Three-Dimensional Assessment of Orbital Contours and Their Significance in Forehead Feminization

PURPOSE: Superolateral orbit reshaping, aimed at reducing the prominence and softening of the superolateral orbital rim, is integral to forehead feminization surgery. However, there is limited literature providing objective anatomical evidence on the sexual dimorphism of orbital features. This study aimed to investigate orbital characteristics between cis-males and females and their implications for forehead feminization. METHODS: An IRB-approved retrospective review of maxillofacial CT scans was conducted on ethnicity- and age-matched groups of cis-male and female patients (2003-2022). Patients were excluded if they had prior sinus surgery, facial skeletal fracture, or craniofacial abnormalities. Three-dimensional reconstruction of the skulls was performed and processed using Mimics and 3-matic software. Data collected included patient sex, age, ethnicity, orbit dimensions, superolateral orbit angle, superolateral orbit rim prominence, and the extent of supraorbital bar protrusion. Inter-orbital and bi-orbital distances were defined as the lengths between right and left dacryons, and between the right and left ectoconchions, respectively. Mann-Whitney test and Pearson correlation were performed to analyze the association between variables. RESULTS: A total of 186 patients (106 males and 80 females) with a mean age of 51.2±20.3 years were included. Compared to the female group, male patients exhibited significantly taller orbits (male: 35.8±2.7 mm, female: 34.3±2.2 mm, p=0.0001), wider orbits (male: 41±2.4 mm, female: 38.8±2.2 mm, p<0.0001), longer bi-orbital distances (male: 100.8±4.5 mm, female: 95.2±7.9 mm, p<0.0001), a more prominent superolateral orbit rim (male: 14±1.9 mm, female: 11.1±1.5 mm, p<0.0001), a narrower superolateral orbit angle (male: 133.7°±6.7, female: 145.7°±5.1, p<0.0001), and greater supraorbital bar protrusion (male: 3.6±1.5 mm, female: 1.7±0.8 mm, p<0.0001). However, the ratios of orbital height/width (male: 0.9±0.08, female: 0.9±0.06, p=0.28) and inter-orbital distance (male: 18.7±3.4 mm, female: 19.4±2.7 mm, p=0.13) were not significantly different between the 2 groups. The prominence of the superolateral orbit rim correlated positively with supraorbital bar protrusion (r=0.45, p<0.0001), orbital height (r=0.22, p=0.003), orbital width (r=0.37, p<0.0001), and bi-orbital distance (r=0.42, p<0.0001), and correlated negatively with superolateral orbit angle (r=-0.56, p<0.0001). CONCLUSIONS: For effective forehead feminization, prioritize proportional adjustments in superolateral orbit rim prominence, superolateral orbit angle, and supraorbital bar protrusion relative to orbit dimensions, rather than absolute values, to ensure balanced aesthetics, acknowledging size variations between cis-male and female skulls.