If a patient has herpes zoster involving the tip of the nose, eye is most likely to get affected due to the involvement of:

Nasociliary is a branch of ophthalmic division of trigeminal nerve. It passes through the superior orbital fissure within the annulus tendon between the the divisions of the third cranial nerve. Anterior ethmoidal nerve is a branch of nasociliary nerve. It enters the anterior cranial fossa and reaches the tip of the nose as the external nasal nerve. So if a patient has herpes zoster and tip of the nose is affected it means the nasociliary nerve is affected and eye will definitely get involved. This is known as the Hutchison's rule. Ref: Textbook of Ophthalmology edited by Sunita Agarwal, page 346