If it's a light scratch, your optician may be able to polish it out, or send it to the manufacturers who can. If it's deep, you're probably stuck with it.
You can polish out scratches from glass with many different types of polish as per the toothpaste/watch mentioned. However, your glasses have a precision ground curved surface and if you polish out a sratch by hand you will probably affect the curvature and get very odd effects when looking at things. best to take it to a pro for help.
Be aware, too, that if the lens has a coating, such as anti-scratch or anti-reflective, trying to polish out the scratch will remove, or at least damage, such a coating.