As shown below, Intacs are two tiny, clear, ultra-thin crescents which are made of the same material that has been used for contact lenses and intraocular lenses (for cataract patients).  Intacs reshape the cornea without disturbing the visual axis and they are usually placed in the eye permanently, but can be removed if needed.  Intacs are made in different thicknesses which determine the amount of flattening of the cornea.  This flattening is what corrects the vision.