A 64 year old, healthy female comes to the emergency room complaining of a sudden, painless loss of vision in her right eye (OD).

Physical examination revealed acuity of 20/20 OS, and 20/200 OD, visual field loss superiorly, normal extraocular movements, pupils of equal size but with a relative afferent pupillary defect (RAPD) OD.  Funduscopy was normal OS, but showed a pale, swollen disc OD (below).