Canthal tilt

Reference range

None.

We have not validated a population reference interval for this photographic method. Published anatomical measurements do not automatically validate mesh-based estimates.

How we calculate it

We take the inner and outer eye-corner landmarks from the face mesh on both sides, correct the whole set for estimated head roll first, then average the left and right angles. Correcting for roll matters: a head tilted five degrees in the photograph would otherwise add five degrees to the result.

What moves the number

Head roll, camera height, a squint or a smile, and landmark placement on soft eyelid edges. Differences of a degree or two between two photographs of the same person are ordinary.

What it cannot tell you

A photograph cannot separate the shape of the bony orbit from eyelid position, and cannot tell whether a tilt is lifelong or recently changed. Typical values also differ between populations, so one band does not describe everyone.

References

• Farkas LG. Anthropometry of the Head and Face. 2nd ed. Raven Press, 1994 — the standard reference for how this measurement is defined and taken.
• Hwang K et al. The Latino Eyelid: Anthropometric Analysis of a Spectrum of Findings. Ophthalmic Plast Reconstr Surg, 2017 — one of many papers showing periorbital norms differ by population.