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Archives of Ophthalmology

Year: 2010  |  Volume: 128  |  Issue: 4  |  Page No.: 413 - 417

Effects of Earth-Fixed vs Head-Fixed Targets on Static Ocular Counterroll

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.

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