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optic neuritis
Optic neuritis is inflammation of the optic nerve. It is also called papillitis (when the head of the optic nerve is involved) and retrobulbar neuritis (when the posterior of the nerve is involved). It is caused by many different conditions, and it may lead to complete or partial loss of vision. The most common cause is multiple sclerosis.
==Signs and symptoms==
Major symptoms are sudden loss of vision (partial or complete), sudden blurred or "foggy" vision, and pain on movement of the affected eye. The vision might also be described as "disturbed/blackened" rather than blurry, as when feeling dizzy. Many patients with optic neuritis may lose some of their color vision in the affected eye (especially red), with colors appearing subtly washed out compared to the other eye. Patients may also experience difficulties judging movement in depth which can be particular troublesome during driving or sport (Pulfrich effect). Likewise transient worsening of vision with increase of body temperature (Uhthoff's phenomenon) and glare disability are a frequent complaint. A study found that 92.2% of patients experienced pain, which actually preceded the visual loss in 39.5% of cases. However, several case studies in children have demonstrated the absence of pain in more than half of cases (approximately 60%) in their pediatric study population, with the most common symptom reported simply as "blurriness." Other remarkable differences between the presentation of adult optic neuritis as compared to pediatric cases include more often unilateral optic neuritis in adults, while children much predominantly present with bilateral involvement. Symptoms peak several days to weeks after onset, while symptoms failing to improve after 8 weeks should suggest a diagnosis other than optic neuritis.
On medical examination the head of the optic nerve can easily be visualised by a slit lamp with high plus or by using direct ophthalmoscopy; however, frequently there is no abnormal appearance of the nerve head in optic neuritis (in cases of retrobulbar optic neuritis), though it may be swollen in some patients (anterior papillitis or more extensive optic neuritis). In many cases, only one eye is affected and patients may not be aware of the loss of color vision until they are asked to close or cover the healthy eye.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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