Inferior Oblique Muscle Overaction: Clinical Features and Surgical Management

PURPOSE: To further define the clinical features of patients with inferior oblique muscle overaction (IOOA) and evaluate the surgical results in a subgroup of these patients. METHODS: The medical records of 173 patients who underwent inferior oblique muscle (IO) weakening surgery due to primary or secondary IOOA were retrospectively reviewed. The patients were assigned a surgical group based on severity of IOOA and presence of dissociated vertical deviation (DVD) or hypertropia. Patients with +1 or +2 IOOA underwent recession, patients with +3 or +4 IOOA underwent myectomy, and patients with any grade of IOOA and DVD or hypertropia underwent anterior transposition (AT) surgery. RESULTS: A total of 286 eyes of 173 patients who underwent surgery due to IOOA were included in the study. IOOA was accompanied by esotropia, exotropia, abnormal head posture (AHP), pattern strabismus, convergence insufficiency, DVD, facial asymmetry, and nystagmus. The most common comorbid disorder was esotropia. The recession was used in 173 eyes, myectomy in 64, and AT in 49. Surgical success was obtained in 96.0% of eyes that underwent recession, in 98.4% of eyes that underwent myectomy, and in 93.9% of eyes that underwent AT. In the follow-up, IOOA occurred in the fellow eye in 36.1% of patients who underwent unilateral surgery. CONCLUSIONS: This study is a comprehensive report on the concomitants of the IOOA. Also, it showed that all of the three surgical procedures including recession, myectomy, and AT are effective in the surgical management of IOOA when performed in select patient groups.