Most common nerve involved with Herpes Zoster is-

Herpes zoster occurs due to reactivation of VZV which remains in latent form in the dorsal root ganglion. Although thoracic dermatomes are most commonly involved ,the ophthalmic division of the trigeminal nerve is also frequently affected ; vesicles appear on the cornea & lead to ulceration. This condition can lead to blindness. Reference Harrison20th edition pg 1001