Horner's muscle: the lacrimal part of the orbicularis

Horner's muscle (or the lacrimal muscle) is the deepest, most medial part of the orbicularis oculi muscle. While most of the orbicularis forms the ring that closes the eyelid, the Horner portion (also called the pars lacrimalis) sits next to the lacrimal sac, near the medial corner of the eye, where tears drain toward the nose.

What is its function?

Its main function is to help pump tears. With each blink, contraction of this part of the orbicularis tenses and compresses the region of the lacrimal sac, which helps draw tears in through the lacrimal puncta and carry them to the duct that opens into the nose. That is why, in people who blink little (such as in front of a screen), the system is less efficient and tears can pool.

When the orbicularis loses tone, or when there is an injury to the lacrimal system, the patient may report constant tearing, which is a medical complaint rather than an aesthetic one.

Where does the anatomy sit?

The medial canthus region is compact and full of important structures: the medial canthal tendon, the lacrimal bone, the lacrimal sac and the start of the tear trough. The orbital septum and the eyelid fat pads lie just below and around it. Knowing this arrangement helps explain why the region is so sensitive to procedures.

To see how the canthus is described in topographic terms, also see medial and lateral canthus.

Why should the HOF professional know it?

Because treatment of the tear trough and under-eye hollows happens right in this neighborhood. Filler in the region requires understanding what is muscle, what is ligament, what is fat and what is the lacrimal pathway. Even if Horner's muscle itself is not the target of any technique, knowing where it is avoids confusion about what is being palpated and what to avoid.

In addition, complaints such as tearing or persistent swelling at the medial canthus after a procedure deserve careful assessment and may justify referral to an ophthalmologist.

In Harmy

The Tear Trough point in the marking simulates filler in the infraorbital region with the volume in ml you enter, seen from the front. The app does not identify muscles or lacrimal structures. The simulation is illustrative, and the anatomy of the medial canthus is assessed and respected by the professional in the clinic.

Also called: lacrimal muscle, pars lacrimalis of the orbicularis.