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Y.–T. Kim, A. Kyeon, P. Sung Eun, O. Sei Yeul; The change of structure and myosin heavy chain isoform expression in global and orbital layer of extraocular muscle after extraocular muscle recession . Invest. Ophthalmol. Vis. Sci. 2004;45(13):5006.
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Purpose: The extraocular muscle(EOM) consists of two layers, which are readily distinguished by their histopathology. This study was conducted to investigate the changes of histopathology, myosin heavy chain isoforms of the global and orbital layers of EOM after recession. Methods: Twelve New Zealand white rabbits were used. The vertical rectus muscles were recessed by 3mm and 8mm. The rectus muscles were harvested on week 1, week 2, week 4 and week 8 after EOM recession. The EOM were serially sectioned in the coronal plane and stained with Masson’s trichrome. The areas of muscle fiber were measured in the middle of the muscles. The changes of MHC isoform were observed with immunohistochemical stain. Results: The areas of EOM fiber in the global layer decreased in 1, 2 and 4 weeks after recession in the 3mm–recessed group and in 1 and 2 weeks in the 8mm–recessed group. The 3mm–recessed group recovered in 8 weeks following recession and the 8mm–recessed group recovered in 4 weeks. However, no significant changes were found in the orbital layer in both groups. The immunohistochemical stains of fast and slow MHC had weakened in the global layer at 1 week and 2 weeks after recession. Conclusions: Changes to the EOM due to the atrophy of EOM was observed after a week in both groups while EOM atrophy recovered at 8 weeks after surgery in the 3mm–recessed group and at 4 weeks in the 8mm recessed group. These changes did not appear on the EOM orbital layer but to the global layer. These results were due to the histological and functional differences of the EOM global and orbital layers.
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