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-77
[Reprinted from the Ophthalmic Review, December, 1897.]
ANOMALIES IN THE FUNCTIONS OF THE
EXTRINSIC OCULAR MUSCLES.^
By F. BuLLER, M.D., Montreal.
The complex phenomena which constitute the act
of vision have been so thoroughly elaborated in the
science of physiological optics, that the ophthal-
mologist justly claims for his work a greater exactness
than pertains to any other department of medicine or
surgery.
Certain well defined laws enable him to detect and
successfully contend with abnormal conditions in
refraction and accommodation. An absolute standard
of visual perfection, both for form and colour, serves as
a guide in every functional examination of vision, and
the ophthalmoscope enables him to discover the most
minute pathological lesions in the interior of the eye
itself. A complete and methodical examination will
often enable him to determine, with surprising pre-
cision, the nature and gravity of morbid conditions
beyond the eye and even in other organs of the body.
When, however, he comes to investigate the compli-
cated problems presented in the function of binocular
vision which, in the presence of a multitude of dis-
turbing influences, may be rendered hopelessly difficult,
he feels that he is still treiiding upon uncertain ground.
Since the majority of eyes possess a normal refraction,
' Read before the Ophthalmological Section at the Meeting of the
British Medical Association held at Montreal, August and September, 1897.
1*-
a definite power of accommodation and acuity of
vision which varies but Htt'e in different subjects,
though in all these particulars a certain physiological
variation is recognised, it would be strange if the
muscular movements of the eyes did not correspond-
ingly follow approximately definite laws. In all
probability they do, and it is not unlikely that estimated
rotating power of the different muscles, as determined
by innumerable examinations of the normal muscular
functions, is fairly correct as regards both monocular
and binocular vision. It is also probable that very
considerable variations from the alleged physiological
standards of motility thus obtained are consistent with
easy and accurate vision. Since, however, slight
errors in refraction in certain subjects unquestionably
give rise to intense visual disturbance, there seems
no reason why the same rule should not apply in cases
of defective or faulty motility, except that in so compli-
cated a piece of machinery it may fairly be assumed
that the physiological limit is still more variable than is
the case with any of the other factors which contribute
to the act of vision. However this may be, there is no
question as to the existence of serious visual and even
systematic disturbances due to faults in the extrinsic
muscles of the eyes, especially those which render the
function of binocular vision difficult and wearisome.
The series of observations which form the basis of
this communication relate, indeed, only to this class of
cases.
To begin with I have relied chiefly upon the
equilibrium tests made at the standard distance of six
metres and assumed that the normal for this distance
is the status known as orthophoria. Allowing for
physiological variation from this, I have attached little
or no importance to lateral deviations of two or three
prism-degrees, and I am quite certain there are many
persons who present much greater deviations than
.:>
this (latent squint) without experiencing the least
discomfort.
I have also neglected all cases of hyperphoria which
could not be shown to exceed one degree. 1 am not
prepared to assert that one degree or less of hyper-
phoria may not in some persons cause more or less
discomfort. If so this should be relieved by wearing
a correcting prism, and I am under the impression
that I have succeeded in relieving a few of these cases
in this way.
The objections charged against prisms of two or
more degrees do not hold good in prismatic action so
feeble as this, and it may be that the mere mental effect
of wearing glasses accounts for the apparent benefit, as
there must be a strong neurotic element in all cases
that experience distress from very slight perturbing
influences, otherwise we should meet with an infinitely
larger number of people disturbed by wearing im-
properly centred glasses than is actually the case. This
statement must not be construed in such a way as to
minimise the importance of wearing properly centred
glasses in all cases. It is merely intended to point out
the incontrovertible fact that there are vast numbers of
persons who can and actually do overcome slight
artificial deviations without difficulty.
It is not an uncommon experience that weak prisms,
worn for the correction of faulty equilibrium, afford
relief for some time and then lose their effect. I have
come to regard this as an indication for operative
interference in some cases where the proper course to
pursue was difficult to determine.
The equilibrium tests were made in distance (6
metres) with prisms, Stevens' phorometer and the
compound Maddox rod coloured red. I regard this
instrument as not less reliable than the Stevens' phoro-
meter, but have habitually used both.
It was essential to have some standard of fusion
power, and the following was accepted as normal. Ab-
duction 5° to 8", adduction 25" to 50°, sursumduction
2° to 3'.
This standard is not absolute, and is chiefly useful
for purposes of comparison. In every case where
there is binocular vision, the range of fusion may be
temporarily increased in any direction by systematic
exercise of the muscles. I have seldom known this
apparent increase in power to be long maintained after
the exercises had been discontinued.
Equal exercise of all the muscles will sometimes
develop a preponderating power in a sense that did
not exist before. This fact, when it occurs, is more
significant than the original latent tendency. An
habitual abduction of 5° and adduction of 25° (in the
absence of hyperphoria) could hardly be regarded as
abnormal, but an abduction of 5° with an adduction
of 60° or more, and esophoria of more than 2° or
3° would probably be sufficient justification for opera-
tive interference.
When there is binocular vision with a latent ten-
dency in any direction, and a considerable relative
excess of power in the muscles acting in that direc-
tion, the fault may safely be corrected by operation —
tendon relaxation or tendon shortening. Relief from
headaches, asthenopia, and neurasthenic symptoms
often follows such operations ; they are, therefore, not
only justifiable, but positively indicated under such
circumstances in the absence of refractive error, or
where the refraction has been corrected without afford-
ing relief. A careful investigation of every case of
muscular anomaly during a number of years in private
practice has furnished from a material of 8,000 patients
no cases that seemed suitable for operative inter-
ference, i.e., about 1*4 per cent.; they may be classified
as follows : —
*
Esophoria
37
Exophoria
31
Hyperphoria
30
Hyper-exophoria
10
Hyper-esophoria
2
no
A tabulated statement showing the principal features
of each case may be of some interest. The figures
showing the degrees of tendency and fusion power are
the average of several, sometimes of many measure-
ments in each case.
It will be seen that the number of cases operated upon
for the three principal forms of deviation are nearly
equal, i.e., 37 cases of esophoria, 31 of exophoria and
30 of hyperphoria. There were only 12 cases requiring
operation for the correction of both horizontal and
vertical deviation, and only 2 of these were for an
upward and inward deviation.
I desire to call attention to this fact, as it is a
striking commentary on the contention of those who
claim that the chief factor in the aetiology of con-
vergent squint is to be found in the presence of
hyperphoria.
A study of the tabulated results shows t';-l there
were 39, or 35*4 per cent, of cases which may fiirly be
classed as cured ; 37, or 33*6 per cent., greatly bene-
fited ; 20, or 18 per cent., somewhat benefited ; 8
unimproved, and in 6 the result was unknown.
Leaving out these last 14 cases the operations would
appear to have benefited in 87 per cent, of all the
cases so treated. This is perhaps as good a result as
attends most surgical operations, and in this connec-
tion I may add that I am not aware of any instance
which the result was actually injurious to the
m
patient. I am therefore justified in claiming that the
usual operations performed for the relief of persons
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suffering from the various annoyances due to faulty
muscular equilibrium, in carefully selected cases are
not only harmless, but in a very large percentage of
such cases they are followed by satisfactory results in
as large a percentage as are obtained, according to
most statistics, in the operations for removal of
cataract.
It will be observed that whilst there were many
cases of refractive error among the no cases, there
were also a great many with little or no refractive
error, and in no case was an operation performed in
the presence of a refractive error in which relief was
not first sought by its correction. I cannot agree with
those who contend that the correction of errors of
refraction will always correct associated muscular
faults. If this be true, how can we account for
the many cases of muscular faults in which refraction
is emmetropic ?
It is undoubtedly true that some of the lower grades
of muscular faults may be benefited by wearing suit-
able prismatic glasses, but the usefulness of these is
exceedingly limited, and those who depend upon them
are doomed to frequent disappointment.
I have not had sufficient experience in the correction
of muscular faults in persons suffering from epilepsy
and chorea to say that they cannot derive benefit from
ocular therapeutics or operations to secure equilibrium,
but so far as my experience goes I am inclined to
believe that little or no relief is to be expected from
such treatment, at least quoad the functional nervous
disorder, but I would not hesitate to recommend the
scrupulous correction of refractive errors in such
persons, or of any considerable muscular fault, if
present, just as 1 would recommend the removal of
every discoverable source of nerve irritation or cause
of ill-health whatever it might be.
A searching analysis of the no cases 1 have tabulated
17
would bring out a good many interesting facts which I
cannot discuss now ; for instance, among those cured
there were two of esophoria with normal refraction in
which the chief complaint was persistent vertigo, both
entirely relieved by tenotomy of the internal recti ;
in neither of these, however, was there anything
approaching epileptiform phenomena.
The clinical investigation of functional muscular
anomalies can only be undertaken at the expense of
enormous loss of time and the exercise of unbounded
patience on the part of the surgeon ; hard conditions,
it is true, but not too hard for him who delights in his
profession and feels the joy of overcoming difficulties
that have baffled others.
If the results I have now placed on record are
reliable, and I believe they are, being the outcome of
many years' patient observation and steady work, free,
I hope, from partiality of any sort, then it follows
that whoever ignores the injurious effects of muscular
faults in ophthalmic practice, fails to accord at least i
per cent, of his patients the benefit which a proper
application of his knowledge should bestow.
1 have purposely abstained from any discussion of
the theoretical aspects of faulty muscular equilibrium,
for the reason that I could not on the present occasion
do justice to this part of the subject, and from a clinical
standpoint it matters not what the cause of physical
distress may be so long as the means employed for its
relief are efficient.
In reply to some points raised in the discussion which
followed the paper, Mr. BuUer said : Mr. President, first
as to the point raised by Dr. Stevens — want of uniformity
in standard of measurement. I claim that it is impossible
to establish a definite standard for all cases, and say that
a man must come up to that standard or he is abnormal.
I think that Dr. Stevens supports me in this contention,
i8
if I remember rif^htly, in his work on functional muscular
disturbances, the first work in which he brought this
subject prominently before tlie public. He admits, I
think, in that work, that there is a difference in individuals,
and that a man may be allowed a certain difference of
muscular power in different ocular muscles, and that what
may be normal for one man is not normal for another. In
other words, that the relative strength of the ocular
muscles has to be taken into account in considering what
is the normal standard.
I said, from five to eight degrees for abducting power
and twenty-five to fifty for adducting power. Now the
relative proportion between these is pretty much the same,
and if a man is comfortable with five degrees of abducting
power and twenty-five degrees of adducting power after a
good many trials as to the strength of the muscles, surely
that is sufficient evidence that, as far as he is concerned,
we may regard this as a normal condition or a fairly
normal condition.
On the other hand, there are a large number of people
who I am perfectly convinced cannot get an abducting
power of eight degrees excepting by long-continued
exercise of the external muscles, and I believe that the
abducting power, if increased by exercise, will lapse back
into the original condition unless the exercise is main-
tained, so that it is exceedingly difficult to establish an
absolute standard, if indeed it is possible.
As for the method of testing for deviations or the relative
merits of the Maddox rod or Stevens' tropometer, I must
say I have not found the tendency to confusion with the
Maddox rod that Dr. Stevens claims to exist. I have,
however, found a somewhat greater degree of deviation by
the use of the Maddox rod than by Stevens' tropometer.
Now as to Dr. Mittendorf's remarks concerning the
frequency of operating. I would have no objection to
doing frequent operations, and getting very little effect at
a time, and repeating the operations as often as seemed
necessary to achieve my results little by little ; indeed I
would prefer to do it in that way if I had such control over
\
19
my patients as would enable me to do it, but 1 am quite
sure that if I were to propose to operate upon my patients
half a dozen times for correction of slight degrees they
would leave me. I have gone on the principle of correcting
as nearly as possible in one or two operations any moderate
degree of defect, or if there is a large degree of defect I
have stated plainly to the patient that I might have to
perform several operations. Sometimes I have operated
upon one muscle more than once, but never more than
twice. That is my position. With regard to the refractive
question I thought I had expressed myself distinctly on
that point. I do attempt to correct every error of refrac-
tion, and correct it as absolutely and completely as I know
how. I cannot do more than that. I am only restrained
from absolute correction of a refractive error by the
ignorance of my patients, most of whom are too ignorant
to tell me the difference between a quarter and an eighth
of a dioptre !
With reference to Dr. Osborne's question as to what is
the proportion of cases in which I have used atropine, I
would say I have used atropine or homatropine in all my
cases, as I consider that it is essential to use one of these
drugs. Homatropine is sufficient in some cases, but in
others I think that atropine is necessary, and I use it in
order to get absolute correction of the refraction, for I
know that in people less than 50 years of age you cannot
depend upon getting absolute correction without using a
mydriatic. I investigate the refractive error most scrupu-
lously before doing anything for the muscular faults. I
think Dr. Howe has misunderstood me in my statement
as to the large number of cases of normal eyes *n which
hyperphoria was discovered. I quite agree with him that
an absolutely normal eye, a physiologically normal eye, is
a rarity, and I thought I had explained that part of my
position sufficiently clearly in saying that I allowed for
physiological deviations to a slight degree, and where there
was no disturbance apparently resulting from abnormal
conditions I certainly would not be in favour of interfering
in any way.
,■>
20
The tests as to muscular strength were made of course
by examinations repeated sufficiently often to justify me in
my own mind, in assuming that I had arrived at about
what was the limit of the muscular power in the individual
before I proceeded to operate.
I have not operated upon any of these cases where it
was fair to assume that the headaches were due to a fault
in the general health. Surely if a person comes to you
with a history of having headaches for fifteen or twenty
years, it is absurd to assume that it is due to some fault
in the general health which can be cured by giving him
some trumpery drug or other. As a general rule, long-
continued trouble of this kind depends upon something
pertaining to the individual, which cannot be so easily cor-
rected. If in the course of ten or fifteen years an individual
has not had opportunity of improving his health in such
a way that he can correct headaches depending on it, it is
certainly remarkable, but if he comes to you with head-
aches, and obvious errors of ocular functions are detected,
such as to entitle one to assume that their correction may
lead to some beneficial result, and after the operation your
patient steadily recovers from the malady which has pur-
sued him for ten or twenty years, surely it is fair then to
assume that at least your result was due to the therapeutic
measures you adopted.
;:%