simply get them buffed from outside... if u wish to clean them from inside too take them out wash them with pure water, and put them in the sunlight to dry. than re fit them again.
for buffing from outside., try the glint glass cleaner might work out... i use them to prevent the fading and shine them like factory. you may also try vim powder, it will remove the fade, than wax them to remove the scratch. (actually it will lighten them)