ABSTRACT
PURPOSE: To report a patient with absence of the superior oblique (SO) muscle of the left eye, who showed improvement after anterior and nasal transposition of the inferior oblique muscle for left hyperdeviation and right head tilt. CASE SUMMARY: A two-year-old boy presented with hypertropia of the left eye and right head tilt. Alternate prism-cover test in the primary position demonstrated 18 prism diopters (PD) of left hypertropia, which increased to 35 PD in the left head tilt position. A version test demonstrated overaction of the left inferior oblique muscle and underaction of the left superior oblique muscle. As an orbit CT scan showed absence of the SO muscle, the patient was diagnosed with congenital absence of SO and left anterior and nasal transposition of the inferior oblique muscle was performed. Three weeks after surgery, the patient presented with orthotropia at distant and near. The version test revealed normal oblique muscles. There was no vertical deviation shown on the Bielschowsky head tilt test. The abnormal head posturing was no longer observed. CONCLUSIONS: The authorsreport a patient manifesting abnormal head posture and hypertropia, diagnosed with absence of SO muscle, which was successfully corrected using anterior and nasal transposition of the inferior oblique muscle.