How do I get rid of scar tissue under eyes after fillers (fat and juvederm)?

I recommend getting a consultation. This may be improved with 5/FU steroids or surgical removal. I hope this helps. 

Thank you for sharing your question and photographs and I am sorry to hear of your difficulties.  I would recommend seeing an oculoplastic or plastic surgeon in consultation to see and feel the tissues of your lower eyes.  Based on your narrative I would assume that this is poorly placed fat from your 3-4 treatment sessions that would need removal in order to improve your results.  This requires an in-person evaluation, however.

Without photos, there is really no way to give you guidance here.  My suggestion would be to seek out a Board Certified Oculoplastic, Facial Plastic, or Plastic Surgeon and meet with them in person to discuss your concerns.  I hope that helps and wish you the very best!-Gregory A Buford MD FACSBoard Certified Plastic Surgeon and Author

I recommend getting a formal evaluation with a facial sculpting expert. Lasers, microneedling/prp, rf treatments may give improvement. Best, Dr. Emer

I am sure you could get help from Plastic Surgeon who does fat transfer and is familiar with this type of complications. Since you have practically eliminated the possibility of filler accumulation with hyaluronidase injections there are few non-surgical options that may be considered. Steroid injections may help if scar tissue is the problem, not so much for fat. I had very good luck with using radio-frequency for the same problem in the same location and in the lips. I used Exilis but in a very modified manner. It is a very small surface area to heat and little room to "escape" with the probe. Since the fat residual is most likely mixed with, or surrounded by, the scar tissue it requires different handling to achieve high enough temperature in this very sensitive area. You can almost eliminate discomfort and reach high temperatures by pre-injecting the area before the treatment. Good luck!