The placement of the human eyeball and canthi in craniofacial identification

An accurate understanding of the spatial relationships between the deep and superficial structures of the head is essential for anthropological methods concerned with the comparison of faces to skulls (superimposition) or the prediction of faces from them (facial approximation). However, differences of opinion exist concerning: (i) the position of the eyeball in planes other than the anteroposterior plane and (ii) the canthi positions relative to the bony orbital margins. This study attempts to clarify the above relationships by dissection of a small sample of adult human cadavers (N = 4, mean age = 83 years, s = 12 years). The most notable finding was that the eyeballs were not centrally positioned within the orbits as the more recent craniofacial identification literature expounds. Rather, the eyeballs were consistently positioned closer to the orbital roof and lateral orbital wall (by 1-2 mm on average); a finding consistent with the earlier anatomical literature. While these estimation errors are small ipsilaterally, several factors make them meaningful: (i) the orbital region is heavily used for facial recognition; (ii) the width error is doubled because the eyes are bilateral structures; (iii) the eyes are sometimes used to predict/assess other soft tissue facial structures; and (iv) the net error in facial approximation rapidly accumulates with the subsequent prediction of each independent facial feature. While the small sample size of this study limits conclusive generalizations, the new data presented here nonetheless have immediate application to craniofacial identification practice because the results are evidence based. In contrast, metric data have never been published to support the use of the central positioning guideline. Clearly, this study warrants further quantification of the eyeball position in larger samples and preferably of younger individuals.