Orbital Volume and Eye Position Changes After Balanced Orbital Decompression

Abstract

To evaluate the changes in eye position and orbital content expansion following medial and lateral orbital wall decompression for thyroid-associated orbitopathy. The authors used a computer software program (syngo InSpace4D, syngo 3D, syngo fusion, and syngo Volume Evaluation; Siemens AG, Forchheim, Germany) to measure the orbital expansion gained by medial and lateral orbital wall decompression and the change in eye position between the digitized preoperative and postoperative orbital CT scans. Twenty patients (16 women and 4 men) with a mean age of 45 years (range, 18-64 years) were enrolled in this study. Of the 20 patients who underwent balanced decompression for thyroid-associated orbitopathy, 18 patients had bilateral medial and lateral orbital wall decompression, and 2 patients had unilateral medial and lateral decompression. The average orbital volume expansion was 3.21 mL (13.51%) of the preoperative orbital volume (2.1 mL [8.98%] gained by medial wall decompression and 1.03 mL [4.53%] by lateral wall decompression). Postoperatively, proptosis decreased by 2.53 mm on average (p < 0.0001). The eyes became closer to each other postoperatively in the horizontal plane by 2.6 mm on average (p < 0.0001). No change in the vertical eye position was detected postoperatively. A significant nasal shift in the eye position was noticed following balanced orbital decompression. Computerized assessment of preoperative and postoperative digitized orbital CT scans helps evaluate the orbital changes in response to different orbital decompression techniques and improve the surgical outcomes in thyroid-associated orbitopathy.