The risk of diplopia following orbital floor and medial wall decompression in subtypes of ophthalmic Graves' disease

We preoperatively divided 58 ophthalmic Graves' disease patients into types I and II categories before two-wall orbital decompression. Type I classification was given to patients who had no diplopia and essentially normal versions. Type IT classification was assigned to patients with restrictive motility loss and diplopia within 20 degrees of the primary position. Ocular motility was assessed before and after two-wall orbital decompression. Only one of 25 type I patients (4%) experienced diplopia after orbital decompression, while seven of 14 (50%) (p = 0.001) type II patients without preoperative primary-position diplopia had primary diplopia postoperatively. Of 12 type II patients who had preoperative primary-position diplopia, esotropia increased by an average of 12.4 diopters postoperatively. Vertical deviation increased an average of 13.4 diopters for 10 patients who underwent unilateral two-wall decompression. The likelihood of new or worsening diplopia in all type II patients following decompression was 22 of 36 (61%). We conclude that adverse motility change following two-wall orbital decompression is rare in type I disease patients, but it occurs 61% of the time in type II disease patients. Predicting preoperatively which patients are likely to develop adverse motility change and diplopia may help clarify indications and risks of orbital decompression surgery in patients with ophthalmic Graves' disease.