Use of 3D orbital reconstruction in the assessment of orbital sexual dimorphism and its pathological consequences.

Introduction: Surrounded by a variety of structures including the facial sinuses and the brain, the human orbit displays unique anatomical features. It is known that orbital volume correlates with age and sex. The aim of this study was to evaluate sexual dimorphism of orbital volume relative to the size of the skull, and to establish criteria for gender determination.
Methods: Orbital volume was measured from 3D models of the orbits. The volumes were expressed in relation to the centroid size of the skull, to ensure that any sexual dimorphism in orbital volume was not simply due to a difference in skull size. Thirty-three male and 42 female subjects were included in the study.
Results: The volume of both orbits were significantly higher in men than in women (P=0.0001). The right, left and total orbital volumes relative to the centroid skull size were also significantly higher in men than women (P<0.05). The method was repeatable and reproducible. A test of gender determination was developed, with a precision of 77.3%.
Discussion: This is the first study showing a sexual dimorphism in orbital volume relative to skull size. This difference in volume could explain the greater predisposition to myopia in women and their more frequent need for orbital decompression in thyroid orbitopathies.
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