Restriction of elevation in abduction after inferior oblique anteriorization

Abstract Purpose: Inferior oblique anteriorization is gaining popularity for the treatment of dissociated vertical divergence associated with inferior oblique overaction. This procedure is based on the theorythat moving the insertion of the inferior oblique muscle anterior to the equator changes its vector of force from one of elevation to one that opposes elevation. The purpose of this investigation is to describe, investigate the cause, and outline treatment for a complication I observed after inferior oblique anteriorization. This postoperative syndrome consists of a motility pattern that resembles marked residual inferior oblique overaction associated with a Y or V pattern. It is probably caused by a restriction of elevation of the abducting eye causing fixation duress, with a resultant upshoot of the contralateral adducting eye. Methods: A retrospective chart review was conducted for all patients on whom I performed bilateral inferior oblique anteriorization for inferior oblique overaction associated with dissociated vertical divergence. Patients in whom this postoperative syndrome developed were compared with those in whom it did not with respect to type and extent of surgery. In addition, cases of patients I treated or examined for this complication but whose inferior oblique anteriorization had been performed by other ophthalmologists were also analyzed. Results: I performed bilateral inferior oblique anteriorization in 77 patients. In 29 patients the inferior oblique muscles were placed level with the insertions of the inferior rectus muscles, in 31 patients they were placed 1 mm anterior to the insertions of the inferior rectus muscles, and in 17 patients they were placed 2 mm anterior. The postoperative syndrome described here developed in two of the 77 patients; both had the inferior oblique muscles placed 2 mm anterior to the insertions of the inferior rectus muscle. These were also the only two patients in this series in whom the new insertion of the inferior oblique muscle was spread out laterally at the time of anteriorization. I have seen an additional six patients in whom this syndrome developed after undergoing operations by other ophthalmologists. In four, the inferior oblique muscles were placed 2 mm anterior to the insertions of the inferior rectus muscles, and in two they were placed 3 mm anterior. Of the eight patients I have observed with this complication, I reoperated on six. The surgical procedure consisted of denervation or extirpation of both inferior oblique muscles in four patients and conversion to standard recessions of the inferior oblique muscles in two patients. In all six patients,the versions were markedly improved and the Y or V pattern was eliminated after reoperation. Conclusions: Anteriorization of the inferior oblique muscles more than 1 mm anterior to the insertions of the inferior rectus muscle may cause a limitation of elevation in abduction, resulting in a Y or V pattern that mimics inferior oblique overaction. This may be more likely to occur if the new insertions of the inferior oblique muscles are spread out laterally at the time of anteriorization.