The Effect of Modified Anterior Transposition of the Inferior Oblique Muscle for Hypertropia in Superior Oblique Muscle Palsy with Inferior Oblique Muscle Overaction

PURPOSE: The authers studied the effect of modified anterior transposition of the inferior oblique muscle for hypertropia in superior oblique muscle palsy combined inferior oblique muscle overaction. METHODS: We retrospectively analysed 19 cases of superor oblique palsy, which were treated by modified inferior oblique muscle anterior transposition from January 1999 to march 2001. Mean follow-up was 14.6 months. The medial portion of inferior oblique muscle was transpositioned to 1mm posterior position of the temporal insertion of inferior rectus muscle and lateral portion of inferior oblique muscle was moved 5mm on imaginary line, which is the line of between temporal insertion of inferior rectus and inferior insertion of lareral rectus muscle, to the direction of inferior insertion of lateral rectus muscle from temporal insertion of inferior rectus muscle, then backward 6mm from that point perpendicularly. RESULTS: The success rates in modified anterior transposition were 94% in under 20delta of hypertropia and 89.5% in over +3 of IOOA. CONCLUSIONS: Modified anterior transposition is an effective procedure of +3 to +4 inferior oblique muscle overaction and hypertropia in superior oblique muscle palsy as a primary surgery.

The Effect of Modified Anterior Transposition of the Inferior Oblique Muscle

Anterior transposition of inferior oblique muscle(ATIO) is known to an effective procedure for correcting marked overaction of inferior oblique muscle. However, depression in abduction and elevation deficiency in primary and abduction positions have occurred without adherence syndrome after this procedure. To avoid these complications, the author modiffied ATIO by transposing only the anterior portion of inferior oblique muscle at 2mm anterior to the temporal insertion site of inferior rectus, and placing the posterior portion of muscle just posterior to the insertion site of inferior rectus. Modified ATIO was performed in 4 cases of inferior oblique overaction(IOOA) with dissociated vertical deviation(DVD), 2 cases of unilateral IOOA withcontralateral superior oblique overaction(SOOA) and 5 cases of superior oblique palsy(SOP) Knapp class IV. They were observed for over 6 months (6~18 months). Three of 4 cases of IOOA with DVD were improved but adherence syndrome occurred in one case and depression in abduction occurred in another case. In 2 cases of unilateral IOOA with contralateral SOOA, hypertropia was decreased from 20delta and 2delta respectively, after the procedure. In 5 cases of SOP Knapp class IV, preoperative hypertropia was 20delta-40delta in primary position. After modified ATIO, hypertropia was 0delta-20delta . The correction effect was 12delta-35delta , with an average of 18.4delta in primary position. In 4 of 5 cases, hypertropia was corrected within 10delta in primary position. Modified ATIO is an effective procedure for unilateral IOOA with contralateral SOOA and SOP Knapp class IV as a single muscle surgery.