In common usage, the eyelid crease is often meant to describe a natural inward creasing of the skin seen in the upper eyelid, typically dividing it into a lower segment adjacent to the upper eyelashes, and an upper segment of skin that runs from the crease to the border of the eyebrow.
The crease is present in about 50% of the Asian population, and found to be more prevalent in all non-Asians. The presence of a crease in an Asian subject is what differentiates a double eyelid (with a crease unequally dividing the lid into two sections, hence ‘double’) from a single eyelid (or mono-lid).
Double-eyelid crease surgery (procedures) is a form of surgery to add or supplement an eyelid crease to an individual who seeks it. This is often for an individual who does not have a crease, or who finds their crease is insufficient, or in whom the crease is unbalanced between the two sides.
The configuration of the upper lid crease in Asians varies greatly. The terminology used to describe these configurations also varies, depending on the ethnic group and language concerned. Figure 1-1 illustrates the Chinese characters for the words ‘double-eyelid fold’. Figure 1-2 shows the Japanese Kanji writing for ‘single [one] lid eye’ and ‘double [two] lid eye’. The characters common to Chinese and Japanese for the operation to construct a lid crease are illustrated in Figure 1-3 .
As described in previous publications by the author, the crease may be asymmetric in its presentation, or be absent in one eye and present in the other. It may be continuous or segmented (fragmented).
Figure 1-4 shows the various configurations of the Asian eyelid.
Figure 1-5 shows an eyelid without a crease. There is a mild degree of upper lid hooding, causing secondary downward rotation of the lashes. Figure 1-6 illustrates an eyelid with a distinctive crease. This is the parallel configuration. Figure 1-7 is an eyelid in which a portion of the crease has been obliterated. An eyelid with an incomplete or partial crease is shown in Figure 1-8 . The crease originates in the medial canthus and medial upper lid fold (supracanthal web) and extends halfway across the upper lid. Multiple creases are illustrated in Figure 1-9 , where two well-defined creases run parallel to each other. Figure 1-10 shows a minimal nasally tapered crease. The lateral third of the crease may be the same distance from the eyelash margin as the central third, or it may rise slightly to form a laterally flared crease, in which the lateral third of the crease is further from the lash margin than the central third. A Caucasian upper lid crease is shown in Figure 1-11 , where the central third of the crease is farthest from the lash margin.
In Asians with a continuous eyelid crease, the crease may be of the nasally tapering type (NTC) (a less desirable term is ‘inside’ fold) in which the crease converges toward the medial canthus, coming closer to the lashes as it reaches the medial canthal angle ( Figure 1-12A ), or it may be a parallel crease (PC) (a less desirable term is ‘outside’ fold), in which the crease runs fairly parallel to the lash margin from the medial canthus to the lateral canthus ( Figure 1-12B ).