Herpes zoster becomes latent in the sensory ganglia after the primary infection and may reactivate many years later to produce shingles in adults. Involvement of the ophthalmic branch of the trigeminal nerve with this virus is called Herpes zoster ophthalmicus (HZO). The eyelid skin, cornea, uvea, retina, optic nerve and other cranial nerves can be affected by HZO. Isolated internal ophthalmoplegia can rarely be seen. Clinicians should be aware of this condition and HZO must be kept in mind in the differential diagnosis of anisocoria.