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M. Fesharaki, D. Tweed, J.A. Sharpe, A.M. F. Wong; Patients With Skew Deviation Have Abnormal Torsion but Obey Listing’s Law . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2921.
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Purpose: Skew deviation is a vertical strabismus caused by supranuclear lesions and often associated with abnormal ocular torsion. We studied whether patients with skew deviation show the normal pattern of 3–D eye control called Listing’s law, which says that ocular torsion is a linear function of horizontal and vertical eye position. Methods: We used search coils to measure eye motion in 9 normal subjects and 6 patients with skew deviation caused by brainstem or cerebellar lesions. With head immobile and one eye covered, subjects made saccades to a target that moved between straight ahead and 8 eccentric positions. Results: If a subject obeys Listing’s law, their 3–D eye–position vectors will all lie in a single plane, called Listing’s plane. We found that patients’ eye–position vectors were almost as well fitted by planes as were the data of normal subjects, and the difference in fit quality was not significant, so the patients did obey Listing’s law. But their planes were abnormally oriented, both horizontally and vertically. Conclusions: That our patients obeyed Listing’s law may mean that their lesions did not disrupt the linear, neural linkage between horizontal, vertical, and torsional eye position, or that adaptation restored that linkage after the lesion. The abnormal plane tilt may reflect altered muscle orientations of the skewed eyes, or it may be a neural adaptation that improves the eyes’ motor efficiency over their altered motor ranges.
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