What is Multiple Sclerosis or MS?
Multiple Sclerosis is an autoimmune inflammatory disease of the myelin sheath that surrounds the nerves in the brain and spinal cord. As the myelin is damaged the nerve conduction is slowed down, diminished, and/or disrupted. This leads to a gradual loss of function to the different areas of the body. More women than men are affected. The exact cause remains unknown. It is felt that genetics, possible infection, other reasons, or a combination of factors may cause Multiple Sclerosis.
What is Optic Neuritis?
Optic neuritis is an acute inflammatory disease of the optic nerve. The optic nerve is responsible for transmitting the vision from the eye to the occipital lobes of the brain which is the vision center in the brain. The condition is characterized by painful vision loss, unilateral, periorbital pain, eye pain when moving the eye, and may or may not have associated neurological symptoms.
Optic Neuritis Associated with Multiple Sclerosis
Optic neuritis may be the first symptom of Multiple Sclerosis in nearly 25% of cases. Approximately 50% of patients with Multiple Sclerosis will have an episode of optic neuritis during the course of the disease. A young woman who presents with a case of optic neuritis is believed to have Multiple Sclerosis until proven otherwise.
Clinical Course of Optic Neuritis
People typically present with vision loss which doesn’t affect the central vision to total loss of vision. The vision usually progressively worsens for the first 2 weeks. The vision slowly returns slowly beginning around the 3rd or 4th week in most cases. The vision returns to a level of 20/20 in approximately 75% of patients.
Visual Field or Peripheral Vision
Some loss of side vision or peripheral vision is common. A visual field test will document the loss of side vision.
The optic nerve may appear normal at the onset of optic neuritis as the swelling and inflammation has started behind the optic disc. The optic disc is the beginning of the optic nerve that can be seen inside the back of the eye. This is called retrobulbar optic neuritis. Usually the optic nerve or disc is elevated, edematous, and the disc margins are blurred. There may be small hemorrhages and exudates around the optic nerve. The disc will begin to become pale after 6 weeks or so depending on the severity of the condition.
Optic Neuritis Diagnostic Tests
Comprehensive Dilated Eye Exam
Complete dilated eye exam with color vision testing and visual field test.
Visual-Evoked Potential or VEP
VEP can be useful in some cases to help diagnose optic neuritis. A VEP measures the electrical activity in the vision center after a stimulus is presented to the eye.
OCT or Ocular Coherence Tomography
OCT measures the nerve fiber layer of the retina as it enters the optic nerve. It can show small losses of the nerve fiber secondary to optic neuritis or other diseases.
Optic neuritis is one of the most common initial presentations of Multiple Sclerosis. The patient should have an MRI of the brain and orbit. The MRI can show if the patient has Multiple Sclerosis or help in predicting the chance of developing Multiple Sclerosis.
Treatment of Optic Neuritis
Short Term Treatment
Corticosteroids have been used to treat optic neuritis but studies have shown that long term there was no benefit to treatment with steroids. There was some short term improvement but long term there was no difference with no treatment. Intravenous immunoglobulin and plasma have been tried with mixed reviews.
Long Term Management
If there is a chance of conversion of the patient to developing Multiple Sclerosis then immunomodulating treatment should be considered. This should be determined by a neurologist.