If it's just fogged/hazed plastic, Meguiars PLASTIC POLISH, plenty of clean white soft cloth changed out often as you polish, if scratches are present you'll need to determine at which paper grit you'll need to start sanding with, if you can't remove the scratches with 600-800 wet/dry paper start looking for new lenses, I generally finish up sanding in the 3000 grit range before polishing by hand with polish