<prompt> Which is the least commonly involved nerve in herpes zoster opthalmicus?Facial nerveFrontal nerveLacrimal nerveNasociliary nerve  <response>: Herpes Zoster Ophthalmicus is defined as Herpes Zoster involvement of ophthalmic division of trigeminal nerve. Branches of ophthalmic divison are frontal, lacrimal and nasociliary . Of these frontal nerve is most commonly involved. Hence, the least commonly involved nerve is the facial nerve. 