Herpetic optic perineuritis presenting as classic abducens nerve palsy.

Optic perineuritis is a rare manifestation of herpes zoster ophthalmicus (HZO). Relative afferent pupillary defect (RAPD) is an important early clue to an impending nerve involvement, and robust clinical examination allows early detection of such rare metachronous manifestation of cutaneous HZ and institution of timely management for such sight-threatening conditions.