Curve or Straight Eyelid? Curious What Determines the Eyelid Above the middle of the Tarsal Plate? (photo)

This is a complex and sophisticated question, and as is so often the case in such situations, there is not a simple answer.  First of all the foundation of the orbit is determined by the underlying bony structure.  This may be the most important factor in what you describe.  Another factor is the soft tissues of the upper eyelid including the structure of the fatty and muscular layers.  Finally there is the geometry of the way the levator aponeurosis inserts onto the tarsal plate.  It may or may not be possible to modify these structures in your individual case.  It all comes down to the physical exam.

The eye shape is created by many things. It is primarily a component of the underlying bony and soft tissue structures and their inter-relationship.