How soon before fat transfer do I need to dissolve filler?

In general, you should not need to dissolve the filler under your eyes before Fat Transfer unless there is a visible lump from the filler. Having filler in place does not affect ability to do Fat Transfer to the same area.

If you are having a problem with the filler that you want to resolve, such as swelling or bluish discoloration in the filler area then you can dissolve the filler with hyaluronidase ASAP. If the filler is not causing any problem then you can leave the filler in place and just augment the volume where needed with the fat. Hyaluronic acid (HA) filler can be very long lasting under the eye and if it is effective at filling in the hollow and reducing the dark circle it can be left alone. You should know that fat transfer under the eyes is technically difficult and most of the time you end up under corrected. Many patients will end up getting filler to augment the fat grafts under the eyes. It is also important to recognize that although it is easy to dissolve HA fillers it is very difficult to remove fat after fat grafting so its best to avoid overcorrection when doing fat transfer on the face, especially in the highly visible lower eyelid area.

Of all the places we do fat grafting, the area with the narrowest margin for error and with greatest complications, is the lower eyelid....at least in my opinion. I would make sure that filler has completely resorbed or been dissolved before proceeding with fat grafting to the lower lids. If you feel the area below your eyelid (the lid cheek junction), you can tell immediately that there is very little space between the skin and the bone. Because of that, there is not much room to place the fat and a high likelihood that it will look lumpy. I would suggest that you see an experienced surgeon because I believe it is necessary to use very small amounts of fat in that location.