A sign that this snake is about to shed its skin is when the eyes turn a cloudy, bluish color. This is because the eye cap, a specially adapted scale which covers the eye, is loosened up in order to be shed along with the skin and causes this change. Just prior to shedding, the eyes will clear up again.
Snake's eyes are covered by their clear scales (the brille) rather than movable eyelids. Their eyes are always open, and for sleeping, the retina can be closed or the face buried among the folds of the body.
Molting occurs periodically throughout the snake's life. Before a molt, the snake stops eating and often hides or moves to a safe place. Just before shedding, the skin becomes dull and dry looking and the eyes become cloudy or blue-colored. The inner surface of the old skin liquefies. This causes the old skin to separate from the new skin beneath it. After a few days, the eyes clear and the snake "crawls" out of its old skin. The old skin breaks near the mouth and the snake wriggles out, aided by rubbing against rough surfaces. In many cases, the cast skin peels backward over the body from head to tail in one piece, like pulling a sock off inside-out. A new, larger, brighter layer of skin has formed underneath. (Source - Wikipedia)
Here is a post I made in reference to a Watersnake With Possible Retained Eye Cap