Surface Anatomy

It is useful to conceptually divide the face into aesthetic units when discussing reconstructive techniques.^1,2 Recognizing the junction lines between neighboring units is important as they conceal surgical scars well. Most authors use the eyebrow as the superior limit of the periocular aesthetic unit; however, the suprabrow area can also be considered to be part of the periocular area, as closures in this area can affect the eyebrow and upper eyelid (Figure 12.1). The infraorbital and nasojugal creases define the inferior border of the periocular unit. The nasofacial sulcus marks the medial border in the medial canthal area, while the frontal process of the zygomatic bone defines the lateral margin. Anatomically, it is also useful to distinguish the palpebral portions of the upper and lower eyelids, which overlie the globe when the lids are closed, from the orbital portions, which continue over the bony orbital margin to the edge of the periocular aesthetic unit.

Figure 12.1 Surface anatomy of the periocular area.

Other naturally occurring skin folds and creases within aesthetic units can similarly be used to hide surgical scars, as these lines appear normal and do not attract attention. The upper eyelid crease, for example, hides upper blepharoplasty incisions. Other aspects of periocular aesthetics should also be considered when moving tissue for reconstruction. The concavity of the medial canthus, the symmetry of the eyelids, and the orientation of eyebrow hairs are some of the more subtle features that can become conspicuous if undesirably altered. Attention to these surface characteristics will help avoid distortion of periocular structures and promote aesthetically proper surgical closures.

Surgical Anatomy

A thorough knowledge of the anatomy of the periocular region is paramount to successful surgery in this area (Figure 12.2). Understanding tissue planes and functional relationships between anatomic structures serve the surgeon well in this complex area. Familiarity with the location of nerves, blood vessels, and “danger zones” is critical to achieving optimal surgical results and avoiding bad outcomes.

Figure 12.2 Surgical anatomy of the periocular area. Note the superficial location of the temporal branch of the facial nerve as it approaches the periocular area. It lies between the thin superficial muscular aponeurotic system (SMAS) layer and the temporalis fascia for most of its course here. Only as it crosses the edge of the frontal bone does it dive under the frontalis muscle and become more protected. Not pictured in this diagram are the superior and inferior palpebral arteries, which arch across the eyelids parallel to the lid margins, piercing the orbital septum above and below the medial and lateral canthal tendons.

The margins of the bony orbit are defined by the frontal bone superiorly, the zygomatic bone inferolaterally, and the maxilla inferomedially. Within the orbit sits the globe with its associated vessels, muscles, nerves, fat, and most of the lacrimal apparatus. The orbital septum, a membranous sheet of connective tissue that arises from the periosteum of the orbital rim and spans across the lids, separates the globe and deeper orbital structures from the more superficial muscles and skin. Within each eyelid is a crescent-shaped tarsal plate, the fibroblastic lamina that provides the semirigid structure of the lid. The medial and lateral ends of these plates are stabilized by the medial and lateral canthal tendons, respectively, which attach to the adjacent bony orbit.

The orbicularis oculi muscle lies superficial to the orbital septum. The sphincter muscle of the eyelids, it controls blinking and forceful eyelid closure. It can be divided into palpebral and orbital portions. The palpebral part, confined to the eyelids, arises from the medial canthal tendon and arches across both lids (anterior to the tarsal plates) to insert into the lateral canthal tendon. In oculoplastic surgery it is useful to further subdivide this part into the pretarsal and preseptal portions. The orbital portion of the muscle, located more peripherally, lies flat on the surface of the orbital margin, bordering the forehead and cheek. Its fibers arise from the medial end of the medial canthal tendon and adjoining bone to extend laterally in a series of uninterrupted concentric loops around the orbit. The elevator of the upper lid is the levator palpebrae superioris, a long, flat muscle above the globe. Its aponeurosis fuses with the orbital septum superiorly to insert into the superior tarsus and skin of the upper eyelid.

The upper eyelid is larger and more mobile than the lower eyelid, and it completely covers the cornea when the lids are closed. The skin of the eyelids is less than 1 mm thick with minimal subcutaneous tissue, and it is tightly adherent to the underlying muscle in the pretarsal region. Over the preseptal and orbital regions, the skin is more mobile. The posterior surface of the eyelids is lined by the palpebral conjunctiva, a thin mucous membrane that reflects in the superior and inferior fornices of the conjunctival sac onto the anterior surface of the globe (the bulbar conjunctiva). Coronally, the eyelids can be divided into two lamellae. The anterior lamella includes the superficial skin and orbicularis oculi muscle, whereas the posterior lamella consists of the tarsal plates, lid retractor muscles, and palpebral conjunctiva.

The lids meet each other at the medial and lateral canthal angles, while the palpebral fissure between them opens into the conjunctival sac and underlying globe. The lateral canthal angle is more acute than the medial, and it lies in direct contact with the globe. The more rounded medial canthus is separated from the globe by a small space, the lacrimal lake, which contains a small mound of tissue, the lacrimal caruncle. The lacrimal gland, situated in the superolateral part of the orbit, lies posterior to the orbital septum and the frontal bone. It secretes tears into the superior fornix of the conjunctiva that wash across the cornea to collect in the lacrimal lake in the medial canthus. Near the medial canthus, both upper and lower eyelids have small lacrimal papules on their margins that contain lacrimal punctor, through which tears drain into the lacrimal canaliculi and to the lacrimal sac. The sac then drains through the nasolacrimal duct to empty into the inferior meatus of the nose. The lacrimal sac lies in a protected position, behind the medial canthal tendon. It is enveloped by fibers of the orbicularis oculi muscle, such that each blink of the eyelids serves to pump tears through the sac and into the nose.

The temporal branch of the facial nerve is the most superficially located (and thus most susceptible) motor nerve in the periocular area. From its emergence beneath the parotid gland in the preauricular region, its course is roughly delineated by drawing one line from 0.5 cm below the tragus to a point 2 cm above the lateral end of the eyebrow and a second along the zygomatic arch.^3,4 The nerve is most superficial in the area of the zygomatic arch, and it is therefore most at risk to damage during a surgical procedure at this site. Anatomically, the four tissue layers of importance in the area of the lateral canthus are the skin and subcutaneous fat, the superficial muscular aponeurotic system (SMAS), the temporalis fascia, and the temporalis muscle. The SMAS is a thin layer of connective tissue that is continuous with the galea superiorly, the frontalis anteriorly, the occipitalis posteriorly, and the muscles of facial expression inferiorly. In the area of the temple, the temporal branch of the facial nerve runs just below the SMAS, within a layer of loose areolar tissue superficial to the temporalis fascia.⁴ At the lateral forehead the nerve dives under the frontalis muscle, becoming less vulnerable to surgical injury. The temporal nerve innervates the ipsilateral frontalis muscle and, to a lesser extent, the orbicularis oculi muscle, and nerve transection leads to weakness of the ipsilateral forehead with droop of the eyebrow and decreased ability to close the eye tightly. The importance of understanding the course of the facial nerve branches and their anatomic relationship to these tissue planes cannot be overstated.

The supraorbital and infraorbital nerves exit the skull via the supraorbital notch and infraorbital foramen, respectively, both located on a vertical line drawn from the medial corneal limbus. Moving clockwise from the supraorbital notch, the supratrochlear and infratrochlear nerves penetrate the orbital septum at the orbital rim. While localizing these can be useful in performing nerve blocks to anesthetize the eyelids and periorbital area, the nerves lie at such a depth that they are relatively protected from inadvertent transection during surgery.

The periorbital area has a rich vascular supply derived from both the internal and external carotid arteries. The ophthalmic artery arising from the internal carotid artery supplies the supraorbital, supratrochlear, dorsal nasal, and palpebral arteries. The superior and inferior palpebral arteries arch across the eyelids parallel to the lid margins, piercing the orbital septum above and below the medial and lateral canthal tendons. The external carotid artery contributes the remainder of the blood supply, including the superficial temporal artery, which emerges from beneath the parotid gland in the preauricular area. The superficial temporal artery’s frontal branch arcs across the temporalis muscle to supply the lateral eyebrow region as it anastomoses with the supraorbital artery, while the transverse facial artery courses over the zygoma to join the infraorbital artery in the lower eyelid. The facial artery ascends along the nasofacial sulcus to anastomose with the infraorbital and transverse facial arteries, above which the facial artery continues superiorly along the medial orbit as the angular artery, merging with the dorsal nasal artery superior to the medial canthus. Although such excellent vascular supply easily supports flaps and grafts in the periorbital region, the thin, distensible tissues can also predispose to significant postoperative ecchymoses. Meticulous intraoperative hemostasis is important in avoiding hematoma development.

Granulation (Second Intent Healing)

Some defects of the periocular area can be allowed to granulate with good functional and cosmetic results. In general, smaller wounds on concave surfaces can achieve excellent cosmetic results through granulation.⁶