Asian Eyelid Anatomy
Eyes with natural double eyelids (i.e., congenital supratarsal folds) have relatively thin and highly elastic skin. When the eyes are closed, the natural folds exhibit a very subtle, extremely thin line at which a fold forms when the eyes open. The dynamics of a fold formation involve a crease that becomes more defined as the eyes open, and fainter as the eyes close. This is what is known as a “dynamic” fold. A surgically created fold should mimic this feature. Unfortunately, in some surgical cases, a conspicuous indentation results at the fold even with the eyes closed. This is the most common indication that a fold has been surgically produced. Poorly executed surgeries typically result in a “static” fold, a noticeable fold that remains whether the eyes are closed or open.
In the natural fold, the eyelid skin connects to the underlying eye-elevating levator muscle via a bridge-like extension of the levator aponeurosis. This indirect connection enables the dynamic fold to take place. To properly emulate this key feature, the surgeon must utilize a loop suture technique or mobilize local tissue in order that the eye elevating component (levator aponeurosis) does not directly connect to the skin. These two mechanisms (suture technique and vector calibrated open technique respectively) allow the eyelid muscle to pull on the loops or the mobilized local tissue and not the skin itself, producing a fold that most resembles a natural fold.
Different Types of Folds
There are various types of folds a patient can achieve through double eyelid surgery. An ideal crease will be based on the patient’s preference and will complement their overall appearance. At times, the type of crease preferred by the patient is not always the suitable size, as it may not be proportional to the patient’s eyes and/or face. In such instances, it is important that the patient rely on a knowledgeable plastic surgeon’s aesthetic abilities when determining the type of fold that is most natural for one’s overall look. A skilled plastic surgeon will recommend the fold that creates facial balance and harmony.
During the consultation, the surgeon will take into account the patient’s overall facial features, such as the presence of an epicanthal fold, size and shape of the eyes, visibility of the iris, underlying bone structure of the eye, droopiness of the eyelid and brow, asymmetry, etc. in assisting patients to choose their ideal folds.
An infold starts below the nasal corner of the eye and is situated lower than an in-out fold or an outfold. Patients that desire an infold tend to be younger, more conservative individuals that seek a more subtle change. Although infolds are more natural and subtle looking, they lack the starker appearance which some of the other types of folds can provide. For patients with a smaller infold who desire a larger fold, they can opt for a larger infold, an in-out fold, or an outfold.
An in-out fold begins in the inner corner of the eye. This type of fold is not as subtle as the infold but still creates a natural looking fold without a drastic change. It provides the most natural looking folds for patients undergoing the open incisional double eyelid procedure.
An outfold begins above the inner corner of the eye and is higher than the infold and the in-out fold. The fold will be created parallel to the curvilinear edge of the eye. This type of fold is most commonly found in non-Asian eyes. Thus, patients who seek an outfold tend to desire a more dramatic change in their appearance.
Fold height refers to how high above the upper lash line the fold is. If the eye is large, a higher crease is recommended. However, the patient must keep in mind that the higher the fold is, the more weight that is placed on the eye elevating muscle. A prior determination must be made whether the patient’s eye elevating muscle can tolerate the additional weight created by a high fold before the surgery.
A high fold is ideal for patients with large eyes and strong eye elevating muscle function. As stated above, a complication associated with a high fold is that additional weight is placed on the eye elevating muscle, as the eyelid skin is attached to the muscle that is situated anterior to tarsus. Therefore, creating a high fold can induce ptosis in patients who have weak eye muscles (Refer to Ptosis). However, if all criteria are met, a high fold can have a dramatic and glamorous effect on someone’s appearance.
A lower fold is ideal for patients with protruding eyes as well as for patients with ptosis. Patients may desire a low fold if they prefer subtle changes. Low folds are prone to more hooding with age, as there is less distance for the skin to descend beyond the double eyelid crease.
An ideal fold size is the height in which the eyelid functions optimally. The eyelid height at which the eyelid functions well tends to look most natural and suitable to a patient’s overall face, hence the phrase “form follows function”. It is important to find a surgeon that understands this balance between form and function of the Asian eye.
Non-Asian Eyes vs. Asian Eyes
This singular layer connection occurs mainly at the site of the crease, whereas for non-Asians it extends from the visible crease all the way down to the lash line. This multilayer of connections present in non-Asian eyes is what provides a more distributed force throughout the eyelid. Therefore, because of this singular connection, even natural Asian eyelid folds tend to be weaker and prone to loosening with age.
LOWER EYELID FEATURE
Asians also have a unique lower eyelid feature of fullness immediately below the edge of the lower lash line. Referred to as “aegyo-sal” in Korean, this feature is present due to the hypertrophic orbicularis muscle in the lower eyelid. Due to the thicker orbicularis muscle among Asians, this feature is much more evident in Asian eyes than non-Asian eyes.
Asian Eyelid Aging Process
Asian eyelids tend to undergo the aging process more rapidly than non-Asian eyelids. This is mainly due to differences in skin thickness and eyelid tissue mass. The skin on Asian eyelids is comparatively thick and heavy, and therefore descends faster with age. Many Asians also either lack the double eyelid fold altogether, or have an infold crease that is barely noticeable, which also contributes to faster eyelid aging. With a substantial fold, the progressive descent of eyelid skin is less conspicuous due to an increased eyelid surface dimension and an indirect attachment of skin to the underlying deep structure. The higher the fold is situated, the greater distance is needed for the skin to descend beyond the upper edge of the eye opening.
As tissue atrophies with age, skin and underlying soft tissue begins to stretch and sag. There is also general loss of volume in the eyelid and orbital region. Some patients begin to notice their eyelid folds have become weaker with age due to the loosening of connections between the eyelid skin and the eye elevating muscles. Furthermore, as the underlying soft tissue atrophies, the space separating the skin from the eye elevating muscle narrows. With the loss in soft tissue volume, the skin begins to indent, forming multiple late-onset pseudo folds. Such folds lack the crispness and sharp dynamicity portrayed in youth, causing one to appear older than their actual age. These late-onset eyelid folds are also transient and can fluctuate depending on the state of underlying soft tissue – weeping, pregnancy, and other factors could cause enough swelling to overpower the loose connections, preventing any fold formation.
The eyelid’s deeper muscle structures undergo aging processes as well. The levator aponeurosis, a connective tissue which connects eyelid cartilage (tarsus) to the levator muscle and aids in eyelid elevation, begins to detach from the eyelid tarsus. The Müller’s muscle, which is located beneath the levator aponeurosis, also undergoes muscle degeneration becoming partially replaced with fat cell depositions and thereby losing muscle functionality. Muscle degenerations can make double eyelid surgery and ptosis repair more challenging. In all upper eyelid procedures, there must be sufficient amount of collagen for the sutures to fasten to, in order to form a secure connection among individual structures. In cases of muscle degeneration, there is a high rate of lid contour deformity and lid asymmetry. Thus, more advancement is needed in ptosis repair and double eyelid surgery to overcome the degeneration of the Müller’s muscle.
The lower eyelid undergoes aging processes as the upper eyelid. Generally, for Asian lower eyelid, aging can decrease the fullness of the “aegyo-sal” due to muscle hypotrophy in the superficial muscle of the lower eyelid.
Another manifestation of aging in the lower eyelid region is fat protrusion (i.e., eye bags). Contrary to its appearance, the cause is not due to increase in fat formation but herniation or loosening of the septum (the layer that covers the fat) along with weakening of the superficial eye muscle. The superficial muscle also descends and loosens the surrounding skin. In addition to the appearance of eye bags, with age, loss in soft tissue mass occurs and there could be convexity and/or concavity in the lower eye/facial region that was not present at a younger age. These issues that occur with age can be effectively corrected by undergoing Youthful Lower Eyelid Fullness Procedure and/or Lower Blepharoplasty.