optic neuritis

Optic Neuritis 

Definition

Optic neuritis is a vision disorder characterized by inflammation of the optic nerve.

Description

Optic neuritis occurs when the optic nerve, the pathway that transmits visual information to the brain, becomes inflamed and the myelin sheath that surrounds the nerve is destroyed (a process known as demyelination). It typically occurs in one eye at a time (70%), and the resulting vision loss is rapid and progressive, but only temporary. Thirty percent of patients experience occurrence in both eyes. Optic neuritis tends to afflict young adults with an average age in their 30s. Seventy-five percent of patients with optic neuritis are women.

Nerve damage that occurs in the section of the optic nerve located behind the eyeball, is called retrobulbar neuritis, and is most often associated with multiple sclerosis. Optic nerve inflammation and edema (swelling) caused by intracranial pressure at the place where the nerve enters the eyeball is termed papillitis.

Causes and symptoms

Symptoms of optic neuritis include one or more of the following:

• blurred or dimmed vision
• blind spots, particularly with central vision
• pain with eye movement
• headache
• sudden color blindness
• impaired night vision
• impaired contrast sensitivity

Optic neuritis is most commonly associated with multiple sclerosis (MS). Other causes include viral or fungal infections, encephalomyelitis, autoimmune diseases, or pressure on the nerve from tumors or vascular diseases (i.e., temporal arteritis). Some toxins, such as methanol and lead, can also damage the optic nerve, as can long-term abuse of alcohol and tobacco. Patients with non-MS related optic neuritis are usually immunocompromised in some way.

Diagnosis

An ophthalmologist, a physician trained in diseases of the eye, will typically make a diagnosis of optic neuritis. A complete visual exam, including a visual acuity test, color vision test, and examination of the retina and optic disc with an ophthalmoscope, will be performed. Clinical signs such as impaired pupil response may be apparent during an eye exam, but in some cases the eye may appear normal. A medical history will also be performed to determine if exposure to toxins such as lead may have caused the optic neuritis.

Further diagnostic testing such as magnetic resonance imaging (MRI) may be necessary to confirm a diagnosis of optic neuritis. An MRI can also reveal signs of multiple sclerosis.

Treatment

Treatment of optic neuritis depends on the underlying cause of the condition. Vision loss resulting from a viral condition usually resolves itself once the virus is treated, and optic neuritis resulting from toxin damage may improve once the source of the toxin is removed.

A course of intravenous corticosteroids (steroids) followed by oral steroids has been found to be helpful in restoring vision quickly to patients with MS-related episodes of optic neuritis, but its efficacy in preventing relapse is debatable. The Optic Neuritis Treatment Trial (ONTT) has shown that IV steroids may be effective in reducing the onset of MS for up to two years, but further studies are necessary. Oral prednisone has been found to increase the likelihood of recurrent episodes of optic neuritis, and is not recommended for treating the disorder.

Prognosis

The vision loss associated with optic neuritis is usually temporary. Spontaneous remission occurs in two to eight weeks. Sixty-five to eighty percent of patients can expect 20/30 or better vision after recovery. Long-term prognosis depends on the underlying cause of the condition. If a viral infection has triggered the episode, it frequently resolves itself with no after effects. If optic neuritis is associated with multiple sclerosis, future episodes are not uncommon. Thirty-three percent of optic neuritis cases recur within five years. Each recurrence results in less recovery and worsening vision. There is a strong association between optic neuritis and MS. In those without multiple sclerosis, half who experience an episode of vision loss related to optic neuritis will develop the disease within 15 years.

Prevention

Regular annual eye exams are critical to maintaining healthy vision. Early treatment of vision problems can prevent permanent optic nerve damage (atrophy).

Resources

Books

Leitman, Mark. Manual for Eye Examination and Diagnosis. 5th ed. Boston: Blackwell Science, 2001.

Periodicals

Cohen, Joyce Render, et al. "Living with Low Vision." Inside MS 1 (2001): 46.

Organizations

Prevent Blindness America. 500 East Remington Road, Schaumburg, IL 60173. (800) 331-2020. http://www.prevent-blindness.org.

Key terms

Atrophy — Cell wasting or death.

Multiple sclerosis — An autoimmune disease of the central nervous system characterized by damage to the myelin sheath that covers nerves.

Temporal arteritis — Also known as giant cell arteritis. Inflammation of the large arteries located in the temples which is marked by the presence of giant cells and symptoms of headache and facial pain.

Visual acuity test — An eye examination that determines sharpness of vision, typically performed by identifying objects and/or letters on an eye chart.

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neuritis /neu·ri·tis/ (ndbobr-ri´tis) Inflammation of a nerve.neurit´ic

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hereditary optic neuritis  Leber's hereditary optic neuropathy.

multiple neuritis  polyneuritis.

optic neuritis  inflammation of the optic nerve, affecting part of the nerve within the eyeball (papillitis) or the part behind the eyeball (retrobulbar n.) .

retrobulbar neuritis  see optic n.

toxic neuritis  see under neuropathy.

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optic neuritis

n.

Inflammation of the optic nerve. Also called neuropapillitis, retrobulbar neuritis.

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optic neuritis

Etymology: Gk, optikos, sight, neuron, nerve, itis, inflammation

inflammation, degeneration, or demyelinization of the optic nerve or optic disc caused by a wide variety of diseases. Loss of vision is the cardinal symptom. Also called retrobulbar neuritis.

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neuritis

pl. neuritides; inflammation of a nerve; also used to denote noninflammatory lesions of the peripheral nervous system. See also neuropathy.

There are many different forms of neuritis. Some increase or decrease the sensitivity of the body part served by the nerve; others produce paralysis; others cause pain and inflammation. The cases in which pain is the chief symptom are generally called neuralgia.

Neuritis and neuralgia affect the peripheral nerves, the nerves that link the brain and spinal cord with the muscles, skin, organs, and all other parts of the body. These nerves usually carry both sensory and motor fibers; hence both pain and some paralysis may result.

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allergic neuritis

see experimental allergic neuritis (below).

autoimmune neuritis

see experimental allergic neuritis (below).

cauda equina neuritis

see cauda equina neuritis.

equine exudative optic neuritis

a cause of sudden blindness in old horses of unknown etiology but sometimes associated with trauma to the head. There are signs of acute inflammation with optic neuritis and later atrophy.

equine proliferative optic neuritis

an incidental unilateral finding in old horses of cauliflower-like mass attached to the optic disk; vision is not impaired.

experimental allergic neuritis (EAN)

an ascending polyneuritis produced experimentally by the administration of nerve tissue. The condition resembles guillain-barré syndrome, cauda equina neuritis in horses, and coonhound paralysis. Called also allergic, autoimmune neuritis.

interstitial neuritis

inflammation of the connective tissue of a nerve trunk.

multiple neuritis

neuritis affecting several nerves at once; polyneuritis.

optic neuritis

inflammation of the optic nerve, affecting the part of the nerve within the eyeball (neuropapillitis) or the part behind the eyeball (retrobulbar neuritis).

parenchymatous neuritis

neuritis affecting primarily the axons and the myelin of the peripheral nerves.

retrobulbar neuritis

optic neuritis affecting the part of the optic nerve behind the eyeball.

toxic neuritis

neuritis due to some poison.

traumatic neuritis

neuritis following and due to injury.

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neuritis, optic

Inflammation of the optic nerve, which can occur anywhere along its course from the ganglion cells in the retina to the synapse of these cell fibres in the lateral geniculate body. If the inflammation is restricted to the optic nerve head the condition is called papillitis (or intraocular optic neuritis) and if it is located in the orbital portion of the nerve it is called retrobulbar optic neuritis (or orbital optic neuritis).In papillitis the optic nerve head is hyperaemic with blurred margins and slightly oedematous. Haemorrhages and exudates may also appear. In retrobulbar optic neuritis, there are usually no visible signs in the fundus of the eye until the disease has advanced and optic atrophy may appear. However, both types are accompanied by a loss of visual acuity along with a central scotoma and impairment of colour vision. The loss of vision may occur abruptly over a few hours and recovery may be equally rapid but in some patients the loss may be slow. In retrobulbar optic neuritis, there is also pain on movement of the eyes and sometimes tenderness on palpation. The disease is usually unilateral although the second eye may become involved later. It is usually transient and full or partial recovery takes place within weeks. The primary cause of optic neuritis is multiple sclerosis but it may also be associated with severe inflammation of the retina or choroid, vitamin B deficiency, diabetes mellitus, thyroid disease, lactation, toxicity or syphilis. See Devic's disease; papilloedema; Marcus Gunn pupil; Kollner's rule; photostress test.

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optic neuritis

Ophthalmology Inflammation of optic nerve, which may cause abrupt, albeit temporary, loss of vision of the affected eye Etiology Idiopathic, possibly due to viral infection, autoimmune disease, multiple sclerosis, resulting in optic nerve swelling and destruction of the optic nerve's myelin sheath