Surgical outcome of graded Harada-Ito procedure in the treatment of torsional diplopia ‒ a retrospective case study with long-term results.

To review and evaluate the surgical outcomes of the Fells-modified Harada-Ito procedure using a dosage scale approach with long-term follow up in patients with torsional diplopia. The records of patients who underwent the modified Harada-Ito procedure by the same surgeon during 2012-2019 were retrospectively reviewed regarding pre- and post-operative data and individual dose-scale used for the surgery. The modified Harada-Ito procedure involved advancing the anterior half of the superior oblique tendon toward the inferior edge of the lateral rectus muscle by a distance determined using a five-graded scale. A total of 27 patients (mean age 57.6 years, range, 22-81 years; 10 female) were included. Evaluating surgical outcome showed a significant difference in pre- to post-operative cyclodeviation (p = <0.001). Pre-operative mean extorsion was -10.4° and mean torsional correction achieved was 7.7°. The dose-effect relationship showed a wide spread effect, yet yielded a high success rate. All but two patients were symptom free from their torsional diplopia at the last post-operative evaluation, on average 24 months after surgery. Post-operative results and the dose-effect of the modified Harada-Ito corresponded with the aimed-for correction of torsional diplopia.. Fusion evaluation and individually based pre-operative assessments proved essential in determining individual doses for successful surgical outcomes.