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Sunny Shen, Arjunan Kumaran, Amy Chan, Kailing Yong; Ethnic variation in bony orbital anatomy and its implications on decompression surgery. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1744. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Orbital decompression surgery is a well accepted treatment for dysthyroid optic neuropathy and disfiguring proptosis in thyroid eye disease. However, the effect of decompression varies between patients. The aim of our study is to describe the differences in bony orbital anatomy (lateral orbital wall, medial orbital wall, orbital floor) between Chinese, Malay, Indian and Caucasian subjects.
Single centre, retrospective, Computed Tomography (CT)-based study. 20 subjects of each ethnicity were used from existing databases, matched for gender, average age and laterality. Subjects below 16 years of age were excluded. Digital Imaging and Communications in Medicine (DICOM) image viewing softwares CARESTREAM Vue PACS (Carestream Health Inc., USA) and OsiriX version 7.5 (Pixmeo., Switzerland) were used to measure lateral orbital wall, medial orbital wall and orbital floor anatomy and statistical analyses performed using Statistical Package for Social Sciences version 21 (IBM, USA).
In each group, there were 12 males (60%) and average age was not significantly different (p=0.682-0.987). Using Chinese subjects as a reference, in Chinese, Malay, Indian and Caucasian subjects, mean trigone thickness was 13.68, 14.02, 11.60 (p<0.001) and 13.80mm, curved total wall length 45.23, 42.29 (p=0.048), 41.91 (p=0.020) and 45.00mm, curved trigone length 23.03, 22.61, 17.19 (p=0.011) and 18.76mm (p=0.030) and trigone volume 3120.97, 3221.01, 1613.66 (p<0.001), 2498.46mm3 (p=0.059) respectively. Similarly, perpendicular orbital depth was 27.54, 24.97, 22.12 (p=0.001) and 25.93mm and diagonal orbital depth was 34.19, 33.27, 29.48 (p=0.01) and 34.63mm respectively. Indian and to a lesser extent, Caucasian subjects have smaller trigones compared to their Chinese and Malay counterparts. Indian subjects also have shallower orbits and due care should be taken during decompression surgery.
We provided an anatomical overview and elucidated the ethnic variation in surgical anatomy of the deep lateral orbital wall, the posterior medial orbital wall and the ethmoidomaxillary transition zone for safe and effective orbital decompression surgery.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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