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

Abstract

Objective Comparison of global versus landmark analyses of facial asymmetry using three-dimensional 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.