Preoperative Orbital Compliance as a Predictor for Outcomes of Fat Decompression in Thyroid Eye Disease

Purpose: To determine the clinical utility of the assessment of preoperative orbital compliance in predicting the amount of postoperative proptosis reduction in patients with stable-phase thyroid eye disease who undergo orbital fat decompression surgery. Methods: A retrospective chart review was conducted of stable-phase thyroid eye disease patients who underwent orbital fat decompression by a single surgeon. Orbital compliance was measured preoperatively as axial globe displacement (in millimeters) using a Hertel exophthalmometer. Displacement ≥2.5 mm was classified as high compliance and <2.5 mm as low compliance. Radiographic thyroid eye disease type, preoperative proptosis, and intraoperative fat volume removed were recorded. Linear regression analysis determined whether orbital compliance independently predicted postoperative proptosis reduction. Levene’s test assessed variability between groups. Results: Forty-six orbits from 24 patients were included, 15 orbits with low compliance and 31 with high orbital compliance. Patients with high orbital compliance had a mean postoperative proptosis reduction of 3.19 mm (range 0.5–6.0 mm) while patients with low orbital compliance had a mean proptosis reduction of 2.67 mm (range 2.0–3.5 mm). On average, higher preoperative orbital compliance led to 0.959 mm greater proptosis reduction compared with low orbital compliance, when accounting for radiographic thyroid eye disease type and volume of fat removed intraoperatively ( p = 0.048). Variability in proptosis reduction was higher among the high orbital compliance group ( p = 0.00085). Conclusions: Higher preoperative orbital compliance results in greater proptosis reduction. However, patients with high orbital compliance have greater variability in proptosis reduction, suggesting that surgical outcomes are less predictable among these patients.