Torsional diplopia after transantral orbital decompression and extraocular muscle surgery associated with Graves' orbitopathy

Graves' orbitopathy can be associated with horizontal, vertical, and torsional diplopia. Of 428 patients treated with transantral orbital decompression, 21 had incycloduction (mean, 12.8 degrees; range, 5 to 20 degrees) and five had excycloduction (mean, 12 degrees; range, 5 to 20 degrees). All 26 patients had had recessions of the medial or inferior rectus muscle (or both) before onset of torsional diplopia. Mean recession was 5.5 mm (range, 4 to 10 mm) and 5.3 mm (range, 2 to 10 mm) of medial rectus muscle and inferior rectus muscle, respectively. An A pattern was often associated with the condition. Superior oblique tenectomy and inferior oblique myectomy were performed most frequently for incycloduction and excycloduction, respectively. Superior oblique tenectomy induced a mean incycloduction decrease of 7.1 degrees (range, 0 to 12 degrees). Exotropia in downgaze was decreased, and a small ipsilateral hyperdeviation was induced. Bilateral inferior oblique myectomy in one patient decreased excycloduction 10 degrees without inducing new deviation. At follow-up (mean, 63.7 months) after last strabismus operation, 15 patients with incycloduction and two with excycloduction had no diplopia.