The medial rectus muscle insertion site in infantile esotropia.

The distance from the corneoscleral limbus to the insertion site of the medial rectus muscle was measured at several stages of medial rectus recession surgery in 20 patients (40 eyes) with infantile esotropia. Disinsertion of the medial rectus muscle resulted in a mean reduction in the distance from the muscle insertion site to the corneoscleral limbus of 0.903 mm (P less than .001), whereas the use of fixation forceps on the insertion to abduct the eye resulted in an additional mean reduction of 0.306 mm (P less than .01). The strabismus surgeon often uses the muscle insertion site as a reference point in determining the desired location for recessing a muscle. Our results suggest that this method of measurement is unreliable in infantile esotropia because the position of the medial rectus muscle insertion site varies considerably during surgery.