Scientific Basis

Scientific basis & references

Every metric the AI agents measure is grounded in facial-aesthetics standards from the plastic-surgery and anthropometry literature.

These metrics are reference standards drawn from scientific studies and are used as guides, not absolute rules. “Ideal” proportions vary by ethnicity, sex, era, and the individual; the sources themselves show the neoclassical canons do not fit everyone.

Tern Plus

Eyes & brows (periorbital)

Proportion and symmetry of the periorbital region.

Canthal tilt

A positive lateral canthal tilt is a youthful, attractive periorbital trait; canthal positions follow the neoclassical orbital canon.

[1] [2]

Brow position & shape

Brow height and peak relative to the bony orbital rim is the classic basis for eyebrow aesthetic analysis.

[3] [2]

Brow symmetry & height asymmetry

Bilateral facial symmetry is among the strongest predictors of perceived attractiveness.

[4] [5]

Interbrow & brow–eye distance

Intercanthal and periorbital distances are part of normative facial anthropometric data.

[2] [3]

Vertical proportion (facial thirds)

Dividing the face into three equal vertical parts is a neoclassical canon of facial proportion.

[1] [6]

Serval Plus

Lower third of the face

Lips, chin, nasolabial region, and jawline.

Horizontal proportion (facial fifths)

Dividing facial width into five eye-widths is a horizontal neoclassical canon.

[1] [2]

Upper-to-lower lip ratio

Specific upper:lower lip ratios correlate with facial attractiveness and have been studied quantitatively.

[7] [6]

Nasolabial angle

The angle between the nasal base and upper lip; its ideal range has been objectively defined.

[8]

Tear trough

The anatomy of the lid/cheek junction is the basis for assessing the under-eye groove.

[9]

Jawline & cervicomental angle

A submental–cervical angle of 105–120° is a visual criterion of a youthful neck.

[10]

Chin projection

Chin–lip relationships to profile reference lines are a principle of facial proportion.

[6] [2]

Lynx Plus

Jaw & cheeks

Jaw shape, facial width, and midface volume (triangle of youth).

Jawline angle

Jawline definition and the cervicomental angle are visual indices of facial proportion and youth.

[10] [2]

Jaw width

Jaw width relative to other facial dimensions is part of normative anthropometric data.

[2] [1]

Triangle of youth (midface volume)

The distribution of cheek/midface fat compartments is the anatomic basis of the “triangle of youth.”

[11]

Vertical proportion (facial thirds)

Equal vertical division of the face is a neoclassical proportion canon.

[1]

Lip ratio

Lip ratios factor into the overall proportion of the lower third.

[7]

Symmetry

Facial symmetry is linked to perceived attractiveness.

[4] [5]

Swift Plus

Nose & profile

Nasal projection, angles, and proportions in profile.

Goode ratio

The ratio of nasal tip projection to nasal length — the classic profile index of tip projection.

[12] [13]

Nasal tip projection

Tip projection can be measured quantitatively, and its ideal ranges have been studied in populations.

[13] [14]

Nasofrontal angle

The angle between the forehead and nasal bridge is a key profile angle.

[15]

Nasolabial angle

The ideal nasolabial-angle range has been objectively defined.

[8]

Alar ratio

Alar width relative to other dimensions is part of the naso-facial proportion canons.

[12] [2]

Vertical proportion (facial thirds)

Nasal height is assessed within the vertical division of the face.

[1]

Foundational basis (shared)

The “golden / divine proportion” and symmetry form the shared theoretical framework behind many of these metrics.

[6][16][17][4]

Reference list

[1] Farkas LG, Hreczko TA, Kolar JC, Munro IR. Vertical and horizontal proportions of the face in young adult North American Caucasians: revision of neoclassical canons. Plast Reconstr Surg. 1985;75(3):328–338.
[2] Farkas LG. Anthropometry of the Head and Face. 2nd ed. New York: Raven Press; 1994.
[3] Gunter JP, Antrobus SD. Aesthetic analysis of the eyebrows. Plast Reconstr Surg. 1997;99(7):1808–1816.
[4] Rhodes G. The evolutionary psychology of facial beauty. Annu Rev Psychol. 2006;57:199–226.
[5] Bashour M. An objective system for measuring facial attractiveness. Plast Reconstr Surg. 2006;118(3):757–774.
[6] Ricketts RM. Divine proportion in facial esthetics. Clin Plast Surg. 1982;9(4):401–422.
[7] Popenko NA, Tripathi PB, Devcic Z, Karimi K, Osann K, Wong BJF. A quantitative approach to determining the ideal female lip aesthetic and its effect on facial attractiveness. Plast Reconstr Surg. 2017.
[8] Armijo BS, Brown M, Guyuron B. Defining the ideal nasolabial angle. Plast Reconstr Surg. 2012;129(3):759–764.
[9] Haddock NT, Saadeh PB, Boutros S, Thorne CH. The tear trough and lid/cheek junction: anatomy and implications for surgical correction. Plast Reconstr Surg. 2009;123(4):1332–1340.
[10] Ellenbogen R, Karlin JV. Visual criteria for success in restoring the youthful neck. Plast Reconstr Surg. 1980;66(6):826–837.
[11] Rohrich RJ, Pessa JE. The fat compartments of the face: anatomy and clinical implications for cosmetic surgery. Plast Reconstr Surg. 2007;119(7):2219–2227.
[12] Powell N, Humphreys B. Proportions of the Aesthetic Face. New York: Thieme-Stratton; 1984.
[13] Crumley RL, Lanser M. Quantitative analysis of nasal tip projection. Laryngoscope. 1988;98(2):202–208.
[14] Ahmed O, Dhinsa A, Popenko N, et al. Population-based assessment of currently proposed ideals of nasal tip projection and rotation in young women. JAMA Facial Plast Surg. 2014;16(5):310–318.
[15] Fontana AM, Muti E. The nasofrontal angle and profile in rhinoplasty. Aesthetic Plast Surg. 1983;7:169–170.
[16] Ricketts RM. The biologic significance of the divine proportion and Fibonacci series. Am J Orthod. 1982;81(5):351–370.
[17] Swift A, Remington K. BeautiPHIcation: a global approach to facial beauty. Clin Plast Surg. 2011;38(3):347–377.

The analysis is a decision-support aid, not a medical diagnosis. Metrics reflect population-level aesthetic studies and are not a substitute for professional consultation.