The teacher introduces us to three idioms connected with eyes. BBC learn english idioms.
To keep an eye on: have an eye on someone or something and keep an eye on someone or something to keep watch on someone or something; to keep track of someone or something. (The an can be replaced by one’s.)
I have my eye on the apple tree. When the apples ripen, I’ll harvest them. Please keep an eye on the baby. Will you please keep your eye on my house while I’m on vacation?
To have eyes at the back of one`s head: Able to see everything. To seem to be able to sense what is going on outside of one’s vision. My teacher seems to have eyes in the back of her head. My teacher doesn’t need to have eyes in the back of his head. He watches us very carefully.
Have eyes bigger than one’s stomach: To have a desire for more food than one could possibly eat. (See also one’s eyes are bigger then one’s stomach.)
I know I have eyes bigger than my stomach, so I won’t take a lot of food. Todd has eyes bigger than his stomach.