A comparative study of different amniotic membrane orientations during extraocular muscle surgery in rabbits.

PURPOSE: To histopathologically compare the effect of different orientations of cryopreserved human amniotic membrane (AM) transplant during extraocular muscle surgery in rabbits. METHODS: Fifty-two albino rabbit eyes underwent 4-mm resection of the superior rectus. Eyes were randomly divided into four groups. In Group C (Control group, 16 eyes) the muscle was not wrapped with amniotic membrane. In the three AM groups, cryopreserved AM was wrapped around the muscle, oriented with either its stroma (Group S, 15 eyes) or epithelium (Group E, nine eyes) towards the muscle, or folded on itself with the epithelium externally (Group F, 12 eyes). The rabbits were sacrificed and the eyes were enucleated 6 weeks after surgery. Histopathological examination was conducted for periamniotic, foreign body, scleral, and conjunctival inflammation, conjunctival vascularity, adhesions and muscle fibrosis. RESULTS: In all AM eyes, the AM was surrounded by periamniotic inflammation, with no adhesions detected between the muscle and surrounding tissues in the segment where the AM was present, but detected elsewhere. Adhesions were detected in all group C eyes. Foreign body inflammation was significantly less in Group C than in each of the AM groups (p < .05), but was insignificantly different among the three AM groups (p > .05). Scleral inflammation was absent in all specimens. No significant differences were noted among all groups in terms of conjunctival vascularity, conjunctival inflammation, or muscle fibrosis (p > .05). CONCLUSIONS: All AM orientations were equally effective in preventing the development of postoperative adhesions between the extraocular muscle and surrounding tissues.