PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “OPTIC PATHWAY”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed1983

Some topological considerations of the optic pathway.

The contralateral projection of the vertebrate retinotopic map has a component of a mirror or uniaxial inversion in it. Here, a simple hypothesis is proposed which explains how this can come about. The emphasis is on topological considerations, in a global sense, of the overall map. An important feature of the hypothesis is that the optic nerve fibres follow pathways such that they retain their nearest neighbour relationships till they terminate in the optic tectum, i.e. no criss-crossing of the fibres is envisaged. Anatomical evidence for this is already available in the case of the optic tract of frog. Some speculations are also suggested concerning the role of this uniaxial inversion in information processing. The observations of optic tracts of other amphibian and some lower vertebrate systems are also considered.

Animals↗
PubMed2001

Lens-injury-stimulated axonal regeneration throughout the optic pathway of adult rats.

Axonal regrowth and restoration of visual function were studied in adult rats. The optic nerve was completely cut behind the eye. The proximal and distal nerve stumps were realigned and the meninges sutured back together. During the same surgical procedure, the lens was lesioned in order to induce secondary cellular cascades, which are known to strongly support the survival of retinal ganglion cells (RGCs) and to promote axonal regeneration. The anatomical and topographic restoration of the visual pathway was assessed neuroanatomically with the aid of anterograde and retrograde tracing using fluorescent dyes. It appeared that the axons formed growth cones at the junction of the suture soon after injury, before glial cells and extracellular matrix proteins were able to cause local scar formation. Growth cones first entered the distal optic nerve stump 3 days after injury, grew through it to reach the optic chiasm approximately 3 weeks after the lesion was made, and terminated within the retinoreceptive layers of the superior colliculus 5 weeks after lesioning. Quantification of the retrogradely labeled cell bodies within the regenerating retina revealed that up to 30% of the RGCs, which includes all major cell types, were capable of regenerating their axons along the entire visual pathway. To assess whether topography was restored, double-labeling experiments were performed, revealing only crude topographic restoration during the initial stages of regeneration. However, visual-evoked potentials could be recorded, indicating that synaptic transmission in higher visual areas was relatively intact. The data show, in principle, that cut axons can regenerate over long distances within the white matter of a central nerve like the adult optic nerve, spanning over 11 mm to the chiasm and between 12 and 15 mm to the thalamus and midbrain. The findings suggest, for the first time, that lentogenic stimulation of RGCs is sufficient to induce the formation of growth cones that can override inhibitors at the site of injury, grow through the white matter of the optic nerve, pass through the optic chiasm, and make synaptic connections within the brain.

Animals↗
PubMed2000

Optic pathway hypothalamic gliomas in children under three years of age: the role of chemotherapy.

OBJECTIVES: Optic pathway/hypothalamic gliomas (OPHGs) tend to occur in young children. Treatment options consist of surgical resection, radiation therapy (RT) and chemotherapy. Due to complications induced by surgery and RT, chemotherapy has gained significant recognition for the treatment of OPHG in young children. Chemosensitivity of OPHG in very young children under 3 years of age has not been well documented. We analyzed 14 patients who were treated with chemotherapy with or without surgery. MATERIALS AND METHODS: Fourteen children younger than 3 years (median age of 10 months) with OPHG were treated between 1988 and 1998. Magnetic resonance imaging was obtained in all cases. Hydrocephalus was present in 8 patients and diencephalic syndrome was noted in 6. Only 3 of these had evidence of neurofibromatosis-1. Five patients had partial tumor resection and 4 had endoscopic biopsy at the time of ventriculoperitoneal shunt placement. Pathological examination revealed low-grade astrocytoma in 5 and juvenile pilocytic astrocytoma in 4. All patients received chemotherapy: carboplatin in 8, a combination of carboplatin and vincristine in 4 and a combination of other agents in 2. RESULTS: Eight (57%) of 14 patients had a sustained reduction of tumor during the follow-up time between 15 months and 8 years. The 5-year progression-free survival was 63%. These tumor reductions were often accompanied by clinical improvements. Diencephalic syndrome responded to chemotherapy alone in 4 of 6 patients. However, 5 others had progressive disease; 3 during the treatment and 2 following the treatment (9 months and 2 years, respectively). All these 5 patients had a partial tumor resection prior to chemotherapy. CONCLUSION: A majority of OPHGs responds to chemotherapy. Due to slow progression of these tumors and adverse effects of other therapeutic modalities, we recommend chemotherapy as a primary treatment for OPHGs. Our present data indicates that partial surgical resection does not enhance chemotherapy effectiveness for OPHGs in infants or children younger than 3 years.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1990

The processing of object and self-motion in the tectofugal and accessory optic pathways of birds.

This paper reviews electrophysiological studies of motion processing in the tectofugal and accessory optic systems (AOS), and suggests these are specialized respectively for the analysis of object motion and self motion. Evidence is presented which shows that directionally specific neurons in the tectofugal system process local motion and are inhibited by wholefield motion. These cells respond to kinematograms and moving occlusion edges and may therefore also be involved in figure-ground segregation and depth perception. In contrast, cells in the nucleus of the basal optic root (nBOR), a component of the AOS, respond best to large slowly moving patterns. These cells are directionally selective preferring either upward, downward or backward directions. In the posterior region of the nBOR some cells have been found which are binocular and prefer either the same or opposite directions of motion in the two eyes. Thus, these cells are tuned to respond optimally to either translational or rotational components of wholefield motion and it is suggested these may be involved in the control of posture and locomotion.

Animals↗
PubMed1989

[Studies on diameter distribution of axons in the optic pathway in human glaucoma].

The distribution of diameters of axons and somas at the level of the optic nerve, lamina cribrosa and retina were compared between human glaucomatous eye and normal control eyes. At the level of lamina scleralis of the glaucomatous eye, there was a tendency for large nerve fibers to be lost in the arcuate nerve fiber area particularly in the inferior arcuate nerve fiber area, where the corresponding visual field defect was detected. The percentages of large axons and somas in the arcuate nerve fiber area decreased in the glaucomatous eye both at the level of the optic nerve, retina but most of all at the level of lamina cribrosa. These results suggest that the mode of optic nerve damage in early glaucoma is characterized by the selective damage of large nerve fibers, which is most severe at the lamina cribrosa.

Axons↗
PubMed1980

[Rare abnormalities of the circle of Willis: infra-optic pathway of the anterior cerebral arteries (author's transl)].

The authors report a new case of "sub optic" course of anterior cerebral arteries with an anterior communicating artery aneurysm controlled at surgery. The patient had also a distal Moya Moya, a median artery of the corpus callosum and an aortic coarctation. He underwent a first operation for cerebral aneurysm and in a second step another for aortic malformation. The authors discuss the anomaly by the way of Lasjaunia's embryologic scheme of ophthalmic arteries formation.

Abnormalities, Multiple↗