Work up for Optic Neuropathy

Lab tests to r/o nfectious, inflammatory or nutritional problems:

• CBC
• C-reactive protein (GCA)
  
• ESR (GCA)
  
• Platelet count
• Lyme titer (infectious)
  
• ANA with reflex titer (rheumatologic)
• ACE (sarcoid)
  
• RPR (syphillis/infectious)
• FTA-ABS (syphillis/infectious)
• Vitamin B₁₂ (nutritional)
• Folic acid (nutritional)
• Methylmalonic acid (occult vitamin B₁₂ deficiency)

Neuroimaging:

• MRI (preferred) or CT scan
  

Differentials:

• a young patient complaining of sudden vision loss will more likely have an optic neuritis (ON)
• a middle-aged person would more likely have nonarteritic anterior ischemic optic neuropathy (NAION).
• an older patient with the same complaint would more likely have arteritic anterior ischemic optic neuropathy (AAION) associated with giant cell arteritis (GCA).
• NAION: no pain, “disk-at-risk” appearance in the fellow eye (small, crowded optic disc with little or no cupping that is predisposed to the ischemic process of NAION), less pale nerve
  
• AAION: pain with eye movements, optic nerve dema usually associated with hemorrhages during the acute phase, more pale nerve
  
• AAION and GCA symptoms: jaw claudication, scalp tenderness, fatigue, loss of appetite and fever.
• ON: pain on eye movement; you will see either a normal optic disc (retrobulbar optic neuritis) or disc swelling without hemorrhages (papillitis).
• Multiple sclerosis (MS) symptoms: weakness, numbness, pares-thesias or any other neurologic symptoms.
  
• Traumatic optic neuropathy: pallor of the neuroretinal rim suggests a longstanding or chronic process
  
• Structural abnormality or mass: non-acute, nonglaucomatous optic neuropathy; patient is in need of neuro-imaging to look for either a structural abnormality such as a mass or abnormal enhancement indicating an inflammatory process, or some form of disruption of the blood-brain barrier.
• GCA: A CBC, ESR, C-reactive protein and platelet count must be performed on patients over the age of 50