Classification of orbital morphology for decompression surgery in Graves' orbitopathy: two-dimensional versus three-dimensional orbital parameters

Br J Ophthalmol. 2013 May;97(5):659-62. doi: 10.1136/bjophthalmol-2012-302825. Epub 2013 Feb 21.


Aim: Three-dimensional (3D) CT reconstruction of the bony orbit for accurate measurement and classification of the complex orbital morphology may not be suitable for daily practice. We present an easily measurable two-dimensional (2D) reference dataset of the bony orbit for study of individual orbital morphology prior to decompression surgery in Graves' orbitopathy.

Methods: CT images of 70 European adults (140 orbits) with unaffected orbits were included. On axial views, the following orbital dimensions were assessed: orbital length (OL), globe length (GL), GL/OL ratio and cone angle. Postprocessed CT data were required to measure the corresponding 3D orbital parameters. The 2D and 3D orbital parameters were correlated.

Results: The 2D orbital parameters were significantly correlated to the corresponding 3D parameters (significant at the 0.01 level). The average GL was 25 mm (SD±1.0), the average OL was 42 mm (SD±2.0) and the average GL/OL ratio was 0.6 (SD±0.03). The posterior cone angle was, on average, 50.2° (SD±4.1). Three orbital sizes were classified: short (OL≤40 mm), medium (OL>40 to <45 mm) and large (OL≥45 mm).

Conclusions: We present easily measurable reference data for the orbit that can be used for preoperative study and classification of individual orbital morphology. A short and shallow orbit may require a different decompression technique than a large and deep orbit. Prospective clinical trials are needed to demonstrate how individual orbital morphology affects the outcome of decompression surgery.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Classification / methods*
  • Decompression, Surgical*
  • Exophthalmos / diagnostic imaging*
  • Exophthalmos / surgery
  • Female
  • Graves Ophthalmopathy / diagnostic imaging*
  • Graves Ophthalmopathy / surgery
  • Humans
  • Image Processing, Computer-Assisted
  • Imaging, Three-Dimensional
  • Male
  • Middle Aged
  • Orbit / diagnostic imaging*
  • Orbit / surgery
  • Tomography, X-Ray Computed*
  • Young Adult