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H. Okanobu, R. Kono, H. Ohtsuki, K. Kinugasa; Does Inferior Oblique Muscle Weakening Surgery Affect Rectus EOM Pulley in Patients With Superior Oblique Palsy? . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5069.
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© ARVO (1962-2015); The Authors (2016-present)
The inferior oblique (IO) muscle has a connective tissue that constitutes pulley structure serving as its functional origin. The orbital layers of the IO insert not only into the IO pulley, but also inferior rectus and LR (lateral rectus) pulleys. We analyzed the effect of IO surgery on rectus EOM (external ocular muscle) pulley in superior oblique palsy (SOP).
Quasi–coronal MRIs of orbital images with high resolution T1–weighted images was collected from 8 patients with unilateral SOP before and after the IO weakening surgery. Imaging was performed with a 1.5T scanner (General Electric Sigma) and quasi–coronal images in the primary position were obtained. On each digital MRI image, the center of the relevant EOM was computed using an X–Y center function of the NIH image program. To normalize the position on the scan plane, all rectus EOM positions were analyzed 9mm posterior to the globe center, the inferred pulley locations. Preoperative coronal plane locations of rectus EOM pulley of patients were compared with postoperative rectus EOM pulley locations.
Compared with both normal and fellow orbits, ipsilateral LR pulleys of 5 patients showing superior oblique muscle belly atrophy were displaced inferiorly significantly from normal preoperatively, but locations of the rectus EOM pulley did not alter postoperatively. Whereas the rectus EOM pulley of 3 patients showing normal superior oblique muscle configuration was located within 2 standard deviations from normal and did not alter postoperatively.
IO weakening surgery did not alter the locations of the rectus EOM pulley independent of muscle configuration. Quasi–sagittal plane MRI was also needed to determine whether the IO connective tissues sleeve is influenced by surgical dissection of the IO sheath and muscle during strabismus surgery.
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