Modified Inferior Oblique Transposition Considering the Equator for Primary Inferior Oblique Overaction (IOOA) Associated with Dissociated Vertical Deviation (DVD)

Purpose: Inferior oblique anterior transposition (IOAT) should be done only in patients with inferior oblique overaction (IOOA) and dissociated vertical deviation (DVD) without fusional potential because the procedure can cause anti-elevation syndrome. This study reports the results of modified inferior oblique transposition onto the equator in 7 patients diagnosed with infantile exotropia or esotropia associated with IOOA and DVD. Methods: We performed modified inferior oblique (IO) transposition onto or considering the equator on 7 patients who had infantile exotropia or esotropia associated with IOOA and DVD. Five patients had infantile exotropia, and the other two patients had infantile esotropia. Six patients had undergone bilateral rectus Bilateral Lateral Rectus (BLR) or Bilateral Medial Rectus (BMR) - recession previously and one patient underwent BLR recession and IO transposition simultaneously. They had more than +1.5 IOOA with DVD in both eyes. IO was transposed vertically onto the equator in this study. The mean distance between the lateral border of the inferior rectus insertion and the equator was 5.6mm (range: 4.5 to 6.5 mm). Three months after the operation, degree of IOOA and DVD in each eye was evaluated. Results: IOOA and DVD were markedly reduced in all patients (+0.5 similar to+1 for IOOA postoperatively). Mild contralateral IOOA was noted but the motility disturbance was successfully corrected in all cases postoperatively. Conclusion: Bilateral IO transposition onto the equator could minimize antielevation and corrected IOOA and DVD successfully in patients with infantile exotropia or esotropia.