In most patients with a swollen optic nerve, the etiology can be established by careful history-taking and clinical examination. In this course from AAO 2022, the instructors use illustrative cases and discussion to identify common causes of optic nerve swelling, such as papilledema, pseudopapilledema, optic neuritis, and ischemic optic neuropathy. At the conclusion of the course, participants should be able to diagnose these common causes, and a systematic approach to evaluation and management will aid them in ordering appropriate tests, identifying patients requiring emergent management, and making appropriate referrals to specialists.