Evaluation of the effectiveness of anterior transposition of the inferior oblique muscle in dissociated vertical deviation with or without inferior oblique overaction

PURPOSE: Anterior transposition of the inferior oblique muscle (ATIO) has been reported to be an effective treatment for dissociated vertical deviation (DVD). In this study, we evaluated the effectiveness of this surgical procedure in patients with DVD alone and in those with DVD with concurrent overactive inferior oblique muscle and compared the results. METHODS: Nineteen eyes with DVD alone (group 1) and 15 eyes with DVD and concurrent inferior oblique overaction (group 2) underwent ATIO. The amount of DVD and inferior oblique overaction before and after the operation was measured and statistically analyzed. RESULTS: The average follow-up time for group 1 and group 2 was 9.4 and 9.0 months, respectively. Of a total of 34 eyes, 7 had DVD of more than 15 prism-diopters (pd) [four eyes from group 1 and three eyes from group 2] in which the residual DVD after surgery was more than 5 pd. However, in the 27 eyes with DVD of 15 pd or less (15 from group 1 and 12 from group 2), the residual DVD after the operation was less than 5 pd. (Fisher's exact test, P = .014). CONCLUSION: ATIO is an effective method for correcting DVD with and without inferior oblique overaction, especially in deviations of less than 15 pd.