Orbicularis oculi is one of the muscles of the eyelid. It is the primary sphincter muscle. It surrounds the orbit and extends out onto the temporal region and cheek. It consists of three parts which vary by location:
- orbital part
- palpebral part
- lacrimal part
Broadly, they arise from the medial orbital margin and the lacrimal sac, extending laterally and concentrically around the orbit to insert into the lateral palpebral raphe.
It is innervated by the temporal and zygomatic branches of the facial nerve (CN VII).
Orbicularis oculi has several functions:
- closure of eyelids eg for facial expression or protection
- distribution of tear film
- facilitates drainage of tears by helping to empty the lacrimal sac
With time, the chronic action of orbicularis oculi produces permanent folds - wrinkles - in the lateral eyelid skin that are colloquially termed "crow's feet". These are the target of injected botulinum toxin therapy for cosmetic purposes.