Efforts to improve the surgical outcome for exotropia and investigation of the insertion locations of the extraocular muscles.

Abstract

In our previous retrospective study, we found that using the strabismus surgery dosages established by western strabismus mentors tends to result in undercorrection of Taiwanese exotropia (XT) patients compared with those in western populations. We also discovered that the location of extraocular muscle (EOM) insertion could vary by ethnicity. In this study, using a generalized estimation equation model, we compared the XT surgery outcome between augmented and original strabismus surgery dosages in Taiwanese patients. We also conducted an observational study to investigate the horizontal EOM insertion location in a Taiwanese population and compared the data with Dr. Apt L.'s study. For Taiwanese XT patients, augmented surgical dosages resulted in significantly better outcome at 6 months and 1 year postoperatively compared with original surgical dosages (p = 0.003 and p < 0.001, respectively). The distance from the lateral recuts muscle (LR) insertion location to the limbus was significantly shorter in Taiwanese than in white Americans (6.5 vs. 6.9 mm, respectively, p = 0.0001). Furthermore, the medial rectus muscle and LR insertion locations differed significantly between males and females (p < 0.001 and p = 0.023, respectively). The patients' sex did not affect the surgery outcome. Augmented surgery doses modified from western strabismus mentors produce better surgery outcome for Taiwanese XT patients. Surgeons may require country-specific guidelines for strabismus surgery dosage. We also demonstrated a simple method for young ophthalmologists to establish their own normograms to improve their surgical success rate. Our study confirms that LR insertion locations differ between Taiwanese and White Americans.