Abstract
The aim of this study was to investigate the relationship among objective and subjective evaluations of facial asymmetry and the results of eye tracking analysis in order to clarify what part of the face medical professionals examine when judging symmetry.
Evaluation was conducted on the preoperative full-face photographs of 30 patients (7 men, 23 women) examined at the Niigata University Medical and Dental Hospital and diagnosed with jaw deformity between June 2002 and May 2008. Evaluators (n=10), comprising 7 oral surgeons and 3 orthodontists, were asked to view a full-face photograph of each patient displayed on a monitor for 20 seconds and to subjectively evaluate and classify them as either 0, ‘almost symmetry’; 1, ‘asymmetry observed, but within permissible limits’; or 2, ‘obvious asymmetry observed requiring treatment.’ Points of gaze were analyzed using an eye-tracking method from the trajectory of the evaluators’ gaze movements during evaluation. We calculated the initial gaze point among the features and gaze time with regard to the eyes, nose, mouth, chin and cheek.
The subjective degree of facial asymmetry was calculated for each patient as the mean evaluation score of the 10 evaluators. Upon comparison with the results of objective photographic analysis, correlations were observed for the degree of deviation of the mental region and oral fissure inclination, angular asymmetry ratio of the mandibular angle, angular asymmetry ratio of the mouth commissure and distance asymmetry of the mandibular angle. Gaze point analysis revealed that the initial gaze point was most often the nose, followed by the lip region. Longest gaze times were observed for the mental region followed by the nose then the lip area; gaze area was focused from the mid to the lower face.
In conclusion, it is suggested that the degree of deviation of the mental region and lip inclination have a large effect on the subjective evaluation of full facial asymmetry.
