[3] The muscle forms an important part of the lateral orbital wall in some animals and can act to change the wall's volume in lower mammals,[4] while in humans it is not known to have any significant function, but its contraction may possibly produce a slight forward protrusion of the eyeball.
[2] Several sources have suggested a role in the autonomic regulation of the vascular system due to the pattern of innervation of the orbitalis.
[5][6] Horner's syndrome causes paralysis of the structures of the eye and orbit that receive sympathetic innervation.
Enophthalmos in Horner's syndrome is an illusion created by the subtle ptosis of the upper eyelid caused by paralysis of the superior tarsal muscle.
[7] Sinking in of the eye (true enophthalmos) is possibly caused by paralysis of the smooth (orbitalis) muscle in the floor of the orbit.