| 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) |
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| 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) |
| ischemic optic neuropathy | Optic nerve neuropathy secondary to hypoperfusion of the low pressure posterior ciliary arteries supplying the optic nerve head (nonarteritic) or to temporal arteritis (arteritic). (05 Mar 2000) |
| optic | Of or pertaining to the eye. Origin: Gr. Optikos = of or for sight (18 Nov 1997) |
| 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) |