Which would be best to treat dark under eye circles and thin skin, a Filler or Cool Laser Treatment? (photos)

I disagree with some of what has been said.  Dark circles are typically a combination of genetics and a reflection of the vascularity that is beneath the skin.  With that said, this is a chronic thing and very few treatments work well.  You can use fillers under the eyes to help camouflage the darkness, I typically use cannulas and a thinner filler such as Belotero for that.  Lasers aren't usually that helpful, although I do a lot of laser genesis and/or Fraxel treatments and patients seem to be very happy with the results.  PRP and fat seem a little aggressive for my taste, and I don't see better results with these treatmetns compared to any of other treatments I currently offer.  Topical creams rarely help, but eye creams with vitamin A, caffeine, coffeeberry/berry extracts, or green tea can sometimes help.  It is important to know that since there are so many treatments out there for this "condition," that means there are very few that work well.  As long as you seek improvement, not cure, you will be happy with any treatment.  Seek a cosmetic dermatologist or plastic surgeon with experience.  Best, Dr. Emer.