OPTIC NEURITIS

OPTIC NEURITIS

• Refers to inflammation or demyelinating disorders of optic nerve.

CAUSES

1. Idiopathic

2. Demyelinating disorders

• Multiple sclerosis (most common)
• Neuromyelitis (Devic’s disease)
• Leucodystrophies (Schilder’s adrenoleucodystrophy, Krabbe’s galactocerbroside dystrophy, Metachromatic sulfatase deficiency, Pelizaeus- Merzbacher disease).

3. Viral infection

• Measles
• Mumps
• Chicken pox
• Whooping cough
• Glandular fever

4. Metabolic/Nutritional deficiency:

• Vitamin B2, B12 deficiency
• Folic acid deficiency
• Thyroid dysfunction
• Diabetes

5. Hereditary

• Hereditary optic neuritis (Leber’s disease)

6. Toxic ambylopia

• Quinine
• Chloroquine
• Ethambutol
• Isoniazid
• Digitalis (digoxin)
• Methyl alcohol, Ethyl alcohol

7. Ischemic

• Giant cell arteritis
• PAN, SLE

8. Infectious optic neuritis

• Cat scratch fever
• Syphilis
• Lyme disease

Optic neuritis can be divided into:

A) Those affecting part of the optic nerve, which is visible ophthalmoscopically.

• So fundus shows various signs of the disease:

1. Papillitis
2. Neuroretinitis

B) Those affecting part of the optic nerve outside the eyeball in the orbit.

• Therefore fundus examination is normal:

1. Retrobulbar neuritis

CLINICAL FEATURES

• Unilateral
• Profound vision loss (major symptom)
• Mononuclear sudden, progressive & profound loss of vision
• Pain behind the eyeball, particularly in retrobulbar neuritis which there is pain on eye movements.
• Visually evoked response (VER) shows reduced amplitude & delayed transmission time. 

SIGNS

1. Clinical signs:

• Reduced visual acuity
• Impaired colour vision
• Pupillary reaction is sluggish & ill sustained
• There may be relative afferent pupillary defect (RAPD)
• Marcus Gunn pupil detected byswinging flash light test.

2. Visual field defect:

• Central or centrocaecal scotoma
• Paracentral, arcuate, sectorial & altitudinal field defects.

3. Ophthalmological findings:

• Disc swellimg rarely exceeds 2-3 D.
• Hyperemia of disc with blurred margin
• Congested, tortuous & distorted retinal veins
• Exudates in disc & retina
• peripapllary flame-shaped hemorrrhages 

TREATMENT

• Treatment hastens visual recovery & decreases the likelihood of recurrence
• Though the long-term visual outcome is no different
• i.v. Prednisolone followed by iral prednisolone for 11 days.
• Oral prednisolone therapy alone is contraindicated 
• Intravenous vitamin C can also ne evaluated for treatment
• MRI of brain & orbit sholud be done begore starting treatment to see the extent of demyelination.

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