Development of a new evaluation method for cheek sagging using a Moire 3D analysis system

Background/aims: Facial sagging becomes progressively noticeable with aging. Previously developed methods to study facial sagging measure the shape of sagging skin, evaluate skin properties such as elasticity or flexibility or visually score the degree of sagging using a photo scale. However, the practical use of these methods has shortcomings and is thus limited to advanced levels of sagging. In this study, we attempted to overcome the shortcomings of those previous methods. Methods: Fourteen points were marked on the cheek of each subject and photographed using a Moire three-dimensional (3D) camera with the subject facing first frontward and then downward. The absolute 3D coordinates (x, y, z) of the 14 points from the control point (0, 0, 0) were calculated. Subsequently, the skin surface displacements at the 14 points between the frontward and downward images were analyzed along the x, y, and z axes. The values were compared by age and by sag scores obtained from the photo scales. Result: The displacement values strongly correlated with age and with the sag score. In addition, this new method revealed characteristic differences of sagging between women in their 60s and those in their 70s. Conclusion: This method, using Moire 3D analysis, revealed slight, continuous and characteristic changes of cheek skin sagging without causing any discomfort to the subjects. These results are consistent with people's visual impression. The results indicate the usefulness of this method in skin research.