How often does the contralateral inferior oblique muscle need to be weakened after a unilateral inferior oblique muscle weakening procedure?

Abstract

Introduction: It has been suggested that if surgery is planned to weaken one inferior oblique muscle, in certain cases, consideration should be given for bilateral surgery as the other inferior oblique will often need correction in the future. Purpose: To determine the frequency of contralateral inferior oblique weakening surgery following a unilateral inferior weakening procedure. Methods: A retrospective analysis of the records of 376 patients, who had unilateral inferior oblique muscle surgery between 1984 and 2005. Results: Two hundred six patients had hypertropia alone with a unilateral inferior oblique muscle overaction and 170 patients had an associated horizontal deviation. Seven percent of all patients (n = 26) required second weakening surgery of the contralateral inferior oblique. The rate for reoperation was higher in patients with esotropia (12.6%) compared with patients with exotropia (5.5%) and only hypertropia (5.3%). The average time interval between the first and second surgeries was 17 months. In six patients (2%) the previously operated muscle had to be reweakened. Discussion: Only 11 of 206 patients with hypertropia that had a weakening procedure of the inferior oblique muscle needed surgery of the contralateral inferior oblique muscle. The need for second surgery was also relatively low in patients with exotropia, and it was slightly higher in patients with esotropia. Conclusions: Single inferior oblique muscle-weakening procedures is effective in the vast majority of patients and the need for weakening the contralateral inferior oblique is low.