Why are my eyelids different shapes? (Photo)

So minor an asymmetry I would NOT offer any therapy to you. .........................................

You have a little ptosis, where the muscle is weak and the lid rides a little low.  This can make you look tired, and may seem worse in photos or when you are tired. You also have a secondary crease on one side.  If these things really bother you they can be surgically corrected.  But you don't look bad!  See an oculoplastic surgeon who can go over these issues with you.   

It is not unusual for the two eyelids to be different.  In fact, no one has two sides of the face totally symmetrical.  Eyelids can be different if one of them has a droopy eyelid (Ptosis) but you don't have that condition.  You just happen to have the left upper eyelid with a little bit of excess skin creating an extra fold.  If this really bothers you, it is very easy to correct by performing a very conservative left upper Blephsroplasty.