A Stratified Surgical Approach for Convergence Insufficiency-Type Exotropia Based on Near Deviation Magnitude: A Retrospective Cohort Study of Motor and Sensory Outcomes.

OBJECTIVE

To evaluate the efficacy and safety of a stratified surgical strategy for convergence insufficiency-type exotropia (CIX(T)) tailored to the magnitude of near deviation, with a primary outcome of postoperative motor success (orthophoria) and a secondary outcome of stereopsis improvement.

METHODS

This retrospective cohort study included 85 CIX(T) patients (near deviation ≥ distance deviation by 15Δ) treated between July 2015 and June 2022. Patients were stratified into three groups based on near deviation magnitude. Group 1 (n=15, <30Δ) underwent unilateral medial rectus resection; Group 2 (n=38, 30-80Δ) received unilateral lateral rectus recession combined with medial rectus resection; Group 3 (n=32, 85-130Δ) underwent bilateral lateral rectus recession plus unilateral medial rectus resection. Ocular alignment (prism cover test) and stereopsis (Titmus test) were assessed preoperatively, at 1 week (short-term), and 3 months (intermediate-term) postoperatively.

RESULTS

Baseline characteristics were comparable across groups, except for the stratification variable of near deviation. At the 3-month follow-up, motor success was achieved in 20.0% of Group 1, 89.5% of Group 2, and 87.5% of Group 3. Group 1 showed a high rate of undercorrection (80.0%), whereas Groups 2 and 3 demonstrated stable alignment with minimal undercorrection (10.5% and 9.4%, respectively). Stereopsis scores significantly improved from preoperative levels in Group 2 (P<0.001) and Group 3 (P<0.001), but regressed in Group 1 (P>0.05). A planned slight initial overcorrection (10-15Δ) at distance was significantly correlated with better intermediate-term alignment (r = 0.68, 95% CI: 0.51 to 0.80, P<0.001).

CONCLUSION

These findings support a stratified surgical approach for CIX(T) based on near deviation magnitude. While combined recession-resection procedures are effective for moderate-to-large angle deviations, unilateral medial rectus resection for small-angle CIX(T) resulted in high rates of undercorrection. This suggests that the surgical plan for small-angle CIX(T) may require more aggressive dosages or alternative strategies.