Canthal tilt
Angle of the line from inner to outer eye corner relative to the interpupillary line, averaged over both eyes.
How to read it
the outer canthi sit level with or below the inner canthi (neutral to negative tilt). Note the ±3° uncertainty: this measurement is highly sensitive to head roll, pitch and camera height, and two photos taken minutes apart routinely differ by 3–5°.
canthal tilt sits within the commonly cited anatomical range (outer canthus 2–4 mm above inner).
the outer canthi sit distinctly higher than the inner canthi (marked positive tilt).
The most over-claimed metric in facial analysis. The 2–4 mm anatomical offset is within about twice the landmark detector's own error (≈2.5 mm at typical resolution). Reported with a wide interval on purpose. A chin-down photo manufactures positive tilt.
Reference values by population
| Reference population | Female (mean ± SD) | Male (mean ± SD) | n | Source |
|---|---|---|---|---|
| North American White | +5.5° ± 3 | +5.5° ± 3 | — | Anatomical norm: lateral canthus 2–4 mm above medial (≈ +4° to +7°). Provisional. prov. |
| East Asian | +5.5° ± 3 | +5.5° ± 3 | — | Anatomical norm: lateral canthus 2–4 mm above medial (≈ +4° to +7°). Provisional. prov. |
| South Asian | +5.5° ± 3 | +5.5° ± 3 | — | Anatomical norm: lateral canthus 2–4 mm above medial (≈ +4° to +7°). Provisional. prov. |
| African / African diaspora | +5.5° ± 3 | +5.5° ± 3 | — | Anatomical norm: lateral canthus 2–4 mm above medial (≈ +4° to +7°). Provisional. prov. |
| Middle Eastern | +5.5° ± 3 | +5.5° ± 3 | — | Anatomical norm: lateral canthus 2–4 mm above medial (≈ +4° to +7°). Provisional. prov. |
| Hispanic / Latino | +5.5° ± 3 | +5.5° ± 3 | — | Anatomical norm: lateral canthus 2–4 mm above medial (≈ +4° to +7°). Provisional. prov. |
| Not specified — show pooled | +5.5° ± 3 | +5.5° ± 3 | — | Anatomical norm: lateral canthus 2–4 mm above medial (≈ +4° to +7°). Provisional. prov. |
Where these numbers come from
Transcribed from the cited anthropometric literature; SDs of ratios are propagated conservatively (independence assumed). Entries marked prov. await line-by-line audit against the primary tables — see the norm provenance note.
Why every value has an error bar
Every value Canthion reports carries a 1σ uncertainty propagated from MediaPipe Face Mesh's published accuracy (3.96% of inter-ocular distance mean absolute error per landmark, Kartynnik 2019). For a typical 300 px inter-pupil photo that is ≈12 px per landmark, which is why small ratios and angles get wide intervals. A number without an interval is a number pretending to be more precise than it is.
References
- Clinical norm: lateral canthus sits ~2–4 mm superior to the medial canthus (≈ +4° to +7° at ICD ≈ 30 mm). Evaluation of Eyelid Function and Aesthetics (Plastic Surgery Key, textbook chapter). plasticsurgerykey.com/evaluation-of-eyelid-function-and-aesthetics/
- Kartynnik, Ablavatski, Grishchenko & Grundmann (2019). Real-time Facial Surface Geometry from Monocular Video on Mobile GPUs. arXiv:1907.06724. arxiv.org/abs/1907.06724
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