Acute demyelinating optic neuritis (ON) is a leading consideration in the differential diagnosis for young adults presenting with sudden onset of painful unilateral visual loss. Multiple sclerosis (MS) is believed to be the most common etiology for ON. Nearly 50% of MS patients will develop ON, and in 15-20% of cases, ON will be the initial manifestation of the illness. Conventional and emerging magnetic resonance imaging (MRI) techniques have provided greater insight into the pathophysiology of ON, and conventional MRI has also allowed clinicians to better estimate the future risk of MS. At 10 years after ON, patients with zero, one, or two or more brain lesions on T2-weighted MRI sequences demonstrated a 22%, 52%, and 56% risk of developing MS, respectively. Treatment with high dose intravenous methylprednisolone may accelerate visual recovery in patients with acute ON, but has little impact on long term visual outcome. Disease modifying therapies in patients with acute demyelinating ON should be considered as a treatment option at the time of initial presentation in those patients whose initial brain MRI shows demyelinating lesions as these therapies have been shown in to be effective at reducing the future risk of MS.