S-BLR Versus C-BLR for CI-IXT in Children (SCCIXT)

Slanted Bilateral Lateral Rectus Recession Versus Conventional Bilateral Lateral Rectus Recession for Convergence Insufficiency Intermittent Exotropia in Children

Children's Hospital of Fudan University, Shandong Provincial Hospital, Shanxi Eye Hospital, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Tianjin Eye Hospital, Renmin Hospital of Wuhan University, Second Affiliated Hospital, School of Medicine, Zhejiang University

This is a multi-center, randomized double-blind controlled trial to compare the effectiveness of S-BLR with C-BLR for the treatment of CI-IXT in children. Specific Aim 1 (Primary): To compare the surgical successful rate of S-BLR with C-BLR for the treatment of CI-IXT in children. Specific Aim 2 (Secondary): To study the suboptimal surgical outcomes between S-BLR and C-BLR for the treatment of CI-IXT in children.

Using conventional surgical procedures, higher postoperative near undercorrection and/or distant overcorrection rates were observed in CI-IXT. To achieve better outcome, S-BLR was introduced. Previous studies showed its efficacy in reducing near exodeviation, distant exodeviation, and NDD. So far, only limited studies have directly evaluated the surgical outcomes between S-BLR and C-BLR. The pilot study done by Snir et al included 12 patients with S-BLR and 6 patients with C-BLR and the success rates of S-BLR vs C-BLR were 92% vs 0 at one-year follow-up. The retrospective study done by Song et al included 17 patients undergoing S-BLR and 14 patients undergoing C-BLR. With stricter successful criteria, the success rates of S-BLR vs C-BLR were 35% vs 7% at six-month follow-up. A large randomized trial is needed to compare the surgical successful rate and suboptimal surgical outcomes of S-BLR with C-BLR in children with CI-IXT. The proposed trial will be conducted in 8 different study sites working in the field of pediatric ophthalmology and strabismus.Each site will have one certified surgeon to do all surgeries. Under general anesthesia, the LR recession is performed using an inferior-temporal fornix incision. For S-BLR, the lower horn of the LR is recessed based on near exodeviation and the upper horn is recessed based on distant exodeviation. For C-BLR, the LR is recessed based on distant exodeviation. Surgical dose is according to the largest preoperative exodeviation at distance (6 meters) or near (1/3 meter) by the prism and alternate cover test(PACT). The extent of the recession is based on Parks' surgical dosage schedule.

For S-BLR, the lower horn of the LR is recessed based on near exodeviation and the upper horn is recessed based on distant exodeviation.

Surgical successful cases/total cases. The successful criterion is a postoperative residual deviation at near and distance between 10 PD of exophoria/tropia and 5 PD of esophoria/tropia with near-distance difference <10 PD.

suboptimal surgical cases/total cases. Suboptimal surgical outcomes include: undercorrection, overcorrection, diplopia, torsional deviation, A-V pattern, abduction limitation and reoperation.

Inclusion Criteria: CI-IXT (at least 15 PD of exodeviation at distance by the prism and alternate cover test (PACT) with appropriate optical correction; ≥10 PD greater exodeviation at near than at distance after 40-minute monocular patching); age from 5 to 12 years at the time of surgery; best-corrected visual acuity (BCVA) in the worse eye 20/40 or better and interocular visual acuity difference of less than 2 lines; Exclusion Criteria: with histories of strabismus surgery or botulinum toxin injection; coexisting vertical deviation greater than 5PD (oblique muscle dysfunction; torsional strabismus; DVD; A-V pattern); restrictive or paralytic strabismus; lateral incomitance; ocular disease other than strabismus or refractive error; craniofacial malformations affecting the orbits; significant neurological disorders

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