optic nerve


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optic nerve:

see visionvision,
physiological sense of sight by which the form, color, size, movements, and distance of objects are perceived. Vision in Humans

The human eye functions somewhat like a camera; that is, it receives and focuses light upon a photosensitive receiver, the retina.
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Optic Nerve

 

(nervus opticus), the second pair of cranial nerves, along which visual stimuli received by the sensory cells of the retina are transmitted to the brain.

The optic nerve is not a typical cranial nerve in structure, but is like brain matter transported to the periphery and connected with the nuclei of the diencephalon, and through them also with the cortex of the large hemispheres. The optic nerve originates in the ganglial cells of the retina. Processes of these cells gather into the optic disk (or papilla), which is located 3 mm closer to the middle from the posterior pole of the eye. Farther on, the bundles of nerve fibers penetrate the sclera in the region of the lamina cribrosa and are surrounded by meningeal structures, forming a compact nerve trunk. Located among the bundles of fibers of the optic nerve are the central artery of the retina and the analogous vein. Together with the ophthalmic artery, the optic nerve passes into the cranial cavity through the optic canal, which is formed by a small wing of the sphenoid bone. Within the cranial cavity, the optic nerve goes from each eye toward the posterior and closer to the middle for about 1 cm, and then approaches the optic nerve of the opposite side over the sella turcica of the sphenoid bone; anterior to the hypophysis the optic chiasma is formed, where there is a crossover only of the axons of the cells of the nasal half of the retina. After the chiasma, the optic nerve continues into the optic tracts.

V. V. KUPRIIANOV

optic nerve

[′äp·tik ‚nərv]
(neuroscience)
The second cranial nerve; a paired sensory nerve technically consisting of three layers of special nerve cells in the retina of the eye; fibers converge to form the optic tracts.
References in periodicals archive ?
Ultrasonography of the optic nerve sheath may be useful for detecting raised intracranial pressure after severe brain injury.
Tumour invasion to lamina cribrosa along with optic nerve sheath and choroidal invasion--Three patients
Medical treatment includes Acetazolamide, Steroids, Topiramate, Frousemide and surgical treatment options include Optic Nerve Sheath Fenestration (ONSF) or CSF shunt (lumboperitoneal shunts, ventriculo-peritoneal shunts, or ventriculoatrial shunt).
2) Thromboembolic occlusion of short posterior ciliary arteries results in the same histopathologic changes to the retrolaminar optic nerve as described in giant cell arteritis and nonarteritic ION.
36,37,38,39,40,41,42) Optic nerve head elevation can be seen on OCT in both clinical conditions, but in disc edema the inner surface of the optic nerve has a smooth edge, whereas in ODD the surface is bumpy and has been termed 'lumpy-bumpy' in the literature.
Some people have low-tension or normal-tension glaucoma, where optic nerve damage occurs even when the IOP is in the normal range of 12 to 22 millimeters of mercury.
22) It has recently been proposed that measurement of the optic nerve sheath diameter through the ocular window may be a non-invasive method for the detection of intracranial hypertension.
Over the long term the optic nerve can become permanently damaged which can lead to blindness if it is not treated.
Frequencies and percentages of the contour of neuroretinal rim, appearance of nerve fiber layer, presence of optic disc hemorrhages, colour of optic nerve head was noted.