Compensatory eye movements during near fixation after fast adaptation to lenses.

When the eyes are converged on a near target, the gain of the vestibulo-ocular reflex (VOR) during a subsequent head rotation is dependent upon both the amount of vergence and the degree to which it is asymmetrical. In conditions without visual feedback, we measured the gain of the VOR in the right eye of observers as they rotated their heads to the right or left while viewing a target placed 22, 32.5 or 200 cm from the centre of head rotation. We then adapted the VOR to the magnifying effects of +5 D lenses, and retested the VOR under the former convergence conditions. We found an inverse relationship such that the greater the VOR gain due to convergence, the less the effect of the rapid adaptation to lenses.