Amniotic Membrane Transplantation in Strabismus Surgery.

PURPOSE: Adhesions between the extraocular muscles and surrounding tissues pose a main cause of failure of strabismus reoperations. Amniotic membrane (AM) transplantation during extraocular muscle surgery, to prevent the formation of adhesions, has been a subject of research during the past decade. This review aims to determine the value, indications, and tips on usage of AM transplantation during strabismus surgery. MATERIALS AND METHODS: All references cited in PubMed in English were searched using the key words: amniotic membrane strabismus or amniotic membrane extraocular muscles, and a brief summary of these was described. In addition, certain articles were chosen to provide introductory information on wound healing and fibrosis, AM properties and how it works after transplantation, and AM processing and preservation. RESULTS: AM used for transplantation during extraocular muscle surgery may be cryopreserved, dried, or fresh. It may be oriented with its stroma or epithelium towards the muscle. It may or may not be fixed with sutures. What were the best choices? Various studies attempted to answer these questions. Many of the studies reviewed, however, were inconclusive or contradictory. Fresh AM seemed effective, but carried a risk of transmission of communicable diseases. Dried membrane was not of value in preventing adhesions. Histopathologically, cryopreserved membrane prevented the development of adhesions in the region of its presence, regardless of its orientation, and without the need for suture fixation. To accentuate this histopathological effect during clinical practice, it was recommended to utilize the largest segment possible of cryopreserved membrane and limit its usage to cases where adhesions are expected to be the main cause of failure of strabismus surgery. CONCLUSION: Cryopreserved AM transplantation was safe and histopathologically effective in preventing adhesions. This effect was, however, less pronounced clinically. Its use during strabismus reoperations is merited if previous recommendations and precautions are considered.

Long-term follow-up of cryopreserved amniotic membrane transplant during strabismus reoperations: Up 85 months' follow-up.

PURPOSE: To evaluate the long-term effect of cryopreserved human amniotic membrane transplant during strabismus reoperations. METHODS: A total of 15 patients with persistent strabismus were included in a prospective study to evaluate the effect of wrapping the extra-ocular muscles with cryopreserved amniotic membrane during strabismus reoperations. The study end-point was the last follow-up visit. A successful outcome was defined as 0-10∆ of horizontal tropia and 0-4∆ of vertical tropia, with no limitation of ductions exceeding -1. A cosmetically acceptable outcome was defined as a tropia of 0-15∆. RESULTS: Maximum follow-up was 85 months (mean: 25.4 ± 25.5 months). At the last follow-up visit, a successful outcome was achieved in 46.7%, a cosmetically acceptable outcome was achieved in 66.7%, and the mean ocular deviation angles improved from 38.60 ± 14.63∆, preoperatively, to 10.6 ± 11.08∆. Motility limitation on the final follow-up visit exceeded -1 in only 4/180 muscles (2.2%). CONCLUSION: The effect of cryopreserved amniotic membrane transplantation on the success of strabismus reoperations was moderate in terms of ocular alignment. Its effect was more pronounced in terms of ocular motility. The latter better reflects the level of adhesions. No long-term complications were documented, denoting safety of cryopreserved amniotic membrane usage during strabismus reoperations.

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.

A controlled study of the role of cryopreserved amniotic membrane transplant during strabismus reoperations.

PURPOSE: To evaluate the effects of using cryopreserved human amniotic membrane (AM) transplant during strabismus reoperations. METHODS: A total of 30 patients with persistent strabismus were included in this prospective study. Patients were divided into two groups of 15 patients each. The AM group underwent strabismus reoperation with wrapping of the muscles with cryopreserved amniotic membrane. Controls underwent strabismus reoperation without an AM wrap. Final follow-up visit was scheduled between 3 and 12 months postoperatively. Surgical success was defined as 0Δ-10Δ of horizontal tropia and 0Δ-4Δ of vertical tropia, with no limitation of ductions exceeding -1. A cosmetically acceptable outcome was defined as a tropia of 0Δ-15Δ. RESULTS: Three patients were excluded in the AM group due to incomplete follow-up. A successful outcome was achieved in 7 patients in each group (58% and 47% in groups AM and C, resp.; P = 0.63). A cosmetically acceptable outcome was achieved in 10 patients in the AM group (83.3%) and 12 (80%) in the control group (P = 0.48). The mean ocular deviation angles improved to 8.7Δ ± 12Δ in the AM group and 12.3Δ ± 17.4Δ in the control group (P = 0.63). Ductions improved in 66.7% and 36.4% of the muscles with limited motility in groups AM and C, respectively (P = 0.019). CONCLUSIONS: Wrapping the extraocular muscles with cryopreserved AM during strabismus reoperations was of limited clinical benefit. We attributed this to the small segment of AM used and to the presence of other causes of failure rather than adhesions.