Are the goggles new, used, or have you had them for a while? You don't need to buy a lens directly from Oakley, though you can. Any authorized dealer can sell you a lens for the Splice with a warranty. If you buy used you take a chance.
Be sure you're letting you goggles air dry between uses i.e. don't store them wet and never use heat to dry. Also don't rub the inside of the lens if it is wet, or has snow/other moisture on it.