A 63 year old female with Grave's disease presents with a 6 day history of "cold" symptoms and 3 day history of a red and painful left eye (OS).   She says that she occasionally noticed scanty yellowish discharge from the eye.

On examination her visual acuity was 20/20 OD and 20/60 OS (pinhole).   Visual fields to confrontation were normal.  Her pupils were equal in size, but there was a relative afferent pupillary defect OS.  Extraocular movements were painful OS.  Funduscopy appeared normal.