Superior oblique weakening as an adjunct to vertical rectus surgery for severe chin-up posture in infantile nystagmus: a case series

Abstract Background Severe chin-up abnormal head posture (AHP) associated with infantile nystagmus (IN) is an uncommon and challenging surgical problem. Correction may require extensive vertical rectus surgery, with potential risks of postoperative motility disturbances, including torsional imbalance and alphabet-pattern deviations. The role of superior oblique (SO) weakening as an adjunct to extensive vertical rectus surgery in severe cases remains incompletely characterized. We describe the clinical outcomes of this combined surgical approach in children with severe chin-up AHP associated with IN. Methods We retrospectively reviewed three children with IN, a downgaze null point, and severe chin-up AHP (≥ 30°) who underwent individualized strabismus surgery combining extensive vertical rectus procedures with bilateral SO weakening. Preoperative and postoperative chin-up posture was assessed from standardized clinical photographs. Clinical characteristics, surgical procedures and dosages, ocular alignment in primary gaze, visual acuity, residual AHP, and postoperative alphabet-pattern or clinically evident torsional abnormalities were evaluated. Results Three patients underwent surgery at a mean age of 6.3 years. Preoperative chin-up posture ranged from 35° to 60°, with a mean of 47°. At postoperative assessment, mean chin-up posture decreased to 7°, representing an approximately 85% reduction. All three patients achieved complete correction of the chin-up posture at final assessment. One patient required staged surgery because of residual AHP after the initial procedure. No clinically evident postoperative alphabet-pattern deviation, symptomatic torsional imbalance, or deterioration of primary-gaze alignment was observed. Visual acuity remained unchanged in the two patients with reliable quantitative measurements. Conclusions In this small retrospective case series, bilateral SO weakening combined with extensive vertical rectus surgery was associated with substantial improvement of severe chin-up AHP in children with IN. The independent contribution of SO weakening cannot be determined from this combined surgical approach; however, these findings support its consideration as an adjunctive component of individualized surgery in selected patients with severe vertical AHP, emphasizing the need for objective torsional assessment and longer follow-up.