This phrase appears in the Bible:
Proverbs 7:1-5
1 My son, keep my words and treasure up my commandments with you; 2 keep my commandments and live;keep my teaching as the apple of your eye; 3 bind them on your fingers;write them on the tablet of your heart.
Deuteronomy 32:10
He found him in a desert land,and in the howling waste of the wilderness;he encircled him, he cared for him,he kept him as the apple of his eye.
Zechariah 2:8
For thus said the Lord of hosts, after his glory sent me to the nations who plundered you, for he who touches you touches the apple of his eye:
Yesterday at bedtime (lots of sweet things go on at bedtime when I take the time...) Elliot was looking at me so seriously. I asked him what he was thinking and he replied "I see me in your eye!". I told him I can see myself in HIS eye. He was so delighted about that. This morning he went checking Daddy's eye to see what was in it. :) It was a beautiful reminder to me of the Lord's teaching.
Figuratively this phrase is something, or more usually someone, cherished above others. How precious that God sees Himself, His teaching in our eye...we should shine with Him and let others see that as well. But even more amazing is that WE are in HIS eye.
On a similar note, this song was my "anthem" in London and still means so much to me. I just grabbed this from YOUTUBE, not my pictures, just listen to the song.