Optic nerve


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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.

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.

optic nerve

2nd 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

Optic nerve

A bundle of nerve fibers that carries visual messages from the retina in the form of electrical signals to the brain.
References in periodicals archive ?
In conclusion, the optic nerve meningioma described here is considered rare in dogs.
Patient's in hospital mortality and morbidity was also noted by his residual losses in brain and motor functions and was later on matched with level of optic nerve sheath diameter (ONSD) at the time of presentation.
Because of the relationship between the optic nerve sheath and cerebrospinal fluid, the diameter of optic nerve sheath changes with alteration of the ICP.
The patients had normal anterior segment structures and important macular and optic nerve abnormalities.
The word schwannoma is not usually associated with either the optic nerve or neurofibromatosis type 1.
As the optic nerve is an extension of the brain, treatment by surgery is currently not available, but extensive research is being carried out to develop new treatments for glaucoma.
The retina and optic nerve head appeared normal on funduscopy with extraocular movements of both eyes within the normal limits.
The most recent posting on the clinicaltrials.gov site is regarding an optic nerve problem called NAION or Non-arteritic Ischemic Optic Neuropathy.
When two of our retinoblastoma patients, whose HP Reports only said: "cut end of the optic nerve not involved", developed orbital and systemic metastasis; we undertook this study to do detailed HP examination of all enucleated retinoblastoma eyes and the histopathological slides.
Dilated funduscopic examination revealed mildmoderate optic nerve head edema with small temporal nerve fiber layer hemorrhage in the right eye and mild optic nerve head edema in the left eye as shown in Figures 3-7.
Magnetic resonance imaging (MRI) of the brain and orbit performed 2 days after the headache incident revealed minimal fluid surrounding the optic nerve sheath suggestive of mild swelling of the optic nerve sheath papilledema.