The anatomy of the eyelids and periorbital region is delicate. The individual anatomic variations determine each person’s eyelid appearance and function. It is essential that every surgeon that evaluates and treats the aesthetic conditions of patients desiring periorbital enhancement understands the association of anatomy and diagnosis. Each periorbital aesthetic diagnosis has an anatomic basis, and knowledge of the applied anatomy allows a targeted treatment plan. This article outlines the layered anatomy with its clinical significance for the eyelids and periorbital region. Specific examples are used to illustrate the applied anatomy. A contemporary treatment plan for each anatomic problem is given.
The orbit and periorbital region is anatomically complex and contains crucial muscular, neurovascular structural components.
A thorough understanding of periorbital anatomy is crucial to safely and effectively addressing periorbital pathology and aging.
The eyelid and eyebrow should be considered in tandem when assessing periorbital pathology.
The eyelids and brows have a variable surface covering that differs from the covering in all other parts of the body. The thin eyelid skin is in stark contrast to the skin adjacent to the eyelids (brow, temple, and cheek), all of which have much thicker skin cover and underlying superficial fat. The skin of the eyebrow is thick, having a variable amount and density of eyebrow hairs.
The vertical distance between the upper eyelid margin and the eyebrow is variable and is related to the eyebrow height. The upper eyelid crease is an infolding of upper eyelid skin and is variable in height and depth. This gently curved upper eyelid crease is formed by the insertion of fibers of the levator aponeurosis into the orbicularis muscle and the eyelid skin ( Fig. 1 ). In whites, the height of the upper lid crease at the midpupillary line is usually between 6 and 10 mm and tapers to 3 to 4 mm medially and laterally. In Asians, the height of the supratarsal fold is usually lower (and sometimes absent) than is the crease in most whites and is approximately 3 to 6 mm in the midpupillary line ( Fig. 2 ). An elevated supratarsal crease can be associated with upper eyelid ptosis, as disinsertion of the levator aponeurosis can cause both malposition of the eyelid margin (ptosis) and elevation of the supratarsal fold.
The lower eyelid skin fold is located approximately 3 mm from the lower eyelid margin. This fold is related to the position and contraction of the orbicularis oculi muscle (OOM) and is more commonly seen in children, descending and becoming more irregular with age.
The palpebral fissure is approximately 10 mm in height and 30 mm in width. The aperture can be decreased from eyelid ptosis (weakening or dehiscence of the levator complex) or from hypertrophy of the OOMs. The level of the upper eyelid margin is usually 1 to 2 mm below the superior limbus, and the lower eyelid margin is usually at the inferior limbus.
The eyebrows are not a part of the forehead or the eyelids but are an important portion of the periorbital complex, as they form the superior frame of the region. For this reason, eyebrow height, orientation, thickness, and general appearance get the attention of patients, surgeons, and cosmetic brow specialists. , The skin of the eyebrow is thick, and it contains dermal appendages that produce short, course hairs. The brow hairs emerge from the skin surface at markedly oblique angles. The shape, thickness, and orientation of the brow hairs vary with personal style and preference and fashion trends.
The height of the brow is based on the movements and relative contraction of the muscles that move the brows ( Fig. 3 ). The only elevators of the eyebrows are the paired frontalis muscles, which form the anterior belly of the occipitofrontalis musculofascial muscle complex. The frontalis muscle is enveloped by the galea aponeurosis. Contraction of this muscle creates horizontal rhytids of the forehead skin and produces brow elevation and scalp tightening. The frontalis muscle has no bony attachments. Superiorly, it thins into an aponeurosis, and inferiorly, its medial attachments are continuous with the procerus muscle and the orbital portion of the orbicularis muscles.
Depression of the eyebrows is accomplished with several muscle groups. The midline procerus muscle arises from the fascia covering the lower portion of the nasal bones and the upper lateral cartilages and inserts into the skin of the central lower forehead. Contraction of the procerus muscle produces a transverse fold at the nasal root and central brow depression. The paired corrugator supercilii muscles are obliquely oriented muscles that originate from medial frontal bone at the superomedial orbit. The muscle passes obliquely in a superolateral direction and inserts into the skin of the eyebrow and deep fascia of the inferior frontalis muscle. Contraction of the corrugator muscle produces vertical glabellar folds and pulls the brow inferiorly and medially. Contraction of this muscle also creates a frowned appearance.
The OOM has pretarsal and preseptal components that act as the protractors of the eyelids ( Fig. 4 ). The more peripheral orbital portion of the OOM interdigitates with the inferior frontalis muscle fibers. These orbital fibers contribute to depression of the eyebrows.
The height and position of the eyebrows are related to the relative contraction of the brow elevators (frontalis muscle) versus the contraction of the brow depressors (corrugator supercilii, depressor supercilii, procerus, and orbicularis oculi). Excessive brow elevation can confer a surprised expression, whereas excess brow depression can depict anger, consternation, or worry. Brow elevation also has a functional purpose, as contraction of the frontalis muscle may compensate for primary eyelid ptosis.
Layers of the eyelid, upper lid
The upper eyelid is composed of very thin skin, structurally dense fibrous tissue (tarsal plate), and muscles that close (protractors) and open (retractors) the eyelids ( Fig. 5 ). The upper eyelid crease is a horizontal indentation formed by the attachment of the superficial levator aponeurosis fibers into the orbicularis oris intermuscular septa and subcutaneous tissue. The crease is located approximately 6 to 10 mm above the eyelid margin centrally in most whites. When present, the upper lid crease in Asians is located at 3 to 6 mm. In patients with dehiscence of the levator aponeurosis, the eyelid crease is usually elevated, and the eyelid is thin. ,
The eyelid is covered by very thin skin, usually only 400 to 500 μm in thickness. , There is almost no subcutaneous tissue in the eyelids. The OOM (protractors of the eyelids) are located just deep to the skin. The orbital septum is located just deep to the OOM. The septum is a thin, multilayered connective tissue beginning at the arcus marginalis along the orbital rim. The septum is a continuation of the periorbita within the orbit and contains the eyelid fat pads, which lie just deep to the septum. The upper eyelid has 2 fat pads: a nasal (medial) fat pad and a central (preaponeurotic) fat pad ( Fig. 6 ). In the lateral portion of the upper eyelid is the lacrimal gland. The medial and central fat pads are separated by the superior oblique muscle and its associated trochlea. The nasal fat pad is whiter and contains more fibrotic fat than does the central pad.