[Clinical observation of bow-tie adjustable suture technique for overcorrection in intermittent exotropia]

Objective: To investigate the clinical effects of the bow-tie adjustable suture technique in managing overcorrection in patients with intermittent exotropia after surgery. Methods: This was a retrospective case series study. Clinical data were collected from children with intermittent exotropia who underwent strabismus correction surgery, including the bow-tie adjustable suture technique and conventional techniques, at the Department of Strabismus and Pediatric Ophthalmology, Shanxi Eye Hospital, from January 2020 to September 2021. Children with postoperative esodeviation≥15 prism diopters (PD) within the first 6 days were treated differently based on the surgical technique and their individual conditions, including suture adjustment and conservative treatment. The overcorrection rate and its changes among different surgical groups, the recovery of ocular alignment and binocular visual function after different treatment methods in children with overcorrection on the sixth postoperative day, and the postoperative complications in different surgical groups were observed. Statistical analysis was performed using independent samples t-test, Wilcoxon rank-sum test, repeated-measures analysis of variance, Bonferroni test, chi-square test, or Fisher's exact probability test, as appropriate. Results: A total of 643 children who underwent intermittent exotropia correction surgery were included in the study. Among them, 325 children underwent the bow-tie adjustable suture technique, with 185 males and 140 females, and the mean age was (9.50±2.69) years. The remaining 318 children underwent conventional techniques, with 176 males and 142 females, and the mean age was (9.90±2.67) years. There were no statistically significant differences in age and gender distribution between the two surgical groups (all P>0.05). On the first postoperative day, among children who underwent the bow-tie adjustable suture technique, 40 had an esodeviation of≥10 PD, resulting in an overcorrection rate of 12.3% (40/325), while among children who underwent conventional techniques, 32 had an esodeviation of≥10 PD, resulting in an overcorrection rate of 10.1% (32/318). On the sixth postoperative day, these rates decreased to 5.5% (18/325) and 3.1% (10/318) in the two groups, respectively. At 1, 6, and 12 months postoperatively, the overcorrection rate in children who underwent the bow-tie adjustable suture technique was 0, while in children who underwent conventional techniques, the overcorrection rate did not show a significant decrease compared to before surgery. The differences between the two surgical groups were statistically significant (all P<0.05). On the sixth postoperative day, among children with an esodeviation of≥15 PD, 13 underwent suture adjustment and 7 received conservative treatment. The results of repeated-measures analysis of variance showed statistically significant differences in near and distance esodeviation angles among children who received different treatment methods (F=145.20, 106.87, both P<0.001), as well as statistically significant differences in near and distance esodeviation angles at different time points within each group of children (F=81.67, 35.09, both P<0.001). There were also significant differences in the trends of change in near and distance esodeviation angles at different time points among children who received different treatment methods (F=79.90, 36.73, both P<0.001). Further pairwise comparisons showed significant differences in near and distance esodeviation angles between the sixth postoperative day and 1, 6, and 12 months postoperatively in children who underwent suture adjustment (all P<0.05), while no statistically significant differences were observed in children who received conservative treatment (all P>0.05). At 12 months postoperatively, among the 13 children who underwent suture adjustment, 12 achieved stereopsis, while among the 7 children who received conservative treatment, all became stereo-blind after removing the prismatic correction. No serious complications occurred in any of the children postoperatively. Conclusion: The proportion of children with intermittent exotropia who achieved orthotropic alignment one year after surgery was relatively low among those who had an overcorrection of≥15 PD on the sixth postoperative day. The bow-tie adjustable suture technique is a simple and effective approach for managing overcorrection in patients with intermittent exotropia. Adjusting the sutures on the sixth postoperative day can reduce the overcorrection rate and is considered a safe and effective method.