The Effect of Modified Anterior Transposition of the Inferior Oblique Muscle

ABSTRACT

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.