Orbital anatomical parameters affecting outcome of deep lateral orbital wall decompression

Purpose: To determine orbital anatomical parameters that affect surgical outcome of deep lateral orbital wall decompression. Methods: Twenty orbits of 20 patients with moderate proptosis (maximum 25 mm) due to thyroid eye disease who were stable for at least 6 months were included in this prospective cohort study. Four parameters including lateral orbital wall distance (LOWD), removable surface area (RSA), removable surface length (RSL), and sphenoid door jamb thickness (SDJ) were evaluated by computed tomography (CT) scan prior to surgery in these patients. Deep lateral orbital wall decompression without fat removal was done in all patients. Relationship between all these factors and proptosis reduction, 6 months after surgery was assessed. Results: Mean proptosis before decompression surgery (mean +/- SD) was 23.22 +/- 1.19 mm and reduction in Hertel exophthalmometry (mean +/- SD) was -3.27 +/- 1.03 mm (p = 0.006). Pearson correlation showed that LOWD, RSL, and SDJ had statistically significant correlation with proptosis reduction (p = 0.017, 0.002, and 0.001, respectively.). Linear multivariate regression analysis showed SDJ as the only independent factor in predicting surgical outcome. Conclusion: several orbital anatomical factors have significant role in predicting surgical outcome following deep lateral wall orbital decompression. Among these parameters, SDJ is an independent factor, whereas LOWD and RSL are dependent factors. Preoperative assessment of the bony sphenoid anatomy may be helpful in predicting the amount of potential decompression.