A 68-year-old woman, with a history of well-controlled type 2 diabetes mellitus and hypertension, presents to an outpatient clinic complaining of a burning sensation and paresthesias on her left forehead for the past two days, followed by the sudden appearance of a painful, vesicular rash in the same region this morning. She describes the pain as severe and sharp, making it difficult to sleep. She denies any recent trauma or contact with irritants. On examination, a cluster of erythematous vesicles and papules is noted on her left forehead, extending to the upper eyelid and the tip of her nose, clearly respecting the midline. There is also mild periorbital edema and conjunctival injection. Her visual acuity is 20/30 in the affected eye and 20/20 in the right eye. There is no proptosis or limitation of extraocular movements. What is the most likely diagnosis and the most appropriate initial management strategy, considering the potential for ocular complications?