Anterior Displacement of Muscle Insertion Site during Strabismus Surgery

ABSTRACT

PURPOSE: To study how far the insertion site of the extraocular muscle is displaced during strabismus surgery. METHODS: We studied 69 eyes of 36 patients for concomitant exodeviation. The distance between the center of the extraocular muscle insertion site and the nearest posterior limbus was measured before and after detaching the lateral rectus muscle. After fixating the insertion stump with forceps, the distance between the same points was measured. RESULTS: The distance between the limbus and the insertion site was measured as 6.54+/-0.65 mm before detaching the lateral rectus, 6.39+/-0.65 mm after detaching the muscle from the insertion, and 6.30+/-0.64 mm fixation of the insertion stump with forceps. Therefore, the muscle insertion site became displaced by 0.15+/-0.18 mm anteriorly from its original site after disinserting the muscle, and displaced anteriorly by a total of 0.25+/-0.22 mm after fixating the insertion stump with forceps. Differences in the distance at each stage were statistically significant (p<0.01, paired t-test). CONCLUSIONS: The insertion site of the lateral rectus muscle may be displaced anteriorly after disinserting the muscle and fixating the insertion stump with forceps. Therefore, the probability of error in strabismus surgery should be considered.