Correlation of retrobulbar volume change with resected orbital fat volume and proptosis reduction after fatty decompression for Graves ophthalmopathy.

PURPOSE: To evaluate the correlation of retrobulbar volume change, resected orbital fat volume, and proptosis reduction after fatty decompression.

DESIGN: Cross-sectional and prospective study.

METHODS: Twenty-two patients (44 orbits) with Graves ophthalmopathy underwent fatty decompression. Preoperative orbital computed tomography (CT) imaging with a 2-mm cut was compared with postoperative imaging carried out 6 months after fatty decompression. The relationship of retrobulbar volume change, resected orbital fat volume, and proptosis reduction was analyzed by Pearson correlation. Linear regression was performed using resected fat volume or proptosis reduction as independent variables and retrobulbar volume change as a dependent variable to validate the effect of fatty decompression.

RESULTS: Mean proptosis reduction was 4.1 ± 0.9 mm. Mean volume of resected orbital fat was 4.4 ± 1.2 mL. Mean retrobulbar volume change in computed tomographic imaging was 3.2 ± 1.0 cm(3). The change in retrobulbar volume was correlated strongly with proptosis reduction and volume of resected orbital fat. Linear regression revealed the following equation for Retrobulbar volume change: 0.546 × Hertel change + 0.945 or 0.293 × Volume of resected orbital fat + 1.917.

CONCLUSIONS: Fatty decompression can reduce proptosis for patients with disfiguring Graves ophthalmopathy. Because of the close correlation of retrobulbar volume change with volume of resected orbital fat and proptosis reduction, we propose that orbital fat removal may be accompanied by decreased retrobulbar volume after fatty decompression. Evidence of decreased retrobulbar volume may result in effective proptosis reduction.