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M. Chandrakumar, A. Blakeman, H. Goltz, A. M. Wong; Static Ocular Counterroll in Patients With Skew Deviation. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2532.
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Static ocular counterroll (OCR) generates compensatory torsional eye movements during static head tilt and it is mediated by the utricles in the inner ear. Skew deviation is a vertical strabismus thought to be caused by imbalance of the VOR pathway that originates from the utricles and projects to ocular motoneurons (i.e. the utriculo-ocular pathway). We hypothesized that if skew deviation is indeed caused by damage to utricular-ocular pathway, patients with skew deviation would show abnormal static OCR gain.
Seven normal subjects and seven patients with skew deviation caused by brainstem or cerebellar lesions were recruited. With one eye occluded, subjects viewed a red laser spot against a grid pattern at 1 m. Ocular responses to static passive head roll-tilts of about 20 deg toward each shoulder was recorded using scleral search coils. Static OCR gain was calculated as the change in torsional eye position divided by change in head position during sustained head tilt.
In normal subjects, OCR gains were symmetric in both eyes, as well as in both clockwise and counterclockwise directions, with a mean gain of 0.19. In patients with skew deviation, mean OCR gain in the hypertropic eye was 0.08±0.02 which was significantly lower than that in normal subjects (p=0.02). Mean OCR gain in the hypotropic eye was 0.15±0.03 and did not differ from normal (p=0.28). No differences in gains were found between clockwise and counterclockwise directions in both hypertropic and hypotropic eyes of patients.
The asymmetric static OCR gain in patients with skew deviation provides support that imbalance of the utricular-ocular pathway is a mechanism for skew deviation.
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