Ophthalmologymiddle twist
A 52-year-old woman wakes with a drooping right eyelid and double vision. She has had a boring pain behind the right eye since yesterday. When the lid is lifted the right eye sits down and outwards and will not turn in. The right pupil measures 6 mm and reacts sluggishly; the left measures 3 mm and reacts briskly. There is no proptosis, the eyelid does not fatigue on sustained upgaze, and the temporal arteries are not tender. Blood pressure is 128/76 mmHg. Which one of the following investigations should be arranged immediately?