Geometric morphometric analyses of orbit shape in Asian, African, and European human populations

Abstract

The variation of orbit shape has been investigated, especially its role in population classification. However, previous studies that treated orbit shape as a linear metric or non-metric trait have not produced conclusive quantitative data to show whether orbit shape is an accurate reflection of population affinity. Thus, in this study in order to examine regional variation in the orbit shape of contemporary Asian, African, and European populations we use geometric morphometrics with a novel standardization technique. A standardized orbital plane was obtained and each specimen was photographed. The results from this study show that regional variation in orbit shape exists. The Asian orbital contour was generally tall, rounded, and its inferior contour was symmetrical. The European tended to be square and more inclined, with the African being shorter. Moreover, the orbit shape of some specimens from these three regions overlapped. The similarities between the Asian and European samples were much smaller than those between Africans and Asians, or Africans and Europeans. Additionally, intergroup variability was larger on the bones of the maxilla and zygoma which form the inferior contour of the orbit, compared with the frontal bone forming the superior contour. The most variable areas of the orbit concentrate on the internal aspect of the upper margin, on the contours near the frontomalare orbitale and zygomaxillare. The application of geometric morphometrics with the newly developed standardization protocol to examine orbit shape between individuals from different geographic areas, has demonstrated its use to measure quantitatively human orbit shape, variation, and population affinity.

Radiologic evaluation of orbital index among Ghanaians using CT scan

“…These bones are arranged to enclose a roughly quadrilateral pyramidal cavity. Among modern human groups, the characteristics of the orbit vary considerably [5]. …”

Ancestral Variation in Orbital Rim Shape: A Three‐Dimensional Pilot Study

“…Recently, a handful of studies have used geometric morphometric techniques (relatively objective, metric methods subject to error assessments) to re‐assess ancestral differences in two‐dimensional orbital rim shape (e.g.,). Urbanová assessed ancestral variation in orbital rim shape in three dimensions using a portable digitizer and elliptic Fourier analysis; however, this study assessed differences between Czech and Portuguese populations only.…”

Orbital indices in a modern Sinhalese Sri Lankan population

“…First, microseme categorisation of our skulls appears to suggest that the orbits have a more rounded morphology than other Asian populations. [1] When this is analyzed against other data from Asian population, it appears that this discrepancy is evident with most of the data available on Egyptian [2] and Indian subpopulations. [12,14,15,18,19,21,26,27] Second, Asian populations seldom display OI sexual dimorphism ( Table 2).…”

“…As landmark features of the skull, morphometric characterisation of the orbits is of value for anthropology, [5] tracing population origins, gaining insight into craniofacial growth due to racial and sexual differences, [6] and quantifying intraspecific variations and forensic osteology. [1,2,4,7] Moreover, comprehensive assessment and preoperative planning in areas of neurosurgery, craniofacial surgery, congenital disfigurement and trauma require specific morphometric data on orbit morphology for the safety and efficacy of clinical treatment. [8][9][10][11] While orbit morphology has not changed significantly over recent human history, advances in surgical practice means that we are now able to utilise more detailed and specific information for the treatment of patients.…”

“…Each orbit is composed of several bones arranged to form quadrilateral pyramids with their bases facing anterolaterally and slightly downward, and their apices projecting posteriomedially. [1][2][3] The orbits contain and protect the eyes, extra-ocular muscles and several neurovascular structures, and also allow for the accurate positioning of the visual axis, [1,4] which is essential for binocular vision. As landmark features of the skull, morphometric characterisation of the orbits is of value for anthropology, [5] tracing population origins, gaining insight into craniofacial growth due to racial and sexual differences, [6] and quantifying intraspecific variations and forensic osteology.…”