Orbital part of orbicularis oculi

The orbital part is the outermost portion of the orbicularis oculi. It surrounds the bony orbit and is responsible for the voluntary, forceful closure of the eyelids during actions such as squinting, reacting to bright light, or protective eye closure. Unlike the palpebral part, which handles gentle eyelid closure, the orbital part is activated when strong muscle contraction is needed. It serves not only a protective function but also plays an important role in facial expressions associated with distress, pain, or intense focus.