title: The aesthetic unit principle of facial aging.
abstract: OBJECTIVE
  In youth, facial aesthetic units flow together without perceptible division. The face appears as a single dynamic structure with a smooth contour and very little if any shadowing between different anatomical regions. As one ages, facial aesthetic units slowly become distinct. This process may be a consequence of differences in skin thickness, composition of subcutaneous tissue, contour of the facial skeleton, and location of facial ligaments. Although the impact of aesthetic unit separation is clinically apparent, its fundamental role in perceived facial aging has not yet been defined empirically.
  
  
  OBJECTIVE
  To evaluate and define the effect of aesthetic unit separation on facial aging and to empirically validate the rationale for the blending of aesthetic units as a principle for facial rejuvenation.
  
  
  METHODS
  We prepared the photographs of 7 women for experimental evaluation of the presence or absence of facial aesthetic unit separation. Photographic stimuli were then presented to 24 naive observers in a blinded paired comparison. For each stimulus pair, observers were asked to select the facial photograph that they considered to be more youthful in appearance. Each stimulus was compared with all others.
  
  
  METHODS
  We calculated a preference score for the total number of times any photograph was chosen to be more youthful compared with all others. Paired t tests were used to compare the preference scores between the facial stimuli with and without aesthetic unit separation.
  
  
  RESULTS
  We generated 4032 responses for analysis. Photographs without facial aesthetic unit separation were consistently judged to be more youthful than their aged original or modified counterparts, with mean preference scores of 0.66 and 0.33, respectively (P ≤ .047). When we selected the paired stimulus that directly compared one photograph with aesthetic unit separation with another with blended aesthetic units (2015 pairs), observers indicated that the photograph with the blended aesthetic unit was younger 95% of the time. Within-rater reliability was found to be very good (r = 0.88).
  
  
  CONCLUSIONS
  Our data support the hypothesis that facial aesthetic unit separation influences perceived facial youthfulness among photographs of women. The presence of facial aesthetic unit separation results in a less youthful appearance. Based on these empirical data, the concept of facial aesthetic unit separation appears to play a significant role in perceived facial aging.
  
  
  METHODS
  NA.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Western University, London, Ontario, Canada.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Tan
authors.affiliation: Division of Facial Plastic and Reconstructive Surgery, Department of Otolaryngology-Head and Neck Surgery, University of Toronto, Toronto, Ontario, Canada3Rehabilitation Sciences, Western University, London, Ontario, Canada.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Brandt
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Yeung
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Western University, London, Ontario, Canada3Rehabilitation Sciences, Western University, London, Ontario, Canada.
authors.forename: Philip C
authors.initials: PC
authors.lastname: Doyle
authors.affiliation: Division of Facial Plastic and Reconstructive Surgery, Department of Otolaryngology-Head and Neck Surgery, St Joseph's Health Care London Health Sciences Centre, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: Corey C
authors.initials: CC
authors.lastname: Moore
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D015331:Cohort Studies; D004954:Esthetics / Q000145:classification*; D005145:Face; D005260:Female; D006801:Humans; D008875:Middle Aged; D015588:Observer Variation; D010781:Photography; D011300:Preoperative Care / Q000379:methods; D012060:Rejuvenation / Q000502:physiology / Q000523:psychology*; D015203:Reproducibility of Results; D015361:Rhytidoplasty / Q000523:psychology*; D015595:Skin Aging / Q000502:physiology*; D014796:Visual Perception