Move the mouse pointer over the image to observe eye movements in different directions. Systemic exam is unremarkable. The left pupil dilates poorly in the dark. There is no Marcus-Gunn pupil. There is 2-3mm ptosis of the left upper eyelid.
Ocular motility is normal bilaterally.
Confrontational visual fields, penlight eye exam, and optic nerve appear normal. In this case, there is residual pupillary and muscle function. Medical Factoid Diabetes mellitus is the leading cause of new legal blindness in working age Americans. The 3rd cranial nerve originates from the rostral midbrain, coursing ventrally through the red nucleus and ipsilateral corticospinal tract. The nerve enters the subarachnoid space, passes between the posterior cerebral and superior cerebellar arteries, and lies medial to the posterior communicating artery.