Measurement of width and distance of the posterior border of the deep lateral orbital wall using computed tomography

IntroductionTechniques of orbital decompression for Graves’ ophthalmopathy continue to evolve. Recently the deep lateral orbital wall has been proposed as the most effective and safe site for a decompression procedure associated with the least complications. Anatomic variations with structures like the middle cranial fossa render decompression of the lateral wall more logical. We aimed to understand the anatomic localization and appearance of the lateral orbital wall by measuring the width and distance of the lateral wall on computed tomography (CT).Material and methodsThe medical records of all patients who underwent orbital CT scans for ocular trauma or for confirmation of orbital disease at the Korea University hospital between January 2005 and May 2008 were reviewed retrospectively.All patients had been scanned with the same CT scanner (Philips Brilliance 64 channel CT; Philips Healthcare Systems). Patients who had normal orbits bilaterally were included in this study.The cut in which the lateral rectus muscle was longest and the lateral bony orbit was thickest was selected from the axial and coronal slices. The point where the lateral rectus muscle contacted the the bone was measured on this axial slice. The width of the lateral wall was measured at the level of superior border of the lateral rectus muscle on thickest part of the coronal slice.ResultsA total of 334 orbits (167 patients) were included. Patients ranged in age from 7 years to 78 years (median age 41.1 years). The average distance of the lateral wall was 26.0 mm OD and 25.0 mm OS. The average width of the lateral wall was 16.0 mm OD 16.2 mm OS. There was no statistically significant difference between right and left. The patients were divided into 8 age groups by decades. There was no statistically significant difference between the groups in either measurement.ConclusionIn this study, we measured the average width and length of the thickest segment of the greater wing of the sphenoid, which can be used as anatomic guidelines during deep lateral orbital decompression surgery, and the basic standard value of the lateral orbital wall.