Dimensions and position of the eye for facial approximations in a South African cone beam computed tomography sample

Abstract

Accurate population and sex-specific normative values for the orbital and ocular dimensions, including the position and protrusion of the eye relative to the orbital rim, are vital for reliable facial approximations. In studies utilizing cadaveric tissue and computed tomography scans, the observed measurements may be influenced by desiccation, distortion or gravity, respectively. This study assessed the dimensions of the eye and orbit and established the position and protrusion of the eye relative to the orbital margin using cone beam computed tomography (CBCT) scans to negate the effect of gravity in the supine position. Scans of 197 adult South Africans (45 Black females, 49 Black males, 55 White females, and 48 White males) were selected retrospectively from private and public hospitals in Pretoria, South Africa. Linear distances were calculated from three-dimensional landmarks placed on the orbital rim and ocular equator using the MeVisLab © v.3.0.2 software. White females presented with significantly larger orbital heights and axial lengths of the eyes compared to Black females, while the eyeballs of Black females protruded more from the superior and lateral orbital margins. Black females presented with significantly smaller dimensions than Black males. On the contrary, White males exhibited significantly larger protrusion values than White females. The results of this study corroborate with the literature that sex, population, and modality significantly influence the position of the eye in the orbit, which emphasizes the necessity of creating population- and sex-specific facial approximations guidelines for the placement of the eye in the orbit.

Keywords: eyeball dimensions; facial approximation; forensic facial reconstruction; ocular position; ocular protrusion; orbital dimensions.

FIGURE 1

Landmark position on the 3D surface mesh of the skull.

FIGURE 2

DICOM slice indicating the landmarks used to calculate ocular distances between the white squares. (A) axial view; (B) coronal view; (C) sagittal view.