Asymmetric Bilateral Inferior Oblique Transposition of a Bilateral Inferior Oblique Overaction Associated with Dissociated Vertical Deviation

Abstract

Purpose: Inferior oblique overaction with a dissociated vertical deviation occurs secondary to infantile exotropia or esotropia. In terms of correction, asymmetric bilateral inferior oblique transposition has been the treatment of choice, but the surgical amount depended largely on the surgeon’s experience. We report successful bilateral inferior oblique transposition using our own standard methods.Methods: We performed a retrospective medical chart review of patients with bilateral inferior oblique overaction and dissociated vertical deviation who underwent bilateral inferior oblique transposition at the Korea University Medical Center from January 2013 to December 2020. We performed either symmetric or asymmetric transposition; the reattachment sites of the bilateral inferior obliques were determined according to preoperative differences of the inter-eye deviations of dissociated vertical deviation. When the differences were < 5 prism diopters, correction was considered successful. To avoid the development of anti- elevation syndrome, the inferior oblique muscles were re-attached near the equator.Results: Twenty-three patients were analyzed, all of whom underwent bilateral inferior oblique transposition; 12 required additional horizontal muscle surgery. The deviation difference (both eyes) and inferior oblique overaction grade were significantly lower postoperatively. We did not encounter any case of anti-elevation syndrome.Conclusions: The surgical extent of asymmetric bilateral inferior oblique transposition should reflect the difference in dissociated vertical deviation the two eyes.