| optic | Of or pertaining to the eye. Origin: Gr. Optikos = of or for sight (18 Nov 1997) |
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| optic agnosia | The inability to recognise objects by sight; usually caused by bilateral parieto-occipital lesions. Synonym: optic agnosia. (05 Mar 2000) |
| optic ataxia | An inability to guide the hand toward an object using visual information; seen in Balint's syndrome. (05 Mar 2000) |
| optic atrophy | Atrophy of the optic disk resulting from degeneration of the nerve fibres of the optic nerve and optic tract. (12 Dec 1998) |
| optic atrophy, hereditary | An inherited disorder in which optic atrophy is associated with muscle weakness, peroneal muscular atrophy and, in some patients, lancinating pains. In these patients the peripheral sensory neurons are probably affected. (12 Dec 1998) |
| optic axis | The axis of the eye connecting the anterior and posterior poles; it usually diverges from the visual axis by five degrees or more. Synonym: axis opticus. (05 Mar 2000) |
| optic canal | The short canal through the lesser wing of the sphenoid bone at the apex of the orbit that gives passage to the optic nerve and the ophthalmic artery. Synonym: canalis opticus, foramen opticum, optic foramen. (05 Mar 2000) |
| optic capsule | The concentrated zone of mesenchyme around the developing optic cup; the primordium of the sclera of the eye. (05 Mar 2000) |
| optic chiasm | <anatomy> The anatomic point of crossing or decussation of the optic nerve fibres. most of the nerve fibres cross to the opposite side. (27 Sep 1997) |
| optic cup | The double-walled cup formed by the invagination of the embryonic optic vesicle; its inner component becomes the sensory layer of the retina, its outer layer, the pigment layer. Synonym: caliculus ophthalmicus, ocular cup. (05 Mar 2000) |
| optic decussation | <anatomy> The anatomic point of crossing or decussation of the optic nerve fibres. most of the nerve fibres cross to the opposite side. (27 Sep 1997) |
| optic disk | The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve. Because the retina at the optic disk has no photoreceptors there is a corresponding blind spot in the visual field. (12 Dec 1998) |
| optic disk drusen | Hyaline bodies occurring in the intra-ocular portion of the optic nerve. They are distinguished from retinal drusen, which lie beneath the retinal pigment epithelium. This disorder is differentiated also from papilledema by the absence of dilated retinal vessels. (12 Dec 1998) |
| optic fissure | In the embryo, the temporary gap in the ventral margin of the developing optic cup. Synonym: choroid fissure, choroid fissure, choroidal fissure. (05 Mar 2000) |
| optic foramen | The short canal through the lesser wing of the sphenoid bone at the apex of the orbit that gives passage to the optic nerve and the ophthalmic artery. Synonym: canalis opticus, foramen opticum, optic foramen. (05 Mar 2000) |
| axis, optic | <microscopy> The direction, or directions in an anisotropic crystal along which light is not doubly refracted. (05 Aug 1998) |
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| 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) |
| 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) |
| 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) |
| depression of optic disk | The normally occurring depression or pit in the centre of the optic disc. Synonym: excavatio disci, depression of optic disk, excavatio papillae, physiologic cup, physiologic excavation. (05 Mar 2000) |