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Original article
Evaluation of optic canal anatomy and symmetry using CT
  1. Xinxin Zhang1,
  2. Yueh Lee2,
  3. Daniel Olson3,
  4. David Fleischman3
  1. 1 School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
  2. 2 Department of Radiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
  3. 3 Department of Ophthalmology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
  1. Correspondence to Dr David Fleischman; david8fleischman{at}gmail.com

Abstract

Objective We aim to describe the anatomy and symmetry patterns of the optic canal in patients having undergone maxillofacial CT imaging.

Methods In this retrospective chart review, we included all patients who received sinus and maxillofacial CT at the University of North Carolina hospitals between 2008 and 2016, without facial or cranial fractures or other medical conditions that would affect optic canal size. We measured the length of ≥75% enclosed canal, minimum cross-sectional area and minimum diameter bilaterally using iNtuition TeraRecon (Durham, North Carolina) and compared bilateral symmetry using a 20 % difference threshold. Each parameter above was compared among white, black, non-white and non-black patients.

Results Of 335 patients, the mean canal length was 5.61±2.22 mm. The mean minimum area was 11.84±3.11 mm2. The mean minimum diameter was 3.28±0.55 mm. A total of 39.4% (132/335) of patients had asymmetric canal lengths, 18.8% (63/335) had asymmetric minimum areas, and 12.5% (42/335) had asymmetric minimum diameters. No differences were found between racial groups. The right optic canal was larger than the left (right: 12.12 mm vs left: 11.55 mm, p<0.0001).

Conclusion Optic canal asymmetry is not uncommon. It may affect risk of papilloedema severity, explain cases of unilateral or asymmetric papilloedema and possibly asymmetric glaucoma.

  • optic canal
  • computed tomography
  • optic canal anatomy

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/bmjophth-2019-000302

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    Footnotes

    • Presented at This manuscript was presented as a paper at the American Academy of Ophthalmology Annual Meeting, 2018.

    • Contributors Conception and study design: DF and YL. Data collection: XZ, DO and DF. Data analysis: XZ and DF. Initial manuscript preparation: XZ and DO. Critical revisions and final approval: all authors.

    • Funding DF is supported by grants from the American Glaucoma Society (2015 MAPS; 2017 Young Clinician Scientists Award), the 2017 Chandler-Grant Society David L. Epstein Award.

    • Competing interests None declared.

    • Patient consent for publication Not required.

    • Ethics approval The Institutional Review Board of University of North Carolina approved this study.

    • Provenance and peer review Not commissioned; externally peer reviewed.