Confirmed: there is no correlation between the insertional distance between the nasal limbus and the insertion of the medial rectus muscle--and the size of the strabismus angle in infantile esotropia.

Introduction: Historical systems of measuring the amount of surgical recession of the medial rectus muscles appropriate to be performed for a given size of angle of infantile esotropia, based upon relative recession measurement from the limbus might have proven to be better than relative recession measurement from the insertion--if a positive correlation were found between the size of the angle of the esodeviation and the distance between the insertion of the medial rectus and the nasal limbus. A search of the scientific literature since 1966 as listed in PubMed (National Library of Medicine, formerly Index Medicus) did not reveal any additional confirmatory study of this type in PubMed. We therefore undertook to perform such a study.

Methods: Using standard strabismus calipers, at surgery for esotropia, intraoperative measurements were made of the insertional distance (in mm between the most nasal point of the clear cornea and, following standard surgical excision of the muscle from the globe, the anterior insertional ridge of the medial rectus muscle of the eye) in a series of 104 consecutive infantile esotropes operated by the author between 1987 and 1991. These data were then graphically plotted as the ordinate with the abscissa defined as the size of the angle of the esotropia measured with the prism alternate cover test the day prior to surgery.

Results: No correlation was found between the medial rectus muscle insertional distance and the size of the preoperative esodeviation in prism diopters, correlation coefficient r=0.14, p=0.078. DISCUSSION OF RESULTS: In this large series, the lack of a correlation has credibility as it fails to achieve conventional limits of a "statistical significance" of the difference.

Conclusion: The lack of correlation between the size of the deviation and the insertional distance offers support for the widespread acceptance and use of the alternative, the dose-response curves based on the mm of recession measured from the anterior ridge of the medial rectus muscle insertion.