Updated anatomy of
the periorbital ligaments

This risk cannot be emphasised enough. The supraorbital, supratrochlear, dorsal nasal, paracentral, central forehead and the majority of the periorbital arteries have direct communication with the ophthalmic artery. This means that filler product has the potential to travel into the orbit and access the central retinal, short ciliary and long ciliary arteries, where it can obstruct the arterial blood supply to the retina.

The retina itself is a specialised type of tissue which originates embryologically from the brain and should be therefore treated as brain tissue in terms of oxygen and nutrient requirements. This explains why treatment of vision loss following filler-related embolisation is successful in less than 50 percent of cases, even when retrobulbar, intra- arterial or endovascular interventions are initiated. The principle of ‘time is tissue’, familiar in stroke management, also applies here, especially when the eye is involved.

Periorbital anatomy

The periorbital region is not well defined in terms of accurate and reproducible anatomic boundaries. In the infraorbital region, for example, the tear trough belongs to both the midface and the periorbital region, according to standard anatomic terminology. In the supraorbital region, the anatomic boundary between the periorbital region and the forehead is defined at the upper margin of the eyebrow cilia, indicating that the eyebrows still belong to the periorbital region and not to the forehead. However, no one mentions how these boundaries change when eyebrow ptosis occurs, and the eyebrows suddenly coincide in location with the skin surface projection of the superior bony orbital rim.

Clinically, the definition of the periorbital region is fairly straightforward, as it includes the area encircled by the bony orbital rim plus one finger-width of surrounding soft tissue. This is based on the fact that treatments within this finger-width-radius have the capability to influence the aesthetic appearance of the periorbital region.

There are important anatomic features that define and connect the periorbital region as a coherent and well-defined entity: the periorbital ligaments. Therefore, an anatomic overview of the periorbital ligaments should be provided.

IT TAKES A SUFFICIENT AMOUNT OF COURAGE TO INSERT A NEEDLE OR A CANNULA IN CLOSE PROXIMITY TO THE EYE, GIVEN THE NUMBER OF PUBLISHED ASSOCIATIONS BETWEEN PERIORBITAL ARTERIAL VASCULATURE AND CASES OF BLINDNESS, ESPECIALLY WHEN IT COMES TO SOFT TISSUE FILLER INJECTIONS.

Orbicularis retaining ligament

The orbicularis retaining ligament (ORL) anchors the orbicularis oculi muscle to the anterior orbital rim. The ORL is a circular ligament that spans the entire orbit and separates the orbital and palpebral portions of the orbicularis oculi muscle. For visualisation, think of the contact interface between a pot and its fitted lid.

What is unfortunate and confusing is that this ligament has different names depending on the precise anatomic location.

In the area of the lateral orbital rim, for instance, this very same ligament is called lateral orbital thickening because it is thick and wide in that region.

In the tear trough region (medial infraorbital region), this very same ligament is called the tear trough ligament – because it’s located in the tear trough and forms its upper anatomic boundary.

The ORL is, in most parts, a thin ligament that can be found on the undersurface of the orbicularis oculi muscle. In the lateral infraorbital region, however, this ligament is multi-laminar and contains intralaminar fat.

During the process of facial ageing, this fat reduces in volume. When the lamellae collapse, the lateral infraorbital region sags and descends, resulting clinically in palpebromalar grooves and lateral infraorbital hollows.

In the tear trough, the ORL is uni-laminar and serves as a direct attachment for the orbicularis oculi muscle to the bone. Here, deep filler injections, especially with repeated cannula passes, can injure the ligament or the underlying muscle, potentially impairing lymphatic drainage, contributing to swelling and allowing product to migrate into the supra- muscular plane.

Zygomatico- cutaneous ligament

As the name indicates, the zygomatic-cutaneous ligament (ZCL) originates from the zygomatic bone and (supposedly) connects to the skin (even though the connection to the skin has never been proven in a scientific investigation). This ligament coincides in location and pathway with the zygomaticus minor muscle and therefore forms the lower boundary of the suborbicularis oculi fat (SOOF); the upper boundary is formed by the ORL.

In the lateral infraorbital region, the ZCL has a horizontal pathway but curves upwards and fuses with the ORL in the medial vertical limbus line. It is exactly in this location of fusion where the ORL changes its name to tear trough ligament. It is also exactly in this location where the facial vein enters into the orbicularis oculi muscle and continues to travel intramuscularly. It is also exactly in this location where the SOOF ends, and the tear trough begins. This transition has multiple clinical implications:

1. Lymphatic drainage patterns

Because of the pathway of the ZCL, the lymphatic outflow from the SOOF can only occur in lateral orientation as here the SOOF is open to the temple and to the lateral midface. Lymphatic fluid cannot drain towards medial, cranial or caudal as all directions are blocked by ligaments. These ligamentous boundaries explain the formation of malar mounds, which look like under-eye bananas.

But upon closer inspection, it is evident that this specific swelling does not extend into the tear trough and not into the middle or lower midface. Malar mounds delineate very clearly the location of the ZCL below and of the ORL above.

2. Filler-related swelling

Soft tissue filler injections into the SOOF carry a risk of infraorbital swelling due to the fact that fillers attract water upon implementation; this water is now trapped and can result in malar mounds.

3. Product tolerance varies by plane

The difference in the number of fascial layers (SOOF = 7; tear trough = 3), means treatments in the lateral infraorbital region allow for much more leeway than the medial infraorbital region. Deposited product medially can be much easier spotted if it’s too much, has the wrong rheologic properties or is injected into the wrong plane. Laterally, no such aesthetic complications can be identified because here sufficient fatty layer coverage is available to camouflage any mishaps during product deployment.

Understanding the ligamentous anatomy of the periorbital region is not an easy task, but it becomes highly valuable in daily clinical practice once understood and applied. The location of the ORL and ZCL can help explain why periorbital swelling occurs and how extensive it may be when performing non-surgical aesthetic treatments. It all starts with anatomy – the rest is just its clinical application.