MS-0861

A 63-year-old male presents with a sudden onset of double vision that has been ongoing for eight hours. He has a medical history of hypertension, which is managed with amlodipine and atenolol, and type 2 diabetes that is controlled through diet. Upon examination, the patient displays watering of the right eye, a slight droop of the eyelid, and displacement of the eye to the right. The left eye appears to have a full range of movements, and the pupil size is the same as on the left. What is the probable cause of his symptoms?