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.
Levator palpebrae superioris
Superior tarsal muscle
Orbital muscle
Inferior tarsal muscle
Head and neck