It has been said that the eyes are the window to the soul, I firmly believe that. The first thing I notice about anyone is their eyes. You can tell what a person's mood is as soon as they walk into aroom by the way their eyes are. Eyes express joy, sorrow, love, thought, bitterness, hurt, and so much more. People can talk without uttering a single word by the look in their eyes.
I think the worst sense to lose would be that of sight. Not being able to see the beauty of God's creation, the faces of loved ones, the words of a book, or the color of a room has to be incredibly tragic. It is said that a picture is worth a thousand words, and without sight that picture cannot be seen.
The Bible speak of the eye in several places. "The hearing ear, and the seeing eye, the Lord has made even both of them." ~Proverbs 20:12 "The light of the body is the eye: therefore if thine eye is single, they whole body also is full of light; but when thine eye is evil, thy body also is full of darkness." ~Luke 11:34