[Delayed onset of diplopia and visual impairment after herpes zoster ophthalmicus]

A 72-year-old man developed herpes zoster ophthalmicus (HZO), involving the ophthalmic branch of the right trigeminal nerve. The rash completely resolved after a 7-day course of oral antiviral therapy. However, 21 days after the onset of the rash, he developed diplopia. A further 8 days later, he experienced visual impairment in the right eye. He was diagnosed with right abducens nerve palsy and retrobulbar optic neuropathy. Gadolinium-enhanced MRI revealed abnormalities around the optic nerve, extraocular muscles (the inferior, medial, and lateral rectus muscles), and the right orbital apex. Cerebrospinal fluid examination was normal, and VZV-DNA was not detected. Treatment with intravenous acyclovir and methylprednisolone led to improvement in visual function within 5 days. The diplopia also completely resolved within approximately 3 months. The pathophysiology was considered orbital apex syndrome caused by ischemia, inflammation, and edema secondary to vasculitis. This case highlights that HZO can cause diverse cranial nerve complications such as diplopia and visual impairment, even after the resolution of skin lesions.