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M. Chandrakumar, Z. Hirji, A. Blakeman, H. Goltz, G. Mirabella, A. M. Wong; Effects of Earth-Fixed vs Head-Fixed Target on Ocular Counterroll. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2875.
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Twelve normal subjects were recruited. The target consists of a central fixation cross against a high-contrast grid pattern at 33 cm. The target was mounted on a vertical wall (earth-fixed), or coupled to the head (head-fixed). Eye movements were recorded using a video-based system. Changes in mean torsional eye position were plotted as a function of head position steps (0±25 deg in 5 deg steps) and five-parameter sigmoidal fits were performed. Mean OCR gains were calculated by taking the derivative of the fitted functions.
Mean OCR gain with a head-fixed target (-0.084) was 40% lower than that with an earth-fixed target (-0.141; p < 0.0001).
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