What could an ideal unit of measurement for Human Facial Features? The Facial Features largely vary with gender, age, genetic and climate. A careful observation of human skull can give the following insights.
- The least changed shape in human skull is eye socket (anatomically known as ‘Orbit’).
- The least changed dimension is the interocular distance.
- Jaw is in its peak shape during the the most reproductive age. This is also the most changing shape on face.
- The face-width has less variation over age, in comparison to face-height.
Considering the above observations, Interocular distance is a good candidate for unit of measurement for structural analysis of face.
Even though Interocular distance is a good candidate, is there any possibility of large variation of its measurements over gender, age, genetic and climate? The interocular distance can be further break down into ‘outer canthal distance’ , ‘interpupillary distance’ and ‘inner canthal distance’
The below figure shows that, inter canthal distance is one feature which has less change over the years of age progression.
The canthal index is one feature what has no significant difference between males and females.
The original equation for canthal index is (inner inter canthal / outer inter canthal × 100). However, to use the canthal index for unit of measurement for factial features from a photograph, it is modified as follows.
Photographic Canthal Index (PCI) = inner intercanthal / outer intercanthal × 10
PCI (Photographic Canthal Index) is the standard used for measuring facial features from an image.
The PCI is also subjected to photographic distortions. https://www.researchgate.net/publication/249562845_The_Non-Realistic_Nature_of_Photography_Further_Reasons_Why_Turner_Was_Wrong. Hence the selection of photographic equipment needed to be carefully considered.
Abnormal Inter Canthal Distances
For a well formed facial structure, the inter canthal distance is correlated with width of eye. If there is an imbalance in inter canthal distance, it can cause ‘Telecanthus’ or ‘Orbital hypertelorism’
Distinctive face features of a child with Fetal Alcohol Syndrome who have brain damage and resulted low intelligence.
The genetical deformity of orbital area can be further studied in the below link.
Word of Caution
This a study based on external sources. This is neither final nor an official one. Please use the information presented here at your discretion.