All motor behavior is characterized by sensory inputs causing specific motor reactions. Because humans modify motor reactions voluntarily or through experience, this input-output relation is more complex in humans than in lower vertebrates. Eye movements provide a window on fundamental brain function, not only for topographic diagnosis of dysfunctions but also for the comprehension of normal brain function. This book highlights basic mechanical properties of eye movements, explains the neuronal basis of the vestibular-ocular reflex, saccadic eye movements, smooth-pursuit eye movements, and vergence eye movements, and deals with their pharmacological manipulation in disorders. Since precise measurement of motor reactions is essential for understanding the oculomotor system, one chapter critically discusses current registration methods, and another one considers the possibilities and limitations of modeling it by control theory methods. Its comprehensive characterization of eye movements and their relation to brain function makes this publication essential reading to ophthalmologists, neurologists, and clinical neuropsychologists.
132 - 157: Mechanics of the Orbita Free
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Published:2007
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Book Series: Developments in OphthalmologySubject Area: Further Areas , Neurology and Neuroscience , Ophthalmology , Psychiatry and Psychology
Joseph L. Demer, 2007. "Mechanics of the Orbita", Neuro-Ophthalmology: Neuronal Control of Eye Movements, A. Straube, U. Büttner
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Abstract
The oculomotor periphery was formerly regarded as a simple mechanism executingcomplex behaviors explicitly specified by innervation. It is now recognized that several fundamentalaspects of ocular motility are properties of the extraocular muscles (EOMs) andtheir associated connective tissue pulleys. The Active Pulley Hypothesis proposes that rectusand inferior oblique EOMs have connective tissue soft pulleys that are actively controlled bythe action of the EOMs’ orbital layers. Functional imaging and histology have suggested thatthe rectus pulley array constitutes an inner mechanism, similar to a gimbal, that is rotated torsionallyaround the orbital axis by an outer mechanism driven by the oblique EOMs. Thisarrangement may mechanically account for several commutative aspects of ocular motorcontrol, including Listing’s law, yet permits implementation of noncommutative motility asduring the vestibulo-ocular reflex. Recent human behavioral studies, as well neurophysiologyin monkeys, are consistent with mechanical rather than central neural implementation ofListing’s law. Pathology of the pulley system is associated with predictable patterns of strabismusthat are surgically treatable when the pathologic anatomy is characterized by imaging.This mechanical determination may imply limited possibilities for neural adaptation tosome ocular motor pathologies, but indicates greater potential for surgical treatments.
