Roughly, to screw up one eye means to tighten and tense up all the muscles surrounding that eye. This is an image of someone screwing up their entire face. Imagine that, but more localized.

Cowardice or loosing control due to fear was nicknamed screwing the pooch. Gus grissom always wanted to be a pilot. He flew over 100 difficult combat missions in an f-86 in korea, became a test …