In this section, drawings are used to depict terminology and to illustrate certain aspects of facial variation.
Many features of the face that are considered abnormal are continuous, quantitative traits, plotting above or below 2 S.D. from the mean. A continuous trait, like ear size, is quite different from a discontinuous trait such as a pre-auricular ear pit since an ear pit is considered either present or absent (figure below).
Thus, there is usually no disagreement among physicians as to whether an ear pit is present or not. However, disagreement can occur when one judges continuous traits based on impression alone, without the benefit of measurement. Nevertheless, visual appraisal alone is often the practical reality in a busy clinic. Facial measurements can be made of certain facial regions (as noted below for example using A for outer canthal distance), and when indicated, can be measured and plotted on growth charts.
In this web page, facial drawings illustrate how certain facial terms are used to describe facial variation.
Hypertelorism is defined by an increased interpupillary distance. Hypertelorism (right); normal (middle); hypotelorism (left).
Palpebral Fissure Length
Often this length is actually measures and plotted. Short (left); normal (middle); large (right)
Palpebral Fissure Slant
This varies greatly with ethnic origin. Up (left); normal (middle); down (right)
Many variations exist. The boy on the left does not have folds. On the right image, the effect of the epicanthal fold extending above the inner canthus is illustrated.
Midface hypoplasia (blue region below) is essentially the same thing as maxillary bone region hypoplasia. Maxillary retrusion is another way of thinking about mid-face hypoplasia. Depressed nasal bridge (not illustrated here) is often another component of mid-face hypoplasia.
The philtral groove can be thought of as representing the resultant folding effects of bilateral, inwardingly migrating neural crest cells that met at the midline. Smooth patterns however can also be normal variants or can be associated with genetic syndromes or caused by teratogens such as alcohol.
Images A show normal ear position. Low set ears are positioned below the horizontal line as illustrated in B. Low-set ears are often posteriorly rotated, reflecting an arrest in the normal anterior rotation that occurred during fetal ear development.