Novel Inferior Oblique Muscle Y Splitting Procedure to Minimize the Anti-Elevation Syndrome: A Pilot Study

Purpose: To describe novel Y splitting procedure of inferior oblique muscle to mitigate the anti-elevation syndrome. Methods: A pilot, prospective interventional study was undertaken to assess the effect of inferior oblique muscle Y-splitting in patients with unilateral 3+ or more overaction. To correct primary gaze hypertropia and the excyclotorsion, a Y-splitting procedure was performed (along with routine horizontal muscle surgery as per the deviation) in 14 subjects. The effect of surgery was assessed at baseline and at 6 months post-intervention. Results: The mean age of 14 subjects was 25.14[+ or -]7.70 years. The mean pre-operative hypertropia, excyclotorsion and inferior oblique muscle over-action was 18.42[+ or -]3.50 PD, 14.14[+ or -]2.65 degrees, and +3.21[+ or -]0.42 respectively. Following surgery, this was reduced to 1.57 [+ or -]1.74 PD of residual hypertropia (a net correction of 16.85[+ or -]2.31 PD, p = 0.005), 3.85 [+ or -]1.46 degrees of residual excyclotorsion (a net correction of 10.28[+ or -]1.72 degrees, p < 0.05), and +0.28[+ or -]0.46 of residual inferior oblique over-action (a net correction ~+3) at the end of 6 months. Amongst fourteen patients, three patients still experienced residual/variable anti-elevation effect, and during the study period none of them experienced any adverse event and none of them required any additional surgeries. Conclusion: While anteriorizing the inferior oblique muscle to correct primary gaze hypertropia and the excyclotorsion, a novel "Y splitting" procedure can be followed to achieve the desired results with mitigated anti-elevation effect. Keywords: inferior oblique muscle surgery, anti-elevation syndrome, Y-splitting of the inferior oblique