Novel approach to orbital hard- and soft-tissue symmetry analysis: a pilot validation

Volume-based orbital symmetry analysis can hardly explain a particular orbital structure’s involvement and contribution to asymmetry. This study aimed to validate a novel approach to orbital surface-based hard- and soft-tissue symmetry analysis, providing comprehensible and clinically applicable interpretation. CT-based segmentation of the orbital hard- and soft-tissue structures was followed by model mirroring, global registration, and surface-based symmetry analysis, with both qualitative and quantitative interpretations in twenty young, healthy subjects. The entire soft-tissue model’s global symmetry was higher compared to the entire hard-tissue volume (p = 0.027), reflecting the potential of the soft tissue to compensate for bone-structure asymmetry. No significant difference in symmetry parameters was found for particular orbital walls (p = 0.803) and intra-orbital soft-tissue structures (p = 0.256). The strong negative correlation between relative global and local symmetry parameters and absolute root mean square (RMS) distance values demonstrates the reliability of the suggested novel approach. Correlations between orbital walls symmetry parameters were higher compared to soft-tissue orbital structures. Aside from the accurate RMS distance calculation, the global and local symmetry analysis presented in this pilot study offers valuable, reliable, and comprehensible information on the contribution of particular orbital hard- and soft-tissue structures to facial symmetry.