A49-year old woman presents to a rural emergency department with acute onset monocular vision loss in her right eye. she denies pain or any other deficits but states she has been feeling nervous and has lost weight over the past three weeks. on physical exam, she has complete visual field loss in the right eye. fundoscopic exam reveals a pale retina and a single bright red spot just off of center. after she is treated appropriately for her emergent problem, what additional testing is most appropriate?