Orbital decompression in Graves' disease. The predictability of reduction of proptosis.

We studied 42 orbits of 23 patients with Graves' disease who had proptosis secondary to the orbitopathy of their disease and had undergone decompressive operations. The patients were evaluated preoperatively and underwent computed tomography. They were also examined frequently during the first postoperative year and the computed tomography was repeated at 6 months. Three variables correlated well with the reduction in proptosis: the percentage of increase in orbital volume after surgery, the absolute increase in orbital volume, and the degree of orbital "stiffness" as measured preoperatively. The first two variables have an inverse correlation with the third. We refer to the loss of resilience of orbital tissues and the increase in adherence between tissue planes, collectively, as orbital "stiffness." While other factors, such as the size of the anterior opening of the orbit, the resistance of the lid diaphragm, and pressure changes within the orbit, may affect the resultant reduction in proptosis, we did not attempt to measure these factors.