The effect of the rotational magnification of corrective spectacles on the quantitative evaluation of the VOR

The gain of the vestibulo-ocular reflex (slow-phase eye velocity/chair velocity, measured in the dark) was compared in 11 normal healthy subjects who habitually wore corrective spectacles of varying strength. The rotational magnification (or prismatic effect) induced by habitually wearing corrective spectacles caused the VOR gain measured in darkness to vary systematically with diopter of correction. Even when allowances were made for the inherent variability of measurement of the VOR gain, myopes tended to have lower gains and hyperopes higher gains. This study demonstrates that the clinician should account for spectacle adaptation to properly interpret the results of vestibular function tests.