How Symmetrical Are Bony Orbits in Humans?

Area of Science:

• Medical Imaging
• Radiology
• Anatomy

Background:

• Accurate measurement of intraindividual orbital volumes is essential for clinical applications like surgical planning.
• Existing methods for measuring orbital volume are unreliable due to challenges in defining orbital boundaries.

Purpose of the Study:

• To introduce a novel approach for analyzing human orbits.
• To quantify bony symmetry in a patient cohort using this new method.

Main Methods:

• Retrospective analysis of computed tomography (CT) scans from 93 patients.
• Quantification of intraindividual volume difference using a surface model from manual segmentations.
• Iterative, nonrigid registration of an average orbit shape to patient orbits for mesh alignment.

Main Results:

• An average orbital volume difference of 600 ± 500 μL (2.1%) was observed between left and right orbits.
• This small volume difference was statistically significant (P = .039).
• The most significant asymmetries were located in the orbital roof and floor.

Conclusions:

• The proposed automated method provides objective orbital volume measurements without requiring a closed orbital volume.
• This technique, utilizing CT and coherent point drift, reveals a ~2% intraindividual orbital volume difference, contradicting previous estimates of 7-8%.