Final answer:
For managing chronic blepharitis in the presented case, erythromycin ointment is the best initial medication to prescribe alongside warm soaks and eyelid scrubs.
Step-by-step explanation:
In the case of a 64-year old male presenting with symptoms of chronic blepharitis, which include itchy, red, watery, and burning eyes with crusts around the lashes, lid erythema, collarettes, and interpalpebral injection, the best initial medical management in addition to warm soaks and eyelid scrubs would be an antibiotic ointment. Since blepharitis can be caused by bacterial infection, erythromycin ointment is typically effective for managing the condition. This treatment will help in controlling any potential bacterial load contributing to the persistent inflammation of the eyelids and will aid in preventing further complications.