expression, godan verb (-ku)
to come to see; to come to understand; to regain sight
Used both literally for recovering eyesight and figuratively for gaining insight or understanding. The figurative use often implies a sudden realization or enlightenment.
手術の後、彼は目が明いた。
After the surgery, he regained his sight.
その本を読んで、ようやく目が明い
After reading that book, I finally came to understand.