A 42-year-old man wakes with a painful rash on the face and has had severe facial pain for four days. What is the most appropriate next step in evaluation?

• A. Perform fluorescein examination
• B. Order an MRI of the facial nerves
• C. Prescribe oral antivirals without further testing
• D. Schedule a CT scan of the sinuses

Answer: (A)

This situation points to herpes zoster involving the trigeminal nerve, with a real risk of eye involvement (herpes zoster ophthalmicus). The most important immediate step is to evaluate the eye for corneal involvement. A fluorescein examination dye helps reveal corneal epithelial defects or keratitis that may not be obvious on inspection alone. Detecting such findings guides urgent management to prevent vision loss, including antiviral therapy and possible ophthalmology involvement. Imaging the facial nerves or sinuses isn’t diagnostic at this point, and starting antivirals without assessing the eye could miss ocular complications. Therefore, performing a fluorescein eye exam is the best next step.