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Optic Neuritis

It includes the inflammatory and demyelinating disorders of the optic nerve.

Etiology :

Idiopathic

Hereditary : Leber's disease

Demyelinating disorders: multiple sclerosis, neuromyelitis optica

Parainfectious :
Mumps, measles, chicken pox, whooping cough and glandular fever

Infectious :
Acute ethmoiditis, syphilis,

Toxic :

Anatomical types :

Papillitis- involvement of optic disc

Neuroretinitis - combined involvement of optic disc and surrounding retina in the macular area

Retrobulbar neuritis - involvement of optic nerve behind the eye ball

Symptoms :

Visual loss - sudden , progressive and profound visual loss

Dark adaptation - lowered

Impairment of colour vision

Impairment of depth perception (Pulfrich's phenomenon)

Pain - mild dull eyeache

Movement phosphenes

Episodic transient obscuration of vision (Uhthoff's symptom)

Signs :

Reduced visual acuity

Impaired colour vision

Marcus Gunn pupil - RAPD

Contrast sensitivity
reduced

Visually evoked response reduced

Ophthalmoscopic features : disc become oedematous and physiological cup is obliterated

Visual field changes : central or centrocaecal scotoma

Treatment :

Corticosteroid therapy may shorten the period of visual loss.

Oral prednisolone therapy alone is contraindicated in the treatment of acute optic neuritis.

Brain MRI scan - If the brain shows lesions supportive of multiple sclerosis, immediate intravenous methyl prednisolone (1 gm daily) for 3 days followed by oral prednisolone (1mg/kg/day) for 11 days.

Indications of intravenous methyl prednisolone in patient with normal MRI :

Visual loss in both eyes

When Only good eye is affected.

When slow progressive visual loss continue to occur.

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