Under eye dent when smiling since I had filler in this area 4 years ago, how do I fix it? (Photos)

At least from the photos and the history of filler use in the area, the problem is likely one that has been nicknamed under-eye "puffy pillows," or more specifically infraorbital lymphedema (lymphatic obstruction) likely secondarily to the use of an inappropriate choice of filler for the area and/or too superficial injection of the filler in that area. Unfortunately, it tends to be a difficult problem to treat and a persistent one, however, I have successfully treated a number of individuals who have come to me with this problem using an algorithm of varying combinations, concentrations and amounts of intralesional anti-inflammatory Agents. You would be wise to consult with an experienced, board certified cosmetic dermatologist. Hope this helps and best of luck.

Based on the posted photos, you have significant tear trough denting that can be addressed with capital HA fillers or nano fat crafting. Best of virtual consult with. Fee from $3000 to $5000