I'm curious about under-eye filler procedures.

Has anyone here had under-eye fillers? My under-eye hollowness and dark circles look severe, so I am considering getting filler treatment. I am curious about the type of filler and the appropriate procedure for my skin condition; since this requires a physical examination, what kind of general fillers are typically used? I am also interested to know how long the effects last, as well as any potential side effects or risks. Additionally, please provide information on pre-procedure precautions, the duration of swelling and bruising, and the time required to return to daily life. I would also appreciate it if you could let me know the approximate cost, whether a single session is sufficient, or if additional treatments are necessary.