Quantitative Assessment of Facial Asymmetry Using Three-Dimensional Surface Imaging in Adults: Validating the Precision and Repeatability of a Global Approach

Objective: Comparison of global versus landmark analyses of facial asymmetry using threedimensional photogrammetry to establish a precise method for evaluating facial asymmetry. Design: The landmark-based approach utilized anthropometric data points. Our global approach involved registration of mirror images, independent of a midplane, to calculate a root mean square (RMS) value. We analyzed precision and technical and operator error of both methods. Participants: Three hundred fifty adults participated in this study. Results: We found that the global method has better precision and repeatability with a significantly lower error rate than the landmark-based method. In adults, the average RMS was 0.6253 mm with a standard deviation of 0.16. Conclusions: Our facial asymmetry measurement is more accurate than landmark-based measurements. This method is quick, reliable, and results in generation of a RMS score and a corresponding color-coded facial map that highlights regions of higher and lower asymmetry. This method may be used as a screening tool for asymmetry in both the clinical and research settings.