Purpose:
The function of the globe is dependent on the underlying bony architecture of the orbit; yet there exists no comprehensive language to describe this complex 3 dimensional relationship. Although Hertel exophthalmometry measures globe position relative to the lateral orbital rim, it does not describe the relationship between the globe and other points on the rim. This study utilizes a novel method for the analysis of 3D models of the globe and bony orbit to accurately measure the position of the globe relative to the orbital rim.
Methods:
3D orbital reconstructions from CT scans of seven sets of orbits with unilateral orbital pathology were generated with ImageJ, and globe and orbital rim anatomy were outlined (Figure 1A.) The distances between the center of the cornea and the coronal projection of the orbital rim, and between the apex of the cornea and the sagittal projection of the orbital rim were measured at 30 degree intervals. A set of plots were developed to display this data (Figure 1B and C.)
Results:
Analysis of four patients with unilateral Graves' disease revealed proptosis of 5.6+/-3.3mm as well as non-axial displacement of 2.2+/-0.7mm temporally and 2.1+/-2.1mm inferiorly of the globe of the affected orbit. Examination of a patient with an extraconal orbital mass demonstrated 5.0mm of proptosis, 0.9mm of temporal displacement, and 0.5mm of inferior displacement. By contrast, analysis of a patient with inferior and medial orbital wall fractures revealed 2.0mm of enophthalmos, 2.4mm of nasal displacement, and 2.0mm of inferior displacement. Finally, examination of a patient with a depressed tripod fracture revealed 5mm of proptosis when measured from the lateral orbital rim. However, when exophthalmometry was calculated from the stable superior orbital rim, just 2.1mm of proptosis was detected.
Conclusions:
3D analysis of orbital anatomy with underlying pathology reveals quantitative changes in orbital rim and globe configurations. This approach permits quantitative assessment of both axial- and non-axial displacement of the globe measured from any point around the orbit. Anatomic analysis, based on 3D orbital imaging, may provide a rational approach for reconstructive orbitofacial surgery.
Keywords: anatomy • orbit • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)