Comparative Anatomy of the Eyelids

The Upper Lid and Crease

Studies have shown that about 50% of Asians do not have an upper eyelid crease; the other 50% have at least some form of crease. Eyes without a lid crease are described as having a ‘single eyelid’ ( Figure 3-1 ), whereas those with two segments of lid between the eyebrow and the eyelashes have ‘double eyelids’ ( Figure 3-2 ). Most of the plastic surgery literature of the 1950s was based on the assumption that all Asians are without an eyelid crease and that all Caucasians have an upper lid crease.


Partially shielded crease over the right upper lid. Absent crease or ‘single eyelid’ over left upper lid.


Double eyelid. Parallel crease configuration.

Asians born with a crease appear to have a wider palpebral fissure and larger eyes and are culturally perceived to be more alert and friendly than those with a single eyelid ( Figure 3-3 ). The cultural ideal of feminine beauty also influences the desire for a double eyelid: having a double eyelid allows greater latitude in the application of cosmetics to make the eyes and face more aesthetically pleasing. It is therefore understandable that some women without a crease may wish for one, provided the means are available.


Left palpebral fissure. (A) Without crease. (B) With crease. The crease gives the impression of a larger eye opening.

To some Westerners, who presume that all Asians have eyelids without a crease, such an endeavor equates to ‘Westernization’ or ‘occidentalization’. In the author’s opinion, however, it merely represents an attempt to look like their fellow Asians who do have a crease over their upper eyelids.

The growing popularity of Asian blepharoplasty has been incorrectly interpreted as resulting from the influence of Western culture after World War II and the Korean war, a manifestation of which was believed to be a desire on the part of Asians to blend in with Caucasians, to look Westernized or occidental. Having traveled and taught extensively in Asia, it is the author’s perception that the idea of beauty transcends time, geographic boundaries and ethnicity. For a growing number of patients undergoing Asian blepharoplasty it has more to do with an increasing awareness that such procedures are available than with the cultural influence of the West. Clinical experience teaches that Asians do not want to look Caucasian. A frequent postoperative complaint is that the procedure results in a semilunar crease, a feature that, although characteristic of Caucasians, is aesthetically displeasing in Asians.

The essential differences in the upper eyelid structure between Caucasians and Asians have been studied in cadaver samples by Doxanas and Jeong et al. The fundamental difference between the subset of those Asian eyelids without a crease and a Caucasian eyelid that possesses a crease appears to be the lower point of fusion of the orbital septum onto the levator aponeurosis in Asians.

Individuals with a Lid Crease

In Caucasians who have a crease ( Figure 3-4 ), the orbital septum fuses with the levator aponeurosis approximately 5–10 mm above the superior tarsal border. Below this point, the terminal interdigitations of the levator aponeurosis insert towards the subdermal surface of the pretarsal and preseptal upper lid skin, with maximal concentration along the superior tarsal border and spreading inferiorly. Collin has detailed electron microscopic findings of fusion of the terminal fibers of the levator aponeurosis with the septae that are between the pretarsal and preseptal orbicularis muscle fibers; he was unable to show any direct attachment to the skin in that particular study.


A typical Caucasian eyelid with a natural upper eyelid crease. Aponeurotic fibers form interdigitations to the pretarsal orbicularis oculi muscle and a subdermal attachment along the superior tarsal border.

There has been a subsequent study in China using scanning electron microscopy that described the presence of aponeurotic fibers penetrating the orbicularis fibers to fuse with the skin underneath a crease. In this study, published in 2001, Cheng and Xu reported using scanning electron microscopy and detecting bunched fibers of levator aponeurosis penetrating through the orbicularis muscle and fusing with the skin on the area of the eyelid crease in those patients born with a crease, versus those without. These differences were not detectable using conventional light microscopy. The authors described the arrangement of these bundled fibers as being different from that of the fibers in the intermuscular septum. The bundles were thinner, unidirectional and aligned as threads. They noted that where these fibers pass through the orbicularis to attach to the subcutaneous fibers they were linear in shape, closely aligned and clearly visualized, whereas the fibers of the intermuscular septum were thicker and aligned in a disorderly fashion. Of interest is the observation that in those eyelids with a crease the orbicularis bundles lying transversely were arrayed sparsely and loosely in a single layer, in contrast to those in a single eyelid (i.e. without a crease), which had muscle tissues that were dense and muscle bundles arrayed in a stratified manner. Their overall conclusion is that a fiber link between levator aponeurosis and the upper eyelid skin results in the formation of the palpebral sulcus (crease) in the double eyelid. They draw the inference that the purpose of most double-eyelid procedures should be to establish a stable attachment between levator aponeurosis and the eyelid skin. They further stated that the obstructing effect of the orbicularis in single-lidded individuals could explain why the surgical outcome is unpredictable with the suturing method. Using the incision method, the excision of a suitable amount of orbicularis muscle changes the dynamics of the upper eyelid and assures a good aesthetic outcome. The authors recommended the incision method with supratarsal fixation in order to establish a stable attachment between the levator aponeurosis and the eyelid skin.

A similar study published in the same year by Morikawa et al. described the scanning electron microscopic findings in single- versus double-eyelid samples taken from Japanese cadaver specimens. They were able to trace the collagen fibers that branched off from the levator aponeurosis, running through the orbicularis oculi muscle layer and inserting at the subcutaneous layer just within the crease space indentation. These fibers do not contact the skin directly, but become continuous with the collagen fibers in the subcutaneous tissues.

Hwang et al. attempted to show that the orbital septum consists of an outer (whitish, superficial) layer and an inner layer which, upon meeting the levator aponeurosis inferiorly, then reflects superiorly and continues with the sheath of the levator muscle, which they termed the levator sheath. Several line drawings in their article attempted to illustrate this concept, and a light microscopic slide showed what purported to be the inner layer of the orbital septum and the sheath of the levator, but the higher-magnification slide did not have a portion showing that the one continues into the other, which was their premise. There had been a previous description of the anterior lining of the levator (levator sheath) descending and then reflecting up the back surface of the orbital septum to reach the superior orbital rim, but there had been no concrete study illustrating that the reverse is true, i.e. that the orbital septum has two layers – a posterior layer that actually reflects back on to the levator surface to form its sheath. Hwang et al. further postulate that the reason for some crease procedures failing to form a crease is owing to the presence of remnants of the inner layer of the orbital septum on the aponeurotic surface, which may have been attached to skin surgically instead of the desired skin–aponeurosis attachment. They also stated that there may be remnants of fat behind this fourth layer, the inner layer of the orbital septum lying on the anterior surface of the aponeurosis and the underlying levator aponeurosis, and that these need to be reflected away before carrying out the skin–aponeurosis fixation.

Bang et al. argued against the conventional theory that the levator termination inserts into the skin to form the crease. The authors proposed that this theory is more accurate, i.e. that the absence of a crease is associated with a lower position of the septum in a single eyelid without a crease, hence there is more inferiorly migrated fat and the eyelid is thicker than one that has a crease, which is thinner and has a tighter pretarsal skin zone. The crease in this theory corresponds to the lowermost edge of the orbital fat, or the lower level of the orbital septum, which is usually 2–3 mm above the highest point of insertion of the levator aponeurosis. In an excellent brief discussion following the above-mentioned paper by Bang et al., Khoo Boo-Chai stated that below the lowermost edge of the orbital fat there are fine filamentous condensations of the connective tissue that connect the aponeurosis to the connective tissue septa between the fibers of the orbicularis oculi muscles. The crease lies in the pretarsal skin at the superior insertion of these fibers and serves as a useful external landmark of the common boundary between the lowermost edge of the orbital fat and the filamentous connective tissue condensation fibers. When the eye opens, the pull of the levator is transmitted via these fibers to the pretarsal skin–muscle complex. The pretarsal skin below the crease moves as a single unit upward and backward, like the visor of a helmet. The orbital fat moves back into the orbit, and the superior palpebral fold is formed by the lid skin scrolling down at the upper lid crease. Khoo Boo-Chai further observed that the pretarsal skin is soft and very thin, with little space between the dermis and the subcutaneous areolar plane to the orbicularis beneath. The skin above the upper lid crease is comparatively thick, with some subcutaneous fat, with the crease lying at the junction of this region. He favored the continued use of the term levator expansion (extension).

The Fat Pads of the Upper Lids

In terms of fat distribution and compartments, Uchida described the presence of four areas of fat pads in Asian upper eyelids. He described the subcutaneous fat, the pretarsal fat, the ‘central’ (submuscular or preseptal) fat pads and the ‘orbital’ fat pad, which is now better known as the preaponeurotic fat pad (see Figure 3-7 ).

Miyake et al. described upper eyelid MRI findings in those with a crease versus those without. He observed that the ‘orbital fat’ normally returns into the orbit as the upper eyelid opens in someone with a crease, but that when the fat does not return then crease formation is prevented. He correctly observed that the crease folds in at the junction between the thin skin without subcutaneous fat (pretarsal area) and the thick skin with subcutaneous fat (preseptal area).

The preaponeurotic fat pad is limited in its inferiormost position by the junction (or reflection) of the septum with the levator aponeurosis and does not tend to interfere with the terminal insertions of the aponeurotic fibers. When the levator contracts and pulls the tarsal plate up, the lid forms a crease just above the superior tarsal border, with the skin superior to the crease forming the fold ( Figure 3-5 ). The rigidity of the upper tarsus and the firm adherence of the skin over the pretarsal region effectively results in a pretarsal platform vectoring superoposteriorly underneath the overhanging fold of skin and the preaponeurotic tissue platform. In elderly people there is frequently a lack of preaponeurotic fat pads and the presence of dermatochalasis causing hooding over the previously distinctive lid crease ( Figure 3-6 ).


Caucasian upper lid creases that are high and semilunar in shape.


Elderly Caucasian patient before blepharoplasty. Redundant preaponeurotic fat pads and dermatochalasis of the upper lid form a hood over the previously distinctive crease.

In those Asians who do not have a lid crease ( Figure 3-7 ) the anatomic studies of Doxanas and Anderson appeared to confirm that they have a lower point of attachment of the orbital septum to the levator aponeurosis, frequently as low as the superior tarsal border. The author has seen patients whose orbital septum fuses with the upper tarsus below the superior tarsal border, halfway down its anterior surface ( Figure 3-8 ). This lower point of fusion permits the presence of the preaponeurotic fat pad at a lower point on the aponeurosis, giving the eyelid a fuller appearance. The lower preaponeurotic fat pad may in turn prevent the attachment of the terminal interdigitations of the levator aponeurosis along the superior tarsal border to the pretarsal orbicularis oculi muscle fibers.


Asian upper eyelid without a crease. Note the absence of terminal interdigitations of the levator aponeurosis and the relatively lower point of fusion of the orbital septum.


Right upper lid with a very low point of fusion of the orbital septum along the anterior surface of the upper tarsus. Preaponeurotic fat can be seen posterior to the surgically opened septum.

Subcutaneous fat, sub-brow (submuscular, suborbicularis, or preseptal) fat and pretarsal fat infiltration as described by Uchida may be seen. The presence of pretarsal fat pads may also disrupt the terminal interdigitations of the aponeurosis, if we are to presume that Collin’s and Cheng’s scanning electron microscopy findings are accurate and applicable to those eyelids in Asians that are without a crease. The clinical picture is a puffy ‘single eyelid’ without a crease ( Figure 3-9 ). With age, the interval change in Caucasians tends to be an increase in prominence of the preaponeurotic and nasal fat pads as they migrate forward and inferiorly. The elderly Asian eyelid tends to simply manifest more skin redundancy, as the lid has always been comparatively full owing to the lower position of the preaponeurotic fat and fascial tissues ( Figure 3-10 ). Some degree of gravitational inward settling of the orbital fat in the upper half of the orbital space does occur with aging, therefore the volume of fat seen clinically over the upper eyelid may be variable.

Jan 26, 2019 | Posted by in OPHTHALMOLOGY | Comments Off on Comparative Anatomy of the Eyelids

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