Optic nerve

optic

 [op´tik]

ocular (def. 1).

optic nerve the second cranial nerve; it is purely sensory and is concerned with carrying impulses for the sense of sight (see vision). See anatomic Table of Nerves in the Appendices.

The rods and cones of the retina are connected with the optic nerve which leaves the eye slightly to the nasal side of the center of the retina. The point at which the optic nerve leaves the eye is called the blind spot because there are no rods and cones in this area. The optic nerve passes through the optic foramen of the skull and into the cranial cavity. It then passes backward and undergoes a division; those nerve fibers leading from the nasal side of the retina cross to the opposite side while those from the temporal side continue to the thalamus uncrossed. After synapsing in the thalamus the neurons convey visual impulses to the occipital lobe of the brain.

Degenerative and inflammatory lesions of the optic nerve occur as a result of infections, toxic damage to the nerve, metabolic or nutritional disorders, or trauma. Syphilis is the most frequent cause of infectious disorders of the optic nerve. Methanol (methyl alcohol) is highly toxic to the optic nerve and can cause total blindness. Diabetes mellitus and anemia are examples of metabolic and nutritional disorders that can lead to damage to the optic nerve and produce serious loss of vision.

Treatment of optic neuritis is aimed at control of the primary cause of the disorder. Cortisone and similar steroids are often used to relieve symptoms; however, nothing can be done to regain sight lost through damage to the nerve.

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

optic nerve

n.

Either of the second pair of cranial nerves that arise from the retina and carry visual information to the thalamus and other parts of the brain.

The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

optic nerve

2^nd cranial nerve Anatomy A bundle of > 1 million nerve fibers that carries afferent/senosry fibers from the retinal gangliion cells, passing out of the orbit via the optic foramen (canal) to the optic chiasm, where part of the fibers cross to the opposite side, passing though the optic tract to the geniculate bodys, pretectum, and superior colliculus in the brain

McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

Optic nerve

A bundle of nerve fibers that carries visual messages from the retina in the form of electrical signals to the brain.

Mentioned in: Eye Examination, Glaucoma, Hyphema, Myopia, Retinoblastoma

Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.