Isolated, complete paralytic mydriasis secondary to herpes zoster ophthalmicus.

Herpes zoster ophthalmicus is a manifestation of herpes zoster when the ophthalmic division of the trigeminal nerve becomes involved. Ocular symptoms are varied and mainly due to inflammatory mechanisms. Total, external and/or internal ophthalmoplegias, as well as isolated third, fourth and sixth cranial nerve palsies have all been reported as complications. In a minority of cases, concurrent pupillary paralysis has been documented. The presentation of complete paralytic mydriasis as the sole cranial nerve complication following herpes zoster ophthalmicus infection is a rare finding. The postulated pathophysiologic aetiology is a partial third nerve palsy with the pupillary fibres for light and accommodation-convergence affected and motor fibres spared. The mechanism responsible for the postulated lesion is speculative.