Impact of oblique muscle surgery on primary position alignment in alphabetic pattern strabismus with a focus on inferior oblique resection technique

To evaluate the safety and efficacy of inferior oblique (IO) resection for A-pattern strabismus, and to determine the impact of combined oblique and horizontal surgery (four-muscle surgery) on primary position horizontal alignment in pediatric patients with A- or V-patterns compared to standard horizontal surgery (two-muscle surgery).

We retrospectively analysed 249 children (3-18 years) with esotropia or exotropia and an A- or V-pattern who underwent either horizontal-only surgery (n = 115) or combined horizontal rectus plus graded inferior oblique recession/resection (n = 134). Six-month outcomes were compared after propensity-score matching (PSM). We also detail the technique of inferior oblique resection for A-patterns.

Combined four-muscle surgery resulted in significantly greater pattern collapse for both A- and V-patterns (p < 0.001) compared to horizontal surgery alone. After propensity-score matching, the addition of inferior oblique resection in A-pattern patients did not significantly alter horizontal alignment improvement, confirming the stability of the procedure in the primary position. Conversely, in V-pattern cases, the four-muscle approach led to significantly greater horizontal correction (p = 0.034 and p = 0.046). Pattern inversion was rare (< 3%) and no major complications occurred.

Inferior oblique resection proved to be a safe, dose-dependent, and reproducible technique for A-pattern strabismus, challenging its historical reputation for unpredictability. Overall, a single-stage, four-muscle approach corrects alphabetic patterns more effectively than horizontal surgery alone while maintaining non-inferior primary position alignment. Single stage surgery with four-muscle approach may reduce the need for reoperation, nevertheless prospective data are needed.