Adhesion after Y-split procedure can affect its mechanism for treating overshoots in Duane’s syndrome

Purpose: To investigate the extent of adhesion and changes in the Y configuration after the Y-split procedure, compared with the posterior fixation suture. Methods: Twelve New Zealand white rabbits were included in the study. The 10-mm Y-split procedure was performed in the superior rectus muscle (SR) of one eye, and the 10-mm posterior fixation suture was made in the SR of the other eye. Six weeks after surgery, the Y arm lengths and lengths of adherence to the sclera were measured. If the adhesion involved the whole Y arm, the distance between the original SR insertion and most proximal part of the adhered SR was measured. In the eyes with posterior fixation suture, the distance between the SR insertion and most proximal part of the adhered SR was evaluated. Results: The average nasal and temporal Y arm lengths were 6.37 ± 0.65 and 6.54 ± 0.63 mm, respectively, a significant decrease from those measured immediately after surgery (P = 0.002 and 0.002, respectively). Adhesions involved the entire Y arms in 11 of 12 SRs (91.7%), with an average adhesion length of 7.01 ± 1.04 mm. In SRs with posterior fixation sutures, the average adhesion was 9.18 ± 0.62 mm from the insertion, which was only 2.17 mm posterior to proximal portion of adhesion in Y-split SR (P < 0.001). Conclusions: Healing process reduces the Y arm length. Adhesion may involve the entire Y arm and could weaken or alter the therapeutic mechanism after the Y-split procedure.