Results of anterior transposition of the inferior oblique muscle in incomitant dissociated vertical deviation.

Objective: Recession with anterior transposition of the inferior oblique muscle has been shown to effectively decrease dissociated vertical deviation in primary position. However, studies to date have not addressed the long-term postoperative results with respect to residual deviation in lateral gaze, development of A-pattern strabismus, and the effect of the procedure on upgaze.

Methods: Twenty-three eyes in 12 patients were treated with recession with anterior transposition of the inferior oblique muscle for dissociated vertical deviation greater in adduction than in abduction (termed incomitant dissociated vertical deviation) associated with inferior oblique muscle overaction. Before the operation, dissociated vertical deviation was measured in primary position and lateral gaze, oblique muscle dysfunction was graded, and A or V patterns were measured. Similar measurements were made after the operation. All patients have been followed up for a minimum of 4 years after the operation.

Results: Recession with anterior transposition of the inferior oblique muscle effectively eliminated the dissociated vertical deviation in primary position and in adduction. The operation was less effective in reducing small amounts of dissociated vertical deviation in abduction. No significant A patterns developed after the operation. Postoperative inferior oblique muscle function ranged from -1 underaction to +2 overaction, and postoperative upgaze in abduction was normal to mildly deficient.

Conclusions: Recession with anterior transposition of the inferior oblique muscle results in long-term improvement of incomitant dissociated vertical deviation, with a low incidence of late development of A patterns and upgaze deficiency.