Asymmetry between the two sides of the face steadily increases with age — a finding with important implications for facial rejuvenation and reconstructive procedures, according to new research. Three-dimensional digital image processing techniques show a subtle but significant aging-related increase in facial asymmetry, especially in the lower two-thirds of the face.
Using a technique called 3D photogrammetry, the researchers performed detailed scans of the facial surface on 191 volunteers, who ranged in age from four months to 88 years. The researchers then calculated the “root mean square deviation” (RMSD) to quantify the degree of asymmetry between the two sides of each face.
This digital imaging approach allowed the researchers to discern very subtle levels of asymmetry — within a fraction of a millimeter. Facial asymmetry was analyzed in terms of age and between the upper, middle and lower thirds of the face. Across age categories, RMSD calculations of facial symmetry were clustered between 0.4 and 1.3 mm.
Asymmetry increased with aging across all thirds of the face, but the changes were greatest in the lower two-thirds — from the eyebrows to the nose and from the nose to the chin — compared to the top third.
