Perfect eyelids in morning but they droop and get worse throughout the day. What causes this?

I would recommend being assessed by an oculoplastic consultant to determine the basis for your concern.  If it is minor, surgery may not be worth your while at this time.  However, knowing why the eyelids are doing this can give you a sense of peace even if you chose not to have surgery at this time.

You need to have your droopy eyelids (ptosis) evaluated by an oculoplastic surgeon to investigate for a myopathic cause of ptosis - like ocular myasthenia.Are you suffering with double vision ?

It sounds like you may have a familial or genetic condition affecting your muscle function. You must consult with a neurologist, as one possible diagnosis, though rare, is a condition called Myasthenia Gravis.

You have droopy eyelids that fatigue with activity and hence noticed at the end of the day.Do you notice that these get worse after being in front of the computer for a prolonged period of time.You should see an Eyelid Specialist who will be able to advise you about your next logical steps