Selective compartmental plication in small-angle convergence insufficiency exotropia: surgical outcomes and predictive model

This study aimed to evaluate a novel surgical approach combining unilateral 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.

A retrospective analysis was conducted on 69 pediatric CI-IXT patients (mean age: 8.13 ± 2.46 years; range: 4-14 years) who underwent unilateral LRc and CIMRP between September 2022 and January 2024 at Tianjin Eye Hospital. All patients completed a minimum 12-month follow-up (mean: 12.41 ± 1.42 months; range: 12-18 months). 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 (12-18 months). Surgical success was defined as an exodeviation ≤ 10 PD or esodeviation ≤ + 5 PD in primary gaze at distance and near, and NDD ≤ 8 PD.

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, Friedman test).Simple linear regression identified an exploratory association between CIMRP amount and corrected NDD (defined as preoperative NDD minus postoperative NDD): Corrected NDD = 5.973 × CIMRP (mm) - 12.48 (P < 0.0001, R² = 0.2042). This indicates that each 1 mm increase in plication amount was associated with an average increase of approximately 5.97 PD in NDD correction within the observed 3.0-4.0 mm range. Surgical success was achieved in 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 (P < 0.001 and P < 0.05, respectively).

Unilateral LRc combined with CIMRP is an effective and safe approach for small angle CI-IXT (< 25 PD). Based on preliminary evidence from this exploratory analysis, we tentatively suggest CIMRP of ≥ 3.5 mm for preoperative NDD > 10 PD, pending prospective validation. While this targeted technique addresses convergence insufficiency with favorable outcomes, further comparative studies are needed to define its clinical role.