What makes Asian eyelids and Caucasian eyelids different?
In a 1999 anatomical study comparing Asian eyelids to Caucasian
eyelids, researchers dissected eyelids of Korean and Caucasian
cadavers and utilized MRI technology on living subjects to answer
why 40 to 60 percent of the Asian population do not have “double
eyelid” folds, while virtually all Caucasians do.
The results showed that Asian eyelids possess more subcutaneous and pretarsal fat (at the edge of the eyelid) than Caucasian eyelids. Asian double eyelids possessed an intermediate level of fat between Asian single eyelids and Caucasian eyelids. In addition, Asian single eyelids showed fusion of the orbital septum (an inner membrane extending from the orbital rims to the eyelids) to the levator aponeurosis (the muscle which elevates the upper eyelid) at a lower point than in Caucasian eyelids, closer to the eyelid margin. Asian single eyelids also possess a pretarsal fat pad not present in Caucasian eyelids. These factors jointly account for an absent or lower crease in Asian eyelids.
For an illustrated diagram of differences in eyelid anatomy: www.drmeronk.com...
Source: Sangki Jeong, MD; Bradley N. Lemke, MD; Richard K. Dortzbach, MD; Yeoung Geol Park, MD; Heoung Keun Kang, MD. “The Asian Upper Eyelid: An Anatomical Study With Comparison to the Caucasian Eyelid.” Arch Ophthalmol. 1999;117: 907-912.