Selective Compartmental Plication in Small-Angle Convergence Insufficiency Exotropia: Surgical Outcomes and Predictive Model

Purpose This study aimed to evaluate a novel surgical approach combining lateral rectus recession (LRc) with compartmentalized inferior medial rectus plication (CIMRP) for treating small-angle (< 25 prism diopters, PD) convergence insufficiency intermittent exotropia (CI-IXT) in pediatric patients. Methods A retrospective analysis was conducted on 69 pediatric CI-IXT patients (mean age: 8.13 ± 2.46 years) who underwent LRc and CIMRP between September 2022 and January 2024 at Tianjin Eye Hospital. Outcomes including near and distance deviations, near-distance difference (NDD), control scores, stereopsis, and complications were assessed preoperatively and postoperatively at 1 day, 2 months, 6 months, and final follow-up (≥ 12 months). Results The mean LRc amount was 7.08 ± 0.48 mm (range: 6.5–7.5 mm), and the mean CIMRP amount was 3.56 ± 0.39 mm (range: 3.0–4.0 mm).Significant reductions were observed in near exo-deviation (median: −30 [− 32, − 28] PD to − 12 [− 16, − 6] PD), distance deviation (− 20 [− 20, − 18] PD to − 6 [− 10, − 1] PD), and NDD (10 [10, 10] PD to 4 [4, 6] PD; all P  < 0.001). Linear regression analysis established a quantitative relationship between the amount of CIMRP and postoperative corrected NDD: Y (Postoperative corrected NDD) = 5.973 × X (amount of CIMRP in mm) − 12.48 ( P  < 0.0001), indicating that each 1 mm increase in plication amount was associated with an average increase of approximately 5.97 PD in NDD correction. The surgical success rate was 88.41% at both 2 and 6 months, decreasing slightly to 81.16% at the final follow-up. The overcorrection rate peaked at 8.7% at 2 months and subsequently stabilized at 2.9%, whereas the undercorrection rate gradually increased to 15.9%. Control scores and near stereoacuity improved significantly after surgery compared with preoperative values ( P  < 0.001 and P  < 0.05, respectively). Conclusion LRc combined with CIMRP is an effective and safe approach for small angle CI-IXT(< 25PD). We recommend CIMRP of ≥ 3.5 mm for preoperative NDD > 10 PD based on the established dose-response model. While this targeted technique addresses convergence insufficiency with favorable outcomes, further comparative studies are needed to define its clinical role.