Affiliations: [a] Jules Stein Eye Institute, University of California at Los Angeles | [b] Cullen Eye Institute and Clayton Neurotology Laboratory, Baylor College of Medicine, Houston, Texas | [c] University of Houston College of Optometry, Houston, Texas
Note: [*] Reprint address: J.L. Demer, Comprehensive Division Jules Stein Eye Institute, 100 Stein Plaza, UCLA, Los Angeles, California 90024-7002, U.S.A.
Abstract: Vestibularly and visually driven eye movements interact to compensate for head movements to maintain the necessary retinal image stability for clear vision. The wearing of highly magnifying telescopic spectacles requires that such compensatory visual-vestibular interaction operate in a quantitative regime much more demanding than that normally encountered. We employed electro-oculography to investigate the effect of wearing of 2×, 4×, and 6× binocular telescopic spectacles on visual-vestibular interactions during sinusoidal head rotation in 43 normal subjects. All telescopic spectacle powers produced a large, immediate increase in the gain (eye velocity/head velocity) of compensatory eye movements, called the visual-vestibulo-ocular reflex (VVOR). However, the amount of VVOR gain augmentation became limited as spectacle magnification and the amplitude of head velocity increased. Optokinetic responses during wearing of telescopic spectacles exhibited a similar nonlinearity with respect to stimulus amplitude and spectacle magnification. Computer simulation was used to demonstrate that the nonlinear response of the VVOR with telescopic spectacles is a result of nonlinearities in visually guided tracking movements. Immediate augmentation of VVOR gain by telescopic spectacles declined significantly with increasing age in the subject pool studied. Presentation of unmagnified visual field peripheral to the telescopic spectacles reduced the immediate VVOR gain-enhancing effect of central magnified vision. These results imply that the VVOR may not be adequate to maintain retinal image stability during head movements when strongly magnifying telescopic spectacles are worn.
Keywords: visual-vestibular interaction, vestibulo-ocular reflex, head motion, telescopic spectacles, plasticity
