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Michael D. Abràmoff, Rachel Kalmann, Mieke E. L. de Graaf, Jan S. Stilma, Maarten P. Mourits; Rectus Extraocular Muscle Paths and Decompression Surgery for Graves Orbitopathy: Mechanism of Motility Disturbances. Invest. Ophthalmol. Vis. Sci. 2002;43(2):300-307.
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purpose. To study possible causes of motility disturbances that may result from
orbital decompression surgery in patients with Graves orbitopathy and
especially the role of rectus extraocular muscle paths.
methods. Sixteen patients with Graves orbitopathy were studied before and 3 to 6
months after translid (6 patients) and coronal (10 patients) orbital
decompression surgery for disfiguring proptosis. Ocular motility
changes were measured by comparing maximum ductions and severity of
diplopia, and the positions and the displacements of the anterior
rectus muscle paths were objectively measured using cine magnetic
resonance imaging (MRI).
results. Averaged preoperative rectus muscle path positions were not different
from those in normal subjects. Averaged postoperative muscle path
positions were generally the same as preoperative paths. The only
significant exceptions were centrifugal (outward from the orbital axis)
displacements of the inferior rectus (IR) muscle path after translid
surgery, and of the medial rectus (MR) muscle path after coronal
surgery. The amount of IR path displacement with translid surgery was
directly correlated with range of depression and with severity of
vertical diplopia. The amount of MR path displacement with coronal
surgery was inversely correlated with range of abduction and
directly correlated with severity of horizontal diplopia.
conclusions. The anterior orbital connective tissue seems to form a “functional
skeleton” that is usually (except as noted for IR and MR) capable of
keeping the rectus muscle paths aligned after decompression surgery and
preserving the normal functions of rectus muscle pulleys. The
centrifugal displacement of the IR and MR may increase the elastic
component of the muscle force, leading to the specific patterns of
motility disturbance that may occur in some patients after translid and
coronal surgery. These findings suggest that standard surgical
management of Graves orbitopathy should be
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