Ptosis surgery is a procedure in which the elevating muscle of the eyelid is tightened to lift the droopy lid to a higher position. This is like raising the shades which cover a window. It is different than blepharoplasty surgery in which redundant skin/muscle and/or fat are excised from the eyelid. Ptosis surgery opens the eye and blepharoplasty surgery lightens the load on the eyelid.  Both ptosis surgery and blepharoplasty surgery can enhance appearance and improve field of vision.  The main issue which arises is when a patient sees a surgeon for droopy lids, and the ptosis component of the heavy lids is missed as the surgeon does not see beyond the eyelid bags.  Blepharoplasty surgery (for eyelid bags) is an easier procedure than ptosis surgery which is generally only performed by a specialist in eyelid surgery (view link

Below are examples of ptosis surgery performed by Dr. Massry