Droopy eyelids or eyelashes? (photos)

I would like to know the cause behind droopy eyelashes/lids (as seen in the photos): is there a way to improve this? It does not seem to be necessarily tied to excess skin/fat above the eyes: this marked downward projection can develop also when eyes are hollow. In all cases the result is a sad, tired, puffy look, which is also my problem. Can this be in any way fixed? Thank you very much for your help!