-evoked VEPs demonstrate intraoperative changes that appear too early and too prominently to be caused solely by manipulation of the optic pathways.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Evaluation of visual pathways in multiple sclerosis. I. After-images compared to visual evoked potentials.

The value of flight of colours (FOC), i.e. the succession of coloured afterimages following light stimulation, in diagnosing and following visual impairment was evaluated in 65 patients with multiple sclerosis (MS). Previous optimistic reports of the use of a pocket flashlight (PFL) method could not be confirmed, and are ascribed to inadequate methods. An electronic flashlight (EFL) method developed by us, proved a significantly better diagnostic tool (61% abnormal versus 18% abnormal). The EFL method was diagnostically less sensitive than pattern reversal visual evoked potential (PR-VEP) (80% abnormal). It did, however, add to PR-VEP by diagnosing 16 eyes with normal PR-VEP latency. The EFL method reflected the degree of degenerative changes in the central visual pathways and may be of value in following the disease activity in MS. The potential of the EFL method may be further improved by proposed modifications.

Afterimage↗