optic chiasma


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Related to optic chiasma: corpus callosum, optic tract

optic chiasma

[′äp·tik kī′az·mə]
(neuroscience)
The partial decussation of the optic nerves on the undersurface of the hypothalamus.
References in periodicals archive ?
Magnetic resonance (MR) imaging was superior to CT in detecting cavernous sinus invasion, tumour relation to ICA, optic chiasma and in internal characterization of the lesion.
Since most of optic pathway gliomas are slow growing especially in children, conservative attitude is advised even if tumour is involving optic chiasma and hypothalamus6.
Unfortunately, the signals from the eyes are mixed almost immediately behind the eyes in the optic chiasma. Nasal fibers representing the temporal view of each eye cross to the other side and continue on.
The precise visual field defect caused by a lesion compressing the optic chiasma depends on location of optic chiasma with respect to sella tursica.
The predilection of tumours to metastasize to posterior pituitary may be due to the fact that the neural portion has a blood supply directly from the systemic circulation while the anterior lobe is supplied by the hypothalamus-hypophyseal portal system.6 In the clinical context of a known cancer patient presenting with diabetes insipidus, MRI of pituitary fossa is very useful in demonstrating metastasis to the pituitary.7 Hypophysis, stalk, cavernous sinuses, sphenoid sinus and optic chiasma are well evaluated on coronal and sagittal T1-weighted MRI both before and after Gadolinium injection.
(6) The optic nerve was called a poros (duct), possibly because of the ophthalmic artery occupying its centre; the origin of the nerve from the floor of the brain (Herophilus' 'centre of intelligence'), its cross-over in the optic chiasma and continuation through the skull to the eyeball, was described.
Enhanced magnetic resonance imaging (MRI) revealed a well defined extra axial solid mass lesion in the anterior cranial fossa about 27x23x26mm causing mass effect over the optic chiasma and also with extension into the right optic canal.