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Year: 2010 | Volume: 128 | Issue: 4 | Page No.: 413 - 417
M Chandrakumar, Z Hirji, H. C Goltz, G Mirabella, A. W Blakeman, L Colpa and A. M. F. Wong
Abstract
Objective To investigate whether static ocular counterroll (OCR) gain is reduced during viewing of an earth-fixed vs a head-fixed target.
Methods Twelve healthy individuals were recruited. The target consisted of a red fixation cross against a grid pattern at a viewing distance of 33 cm. The target was mounted on a wall (earth fixed) or was coupled to the head (head fixed). Changes in mean torsional eye position were plotted as a function of head position steps (0° ± 25° in 5° steps), and sigmoidal fits were performed. Mean static OCR gain was calculated by taking the derivative of the fitted functions.
Results Mean static OCR gain was 40% lower with a head-fixed target (–0.084) than with an earth-fixed target (–0.141) (P < .001).
Conclusion The reduction in static OCR gain during viewing of a head-fixed target indicates that static OCR is partially negated when a target moves with the head.