Chandrakumar M, Hirji Z, Goltz HC, Mirabella G, Blakeman AW, Colpa L, Wong AMF. Effects of earth-fixed vs head-fixed targets on static ocular counterroll.
ACTA ACUST UNITED AC 2010;
128:413-7. [PMID:
20385936 DOI:
10.1001/archophthalmol.2010.14]
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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 degrees +/- 25 degrees in 5 degrees 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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