How wonderful, how blessed to have eyesight! The hearing ear, and the seeing eye, the LORD hath made even both of them. Proverbs 20:12.
The human eye has two million moving parts and processes 36,000 bits of information every hour at 576 megapixels, working without stop. We blink more than 10,000 times a day, up to 5 times a second! The eye can detect a candle 14 miles away under the right conditions. Your eyes receive information and send it to the brain by way of your optic nerve. Real seeing takes place in the brain, howbeit upside down. The brain interprets information correctly, even filling in your blind spot where the optic nerve crosses the retina.
The retina is the light sensing tissue lining the inner surface of your eye like film in old fashioned cameras. The pupil is the hole in the center of the eye that opens and closes to let in more or less light. Your eyes can see light and dark and distinguish shape and color (including ten million color hues and 500 shades of gray) and depth. The eyes themselves come in a variety of colors including brown (most common), blue, green, gray, black, hazel, etc.
The eyes are very sensitive. We have an eyelid to protect the eyes from dirt and grime. (Camels have three eyelids protecting them from the dust and sand of the desert.) In addition we have tears that continually wash the eye every time we blink. Then there are eyelashes that keep out dirt, and eyebrows that keep out sweat. We blink when something comes close. We even blink when we sneeze. We are very careful to protect our eyes. They are very sensitive indeed.
God is very sensitive concerning His people. "The LORD's portion is His people; Jacob [Israel] is the lot of His inheritance. He . . . led him about, He instructed him, He kept him as the apple [pupil] of His eye" (Deuteronomy 32:9-10). Again, God says concerning His people, ". . . he that touches you touches the apple [pupil] of His eye" Zechariah 2:8.
We would not let anyone poke his finger in our eyes. God will not let anyone or anything ultimately bring hurt or harm or ruin to His people. God cares for His own and will cause "all things [to] work together for good to them that love God, to them who are the called according to His purpose" (Romans 8:28). Even Satan had to get God's permission to touch the man, Job's life (see Job chapters one and two). Satan might walk around as a roaring lion seeking to devour us, but we can cast all our care upon Him; for He cares for us. (See 1 Peter 5:7-8.)
Do we, even so, care for God? To us He says, "keep my commandments, and live; and my law as the apple of your eye" Proverbs 7:2.