AKT-2101

AKT-2101

A 65-year-old man presents with a brief history of painless diplopia that he first noticed while reading. The images are horizontally and vertically separated, although he notes that the degree of separation varies. During examination, the visual acuities are 6/6 in either eye. There is no pupil abnormality. There is a left ptosis, partially covering the pupil, and reduced abduction and depression of the left eye, both in abduction and adduction, with other ocular movements appearing normal. There is no other abnormality on examination. He reports that his right upper eyelid sometimes droops as well.
What is the most probable diagnosis? Choose ONE option only.