Chapter

Eye Movements, Vision, and the Vestibulo-Ocular Reflexes

Alessandro Serra, Karim Salame, Ke Liao and R. John Leigh

in Oxford Textbook of Vertigo and Imbalance

Published on behalf of Oxford University Press

Published in print February 2013 | ISBN: 9780199608997
Published online February 2013 | e-ISBN: 9780191754227 | DOI: http://dx.doi.org/10.1093/med/9780199608997.003.0003

Series: Oxford Textbooks in Clinical Neurology

Eye Movements, Vision, and the Vestibulo-Ocular Reflexes

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The vestibulo-ocular reflexes (VORs) evolved to optimize vision during locomotion, which causes high-frequency angular and linear perturbations of the head. Visual processing is slow (latency > 70 ms) but the angular VOR is prompt (latency < 15 ms) and can compensate for rotational head perturbations, thereby sustaining a clear and stable view of the environment. Loss of the angular VOR, which depends on the labyrinthine semicircular canals, causes excessive motion of images on the retina during locomotion, leading to blurred vision and the illusion of motion of the environment (oscillopsia). A range of clinical disorders impair the angular VOR, of which an important preventable entity is the toxic effect of aminoglycoside antibiotics. The linear VOR, which depends on the otolithic organs, does not compensate for head translations by holding the line of sight on the object of regard; rather, it acts to minimize retinal image slip of both near and far components of the visual environment, so that motion parallax can be optimized during locomotion. Impairment of the linear VOR has been demonstrated in a number of neurological disorders including progressive supranuclear palsy (PSP) and cerebellar ataxia; affected patients often also have impaired otolith-spinal reflexes, leading to falls. Whereas the angular VOR is readily accessible to bedside tests, such as the head impulse test, at present, the linear VOR is more reliably evaluated in the laboratory using moving platforms. Development of clinical tests for the linear VOR requires consideration of the visual demands for which this reflex evolved.

Chapter.  5285 words.  Illustrated.

Subjects: Neurology

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