14.2Anatomic Considerations of the Asian Upper Eyelid

The fundamental anatomic difference between Asian and Caucasian eyelid appearance pertains to the location of orbital septum insertion on to the levator aponeurosis. This attachment is lower in Asian eyes, even as low as the lower tarsal border. This lower point of insertion allows the preaponeurotic fat pad to descend lower on the aponeurosis, yielding a fuller eyelid appearance. In addition, the more inferior location of fat blunts the aponeurotic attachments to the orbicularis muscle. Clinically, these anatomic characteristics yield a puffy eyelid without, or with an indistinct crease. Consequently, approximately half of Asians do not have an upper eyelid crease while the remaining have some form of crease. Asians with a crease have a larger apparent palpebral fissure giving the appearance of a larger eye. The actual vertical palpebral fissure (upper to lower lid margin) does not change. However, an eyelid crease creates a tarsal platform (lid margin to upper lid skin fold). This additional pretarsal eyelid show makes the palpebral fissure appear larger. This feature is desirable aesthetically as it confers a more feminine appearance, and because it facilitates application of eye cosmetics.

Another anatomic difference between Asian and Caucasian eyelid anatomy helps account for increased fullness of the Asian upper eyelid. In Asians the brow fat pad has continuity into the post-orbicularis space of the eyelid proper. This preseptal (submuscular) fat can continue as low as the tarsus in many cases. In Caucasian eyelids the brow fat pad extension into the eyelid is an areolar connective tissue called the postorbicularis fascia. The preseptal fat present in Asian eyelids adds to the more inferiorly displaced preaponeurotic fat (postseptal fat) to create a fuller Asian eyelid.

Figures 14.1 and 14.2 demonstrate the anatomic differences between Caucasian and Asian eyelids described above.

14.2.1 Musculature

The orbicularis oculi muscle serves as the sphincter of the upper and lower eyelids and is innervated by the temporal, zygomatic, and buccal branches of the facial nerve. The transverse facial, supratrochlear, and supraorbital vessels supply the muscle. The muscle is divided into orbital and palpebral portions. The orbital portion is darker and thicker and is under voluntary control. It functions to close the eyelids, and secondary acts as a brow depressor. The palpebral portion acts involuntarily to close the eyelids or reflexively blink. The palpebral portion is thinner, lies directly over the eyelids, and is further subdivided into preseptal and pretarsal segments according to the anatomic structures they overlay [1–3].

Fig. 14.1 Artist’s drawing of Caucasian eyelid anatomy. Note the conjoined attachment of the orbital septum to the levator aponeurosis. This attachment point limits inferior displacement of eyelid fat. The levator sends fibers to the orbicularis and skin just below this attachment forming an eyelid crease (dotted line). Also note the absence of a preseptal fat layer (present in Asian eyelids). Instead there is an areolar connective tissue layer called the post-orbicularis fascia (not pictured)

Fig. 14.2 Artist’s drawing of Asian lid anatomy. Note the lower conjoined attachment of the orbital septum to the levator aponeurosis. This allows inferior displacement of eyelid fat and blunts levator attachments to the orbicularis and skin. The result is a fuller eyelid and variable crease formation. Also note the presence of a preseptal (submuscular) fat layer which is absent in Caucasian lids. This adds to the fullness of the Asian upper eyelid

14.2.2 Orbital Septum

The orbital septum lies beneath the preseptal division of orbicularis oculi muscle and is a continuation of the periorbita. The portion above the tarsus separates the muscular from the orbital fat compartment, while the inferior portion fuses with the anterior part of the tarsus [2]. The orbital septum is the anatomic separation of the eyelid from the orbit and segregates the fat. The upper eyelid crease is formed from the attachment of the levator fibers to the orbicularis muscle and eyelid skin.