| optic tract | The continuation of the optic nerve fibres beyond (behind) the latter's hemidecussation in the optic chiasm; each of the two symmetrical optic tracts is composed of fibres originating from the temporal half of the retina of the ipsilateral eye and a nearly equal number of fibres from the nasal half of the contralateral retina; it forms a compact, somewhat flattened fibre band passing caudolaterally alongside the base of the hypothalamus and over the basal surface of the crus cerebri; most of its fibres terminate in the lateral geniculate body; a smaller number of fibres enter the brachium of the superior colliculus, to terminate in the superior colliculus and the pretectal region. Synonym: tractus opticus. (05 Mar 2000) |
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| medial root of optic tract | The smaller division of the posterior end of the optic tract that disappears under the medial geniculate body. Synonym: radix medialis tractus optici. (05 Mar 2000) |
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| lateral root of optic tract | The larger division of the posterior end of the optic tract that terminates in the lateral geniculate body. Synonym: radix lateralis tractus optici. (05 Mar 2000) |
| axis, optic | <microscopy> The direction, or directions in an anisotropic crystal along which light is not doubly refracted. (05 Aug 1998) |
| ganglionic layer of optic nerve | <anatomy, nerve> The inner layer of multipolar neurons in the retina consisting of the relatively large neurons that give rise to the fibres of the optic nerve. Synonym: stratum ganglionare nervi optici. (05 Mar 2000) |
| vascular circle of optic nerve | <anatomy, nerve> A network of branches of the short ciliary arteries on the sclera around the point of entrance of the optic nerve. Synonym: circulus vasculosus nervi optici, circulus arteriosus halleri, circulus zinnii, Haller's circle, Zinn's corona, Zinn's vascular circle. (05 Mar 2000) |
| glioma of optic chiasm | A slow-growing tumour, usually an astrocytoma, of the optic chiasm in children. (05 Mar 2000) |
| Graves' optic neuropathy | Visual dysfunction due to optic nerve compression in Graves' orbitopathy. (05 Mar 2000) |
| pigment epithelium of optic retina | pigmented part of retina |
| coloboma of optic nerve | <anatomy, nerve> A congenital notch in the formation of the optic nerve, appearing as a craterlike excavation at the optic disk. (05 Mar 2000) |
| postlaminar part of optic nerve | <anatomy, nerve> The portion of the optic nerve posterior to the lamina cribrosa of the sclera. Synonym: pars postlaminaris nervi optici. (05 Mar 2000) |
| prelaminar part of optic nerve | <anatomy, nerve> The portion of the optic nerve anterior to the lamina cribrosa of the sclera. Synonym: pars prelaminaris nervi optici. (05 Mar 2000) |
| principal optic axis | A line passing through the centre of the lens of a refracting system at right angles to its surface. (05 Mar 2000) |
| septo-optic dysplasia | <radiology> Blindness, hypopituitarism, hypoplastic optic nerves, optic chiasm rotated 90 degrees, bulbous 3rd ventricle, CT findings: absent septum pellucidum, small optic nerves (12 Dec 1998) |
| neural layer of optic retina | See: retina. (05 Mar 2000) |
| neuroma, optic | A benign tumour of the optic nerve. (12 Dec 1998) |