Crease: Approximately half of Asian patients possess an upper eyelid with a low but defined upper eyelid crease (which segments the lid into two visible parts and is called a "double eyelid"), while the other half show little or no sign of crease formation ("single eyelid").
Even when present, the Asian crease differs significantly from a typical Occidental crease. In general, the Asian upper eyelid crease forms closer to the eyelashes, is shaped differently, and is sometimes incomplete or broken into multiple folds.
Differences in the position and shape of the eyelid crease (red arrow) are explained by subtle variations in the internal anatomy that are not fully understood.
Classical explanation: Because the Asian orbital septum fuses with the levator aponeurosis (tendon of the muscle that lifts the lid) at a lower level, orbital fat positioned between these two structures extends further down into the eyelid. By acting as a barrier, this lower junction (the "septoaponeurotic sling") may act as a barrier that interferes with or prevents tiny finger-like extensions from the levator aponeurosis from reaching the back of the skin. Traditionally, it has been taught that these extensions pull the skin into a crease when the eye is opened. In recent years, this explanation has been questioned as an anatomic oversimplication.
Modern explanation: In a creased eyelid, there appears to be a strong natural adherence between the front of the tarsal plate and the back of the skin created by fibrous connections that pierce the orbicularis muscle. These connections (noted in the diagram by the curved black lines) are weak or absent in an uncreased Asian eyelid. When a creased eye opens and the levator muscle pulls upward, this skin-orbicularis-tarsal plate complex is lifted higher as a single tight unit, allowing the higher non-adherent skin above it to drape down over it and generate the crease. If, however, these natural connections are weak or absent, the lower skin and orbicularis muscle simply slip down along the rising tarsal plate to form a smooth curtain.
As one explanation does not exlude the other, the most complete and accurate description of crease formation may well incorporate some contribution from each.
In fact, there are other anatomical findings not noted above that may be equally or even more important (for instance, presence of a horizontal ligament in the Asian eyelid near the fusion of orbital septum and levator aponeurosis) in explaining decreased crease formation.
Despite ongoing uncertainty, incisional double eyelid surgery creates internal anatomic change that addresses crease causation proposed by all major explanations.
Fullness: The Asian upper eyelid appears puffier than the Occidental upper eyelid due to:
• the downward extension of orbital fat
• a slightly weaker orbital septum that allows the fat to bulge
• an eyebrow fat pad that is thicker and projects lower into the eyelid
• a much thicker subcutaneous fat layer positioned just below the skin that adds noticeable "padding" over the entire eyelid and may interfere with crease formation.
Epicanthal Fold: The epicanthal fold is a small crescent of skin that is usually present between the inner eyelid corner and the nose. The eyelid crease, when present, may taper down and blend into it.
Skin: While Asian skin tends to resist age-related fine wrinkling longer than Occidental skin, Asian skin also seems tends to grow "baggier" at an earlier age. The typical Asian olive skin tone is classified as a "Fitzpatrick Type IV," which makes it not the ideal candidate for resurfacing techniques such as chemical peel and laser resurfacing.
Eyelashes: Because the eyelashes of the less-creased Asian eyelid tend to bend downward, the opening between the upper and lower eyelids may appear partially obstructed.
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Just as there are fundamental differences between Asian and Occidental eyelids, there are also distinct anatomical differences between and within the many subgroups of Asian descent as well as differences introduced by the blending of subgroups through intermarriage. Interestingly, there are some Asian eyelids that possess high and very distinct natural creases, just as there are some Occidental eyelids that demonstrate little or no crease at all.
• Atlas of Eyelid Anatomy
