If someone is eagle-eyed, they notice small things other people miss — a tiny mistake on a page, a face in a crowd, a change in a picture. We say it because eagles can see very far and very clearly. You can call a person eagle-eyed, or talk about an eagle-eyed teacher or an eagle-eyed look. Though actually, it is not a doctor's word about healthy eyes, and it is not about glasses. It is about paying sharp attention. It is a warm, colourful compliment, a little like calling someone “眼尖,” not a cold lab term.