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Giles Christopher Savage.

Ophthalmic neuro-myology : a study of the normal and abnormal actions of the ocular muscles from the brain side of the question online

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OPHTHALMIC
NEURO- MYOLOGY



A STUDY OF THE NORMAL AND ABNORMAL ACTIONS OF THE

OCULAR MUSCLES FROM THE BRAIN SIDE

OF THE QUESTION



G. C. SAVAGE, M. D.



Professor of Ophthalmology in the Medical Department of Vanderbilt University; Author of Nev

Truths in Ophthalmology " (1895) , of "Ophthalmic Myology "( 1901) ; Ex-President

of the Nashville Academy of Medicine; Ex-President of the

Tennessee State Medical Association



Thirty-nine Full Page Plates and Twelve Illustrative Figures



PUBLISHED BY

The Author, 157 Eighth Avenue, North, Nashville, Tenn.

PRINTED BY

Keelin-W'illiams Printing Co., Nashville, Tenn.



r- oa><



Entered, according to the Act of Congress, in the year 1905,

By G. C. Savage,

In the Office of the Librarian of Congress.
All rights reserved.



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PREFACE. — ~^

It has long been the desire of the author to help make the
ocular muscle problem easy of solution. With this object in
view he undertook the study of the normal and abnormal actions
of the ocular muscles, from the brain side of the question. The
results of this labor are set forth in this book, which might be
entitled "The Muscle Study Made Easy;" but the title chosen
is Opthalmic Neuro-Myology, the name implying the nature
of the study.

This book is intended as a companion volume to Ohthalmic
Myology. In the light of this newer study, not a word need
be changed, in the older treatise, concerning the detection and
treatment of heterophoric conditions.

The hypothesis on which Opthalmic Neuro-Myology is
founded, may be stated as follows: There are eight conjugate
brain centers, in the cortex, by means of which the several
versions are effected, and one conjugate center by which con-
vergence is caused. These conjugate centers act alike on ortho-
phoric and heterophoric eyes, and when there is only one eye.
Each of these is connected with two muscles, and the work
done by the center and its muscles, under the guidance of volition,
is normal work. The conjugate centers have no causal relation-
ship with the heterophoric conditions, nor have they any power
for correcting them.

There are twelve basal centers, each connected with only
one muscle. If the eyes are emmetropic-orthophoric, these

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M282512



,v PREFACE.

centers are forever at rest; but when there is any form of hetero-
phoria, one or more of these centers must be ever active, during
all working' hours. These centers do not cause heterophoria,
but they stand ready to correct it. Under the guidance of the
fusion faculty, each basal center stands ready to act on its muscle,
whenever there is a condition that would cause diplopia. They
mav be called fusion centers.

If the above hypothesis accounts for every phenomenon con-
nected with the normal and abnormal actions of the ocular
muscles, as it seems to do, then it ceases to be an hypothesis
and becomes a scientific fact.

Plates I to XXXVII were executed, after the design of the
author, by his niece, Miss Christine Johnson, for which she
deserves this public acknowledgment.

For the mechanical excellencies of the volume, the author,
who is also the publisher, is indebted to the printing establish-
ment whose inscription can be found on the title-page.



ILLUSTRATIONS.



The Ocular Nerves.

PLATES I. TO VI.

Plate I. — Represents the connection between basal and cortical centers and

ocular muscles, by way of right third nerve cable 64

Plate II. — The brain and muscle connections through left third nerve cable 65
Plate III. — The brain and muscle connections through the right fourth

nerve cable 70

Plate IV. — The brain and muscle connections through the left fourth nerve

cable 71

Plate V. — The brain and muscle connections through the right sixth nerve

cable 74

Plate VI. — The brain and muscle connections through the left sixth nerve

cable 75

Emmetropic-Orthophoric Eyes.

PLATES VII. TO XVI.

Plate VII. — Brain and muscle rest, in direct distant vision 78

Plate VIII. — Brain center and muscle activity in accommodation-convergence 79

Plate IX. — Brain center and muscle activity in right version 84

Plate X. — Brain center and muscle activity in left version 85

Plate XI. — Brain center and muscle activity in superversion 88

Plate XII, — Brain center and muscle activity in subversion 89

Plate XIII. — Brain center and muscle activity in right-up oblique version. 90

Plate XIV — Brain center and muscle activity in left-down oblique version 91

Plate XV. — Brain center and muscle activity in left-up oblique version 94

Plath XVI. — Brain center and muscle activity in right-down oblique version 95

Emmbtrophic-Esophoric Eyes.

PLATES XVII, TO XX.

Plate XVII. — Brain center and muicle activity in straight-forward distant

vision 98

(v)



vi ILLUSTRATIONS.

Plate XVIII. — Brain center and muscle activity in accommodation-con-
vergence 99

Plate XIX. — Brain center and muscle activity in right version ioo

Plate XX. — Brain center and muscle activity in left version 101

Emmetropic-Exophoric Eyes.

PLATES XXI. TO XXIV.

Plate XXI. — Brain center and muscle activity in straight-forward distant

vision 1 06

Plate XXII. — Brain center and muscle activity in accommodation-converg-
ence 107

Plate XXIII. — Brain center and muscle activity in right version 108

Plate XXIV. — Brain center and muscle activity in left version 109

Emmetropic Hyper- and Cataphoric Eyes.

PLATES XXV. TO XXVII.

Plate XXV. — Brain center and muscle activity in straight-forward vision .... 112

Plate XXVI. — Brain center and muscle activity in superversion 114

Plate XXVII. — Brain center and muscle activity in subversion 115

Emmetropic and Cyclophoric Eyes.

plates XXVIII. TO XXXI.
Plate XXVIII. — Brain center (possible) and muscle activity in distant

vision of plus cyclophoric eyes 118

More probable brain center activity is shown in Plate XXXVI 178

Plate XXIX. — Brain center an muscle activity in subversion of plus cyclo-
phoric eyes 119

Plate XXX. — Brain center (possible) and muscle activity in distant vision

of minus cyclophoric eyes 122

More probable brain center activity is shown in Plate XXXVII 179

Plate XXXI. — Brain eenter and muscle activity in subversion of minus

cyclophoric eyes 123

Ametropic and Heterophoric Eyes.

Plate XXXII. — Brain center and muscle activity in convergence of myopic-

orthophoric eyes 138



ILLUSTRATIONS. vii

Plate XXXIII. — Brain center (possible) and muscle activity in direct dis-
tant vision of myopic-exophoric eyes 139

More probable brain center activity is shown in Plate XXI 106

Plate XXXIV.— Brain center and muscle activity in direct distant vision of

hyperopic-orthophoric eyes 146

Plate XXXV. — Brain center and muscle activity in both far and near see-
ing of hyperopic-exophoric eyes 158

Plate XXXVI. — Brain center and muscle activity in direct distant vision of
oblique astigmatic eyes, with meridians of greatest curvature
in upper temporal quadrants 178

Plate XXXVII. — Brain center and muscle activity in direct distant vision
of oblique astigmatic eyes, with meridians of greatest curv-
ature in upper nasal quadrants. 179

Plate XXXVIII. — Shows absence of torsion in the fusion of the images of a

rectangle, in vertical and horizontal astigmatism 182

Plate XXXIX. — Shows torsioning necessary for fusing the two images of a

rectangle, in non-symmetric oblique astigmatism 183

Illustrative Cuts.

Fig. i. — Illustrates plus cyclophoria of left eye 24

Fig. 2. — Illustrates minus cyclophoria of left eye 24

Fig. 3. — Illustrates plus cyclophoria of right eye 25

Fig. 4. — Illustrates minus cyclophoria of right eye 25

Fig. 5. — Illustrates retinal fusion area 39

Fig. 6. — Illustrates visual results of unequal refraction 164

Fig. 7. — Shows character of images of a horizontal arrow in vertical or

horizontal astigmatic eyes 172

Fig. 8.— Shows oblique images of a horizontal arrow in symmetric oblique

astigmatic eyes '173

Fig. 9. — Shows oblique image in right eye and horizontal image in left eye 174
Fig. 10. — Shows oblique image in right eye and horizontal image in left eye 175
Fig. 11. — Shows character of images in oblique astigmatic eyes, when me-
ridians of greatest curvature diverge 176

Fig. 12. — Shows character of images in oblique astigmatic eyes, when merid-
ians of greatest curvature converge 177



Ophthalmic Neuro-Myology.



CHAPTER I.



OCULAR ROTATIONS AND THE MUSCLES
EFFECTING THEM.



The nervo-muscular mechanism, by which the eyes are
moved, cannot be properly understood in the absence of a
correct understanding of the globes that are to be rotated.

It is as strange as it is true that the poles of the eye have
not been correctly located by previous investigators. Error
in locating the poles led to the greater error of falsely locat-
ing the axes of all rotations. These errors have been
pointed out in Ophthalmic Myology, but not so clearly nor
so forcibly as the author hopes to do in this little book.
A wrong beginning means a wrong ending. The error in
locating the poles was in first selecting the center of the
cornea for the anterior pole, and then locating the posterior
pole by extending a line from the supposed anterior pole,
through the center of rotation, to the retina. This line
was called, or miscalled, the optic axis, or the anteropos-
terior axis. By it the posterior pole was located, as a rule,



2 OCULAR ROTATIONS AND THE

between the macula and the optic disc, rarely at the macula,
and more rarely still to the temporal side of the macula.

At the Saratoga meeting of the American Medical Asso-
ciation, in 1902, twelve of the leading Ophthalmologists
present were asked this question: "At what point in the
retina do all the corneo-retinal meridians cross?" With but
little hesitation on the part of any one, they all answered,
"at the center of the macula." In thus answering they
all placed the posterior pole at the fovea centralis; for a
pole is that point in a spherical surface through which all
the meridians pass. Since the posterior pole is always de-
termined by the location of the macula, it becomes evident
that, in constructing the optic axis, the beginning should
be made at the fovea centralis, that it should then be car-
ried through the center of rotation, and thence to that point
of the cornea through which it would pass, if prolonged,
regardless of whether it be the center of the cornea, or on
either the nasal or temporal side of the center. This point
on the cornea is 180° from the center of the macula, or
posterior pole, and it must be the anterior pole, for the two
poles of a sphere are 180° degrees apart. The straight line
connecting these poles is not only the true antero-posterior
axis of the globe, or optic axis, but it is also the visual
axis.

Every time the Javal ophthalmometer, or any other oph-
thalmometer, whose disc is bordered with a white band, is



MUSCLES EFFECTING THEM. 3

used, the anterior pole is located, nearly always to the nasal
side of the center of the cornea. The corneal meridians
that are measured by the ophthalmometer are those lines
which cross at that point of the cornea which is cut by the
visual axis; for this axis is always directed to the center
of the distal opening of the telescopic tube. On looking
above the tube, while the patient looks into the center, the
operator may find the center of the reflected disc and the
corneal center the same ; but as a rule the center of the re-
flected disc is nasal-ward from the corneal center, but
wherever it is, there is the anterior pole. The ideal eye,
and the best seeing eye, other things being equal, is the one
whose corneal center is the anterior pole. If the anterior
pole is removed more than 5° from the corneal center it is
not possible for such an eye to have perfect vision for the
reason that the rays of light cannot be perfectly focused
on the macula. The best refracted rays are in that cone
of light whose axial ray cuts the corneal center. Inciden-
tally it may be suggested that a displaced anterior pole ac-
counts for the fact that, in most cases, the ophthalmometer
shows an excess of curvature of the vertical meridian,
amounting usually to .50 D when the astigmatism is accord-
ing to the rule, making it necessary to take .50 D from the
cylinder. The same reasoning accounts for the fact that,
in astigmatism against the rule .50 D must be added to the
cylinder indicated by the ophthalmometer. In any case it



4 OCULAR ROTATIONS AND THE

is the vertical corneo-retinal meridian which is measured.
When this coincides with the curve that lies in the vertical
plane which cuts the center of the cornea, there will be
nothing to add to, or subtract from, the ophthalmometer
reading; when it lies in the plane a few degrees removed
from the vertical plane which cuts the center of the cornea,
whether to the nasal or temporal side, there must be, in
astigmatism against the rule, an addition to the ophthalmo-
meter reading; likewise there must be, in astigmatism ac-
cording to the rule, a subtraction from the ophthalmometer
reading. The addition in the one case and the subtraction
in the other case vary, as to the amount, with the distance
the true anterior pole is from the center of the corneal curve.
The horizontal corneo-retinal meridian has lying in it, prac-
tically always, both the anterior pole and the center of the
cornea, howsoever widely these two points may be sep-
arated. It is also w r ell known that neither addition to, nor
subtraction from, the ophthalmometer reading is necessary
in astigmatism in which one principal corneo-retinal me-
ridian is at 45° and the other at 135°, for the one meridian
misses the center of the corneal curve to the same extent
as does the other, hence an error in the measurement of
the one meridian is the same in kind and quantity as the
error in the measurement of the other. To make plainer
the error in measurement of the vertical corneo-retinal me-
ridian when the anterior pole is 5° nasal-ward from the cor-



MUSCLES EFFECTING THEM. 5

neal center, two vertical planes forming an angle of 5°
should be constructed, the one cutting the corneal center,
the other cutting the anterior pole, the center of rotation
lying in both planes. In the latter will lie the vertical cor-
neo-retinal meridian, and in the other will almost lie the
corneal refraction curve which cuts the center of the cornea.
The radius of the former corneal curve is shorter than the
radius of the latter, hence the difference in the measure-
ment of the two by the reflected images of the mires. The
refraction of the corneal surface is by the curved lines
whose planes all cross each other at the center of the cornea,
which, as already shown, may or may not be the anterior
pole. These lines should be called the corneal refraction
curves, and not the corneal meridians, to avoid confound-
ing them with the corneo-retinal meridians.

With the poles and the axis correctly located, the true
equatorial plane is easily constructed. Since the equator
is a line equally distant, at all points, from the two poles,
the equatorial plane must be at right angles to the axis,
and must cut it at its central point. This point in the eye
is the center of rotation.

Whenever the eye is moved from one point of view to an-
other, it takes the shortest course, that the movement may
be accomplished in the quickest time, and at the least ex-
pense of nerve force and muscle energy. This being true
it is clear that the visual axis has moved in a plane common



6 OCULAR ROTATIONS AND THE

to both its first and second positions. Helmholtz's rule for
locating the axis of any possible ocular rotation, whether by
the action of one muscle or by the combined action of two
or more muscles, must forever stand, for it is true. This
is his simple rule : "The axis of any rotation of the eye is
a line passing through the center of rotation, at right angles
to the plane common to both the primary and secondary
positions of the visual axis." It needs no further argu-
ment to show that the axis of every ocular rotation must
lie in the true equatorial plane.

Listing's plane would never have been constructed if the
error had not previously been made in first locating the an-
terior pole in the center of the corneal curve, and then find-
ing the posterior pole by extending a line from the supposed
anterior pole, back through the center of rotation, to the
retina, and naming it the antero-posterior, or optic, axis.
The circle equally distant from these two so-called poles
could not coincide with the true equator except in an ideal
eye — one whose visual axis cuts the center of the cornea —
but such an eye is rarely found.

The confusion arising from wrongly locating the poles
led Listing to construct his plane, a fixed vertical plane, cut-
ting the centers of rotation of the two eyes, and then to
declare that the axes of all ocular rotations lie in this plane.
Helmholtz accepted the plane but rejected, in part, the teach-
ing of Listing as to the location of the axes of rotations.



MUSCLES EFFECTING THEM. 7

Helmholtz accepted the teaching that the axis of a rotation
from the primary position to a secondary position, or vice
versa, lies in Listing's plane, and in this he was correct;
but he claimed that the axis of a rotation from one second-
ary position to another secondary position must lie in a
plane bisecting the angle between the Listing plane and the
so-called equatorial plane. The so-called equatorial plane
is at right angles to that axis whose anterior pole is the
center of the corneal curve; the real equatorial plane is at
right angles to that axis whose posterior pole is the fovea
centralis. If the angle between the true axis (the visual
axis) and the false axis (the so-called optic axis) is 5°,
the angle formed by the intersection of the true equatorial
plane and the false equatorial plane must be 5°. In only
a limited number of rotations from one secondary position
to another secondary position would the true equatorial
plane bisect the angle formed by the Listing plane and the
false equatorial plane. Helmholtz was entirely correct in
teaching that the axis of rotation from the primary to any
secondary position lies in the Listing plane ; he was also en-
tirely correct when he taught that the axis of a rotation
from one secondary position to any other secondary position
does not lie in the Listing plane ; but he was incorrect in his
teaching that the axes of rotations from secondary positions
to secondary positions must always lie in a plane bisecting
the angle formed by the so-called equatorial plane and the



8 OCULAR ROTATIONS AND THE

Listing plane. He was near the truth and yet did not grasp
it, else he would have taught that every rotation, whether
from the primary position to a secondary position, from a
secondary position back to the primary position, or from
one secondary position to any other secondary position,
must have its axis in that movable plane which is always at
right angles to the visual axis. As has been shown, this is
the true equatorial plane. When the axis is in the Listing
plane it is also in the equatorial plane ; when the axis is not
in the Listing plane it is, never-the-less, in the equatorial
plane. Therefore the Listing plane has no place in the
study of ocular rotations.

The Listing plane is of no value as a plane of reference,
for the only two reference planes needed are the median
vertical and the horizontal fixed planes of the head.

The ocular muscles and their innervation centers work in
the interest of binocular single vision and correct orienta-
tion. For the accomplishment of these two purposes the
muscles of the eyes are concerned only with the visual axes
and the vertical axes. In the final result of their action,
the recti muscles are concerned only with the visual axes,
while the oblique muscles are concerned only with the ver-
tical axes. The law governing all possible ocular rotations
may be thus stated: "The recti muscles must control the
visual axes, the superior and inferior recti keeping them al-
ways in the same plane, the external and internal recti



MUSCLES EFFECTING THEM. 9

making them intersect at the point of fixation. The obliques
must keep the vertical axes parallel with each other and
with the median vertical plane of the head."

The law of rotation of a single eye may be stated as fol-
lows: "The axis of every possible rotation, whether effected
by the action of one muscle or by the combined action of
two or more muscles, must lie in the movable equatorial
plane and must always be fixed at right angles to the plane
through which the visual axis moves from the first to the
second position."

Each of the extrinsic ocular muscles has its individual
plane of action, and if each muscle acted by itself, the visual
axis would move in this plane, the axis of rotation being at
right angles to it. The plane of rotation of an individual
muscle must pass through three points, viz.: the center of
the origin and the center of insertion of the muscle, bisect-
ing it from end to end, and the third point is the center of
rotation of the eye. Only the lateral recti muscles with ideal
origins and insertions, their planes coinciding with the hori-
zontal plane of the eye, can act alone and obey the law of
ocular rotations. A too high or a too low insertion of an
externus or an internus would tilt the muscle plane so that
it could not coincide with any meridian of the eye, and
therefore its axis of rotation could not be in the equatorial
plane. With such faulty attachment the internus unaided
cannot rotate the eye directly in. The muscle plane of a



10 OCULAR ROTATIONS AND THE

superior or inferior rectus does not coincide with the plane
of any corneo-retinal meridian, therefore the imperious law
of ocular rotations will not allow either of these muscles to
act by itself, since the axis of such a rotation could not lie
in the equatorial plane. The same is true of the obliques. In
ideally attached muscles, rotation directly out is effected by
one muscle, the externus; rotation directly in is accom-
plished by one muscle, the internus; rotation directly up
is effected by two muscles, the superior rectus and the in-
ferior oblique; rotation directly down is accomplished by
two muscles, the inferior rectus and the superior oblique.
Rotations obliquely up or down in any plane between 90°
and 180° is accomplished by three muscles, two recti and
one oblique, and, if it be the right eye and the rotation is
up and to the right, these three muscles are the superior
and external recti and the superior oblique; and if down
and to the left, they are the inferior and internal recti and
the superior oblique; but if it be the left eye rotating in
either of these directions these muscles are, respectively, the
superior and internal recti and the inferior oblique, and
the inferior and external recti and inferior oblique. Rota-
tions obliquely up or down in any plane between zero and
90°, this plane being up and to the left and down and to
the right, is accomplished by three muscles, two recti and
one oblique. If it be the right eye and the rotation is up
these three muscles are the superior and internal recti and



MUSCLES EFFECTING THEM. 11

the inferior oblique ; and if down, they are the inferior and
external recti and inferior oblique. But if it be the left eye
and the rotation is up, these three muscles are the superior
and external recti and the superior oblique, and if down
they are the inferior and internal recti and the superior
oblique.

Whenever the plane of rotation is oblique the visual axis
could not move in it without torsioning the eye, if this evil
effect were not counteracted by an oblique muscle. The
work accomplished by the oblique muscle, in an oblique
rotation, is in maintaining parallelism between the vertical
axis of the eye and the median plane of the head. When
the two planes of binocular rotations are between 90° and
180°, whether the visual axes are made to sweep above or
below the fixed horizontal plane of the head, the torsional
tendency is such as would make both vertical axes incline
to the right; but this, in the right eye, is' prevented by the
superior oblique, while in the left eye it is prevented by the
inferior oblique. When the two planes of binocular rota-
tions are between zero and 90°, whether the visual axes are


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Online LibraryGiles Christopher SavageOphthalmic neuro-myology : a study of the normal and abnormal actions of the ocular muscles from the brain side of the question → online text (page 1 of 11)