Evaluation of superior rectus muscle attachment following hang-back recession in rabbit eyes.

PURPOSE The hang-back suture technique has been advocated to decrease the risk of scleral perforation during strabismus surgery. In this study, we evaluated the muscle insertion site in rabbits 4 weeks after a hang-back recession was performed. METHODS Twenty-five eyes of 13 rabbits underwent hang-back recessions of between 5 and 8 mm of the superior rectus muscle. Four weeks later, the attachment sites were examined. RESULTS Four weeks following the surgery, 14 muscles (n=25, 56%) were anteriorly displaced. In the 5 mm recession group, one muscle was anteriorly displaced (n=7, 14.3%). In the 6 mm recession group, 50% of the muscles recessed were displaced anteriorly (n=8). The 7 mm hang-back recession group demonstrated forward displacement in five muscles operated (n=6, 83%) and in the 8 mm recession group, all four muscles (100%) were anteriorly displaced. The magnitude of displacement was positively correlated to the amount of the hang-back recession performed (Pearson correlation p<0.001). CONCLUSIONS Anterior displacement of muscles using the hang-back technique in the rabbit eye is unacceptably high and occurred in 56% of the cases. A positive, statistically significant correlation exists between the amount of recession performed and the number of muscles displaced from their new insertion. Therefore, when performing large recessions using the hang-back technique displacement should be anticipated.