Optic neuritis usually presents with painful monocular vision loss in younger patients. Spontaneous improvement in vision occurs over weeks, and treatment with high-dose intravenous steroids increases the rate but not extent of visual recovery. Risk of progression to multiple sclerosis (MS) is largely dictated by baseline brain magnetic resonance imaging (MRI). Those with a normal MRI finding at the time of optic neuritis diagnosis have a lower rate of progression to multiple sclerosis than those with T2 hyperintense white matter lesions on MRI. High-dose intravenous steroids should be considered acutely in optic neuritis, and disease-modifying therapy should be considered in patients at high risk of MS as defined by MRI.