The lower eyelid skin is very delicate. It is also very thin. Any irregularity shows through. One of our most common reason for performing revision lower eyelid surgery is palpable and visible lumpiness from prior fat injections. Many of the revisions are minor. Often, however, there are uncorrectable problems from gristly fat located in many planes of tissue. The reason for this is in the biology. Fat injections cells are harvested by liposuction. the fat cells are then usually spun in a centrifuge and then injected back in. During this process, most cells die. The number is debatable, depending on whether the viability is judged by microscopic examination of the cells (ie trypan blue exclusion method), or by metabolic methods, measuring the cellular machinery. However, the number of live cells is in my opinion between 3% and 25%. The rest are dead. As the dead cells are eaten away, an inflammatory reaction develops characterized by macrophages (large white blood cells), chronic inflammation and coalescence of fatty cysts, or dead liquid fat. We have presented and published our results on the histology of fat injection specimens. We have found the belief that volume existing at 6 months after fat injection technique consists of live cells to be false. Rather, the bulk that remains consists of all the cellular elements above, still very actively eating away and walling off the dead cells and fatty cysts. The bottom line is that intense cellular changes continue to occur with fat injection, usually characterized by further loss of fullness, even at 1 1/2 years after injection. This does not mean that there are not many happy patients out there with fat injections to the lower eyelids. There are especially when the technique is conservatievly performed in highly skilled hands. Just be cautious before injecting fat into the lower eyelids.
