The Study of Axial Length and Functional Equator in Strabismus Surgery

ABSTRACT

PURPOSE: We are to know the distribution of the axial lengths and functional equators in strabismus patients and to establish surgical formula considering axial lengths in addition to the preoperative deviation angle. METHODS: Included were 100 eyes of 50 strabismus children under 12 years old who do not have other organic disorders and received strabismus surgery under general anesthesia. We measured axial lengths and calculated functional equators. RESULTS: Mean value of axial length was 22.01 +/- 0.97 mm. The distances from limbus to the functional equators of medial and lateral rectus muscles were 11.35 +/- 0.67 mm and 18.48 +/- 0.94 mm each and direct distance for that were 10.86 +/- 0.62 mm and 16.40 +/- 0.79 mm. CONCLUSIONS: By the conventional amount of both medial rectus muscle recession in esotropia patient, the recession for the preoperative deviation angle of 40 prism diopter locates medial rectus muscle at the functional equator. So taking both axial length and preoperative deviation angle into account, we proposed new surgical formula for esotropia as follows. For the preoperative deviation angle of 40 prism diopter, we are to recess both medial rectus muscles to the functional equator calculated by axial length and for the preoperative deviation angle smaller or larger than 40 prism diopter, recess to the site anterior or posterior to the functional equator proportionally.