Canthal tilt
How much the outer corner of the eye sits above or below the inner corner, measured as an angle against the line joining the pupils and averaged over both eyes.
Also searched as positive canthal tilt, negative canthal tilt, hunter eyes and how to measure canthal tilt.
How to read it
the outer corners sit level with or below the inner corners (neutral to negative tilt). Mind the ±3° interval. Head roll, pitch and camera height all move this number, 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). On a typical photo with 300 px between the pupils, that is about 12 px of wander on every point. Small ratios and angles inherit it, so their intervals are wide. 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
Common questions
What is canthal tilt?
How much the outer corner of the eye sits above or below the inner corner, measured as an angle against the line joining the pupils and averaged over both eyes. Positive = outer corner higher.
How is canthal tilt measured from a photo?
It is computed from the face-mesh landmarks (en_R, ex_R, en_L, ex_L, iris_R, iris_L): mean over eyes of atan2(en.y − ex.y, |ex.x − en.x|), after rotating so the interpupillary line is horizontal. Every value carries a 1σ error bar propagated from the landmark detector's published accuracy, with a floor of ± 3°, so a small difference inside the interval is not a difference.
What is a normal canthal tilt?
Across the reference populations the anatomical norm is the same: +5.5° ± 3 for women, +5.5° ± 3 for men. This value is provisional and awaits line-by-line audit against the primary tables. Your own value is placed on the distribution you choose, as a percentile with its error bar.
What does a low or high canthal tilt mean?
Below the mean: the outer corners sit level with or below the inner corners (neutral to negative tilt). Mind the ±3° interval. Head roll, pitch and camera height all move this number, and two photos taken minutes apart routinely differ by 3–5°. Above the mean: the outer canthi sit distinctly higher than the inner canthi (marked positive tilt).
How reliable is canthal tilt from a photograph?
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.
Related measurements
The rest of the eyes set, then the nearest measurements elsewhere on the face. Every one is computed on the same photograph, in the same run, with its own error bar.
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