METHODS: Fifteen patients with IR muscle palsy further presenting with abnormal compensatory head posture of facial rotation were retrospectively identified from May 2014 to July 2018. Changes in the degree of facial rotation in patients were evaluated using an orthopedic goniasmometer. Variations in vertical and horizontal deviations were measured through prism and alternate cover tests, and changes in cyclotropia of pre- and postoperation were assessed by objective evaluation of eye torsion with fundus photography. IR resection was the main surgical treatment.

RESULTS: Among the 15 patients, 13 who were subjected to IR muscle resection or IR muscle resection combined with superior rectus muscle recession showed good results after surgery. These results included improved underaction of IR, coordination of eye movement, disappearance of abnormal facial rotation of compensatory head position, and total correction of vertical and horizontal deviation and cyclodeviation. Furthermore, each 1 mm resection of IR can correct 1.54±0.93° incyclotropia. In the other two patients with small vertical deviation who were done by inferior oblique myectomy, the improvement in facial rotation was unsatisfied, and eye motion remained uncoordinated.

CONCLUSION: Congenital isolated IR muscle palsy characterized by compensatory head posture of facial rotation is the main compensatory head posture. The resection of IR is effective and perfect. Mild overcorrection and undercorrection do not influence curative effect.