What is it?

Inflammatory demyelination of the optic nerve

     -  Usually idiopathic, rarely infectious, and often associated with MS

Classic symptoms:

Progressive visual loss, associated with:

     -  Eye pain, often mild, pain can precede visual loss

     -  Color vision changes

     -  Pain with extraocular motion

     -  Afferent pupillary defect

     -  Headache

Natural history:

     -  If left untreated, on average gets gradually worse over 10 days then gradually better over weeks, with good but usually not perfect recovery of vision

Association with multiple sclerosis:

     -  30% of patients diagnosed with optic neuritis with develop MS within 5 years

     -  Bilateral intranuclear ophthalmoplegia (INO) in otherwise healthy patient à highly suggestive of MS

     -  MRI can help risk stratify for development of MS by identifying white matter lesions

Diagnosis:

     -  Clinical +/- MRI

     -  Physical exam: eye appears normal, afferent pupillary defect, pain with EOM

     -  MRI: not necessarily needed, but helpful

               -  Confirm diagnosis

               -  Rule out other diseases

               -  Assess for white matter lesions (predict MS)

     -  Fundoscopic exam is often normal because the inflammatory changes are retrobulbar. While you can sometimes see mild changes, profound disc edema is not classic

     -  Possible role for US? May have discrepancy in size of optic nerve sheath diameter between affected and unaffected eye

     -  DDx: acute angle closure glaucoma, scleritis, anterior uveitis, optic neuritis, keratitis, and corneal abrasion

Management:

     -  Optho & neuro consult

     -  Steroids (usually started IV) - may speed visual recovery but little/no long term benefit

References:

1) Germann CA, Baumann MR, Hamzavi S. Ophthalmic diagnoses in the ED: optic neuritis. Am J Emerg Med. 2007 Sep;25(7):834–837

2) Mark Philip Saigh, H. Martin Plauché, Christine Butts, Amer Karam Karam, Salvador J. Suau, Lisa Moreno-Walton. Acute Optic Neuritis Diagnosed by Bedside Ultrasound in an Emergency Department. The Journal of Emergency Medicine. Aug 2019; 57 (2):207-211