Thanks for your question. Either fat or filler may be used to inject in the tear trough areas to improve hollowness. Each one has advantages and disadvantages. First, it is necessary to determine that volume is needed in the lower lid/tear trough areas. The patient needs the right anatomy- hollowness without significant skin excess and without herniating fat in the area. Usually the patients are younger. Once it has been determined that volume is needed and nothing else, then deciding on fat vs fillers is necessary. Fat has the advantage of being permanent and natural, and the stem cells in fat are thought to help with the dark pigment in some patients. It has the disadvantages of requiring a surgical procedure, is more expensive, and the success can be variable. Patients will sometimes need multiple rounds of fat grafting to get the desired result. Filler, on the other hand, is easy to inject, can be done in the office in a few minutes, has little downtime, and is relatively inexpensive. However it is not permanent, and there is risk of contour irregularities that may not smooth out over time. There is no greater increase in risk by injecting fat compared to filler, in my opinion. The main safety point is to be sure the injections are done with low pressure and in the correct plane in order to avoid the complication of an embolus which can cause blindness. This can happen with either fat or fillers. Fortunately this is very rare but does illustrate why it is important to get this done by a physician who understands the anatomy and injection technique. Best wishes, Rohit Jaiswal, MD Plastic Surgeon, Las Vegas, NV