Workup will focus will vary significantly based on the differential and clinical presentation
In general it includes:
ECG
CT brain non con and CTA head and neck
CXR
Basic Metabolic Panel
CBC (to assess for severe anemia or thrombocytosis)
INR (if patient is anticoagulated)
MRI (if suspicion for CVA, Multiple Sclerosis, or undifferentiated mass lesion)
Ocular ultrasound (evaluate for retinal detachment or hemorrhage)
Amaurosis fugax
Causes are divided into embolic, hemodynamic, ocular, neurologic, and idiopathic [3]
Pellagra
Carotid emboli or Cardiac emboli in origin causing
Traumatic mydriasis
Central Retinal Artery Occlusion 
Proctalgia fugax
Central Retinal Vein Occlusion 