A 42-year-old woman is evaluated for progressive difficulty with eyelid closure. She initially noticed frequent blinking 3 years ago; within the past year, she also began having unintended, prolonged, and forceful closure of both eyes that now prevents her driving. Bright light, prolonged conversation, and psychological stress aggravate her symptoms. The severity of symptoms fluctuates from day to day, but she does not have any symptom-free days. She reports occasional blurry vision but has had no visual field loss or diplopia, has no sensory numbness, and has had no other abnormal movements involving the face, head, limbs, or trunk.
On physical examination, vital signs are normal. Examination of the eyes shows repetitive and bilateral clonic eyelid closures that occasionally involve forceful closure of the eyes that the patient cannot resist or suppress. The intensity of these movements varies during the examination. No facial grimacing, asymmetry, or other abnormal movements are noted. Other findings of the general medical and neurologic examinations are normal.
An MRI of the brain is unremarkable.
Which of the following is the most appropriate treatment?