Final answer:
The most likely diagnosis for an 80-year-old man with painful vesicles along the distribution of the right infraorbital nerve is herpes zoster, also known as shingles.
Step-by-step explanation:
The most likely diagnosis for an 80-year-old man with multiple painful skin vesicles along the distribution of the right infraorbital nerve is herpes zoster. Herpes zoster, also known as shingles, is caused by the reactivation of the varicella-zoster virus, which can remain latent in nerve cells for decades. The virus moves along sensory nerves to the skin of the face or trunk, resulting in the development of painful lesions.