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      Innervated Myotendinous Cylinders Alterations in Human Extraocular Muscles in Patients With Strabismus

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          Abstract

          Purpose

          To analyze innervated myotendinous cylinders (IMCs) in the extraocular muscles (EOMs) of normal subjects and strabismic patients.

          Methods

          The rectus muscles of 37 subjects were analyzed. Distal myotendinous specimens were obtained from 3 normal subjects, 20 patients with acquired strabismus, 11 with infantile strabismus, and from 3 with congenital nystagmus, and were studied by using light microscopy. Some specimens (6 rectus muscles) were also examined by transmission electron microscopy.

          Results

          IMCs were found in the distal myotendinous regions of EOMs. The IMCs of patients with acquired strabismus showed no significant morphological alterations. However, significant IMCs alterations were observed at the distal myotendinous junction of patients with congenital strabismus and congenital nystagmus.

          Conclusions

          This study supports the notion that IMCs in human EOMs function mainly as proprioceptors, along with effector properties, and a disturbance of ocular proprioceptors plays an important role in the pathogenesis of oculomotor disorder. We suggest that a proprioceptive feedback system should be stimulated and calibrated early in life for the development of binocular vision.

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          Most cited references 35

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          The functions of the proprioceptors of the eye muscles.

          This article sets out to present a fairly comprehensive review of our knowledge about the functions of the receptors that have been found in the extraocular muscles--the six muscles that move each eye of vertebrates in its orbit--of all the animals in which they have been sought, including Man. Since their discovery at the beginning of the 20th century these receptors have, at various times, been credited with important roles in the control of eye movement and the construction of extrapersonal space and have also been denied any function whatsoever. Experiments intended to study the actions of eye muscle receptors and, even more so, opinions (and indeed polemic) derived from these observations have been influenced by the changing fashions and beliefs about the more general question of how limb position and movement is detected by the brain and which signals contribute to those aspects of this that are perceived (kinaesthesis). But the conclusions drawn from studies on the eye have also influenced beliefs about the mechanisms of kinaesthesis and, arguably, this influence has been even larger than that in the converse direction. Experimental evidence accumulated over rather more than a century is set out and discussed. It supports the view that, at the beginning of the 21st century, there are excellent grounds for believing that the receptors in the extraocular muscles are indeed proprioceptors, that is to say that the signals that they send into the brain are used to provide information about the position and movement of the eye in the orbit. It seems that this information is important in the control of eye movements of at least some types, and in the determination by the brain of the direction of gaze and the relationship of the organism to its environment. In addition, signals from these receptors in the eye muscles are seen to be necessary for the development of normal mechanisms of visual analysis in the mammalian visual cortex and for both the development and maintenance of normal visuomotor behaviour. Man is among those vertebrates to whose brains eye muscle proprioceptive signals provide information apparently used in normal sensorimotor functions; these include various aspects of perception, and of the control of eye movement. It is possible that abnormalities of the eye muscle proprioceptors and their signals may play a part in the genesis of some types of human squint (strabismus); conversely studies of patients with squint in the course of their surgical or pharmacological treatment have yielded much interesting evidence about the central actions of the proprioceptive signals from the extraocular muscles. The results of experiments on the eye have played a large part in the historical controversy, now in at least its third century, about the origin of signals that inform the brain about movement of parts of the body. Some of these results, and more of the interpretations of them, now need to be critically re-examined. The re-examination in the light of recent experiments that is presented here does not support many of the conclusions confidently drawn in the past and leads to both new insights and fresh questions about the roles of information from motor signals flowing out of the brain and that from signals from the peripheral receptors flowing into it. There remain many lacunae in our knowledge and filling some of these will, it is contended, be essential to advance our understanding further. It is argued that such understanding of eye muscle proprioception is a necessary part of the understanding of the physiology and pathophysiology of eye movement control and that it is also essential to an account of how organisms, including Man, build and maintain knowledge of their relationship to the external visual world. The eye would seem to provide a uniquely favourable system in which to study the way in which information derived within the brain about motor actions may interact with signals flowing in from peripheral receptors. The review is constructed in relatively independent sections that deal with particular topics. It ends with a fairly brief piece in which the author sets out some personal views about what has been achieved recently and what most immediately needs to be done. It also suggests some lines of study that appear to the author to be important for the future.
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            The role of ocular muscle proprioception in visual localization of targets.

            The role of ocular muscle proprioception in the localization of visual targets has been investigated in normal humans by deviating one eye to create an experimental strabismus. The passively deviated eye was covered and the other eye viewed the target. With a hand-pointing task, targets were systematically mislocalized in the direction of the deviated nonviewing eye. A 4- to 6-degree error resulted when the nonviewing eye was offset 30 degrees from straight ahead. When the eye was deviated, the perceived "straight-ahead" was also displaced, by a similar amount, in the same direction. Since the efferent motor commands to the displaced and to the nondisplaced eyes are presumably identical by the law of equal innervation, the mislocalization of visual objects must be attributed to the change in proprioceptive information issued from the nonviewing, deviated eye. Thus proprioception contributes to the localization of objects in space.
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              Influence of extraocular muscle proprioception on vision.

               P Buisseret (1995)
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                Author and article information

                Journal
                Korean J Ophthalmol
                KJO
                Korean Journal of Ophthalmology : KJO
                The Korean Ophthalmological Society
                1011-8942
                June 2009
                09 June 2009
                : 23
                : 2
                : 93-99
                Affiliations
                [1 ]Department of Ophthalmology, Eulji University School of Medicine, Eulji General Hospital, Seoul, Korea.
                [2 ]Department of Ophthalmology, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul, Korea.
                Author notes
                Reprint requests to Sei Yeul Oh, MD. Department of Ophthalmology, Samsung Medical Center, 50 Ilwon-dong, Gangnam-gu, Seoul 135-710, Korea. Tel: 82-2-3410-3566, Fax: 82-2-3410-0074, syoh@ 123456skku.edu
                Article
                10.3341/kjo.2009.23.2.93
                2694299
                19568357
                Copyright © 2009 by the Korean Ophthalmological Society

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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