Hi I had revolax injected in the tear trough area 4 years ago. I had very bad swelling and waited 18 months for the filler to dissolve naturally. Unfortunately this did not happen so I had surgery to remove it. It is 2 1/2 years since surgery and my eyes are still swollen. An mri has shown that some of the filler is still there. Why would it last so long and why do the companies who sell it say it dissolves after 9-18 months??