Why does the back of the eye look older after under-eye fat repositioning?

I am considering lower eyelid fat repositioning, and I am curious about how this surgery actually affects my age. I have heard many people say that the under-eye area becomes more prominent as you get older, so can I expect a youthful effect on the back of my eyes? I would also like to know how to handle any side effects or problems that may arise after the surgery. I really need your experiences and advice.