Racial and sexual differences of eyebrow and eyelid morphology: three-dimensional analysis in young Caucasian and Chinese populations.

Background: With globalization, oculoplastic surgeons must understand the intricate morphological nuances of the periocular region across ethnicities to ensure precise treatment and avoid facial disharmony or dysfunction. Direct comparisons in two-dimensional (2D)-based periocular morphology between studies can be challenging due to the limited number of parameters and complicated variations in equipment, environments, measurement personnel, and methods. Therefore, it is imperative to explore the detailed three-dimensional (3D) periocular morphological disparities between young Caucasian and Chinese populations. This study aimed to establish gender- and ethnicity-specific 3D anthropometric data in periocular soft tissue for young Caucasian and Chinese adults and to determine the inter-racial and inter-gender differences. Methods: This descriptive, cross-sectional study enrolled 46 Asians and 101 Caucasians aged 18 to 30 years. 3D models were analyzed with 32 landmarks, yielding 21 linear distances, three curvatures, six angles, and three proportions. Comparisons were made across left and right eyes, ethnic groups, and sexes to assess ethnic disparities and sexual dimorphism. Results: Twenty-nine measurements were compared between the left and right sides revealing significant differences (P<0.002) in two measurements for Caucasian and Chinese females, respectively. However, these differences were submillimeter levels and potentially inconsequential in practical settings with left-right differences of -0.58 and -0.57 mm (P<0.001) for double-eyelid fold-palpebral margin distance (medial) (FPDm) and double-eyelid fold-palpebral margin distance (medial limbus) (FLmD) in Chinese females and -0.38 and -0.52 mm (P<0.001) for palpebral fissure width (PFW) and lower palpebral margin length (LPML) in Caucasian females. Caucasian males displayed significantly larger palpebral fissure height (PFH), iris diameter (ID), LPML, lateral canthal angle (LCA), canthal tilt (CT), palpebral fissure index (PFI), and canthal angular index (CAI), as well as smaller inner intercanthal distance (EnD), outer intercanthal distance (ExD), and canthal index (CI) than Chinese males (P<0.05). In contrast, Caucasian females showed significantly larger PFW, ID, LPML, LCA, CT, and CAI, as well as smaller EnD, ExD, CI, and medial canthal angle (MCA) than Chinese females (P<0.05). Furthermore, Caucasians showed more prominent double-eyelid folds, except at the pupil center in females. In eyebrow measurements, Caucasian males exhibited non-significant differences with Chinese males, while Caucasian females had significantly larger measurements at lateral positions but smaller ones at the endocanthion than Chinese females (P<0.05). Conclusions: This study established sex- and ethnicity-specific 3D anthropometric data for the periocular region of young Caucasian and Chinese adults. These findings must be considered for periocular disease diagnosis, surgical planning, and outcome evaluation across diverse sexual and ethnic populations.