Enophthalmus is due to palsy of
Ref: BD Chaurasia's HUMAN ANATOMY, Volume 3, 4th edition. Enophthalmos (i.e. retraction of the eyeball); is possibly caused by paralysis of the smooth (orbitalis) muscle in the floor of the orbit.
Head and neck
Levator palpebrae superioris
Superior tarsal muscle
Orbital muscle
Inferior tarsal muscle
Orbital muscle