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From: Primary Oblique Muscle OveractionThe Brain Throws a Wild Pitch
Arch Ophthalmol. 2001;119(9):1307-1314. doi:10.1001/archopht.119.9.1307
Figure Legend:
Physiologic effects of gravistatic(postural) and visual input to the oblique muscle tonus in fish. These bilateral torsional eye
movements function to align the eyes with the perceived visual vertical by modulating oblique muscle tonus. A, A pitch-down body
movement evokes increased inferior oblique muscle tonus and extorsion of the eyes. B, A pitch-up movement evokes increased
superior oblique muscle tonus and intorsion of the eyes. C, In the unrestrained fish, an anterior light source evokes a pitch-down
body movement. D, In the unrestrained fish, a posterior
source
evokes
a pitch-up body movement. E, In the restrained fish,
Copyrightlight
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American
Medical
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anterior
movement4/29/2017
of overhead light evokes increased
superior
oblique
muscle
Association. All rights reserved. tonus and intorsion of both eyes. F, In the restrained
fish, posterior movement of overhead light evokes increased inferior oblique muscle tonus and extorsion of both eyes.
From: Primary Oblique Muscle OveractionThe Brain Throws a Wild Pitch
Arch Ophthalmol. 2001;119(9):1307-1314. doi:10.1001/archopht.119.9.1307
Figure Legend:
Overhead view of a rabbit fixating an object in the right posterior visual field. Solid lines correspond to the visual axis of the abducted
right eye and the adducted left eye. When the rabbit pitches forward (as when starting to run down a hill), the head rotates
downward and the tail rotates upward. Although both eyes move downward in space, the left visual axis (which is directed toward
the nose) rotates downward, while the right visual axis (which is directed toward the tail) rotates upward(curved arrows). This
divergence of the visual axes corresponds to a right
hypertropia
must Medical
be neutralized by vestibular innervation to elevate the
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lowerofleft
eye and 4/29/2017
depress the higher right eye. The
compensatory
vertical
divergence for a pitch-forward position corresponds to
Association. All rights reserved.
primary inferior oblique muscle overaction.
From: Primary Oblique Muscle OveractionThe Brain Throws a Wild Pitch
Arch Ophthalmol. 2001;119(9):1307-1314. doi:10.1001/archopht.119.9.1307
Figure Legend:
The close anatomical relationship of the semicircular canals and the extraocular muscles in humans is shown. Figure modified with
permission from Simpson and Graf.
Date of download: 4/29/2017
Copyright © 2001 American Medical
Association. All rights reserved.
From: Primary Oblique Muscle OveractionThe Brain Throws a Wild Pitch
Arch Ophthalmol. 2001;119(9):1307-1314. doi:10.1001/archopht.119.9.1307
Figure Legend:
Neuroanatomical projections from the labyrinths to the extraocular muscles. The orientation of the anterior semicircular canal
corresponds to that of the ipsilateral superior rectus and contralateral inferior oblique muscles. The orientation of the posterior
semicircular canals corresponds to that of the ipsilateral superior oblique and contralateral inferior rectus muscles. The orientation of
each horizontal canal corresponds to that of the horizontal rectus muscles. Turning the head to the right stimulates the right
horizontal canal to increase excitatory innervation
to the right
medial
rectusMedical
muscle and left lateral rectus muscle so that the eyes
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rotateofequally
and4/29/2017
opposite to the direction of headAssociation.
rotation. HC
indicates
horizontal
canal; AC, anterior canal; PC, posterior canal;
All rights reserved.
LVN, lateral vestibular nucleus; MVN, medial vestibular nucleus; VI, abducens nucleus; MLF, medial longitudinal fasciculus; IV,
From: Primary Oblique Muscle OveractionThe Brain Throws a Wild Pitch
Arch Ophthalmol. 2001;119(9):1307-1314. doi:10.1001/archopht.119.9.1307
Figure Legend:
Segregation of pathways controlling anterior and posterior canal tone. Only the anterior canal pathways receive inhibitory
innervation by the cerebellar flocculus. A loss of modulation from the cerebellar flocculi could disinhibit the anterior canals and
produce an upward tonus imbalance, leading to bilateral inferior oblique muscle overaction, bilateral extorsion, and V-pattern
strabismus. FLO indicates flocculus; NOD, nodulus; AC, anterior canal; PC, posterior canal; HC, horizontal canal; SVN, superior
vestibular nucleus; VTT, ventral tegmental tract;Copyright
MVN, medial
vestibular
© 2001
Americannucleus;
Medical MLF, medial longitudinal fasciculus; BC, brachium
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4/29/2017
conjunctivum;
III N,
oculomotor nucleus (S, I, O, and
M
represent
the
oculomotor
Association. All rights reserved. subnuclei); SR, superior rectus muscle; and IR,
inferior rectus muscle. Data modified with permission from Tusa.
From: Primary Oblique Muscle OveractionThe Brain Throws a Wild Pitch
Arch Ophthalmol. 2001;119(9):1307-1314. doi:10.1001/archopht.119.9.1307
Figure Legend:
Superior oblique muscle overaction. A, Vestibular innervation. A central vestibular tonus imbalance corresponding to bilateral
posterior canal predominance would produce tonic downgaze, divergence, and intorsion of the eyes if unopposed by fixational
innervation. B, Vestibular plus fixational innervation. Fixational innervation, which conforms to the Hering law, recruits bilateral
innervation to the superior rectus and inferior oblique muscles to negate the vertical component of the downward tonus bias.
Fixational innervation allows a disconjugate intorsional
bias
to persist.
PC Medical
indicates posterior canal; HC, horizontal canal; and AC,
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4/29/2017
anterior
canal.
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From: Primary Oblique Muscle OveractionThe Brain Throws a Wild Pitch
Arch Ophthalmol. 2001;119(9):1307-1314. doi:10.1001/archopht.119.9.1307
Figure Legend:
Superior oblique muscle overaction. The observed eye movements in different fields of gaze are a summation of fixational
innervation that conforms to Hering's law, and an underlying central vestibular imbalance that does not. All 4 depressors are
receiving excessive vestibular innervation. Since the vertical action of the superior oblique muscles is maximal in adduction, the
adducting eye exhibits a downshoot in adduction relative to the abducting eye. The tertiary abducting effects of the overacting
superior oblique muscles are maximized by vestibular
innervation
in downgaze
and minimized by fixational intervation in upgaze,
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© 2001 American
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producing
an A pattern.
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From: Primary Oblique Muscle OveractionThe Brain Throws a Wild Pitch
Arch Ophthalmol. 2001;119(9):1307-1314. doi:10.1001/archopht.119.9.1307
Figure Legend:
Primary inferior oblique muscle overaction. A, Visuovestibular innervation. Failure to develop normal binocular vision is associated
with increased upward tonus to the eyes, perhaps through reduced anterior canal inhibition from the cerebellar flocculi. A central
vestibular tonus imbalance corresponding to bilateral anterior canal predominance would produce tonic upgaze, horizontal
divergence, and extorsion of the eyes if unopposed by fixational innervation. B, Visuovestibular plus fixational innervation. Fixational
innervation recruits equal innervation from the inferior
rectus
andAmerican
superior Medical
oblique muscles to negate the vertical component of the
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© 2001
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of download:
4/29/2017
upgaze
bias, and allows
the disconjugate extorsional
bias
to
persist.
PC
indicates
Association. All rights reserved. posterior canal; HC, horizontal canal; and AC,
anterior canal.