Sclera

Iris/pupil

The cornea over the iris/pupil bulges out from the eyeball. This bulge presses up the eyelid, so if the pupil looks to the left, the opening of the eyelid also moves left. This image illustrates that the direction of the gaze doesn't affect only the pupil, but the entire eye.

This part is the widest.

This part is the widest.