This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Enophthalmos is an uncommon feature of Horner's syndrome. Enophthalmos is due to palsy of? 
Select and explain. 
A. Levator palpebrae superioris, B. Superior tarsal muscle, C. Orbitalis muscle, D. Inferior tarsal muscle
C: Orbitalis muscle
Answer: C: Orbitalis muscle 
Explanation: Enophthalmos (sinking of the eye) is the inward displacement of the eyeball. It results from paralysis of the orbitalis muscle (a smooth muscle that spans the inferior orbital fissure and may contribute to maintaining the normal position of the eyeball).