Optic neuritis is an inflammation of the optic nerve. The most common form of optic neuritis is an acute idiopathic inflammatory demyelinating optic neuropathy. This form is strongly associated with multiple sclerosis (MS) and is often the first presenting sign of the disease. Optic neuritis is sometimes due to an infectious process involving the orbits or paranasal sinuses. 

In the United States, the prevalence of optic neuritis in a predominately white population is 115 per 100,000. Most cases occur in white women between the ages of 15 and 45.

Patients with idiopathic acute optic neuritis typically present with pain and unilateral visual loss over days without systemic or neurological symptoms. Pain is present in more than 90% of cases and often worsens with eye movements. The extent of vision loss can vary and is associated with a loss of color perception. One-third of cases of optic neuritis involve swelling of the optic disc, while most cases have a normal funduscopic examination with retrobulbar optic nerve involvement. As optic neuritis is usually unilateral, an afferent pupillary defect is usually present.  

Pediatric Patient Considerations: 
While children may experience bilateral optic neuritis more commonly, involvement of both eyes should prompt a search for other causes.