While autologous fat can certainly be used for filling the delicate tear trough area, I would be reluctant to use it. For one thing, retrieving the fat for use in this way is a two procedure method. Fat must be withdrawn under local anesthesia from an an area, such as the thigh, abdomen or buttocks (procedure #1), processed, and then reinjected into the tear troughs (procedure #2).
Since the true longevity of transplanted fat grafts is still a subject of some dispute, and since often fillers placed in the tear trough area--where there is relatively little movement that can contribute to mechanical breakdown-- fillers injected into that region often maintain correction for well over a year, if not several years. (Anectdotally, I treated my own tear troughs six years ago as a birthday gift to myself and still do not need any re-treatment).
I have more than twenty years of experience in treating tear troughs with all kinds of materials, including Zyderm and Evolence. Because hyaluronic acid fillers, such as Juvederm Ultra XC, can be injected smoothly into this region in microdroplets, and may be quickly, easily, and completely dissolved afterward with an enzyme, hyaluronidase if so desired, I prefer this to far less forgiving materials, such as fat or permanent fillers, like Artefill.