Fate of donor sclera used to lengthen extraocular muscle in a rabbit model of strabismus surgery

Purpose To evaluate the fate of donor sclera used to elongate the superior rectus muscle in rabbit eyes. Donor sclera is sometimes used to further weaken an extraocular muscle in patients that have had previous strabismus surgery. The fate of the donor sclera is, at present, unknown and a question posed by many patients. Methods The superior rectus (SR) muscle was elongated with a 5 mm piece of donor sclera and examined at 1, 2, 4, 12 and 16 weeks postoperatively in a total of 20 rabbits. The SR muscles along with the attachment to the eye were collected, immediately frozen and later serially sectioned and processed for H&E and immunohistology. Multiple antibodies were used to detect the donor and bulbar sclera, as well as activation and proliferation of muscle progenitor cells on the serial sections. Results The donor sclera was easily identified in the collected specimens until 4 weeks postoperatively. At 12 weeks, only smaller rests of donor sclera were present. Nuclei and muscle progenitor cells were not detected in the donor sclera. At 16 weeks postoperatively, the donor sclera could no longer be identified and the SR insertion on to the bulb was found approximately 5 mm posteriorly from its normal insertion site. Staining for NCAM, myogenin, MyoD and KI‐67 were present in the repairing area in all specimens collected at the 1–12 weeks but practically absent from the specimens collected at 16 weeks. Conclusions Muscle progenitor cells did not invade the donor sclera and the donor sclera was gradually reabsorbed and no longer present after 16 weeks after surgery, in this rabbit model of strabismus surgery. The method was effective for achievement of a new, more posterior insertion site of the SR.