Reliability between measurements obtained by caliper and digital photography in facial anthropometry.

Only a handful of facial points were measured, and the method does not correct for pixel size. Even after the 10 mm calibration line, the values from the photographs remained in pixels rather than millimetres, so caliper and photographic numbers are not on the same scale at all. The repeat-measurement checks, within and between evaluators, were run only on the photograph-based measurements, not on the caliper measurements, because repeating the in-person caliper work was difficult. The sample was one of convenience: 60 healthy young adults with a normal bite and nasal breathing. Nothing here speaks to people with facial asymmetry, malocclusion or the conditions a clinician actually treats. The paper says there are no comparable studies using the same methods, so the authors could not place their figures against anyone else's. The paper notes that a single 2D image can over- or under-estimate a measurement depending on the angle and orientation it was taken from. The authors state they did not apply the facial asymmetry index described in the literature, which they call a limitation of the study. The authors themselves conclude that further work is needed before reliable reference values for clinical use can be set.

The paper declares no financial support and no conflicts of interest.

Do not read the high agreement figures as meaning the caliper and the photographs can be used interchangeably. Repeated measurements with the same tool matched closely, but the photographs consistently gave smaller values than the caliper at every point and in both sexes, so a number from one method cannot stand in for a number from the other.