Medial rectus insertion site in congenital esotropia.

Because of the clinical observation that in patients with congenital esotropia the medial rectus is inserted closer to the limbus than we have classically been taught, the distance between the medial rectus insertion site and the limbus was measured at the time of corrective surgery in 26 infants under 1 year of age with congenital esotropia. The distance in the 52 eyes was found to vary between 3.0 and 5.5 mm (mean 4.5 mm; standard deviation 0.57 mm). Of the 25 patients available for follow-up assessment 8 required another operation because of a residual esodeviation greater than 10 prism diopters, yet in some of the 8 a maximum recession of the muscle (6 mm from the insertion site) had been done. It is proposed that the maximum recession be increased to 11.5 mm from the limbus. This might reduce the risk of undercorrection, especially in patients with an esodeviation above 70 prism diopters. Further studies need to be done to evaluate the normal insertion sites of the extraocular muscles in the different pediatric age groups.