If a patient refuses the prescription, what must I do? For example, the patient might have already decided to buy glasses at my office.

You should insist that the patient take the prescription. If they refuse to accept it, then keep the written, signed, and dated copy of the prescription in the patient’s record and let the patient know they can pick it up at any time. You should note in the record that the patient declined the prescription. You should explain to patients that you’re required to give them a copy of their prescription and that it’s in their interests to keep a copy for their records should they need it to replace broken, stolen, or lost glasses.