Measurement of Intra-Orbital Structures in Normal Chinese Adults Based on a Three-Dimensional Coordinate System

ABSTRACT

Purpose of the study

This study was to establish a three-dimensional (3D) coordinate system and to study the normal dimensions of intra-orbital structures in Chinese adults.

Materials and methods

One hundred and forty-five adult Chinese were selected from patients who had undergone cranio-facial computed tomography scans with diagnosis other than orbital or ocular abnormality. An orbital 3D coordinate system was built on the basis of the scans. Morphological variables of intra-orbital structures were measured in this coordinate system. Bilateral symmetry, sexual dimorphism, and correlations between variables were investigated.

Results

No evident laterality was found in bilateral intra-orbital structures. The distance from the center of the eyeball to the prechiasmatic groove, the length of the optic nerve, and the thickness of rectus extraocular muscles were larger in males than in females. No sex-related difference was observed in the anteroposterior diameter of the eyeball or the exophthalmometric value. The exophthalmometric value was found to be related to the anteroposterior diameter of the eyeball, whereas the y-coordinate of the center of the eyeball had no correlation with the anteroposterior diameter of the eyeball. The optic nerve length was closely correlated to the distance from the center of the eyeball to the prechiasmatic groove.

Conclusions

The 3D coordinate system and measurement method established in this study can be applied to the standardization of orbital morphometry. The measurements obtained from normal Chinese adults may provide reference values for the morphology of intra-orbital structures.

KEYWORDS:

• Three-dimensional coordinate system
• orbital morphometry
• exophthalmometry
• optic nerve length
• thickness of extraocular muscles

Acknowledgments

The authors thank Qian Xu, Heng Lin, Chaowei Wu, and Xuan Xu (Shanghai Jiao Tong University) for their great help in image processing.

Declaration of Interests

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (31600971, 31701046 and 81600766), the Science and Technology Commission of Shanghai (17DZ2260100) and the National Key Research and Development Program of China (2016YFC0106200).