keep one’s eyes open—be watchful and alert:
- During the three weeks I stayed in Dar-es-Salaam, keeping my eyes open, I was hard put to find evidence of Chinese influence.
open someone’s eyes—make a person acutely aware of the truth of a situation:
- Attending Harvard only served to open her eyes to a whole new range of inequalities that exist in society.
Cf.: eye opener—a startling or shocking revelation:
- It was a real eyeopener for the adults. The ease that the children displayed with the technology was enough to amaze even a veteran.
See also: with one’s eyes closed / with one’s eyes open.