You could do a search and find several methods of clearing the plastic headlight lenses complete with before and after photos. Some people have used various grades of sand paper from hardware or auto parts stores, wet sanded their headlights and then finished the headlights off with a clear spray lacquer. Others like me have used Crystal View headlight refinishing kits that can be bought at auto parts and discount stores which include the needed sand paper, lacquer and applicators:
http://us.lexusownersclub.com/forums/index...&hl=CrystalPlastX works pretty well unless the plastic lenses are really trashed. My understanding is that headlight clearing methods that involve using a final clear coat usually last longer than PlastX and hide the imperfections that PlastX can not hide. My headlights refinished with Crystal View look far better than my foglights cleaned with PlastX ... I was too cheap to buy another Crystal View kit to do the foglights.
PlastX seems to work pretty well even if it is a temporary fix. I sometimes think it would be fun to carry a bottle of PlastX and a small towel and do a stealth cleaning of some of the badly discolored headlights I see during my daily walk. If I did, I would clean only one headlight on each car -- wouldn't that be fun? But I'd probably get nailed for vandalism if I tried something like that.