Horner's muscle and the lacrimal system
N. C. Ahl and J. C. Hill
Anatomical dissections were performed on eight fixed cadavar orbits to
observe the relationship of the pretarsal, preseptal, and Horner's muscle
to the canaliculus. The attachments of Horner's muscle and the deep
preseptal muscle to the lacrimal diaphragm reflected their important role
in the lacrimal diaphragm's function. In addition, the muscles involved in
lacrimal drainage were mechanically pulled with a forceps to induce
canalicular pressures. Shortening and compression of the canaliculus by the
pretarsal, preseptal, and lateral Horner's muscle increased canalicular
pressure, whereas Horner's muscle and the deep preseptal muscle induced
negative lacrimal pressures. A positive-to-negative pressure gradient in
the lacrimal drainage system was proposed as the main force in lacrimal
tear transport.
