Optic neuritis


Optic neuritis

Description, Causes and Risk Factors:

Abbreviation: ON.

ICD-10: H46.9

The optic nerve (2nd pair of cranial nerves) is not a nerve in the common use of the term, but, morphologically and functionally, a diencephalic projection. It is made up of the axons of retinal ganglion cells. It extends from the retina to the optic chiasm enveloped in its sheath, the dura mater, arachnoid and pia mater, in continuation with the meningeal.

The optic nerve originates from the eye bulb, 1 mm below and 3-4 mm medially to its posterior pole; the length considerably varies (between 35 and 55 mm) even among the two eyes of the same individual; in the intraorbital tract its diameter is 3-4 mm and in the intracranial tract it is 4-7 mm.

Optic neuritis is a medical term to describe inflammation of the optic nerve. The optic nerve is the nerve of vision - the pathway that carries massages from the eye to the brain. If the nerve fibers do not do their job, vision becomes affected. The patient with optic neuritis are typically young with a peak incidence in the third and fourth decade, and more woman than men are affected.

The pathogenesis of optic neuritis is generally considered to be immune-mediated demyelination of the optic nerve. There are several possible causes of optic neuritis, but often specific underlying causes cannot be discerned.

This condition usually develops due to an autoimmune disorder that may be triggered by a viral infection. In some people, signs and symptoms of optic nerve inflammation may be an indication of multiple sclerosis, a condition resulting in inflammation and damage to nerves in your brain and spinal cord. Other causes include Lyme disease, tuberculosis, syphilis, lupus, diabetes, and viral agents such as HIV, hepatitis B virus, herpes virus, and cytomegalovirus. Optic nerve inflammation also can occur as a complication of radiation therapy.

Bilateral optic neuritis is a relatively rare presentation among adults. In children, however, it is more commonly encountered and frequently associated with viral infection such as measles, mumps, and chickenpox. The association with vaccination is very rare.

Optic neuritis is associated with various diseases and conditions, such as:

    Vascular occlusions of the optic nerve.

  • Mumps.

  • Measles.

  • Influenza.

  • Leber's optic neuropathy (a rare eye condition that runs in families);

Symptoms:

Common presenting symptoms of ON include:

    Blurred vision.

  • Subacute reduction of visual acuity (usually monocular).

  • Dyschromatopsia (loss of color vision).

  • Photopsias.

  • A relative afferent pupil defect.

  • A normal-appearing optic nerve or mild optic disc.

  • Swelling.

  • Pain in the back of the eye socket.

  • Pain when moving the eyes.

Diagnosis:

Mostly ophthalmologist will diagnose optic neuritis by asking about a person's history and observing typical signs. A blood test may be carried out to help identify the cause. Electrical testing of how the nerves are working (visual evoked potentials) or scans of the optic nerves can sometimes help as well.

Pain with eye movement is ahallmark symptom of optic neuritis. The doctor may evaluate the pupils' reaction to light andorder tests such as: visual field, color vision, and imaging of the brain (MRI).

Morphologic aspects:Ophthalmoscopy, fluoroangiography, OCT (optical coherence tomography),HRT (Heidelberg retina tomograph).

Other tests may include:

    Antinuclear antibody.

  • Erythrocyte sedimentation rate (ESR).

  • Antibodies to NMO-IgG.

Treatment:

In most cases, vision will either improve significantly or return to normal. Some patients, however, may not recover their normal vision, particularly if they have a pre-existing condition such as multiple sclerosis (MS).

Medications May Include:

    Intravenous corticosteroid medication such as methylprednisolone (Solu-Medrol, Depo-Medrol).

  • Oral corticosteroids such as Prednisone (Deltasone), methylprednisolone (Medrol).

Doctors have discovered that treating patients with intravenous steroid medication (but not oral steroids) reduces the risk of developing MS later on. This finding is very significant since approximately 50% of those who experience an initial occurrence of optic neuritis will develop MS. While this treatment has little if any impact on vision, it is important for overall health.

Medication side effects must be discussed with your PCP.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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