One point regarding contact lenses and spare spectacles - consider if one lens falls out/is lost or gets dust contamination - then the other lens has to be also removed before putting on the spectacles otherwise one becomes monocular! Not so easily done in a hurry or when wearing gloves.
Under the most perfect circumstances, let along when operating an aircraft, there is nothing simple or easy about dealing with contact lenses that have become contaminated with grit or moved out of place. That said, it seems to have worked for some from the comments in this thread. Respect.