The IONDT Followup Study will continue to monitor vision and other health outcomes in patients originally enrolled in the IONDT, whether randomized to one of the two treatment groups or whether followed as part of the natural history cohort. All IONDT patients were diagnosed with NAION within 14 days of onset of symptoms, have had a minimum of 2 years of continuous followup, and will be followed for an additional 4 years in the Followup Study. Patients will have annual visits at the original IONDT Clinical Center or, if necessary, with a surrogate provider. If NAION occurs in the second eye, the patient will be asked to visit the clinic for a special visit. The Coordinating Center will telephone the patients on a quarterly basis, between annual visits. Outcomes that will be examined include: