expression, godan verb (-su)
strain one's eyes; stare intently
Used when focusing one's gaze sharply, often to see something small, distant, or unclear. Similar to 目を凝らす but with a slightly more literary or poetic feel due to 瞳.
See also: 目を凝らす
暗闇に瞳を凝らして、何か動くものがないか探した。
I strained my eyes in the darkness, searching for anything moving.
彼は遠くの船を確かめようと、瞳を凝らした。
He stared intently, trying to make out the distant ship.