THE ANOMALIES OF THE OCULAR 
MUSCLES 
BY 
Dr. GEORGE T. STEVENS, New York 
FIRST PAPER 
[Reprinted from the Archives of Ophthalmology, Vol. xvi., No. 2, 1887] THE ANOMALIES OF THE OCULAR MUSCLES. 
Dr. GEORGE T. STEVENS, New York. 
FIRST PAPER. 
I. 
AFFECTIONS of the ocular muscles may be divided 
into those-which are physiological peculiarities and 
those which result from pathological conditions. It is pro- 
posed now to consider the first of these two groups. 
In the normal adjustments of the eyes in the act of vision, 
two distinct classes of muscles perform each its separate 
office. The muscle of accommodation situated within the 
eyeball acting as focal adjuster for each eye, while the long 
muscles within the orbit direct the eyeballs in such a way 
as to bring the visual axes of the two eyes to bear upon the 
point for which the focal adjustment is made. 
The two classes of muscles are in a sense independent of 
each other, yet in a very important sense in close and inter- 
dependent relation. In the discussion of the anomalies of 
the ocular muscles, then, the relation of these two classes is 
to be constantly regarded. The affections of the ciliary 
muscles, constituting the essential factor in the subject of 
the accommodation of the eye, become a subject of special 
study, and not to be considered in this connection further 
than in respect to the reciprocal influences of the two classes 
of muscles. 
Such special conditions of the muscles of accommodation 
as may be necessary to refer to in order to obtain a proper 
understanding of their relations with the class of muscles 
more directly under consideration will be introduced as 
occasion demands. 
Reprinted from the Archives of Ophthalmology, Vol. xvi., No. 2, 188’ George T. Stevens. 
150 
The subject of anomalies of the directing muscular ap- 
paratus of the eyes divides itself again into two classes : 
first, those which permit of habitual binocular vision ; 
second, those in which a blending of the images of the 
two eyes is so difficult as to be, in most instances, impossi- 
ble. In the first of these two classes of faults, binocular 
vision is maintained by the expenditure of a greater amount 
of force than is demanded in perfect equilibrium of the 
ocular muscles ; in the second, a psychical disturbance re- 
sults which may have an important bearing upon the gen- 
eral physical condition of the individual subject of the 
anomaly. The two classes are in reality but different de- 
grees of similar affections, and the classification depends 
upon the psychical presence or absence of the phenomenon 
of a fusion of images. Indeed, under certain circumstances, 
one of these conditions may pass into the other, and one who, 
in robust health, blends images habitually and with difficulty 
may, in a condition of impaired nervous energy, be quite 
unable to maintain a fusion of the images of the two eyes. 
Even the presence or absence of binocular vision, then, does 
not constitute an absolute and sharply defined line of classi- 
fication. It also often happens that, with gross departures 
from the standard of equilibrium of the ocular muscles, 
habitual binocular vision is sometimes maintained, while in 
other instances comparatively moderate anomalies give rise 
to diplopia. 
Such conditions must, however, be regarded as excep- 
tional, and if the boundary, the sustained presence of single 
vision, like many of the boundaries of classification in science, 
is sometimes vague, it will on the whole be found practical 
and satisfactory. 
Directing our observations first to the class of anomalies 
in which habitual binocular vision is maintained, we shall 
find a theme rich in interest and of pre-eminent importance 
in its practical bearing. 
While it is true that some of the most illustrious names 
among those who have contributed to the notable progress 
of modern ophthalmology have been identified with the 
discussion of this subject, it is nevertheless also true that, The Anomalies of the Ocular Muscles. 
151 
considered in respect to its importance, comparatively 
slight attention has been bestowed upon it in the litera- 
ture devoted to ocular affections. For the most important 
expositions in this department of ophthalmology we are 
indebted to Von Graefe, who left to the world, among his 
richest contributions to the literature of science, extensive 
memoirs upon subjects connected with the ocular muscles, 
replete with learning and original research. Investigators 
from his time have been, in large measure, content to ac- 
cept the results of his splendid genius as in the main con- 
clusive, and since his death it cannot be said that any very 
striking advance has been made in this direction. But 
Graefe’s observations were those of a pioneer. They were 
not exhaustive, indeed they were, in respect to the class of 
affections now under consideration, incomplete and confined 
mainly, it may be said almost exclusively, to a single 
anomaly among several, and that one, as it will be seen, 
not the one of greatest practical importance. In these 
muscular affections in which, with absence of equilibrium 
the ability to maintain binocular vision remains, there is a 
tendency on the part of the eyes to permit the visual lines 
to deviate from parallel directions. Graefe, with others, 
taught that when the ocular muscles are all accurately pro- 
portioned in respect to their dynamic conditions, and the 
performance of binocular vision is accompanied with the 
least expenditure of energy, the ocular muscles are to be 
regarded as in “ equilibrium.” The tests, however, which 
have been applied to the determination of the presence or 
absence of equilibrium have not in all cases been sufficiently 
trustworthy, and it is desirable in the beginning of this dis- 
cussion to determine precisely what is indicated by the 
term equilibrium, and to establish definite means of ascer- 
taining, by the most conclusive methods attainable, the 
true conditions of the muscles in this respect. 
Graefe regarded the ability to direct the axes of the two 
eyes to the same point, at the usual distance of reading, 
without excessive effort, as a practical standard of equi- 
librium, and taught that this should be gained even at the 
expense of very great loss of equilibrium at greater distan- 152 
George T. Stevens. 
ces. Thus, in operating for relief of “ insufficiency of the 
interni,” he was ready to induce very high degrees of 
“ insufficiency of the externi,” or even homonymous di- 
plopia at a distance. As Graefe's operations were in large 
measure designed for the relief of “ insufficiency of the 
interni,” in cases of high grades of myopia, the great disad- 
vantages of the loss of equilibrium at a distance were less, 
pronounced than would have been the case under other 
circumstances. Such a standard of equilibrium should not 
be accepted. Equilibrium does not exist when compara- 
tively easy fusion of images is gained at one point at the 
expense of difficulty or impossibility of fusion at another. 
In equilibrium, the visual lines of the two eyes should be 
parallel when the force of the will in accommadating or 
adjusting the eyes is removed—that is, when the minimum 
of nervous impulse is directed to the ocular muscles. Devia- 
tions from a given standard of equilibrium short of the loss 
of power of fusion of images have been known as “insuffi- 
ciencies.” The term has, however, been mostly applied to 
an inadequate converging power for the distance of read- 
ing or ordinary work, and it has often, even by Graefe, 
been employed in connection with low grades of actual 
strabismus. 
In the conditions of absence of equilibrium now under 
consideration, and as they will be discussed in this paper, 
there is, in the act of vision, no actual turning of one visual 
line in a direction differing from that of the other when 
looking at a distant point. Indeed, in gazing directly 
forward at a distant object parallelism is supposed. There 
is, however, in these conditions, on the part of some 
one or more muscles, a tendency to disturb the balance ; 
and should the nervous control be so removed as to permit 
of the consummation of this tendency, an actual deviation 
would result. Such irregular tendencies, then, may exist in 
as many directions as there are forces to induce irregular 
tension—that is, not only in as many directions as there 
are muscles to act, but in as many directions as the muscles 
may combine to act. In short, then, these tendencies may 
exist in all directions. Without stopping here to discuss The Anomalies of the Ocular Muscles. 
153 
the question whether it is important to discover and to es- 
timate the degree of all these deviations—a subject which 
will engage our attention further on,—we may here assume 
that all are important, and that no just appreciation of the 
conditions which induce asthenopic or kindred troubles can 
be acquired which does not take them all into account. It 
becomes necessary, then, to establish some method of in- 
vestigating and of recording such anomalies. 
So long as the increased tension upon the interni, in the 
act of reading, or in other continued work at a like distance, 
was regarded as the main, if not the only important factor 
in the causation of muscular fatigue, aside from accommo- 
dative lesions, the test of the dot and line, as suggested by 
Graefe for this condition, appeared to answer the require- 
ments. This familiar test was made at reading distance, 
although Graefe counsels that, after having determined the 
degree of insufficiency for this distance, we should examine 
in the same way for greater distances. Without specifying 
the distances, he, in close relation to this part of the dis- 
cussion, mentions his experience at abduction and adduc- 
tion at a distance of six feet. This counsel, to determine 
the insufficiency at greater distances, judging from the 
literature of text-books, has been mainly disregarded, and 
indeed Graefe himself considered it of secondary, if not in 
most cases of little importance. The facts remain that in 
respect to this one test for a single condition there is not 
a well-established rule or custom. Even were complete uni- 
formity observed in the examinations or records of this 
condition of the ocular muscles, this method is quite inade- 
quate for the determination of several other conditions, 
and, as will be seen hereafter, extremely unreliable even for 
this one. 
No just appreciation of the muscular balance can be 
arrived at while the accommodation is considerably exer- 
cised. Hence the principal determinations should be made 
at such distance as to render the accommodation practically 
relaxed, and while the determination of the inclination of 
the visual lines in the act of accommodation may be of im- 
portance, and may throw some light upon the false tendem 154 
George T. Stevens. 
cies, it should not be regarded as a method representing 
the presence of equilibrium or of the degree of deviation 
from it. 
Elsewhere1 I have discussed the manner in which one 
may discover these faulty conditions. In order that in 
what is to follow there may be no misunderstanding, that 
the conditions under which the investigation of these visual 
tendencies are to be made and the manner of making them 
may be definitely understood, I trust that I may be par- 
doned for restating in as brief a manner as possible what 
was there more fully discussed. The head being in the 
“ primary ” position and the ocular muscles relaxed, while 
ametropia, if existing, is corrected by appropriate glasses, 
the subject of examination directs the eyes at an object, 
preferably a lighted candle against a dark background, situ- 
ated at the distance of twenty feet. Diplopia is then pro- 
duced by a prism. First of all diplopia should be produced 
in the horizontal direction, in order to determine the rela- 
tive tendencies of the visual lines in the vertical meridian. 
If the prism is first employed with its base up or down, 
and especially if it is held before the eye for some seconds, 
there will follow a partial adjustment of the visual axes to 
the new condition, and if then the prism is placed horizon- 
tally, this temporary adjustment may appear in the test 
which is about to be made. A very slight adjustment of 
this kind is of much less importance in the tests for the la- 
teral relations. A prism sufficient to prevent fusion of 
images at the given distance, but not so strong as to cause 
a wide separation of the images, is to be placed with its base 
inward and exactly horizontal. If now the two images of 
the object looked at appear to be precisely in the same 
plane, no tendency of one visual line to rise above the other 
has been shown. If on the other hand the images appear 
not in the same plane, a prism should be placed before one 
eye with its base up or down, and of such grade as will 
bring the mounting line down or the depressed one up to 
the plane of the other. The degree of prism marks the 
1 Archives d’Ophtkalmologie {Paris), Nov., 1886 ; New York Medical Journal, 
Dec. 8, 1886. The Anomalies of the Ocular Muscles. 
155 
ascertained degree of tendency to deviate from the plane. 
For convenience in making this determination I have had 
made several pairs of spectacles containing, in each side, 
prisms of equal grade, 50, 6°, and J° each, with their bases 
in. The glasses are quite long and in the form of a paral- 
lelogram, in order that their exact position on the face may 
be accurately known. These spectacles are convenient in 
saving time and in assisting toward greater accuracy in the 
examination than is likely to be obtained by the use of the 
ordinary trial frame or from prisms held in the hand. 
This test having been made with care, the prism is then 
placed before one eye with its base up or down. Graefe 
used a prism of 150 ; for his tests were made at near range, 
but one of 70 or even less will, in ordinary cases, induce 
diplopia, and permit of more accurate judgment of the rela- 
tive position of the images on the part of the patient. Any 
deviation from the vertical line is to be measured by the 
prism which will bring the images in line, as suggested by 
Graefe. By turning the first prism a certain number of de- 
grees until the correction is made, we may also, the grade of 
the prism and the degree of the turning being known, esti- 
mate the degree of deviation. By these two procedures infor- 
mation in two very important directions is obtained ; but the 
absence of positive evidence of anomalous tendencies, as 
shown by these tests, does not by any means prove the 
presence of equilibrium, and other means must be tried. 
Here the method of producing abduction and adduction 
is to be resorted to,- not, however, at six but at twenty 
feet. 
An experience in many thousand examinations leads me 
to believe that the standard of normal abduction should be 
about 8°, and that of adduction at about 50°. In respect to 
this last, however, the ability to overcome prisms equal to 
50° implies, in most cases, an ability indefinitely exceeding 
this, and many who at the first trial can accomplish only 
one half of this will, after two or three attempts on different 
days, succeed in uniting images with the full strength of 
the adducting prisms. On the other hand, while the failure 
to overcome at twenty feet a prism of 8° with its base in 156 
George T. Stevens. 
should be regarded as suggesting an excess of energy over 
the others on the part of the interni, and while power to 
overcome a higher prism suggests a balance in the opposite 
direction, many cases occur in which the absence of ability 
to overcome a prism of 50 does not prove an inward ten- 
dency of the lines, nor does the blending with a prism of 
io° or 120 prove a tendency outward. The ability to over- 
come a very strong prism with its base inward may be 
associated with actual converging strabismus, and the fail- 
ure to overcome a comparatively weak one may be asso- 
ciated with an outward balance. 
These results are to be compared with those already 
obtained by the diplopia tests when the prism is held 
vertically, but especially should they be considered in re- 
gard to any tendency of the visual axes to deviate in respect 
to the horizontal plane, for, as it will be seen, a very slight 
anomaly in this respect may modify the abducting or ad- 
ducting power materially. In a like manner also, the ability 
to overcome a prism with its base up or down should be 
ascertained. Graefe declared his inability to overcome a 
prism of more than one degree in this direction at six feet, 
and states that, for nearly all those whom he tried, a prism 
of 2° was too strong. My own experience varies from this, 
for I have found that a very large proportion of the persons 
whom I have examined can overcome 2° or 30 at twenty 
feet, and I should place the average ability in cases in 
which no false tendencies exist in this direction at about 
30. It is not very uncommon to find persons who will 
overcome 90 or more in this direction. But it would ap- 
pear to be of slight consequence whether the adjusting 
ability in this direction is rather more or less than 30, if the 
power in one direction is equal to that in the other. An 
excess of power, however, leads to the suspicion that exces- 
sive demands arising from anomalous conditions have been 
imposed upon the muscles. The adjusting power is, in this 
respect, to be proved by placing the strongest prism which 
can be overcome before one and then the other eye in the 
same manner, or by reversing the prism before the same 
eye ; for the effort qt overcoming a prism with its base The Anomalies of the Ocular Muscles. 
157 
down before one eye, is identical with that for uniting with 
its base up before the other. If we consider the results of 
the examination in the horizontal direction in relation to 
those in the vertical, we shall be able to form an opinion 
concerning the presence or absence of equilibrium, and, if 
manifest deviating tendencies exist, of the direction and 
extent of such tendencies. It is not, however, to be as- 
sumed that these indications are absolute. They are, as a 
rule, correct so far as they are positive, but they do not 
of necessity permit us to determine the absolute degree 
of deviating tendency. Here, as in hyperopia, a latent 
anomalous tendency may exist but, unlike hyperopia, we 
have here no means of ascertaining at a single examination 
the absolute departure from the ideal standard. Notwith- 
standing no proof may have been obtained by these trials, 
latent tendencies of great importance may exist. Our tests 
determine the manifest conditions only, and it is a safe rule 
to consider that the deviating tendencies are never less than 
are shown by our trials, but that they may greatly exceed 
that which we are able to demonstrate. 
Having determined in this manner the approximate con- 
dition of muscular adjustment when no effort of accommo- 
dation is demanded, we may proceed to a similar examina- 
tion at a near point. For convenience we may adopt the 
distance at which the majority of people hold the page 
when reading. Tests made at the distance of one half 
metre will sufficiently indicate the tendencies when the 
eyes are in accommodation for near work. Here prisms of 
greater angle than those employed for producing diplopia 
at a distance will be required, but the determinations may 
be made in the same general manner. Presbyopic persons 
should be supplied with reading-glasses in making this test, 
and the glasses for myopes should be such as are suited for 
the prescribed distance. 
Terms by which we may express all the deviating tenden- 
cies which may be discovered in the manner indicated have 
been wanting. The imperfections of the nomenclature for 
ocular muscular anomalies have been discussed by myself in 
the articles already referred to, and a system of terms has 158 
George T. Stevens. 
been suggested. While, in order to avoid misunderstand- 
ing, the terms already familiar will, to a certain extent, be 
employed in this discussion, those which I have proposed 
will be used as the standard, and without apology for the 
innovation beyond what I have expressed in the former 
papers. The signification of these terms is repeated here: 
“I. Generic terms. Orthophoria (opdoS, right, cpopoS, a 
tending): a tending of the visual lines in parallelism. Hetero- 
phoria (erepo?, different): a tending of these lines in some 
other way. 
“II. Specific terms. Heterophoria may be divided into : 
(i) esophoria: a tending of the visual lines inward; (2) 
exophoria: a tending of the lines outward ; (3) hyperphoria 
(right or left): a tending of the right or left visual line in a 
direction above its fellow. 
“ This term does not imply that the line to which it is 
referred is too high, but that it is higher than the other, 
without indicating which may be at fault. 
“III. Compound terms. Tendencies in oblique directions 
may be expressed as hyperesophoria, a tending upward and 
inward ; or hyperexophoria, a tending upward and outward. 
The designation ‘ right ’ or ‘ left ’ must be applied to these 
terms. 
“ In recording the respective elements of such compound 
expressions I have employed the sign l_ . For example, if 
it is desired to indicate that the right visual line tends above 
its fellow 30, and that there is a tending inward of 40, the 
facts are noted thus : Right hyperesophoria 30 l— 40.” 
II. 
HYPERPHORIA. 
By hyperphoria is meant the condition of the ocular mus- 
cles in which, with a minimum of tension, a deviation of one 
visual line above the other would result. Habitual binocu- 
lar vision is assumed, although we shall see that it is proba- 
ble that in a considerable proportion of cases in which 
hyperphoria of more than a single degree exists, the ten- 
dency to diplopia is so great that the subjects of the The Anomalies of the Ocular Muscles. 
159 
affection often surrender to it—a fact confirmed by the 
marked amblyopia often found associated with this muscu- 
lar condition. 
Among the varieties of heterophoria none exerts a more 
disturbing or injurious influence than hyperphoria. It is 
not only a condition giving rise in itself to great fatigue and 
perplexity, but it complicates and exaggerates all other 
faulty tendencies. When we recall the fact that with a 
fair adducting power one may overcome prisms of 50° with 
the base to the temples, and that with a good abducting 
ability a prism of y° or 8° is easily overcome in the opposite 
direction, it will be apparent that muscles which do not 
ordinarily overcome more than a prism of three degrees, as 
is the case when the prism is placed with its base up and 
down, must be in a condition of great disadvantage when 
hyperphoria of one or two degrees exists. If we were to 
compare the relative nervous impulse demanded by the 
grade of the prism, which can be overcome in the different 
directions, then a deviating tendency of one visual line 
above the other (hyperphoria) of one degree would be 
equal to a deviating tendency outward (exophoria, insuffi- 
ciency of the interni) of more than fifteen degrees. In 
other words, a faulty tendency of one or two degrees in the 
vertical direction falls little short of a diverging strabismus 
in importance. That this is actually nearly the relative im- 
portance of the two conditions appears evident from several 
considerations which arise from conditions found associated 
with hyperphoria. These conditions are local and remote. 
The local relate directly to the function of vision, to the ad- 
justments of the eyes in the performance of the visual 
function, and to nervous disturbances of a functional or 
trophic nature in and immediately about the eyes. 
The remote conditions relate to a great variety of dis- 
turbances of a nervous character in parts more or less 
removed from the eyes. 
Hyperphoria of a low grade, as determined by a correct- 
ing prism, is very frequently attended by amblyopia. It is 
no unusual occurrence to find, in a case of hyperphoria 
which may be measured by a prism of i° or 20, vision of 160 
George T. Stevens. 
only £■§■ or even less, while the refractive conditions are not 
far removed from emmetropia, and the ophthalmoscope 
reveals either no pathological state or only a slight tendency 
to the hyperaemia about the disc which is characteristic of 
irritability of the eyes from muscular irregularities. The 
relative number of cases in which such defective visual 
power exists will, to one who has not well considered the 
subject, appear to be out of proportion to the muscular 
defect. The surprise will, however, give place to convic- 
tion if we bring clearly to mind the actual effects from the 
standpoint of physiological optics, of a very slight faulty 
tendency in the vertical direction. An actual deviation of 
a single degree would result in a separation of images at a 
distance of one half metre, approximately of 6.4 mm. A 
patient, then, with this amount of deviating tendency, who 
would bring the letters of the type in which this page is 
printed, even in contact, the lower border of the upper image 
touching the upper border of the lower, would require to 
exert a force upon the superior and inferior muscles greater 
than Graefe was able to exercise. If, however, by long 
practice, the muscles engaged in overcoming this fault 
acquire unusual strength, as is actually the case, still, when 
the tension has been continued for a considerable time, or 
when the general nervous tone is diminished from fatigue 
or ill health, an almost irresistible tendency to diplopia 
will occur. The remedy for the confusion thus induced is 
a renewal of the inordinate muscular tension or the sup- 
pression of the image of one of the eyes. This later really 
takes place, and the image suppressed is liable to be that 
of the eye in which greatest refractive anomaly is found, if 
a difference exists, or if the eyes are equally well adapted 
for clear vision the suppression occurs alternately. Hence, 
with a greater refractive anomaly in one eye, amblyopia will 
usually be found principally in the less perfectly constructed 
eye, while if the eyes are nearly or quite alike, the ambly- 
opia will exist equally in the two eyes. Exceptions to this 
rule exist, especially in cases where, with myopia as the ame- 
tropic condition, the myopic eye is employed at the near 
point, while the more perfect eye is used for distant seeing. The Anomalies of the Ocular Muscles. 
161 
The extent to which amblyopia exists in connection with 
hyperphoria is illustrated in the following tables. One 
hundred consecutive cases in which there existed hyper- 
phoria, and in which no disease or injury of the eyes was 
found, and in which the refractive errors were not sufficient 
to account for any considerable defect of vision when cor- 
recting glasses were used, are included in the tables, ex- 
cluding cases of high grades of refractive errors. The 
highest grade of astigmatism not exceeding 3.00 D, the 
highest of hyperopia not exceeding 4.00 D, and the highest 
of myopia not exceeding 5.00 D. 
TABLE I. 
Refractive error. 
1.00D or 
less. 
More than 1.00 
D ; not exceed- 
ing 2.50 D. 
More than 
2.50 D to 
4.00 D. 
More than 
4.00 D to 
5.00 D. 
Total. 
Emmetropia 
45 
Myopia . . . 
9 
19 
7 
7 
42 
Hypermetropia 
37 
24 
12 
73 
Astigmatism 
28 
7 
5 
40 
74 
50 
24 
7 
200 
Refractive error. 
Acuteness of 
vision. 
More than i.ooD; 
More than 2.50 D; 
i.oo D or less. 
not exceeding 
not exceeding 
Total. 
2.00 D. 
5.00 D. 
Best eye. 
Worst 
eye. 
Best eye. 
Worst 
eye. 
Best eye. 
Worst 
eye. 
20 
■sir 
38 
21 
7 
7 
4 
4 
81 
20 
817 
22 
15 
8 
8 
1 
5 
59 
20 
TO" 
6 
8 
3 
7 
3 
4 
3i 
inx 
I 
2 
2 
5 
1 
2 
13 
TT7 
I 
I 
I 
2 
2 
2 
9 
20 
rwG 
3 
2 
5 
20 
i 
I 
2 
Total 
68 
5i 
21 
29 
11 
20 
200 162 
George T. Stevens. 
In the first table the proportion of eyes affected with 
different grades of refractive errors is shown ; in the sec- 
ond, the acuteness of vision according to the refractive 
condition. 
The vision of the best- and worst-seeing eyes in each 
grade is given but for convenience, in the estimate of the 
comparative value of the best and worst, in all cases where 
vision is equal in the two eyes one is reckoned as best and 
the other worst. If anisometropia exists to the extent of 
bringing the refractive conditions of two eyes in different 
columns, the vision of one eye only is placed in each 
column. 
From the above tables we obtain the following approxi- 
mate results: 
Average Vision of Best Eyes. 
Sixty-eight with less than i.oo D refractive error, 
Twenty-one with more than i.oo D and less than 2.50 
refractive error, 
Eleven with more than 2.50 D and less than 5.50 D re- 
fractive error, 
General average of vision of 100 best eyes, 
Average Vision of Worst Eyes. 
Fifty-one with less than i.oo D refractive error, 
Twenty-nine with more than i.oo D and less than 2.50 D 
refractive error, 
Twenty with more than 2.50 D and less than 5.50 D re- 
fractive error, 
General average of vision of 100 worst eyes, f-g-. 
It will be seen from the above table that defective vision 
is rather the rule than the exception in moderate degrees 
of hyperphoria. It is a fact that must have occurred to 
every experienced oculist, that in anisometropia a material 
difference in the visual power of the two eyes is exceedingly 
common. But it is also true that in anisometropia a differ- 
ence in the form of the orbit is quite common, a fact which 
would tend to a failure of equilibrium in the length or 
strength of the motor muscles of the eyes. Experience The A nomalies of the Ocular Muscles. 
163 
confirms this reasoning, and I have found that instances of 
even approximate balancing of the eye muscles in aniso- 
metropia is rather exceptional. 
From the facts thus ascertained it becomes evident that 
amblyopia is not only very commonly associated with 
hyperphoria, but that it is not uncommonly a result of that 
anomalous condition. 
A peculiar and interesting visual disturbance, related to 
yet differing from amblyopia, is the inability of the subject 
to see small objects clearly, although for larger objects, at 
the distance of some feet, the visual power is fair or even 
good. Thus, one may be able to read No. XXX., or even 
No, XX. of Snellen’s scale, and may have no especial 
fault of accommodation, yet when No. I. is presented at 
the distance of one foot, the patient is quite unable to 
read. Small objects or characters are seen indistinctly or 
not at all. The fault in these cases appears to consist in 
an inability completely to fuse the images of the two eyes, 
while the separation is not sufficiently great to enable 
the patient to easily suppress one of them. This phenome- 
non is illustrated in the confusion which appears when 
one reads the word here doubly printed : MssgMtSdS&StF 
If we cover with a card the lower range of type, the word 
is perfectly clear. A corresponding result may be effected 
in a considerable degree of hyperphoria by the mental sup- 
pression of the upper or lower rank of letters. If, how- 
ever, the separation is less complete, as in this instance : 
gfeegmmod&tim we are quite unable to exclude either of 
the confusing ranks, as in the former experiment with 
the card, and the difficulty of a mental exclusion on the part 
of the subject of hyperphoria in this latter case is likewise 
greater than in one of more complete displacement. That 
only a comparatively small proportion of hyperphoric per- 
sons experience in marked degree this inability to see small 
objects well, is probably to be accounted for on the princi- 
ple that in the great majority of instances the subject of 
hyperphoria is able either to fuse the images completely, or 
to displace them to such an extent as to enable a mental 
exclusion of one image to take place. 164 
George T. Stevens. 
The conditions in hyperphoria relating to the adjustments 
of the eyes through the influence of their motor muscles 
are extremely interesting and important. The disturbing 
effects upon the lateral equilibrium is especially noticeable, 
and is a source of great perplexity to the oculist in his 
examinations of the muscular conditions. In hyperphoria 
the tests for lateral deviations are very often contradictory, 
and in a very considerable proportion of cases unsatisfac- 
tory. Unless the examiner is on his guard against the 
anomaly under consideration, he is liable to fall into grave 
errors of diagnosis and of practice. These errors are espe- 
cially liable to occur if we rely for evidence for muscular 
balance upon the near test as suggested by Graefe. By 
such a trial we are, in moderate degrees of hyperphoria, 
likely to find extreme grades of “ insufficiency of the in- 
terni,” when in fact, if the test is made at a distance of 
twenty feet, the contrary condition is found. It is not an 
unusual occurrence with the existence of a single degree, or 
even less, of hyperphoria, to observe with actual esophoria 
of 2° or 30 (prism) an apparent exophoria in accommodation 
of io° or even 150. Such results illustrate forcibly the dan- 
ger of relying upon the dot and line test, or upon any 
similar test at the near point, for determining the propriety 
of an operation for tenotomy of the externi. Indeed it will 
not be out of place to remark in the most emphatic manner 
that the test for “ insufficiency ” made at the near point 
should never be taken as a guide for an operation. 
This principle of apparent contradiction is well illustrated 
in the following interesting case. A gentleman was found to 
haveso stronga tendency of the visual axes to deviate inwards 
that at distances of twenty feet much difficulty was experi- 
enced in maintaining single vision. A relaxation of the force 
of the external recti muscles habitually resulted in homony- 
mous diplopia. The insufficiency as measured by prisms 
was, however, not more than four degrees. On the contrary, 
if the gentleman held a pencil or his finger before him at the 
distance of fifteen or eighteen inches from his eyes, crossed 
diplopia occurred from “ insufficiency of the interni.” A 
pencil held at fifteen inches was doubled to such an extent The Anomalies of the Ocular Muscles. 
165 
that the two images appeared about an inch separated. By 
the test of the dot and line the insufficiency was only about 
6° or 7°. 
This gentleman was found to have hyperphoria of 5°, and 
an operation for the relaxation of the superior rectus of 
one eye was made, followed a day or two later by relaxation 
of the inferior rectus of the opposite eye. On the day 
following the last operation there was no diplopia or even 
“ insufficiency of the interni ” at the near point, and binocu- 
lar vision was maintained with ease at the distance. Several 
months later the gentleman again complained of double 
vision at near points, and it was found that hyperphoria of 
2° in the same direction as before was now manifest. The 
inferior rectus of the upward tending eye was now ad- 
vanced, bringing the visual axes to the same plane, when 
again the troublesome diplopia at the near points dis- 
appeared entirely. 
A lady has crossed (heteronymous) and vertical diplopia, 
both for distant and near points. If a prism of 12° with its 
base down is placed before one of the eyes, she has at the 
distance of twenty feet “ insufficiency of the externi ” of 30, 
but if no vertical prism is used, one of 40 with its base in 
will bring the two images to a vertical line, thus showing 
insufficiency of the externi with the strong vertical prism, 
and “ insufficiency of the interni ” without it. If now a 
prism of 6° with its base up before the right eye, or with its 
base down before the left eye, is used, the images of the 
two eyes blend perfectly. 
Thus it appears that as the result of the deviating ten- 
dency upward an “ insufficiency of the interni,” both at 
near and distant points, may be simulated, while in fact the 
visual axes may be inward. Not only does the existence 
of hyperphoria often give rise to an apparent exophoria in 
accommodation when the real tendency of the eyes is in- 
ward, it also frequently presents the indications of exophoria 
at a distance while the abducting power is much restricted. 
We may, for instance, find exophoria 2° or 30 (prism), or 
even more, with a power of abduction not exceeding the 
apparent exophoria. Here is an evident contradiction, and 166 
George T. Stevens. 
it may be, so long as the hyperphoria exists, impossible to 
determine whether our tests actually indicate an inward or 
an outward tendency of the visual lines, or neither of these 
conditions. It is because this important fact of the differ- 
ence between the relation of the visual lines at a distance 
and those at near points has in many cases been over- 
looked, that surgeons of distinguished ability have some- 
times performed tenotomy of the externi in cases of sup- 
posed “insufficiency of the interni ” with the result of 
obtaining homonymous diplopia, without relief to the 
symptom of asthenopia. When once the hyperphoria is 
relieved by operation, we may hope for a more perfect 
determination of the condition of the lateral muscles. It 
is not proposed here to discuss the physiological reasons for 
the complications found in the muscular test when hyper- 
phoria exists ; this is a subject presenting many important 
difficulties, and the phenomena described can be fully ex- 
plained only by actual experiments upon the muscles them- 
selves. The evidences which may be found, however, that 
very marked “insufficiency of the externi ” may exist when 
the accommodating and converging functions are at rest, 
and of “ insufficiency of the interni,” of possibly very high 
grade when these functions are exercised, illustrate the very 
unsatisfactory nature of the terms which have been so long 
employed in this connection, and appear to demonstrate 
that the use of terms having such opposite and misleading 
significations should be discontinued. The relation of 
myopia to muscular anomalies should occupy a prominent 
place in the discussion of the conditions dependent upon 
hyperphoria, but for reasons which will be given, that sub- 
ject will be reserved for examination in the chapter on 
exophoria. 
Another local affection caused by hyperphoria is hyper- 
secretion of tears, by which the fluid fills the conjunctival 
sac and overflows the eyelids, causing much inconvenience 
and often disturbance of vision. These cases simulate the 
conditions found in obstruction of the nasal duct, and the 
absence of a general understanding of their nature is illus- 
trated in the frequency with which such cases present them The A nomalies of the Ocular Muscles. 
167 
selves for treatment, after having been subjected perhaps 
for many months to the process of probing the tear pas- 
sages without any success in relieving the affection. 
A branch of the fifth nerve supplies the lachrymal gland, 
and irritations to this nerve resulting from the efforts of 
correcting hyperphoria may result in so stimulating the 
gland as to induce the hypersecretion of tears, or it is quite 
possible that the pressure of the eyelids, which is often 
brought to bear to assist the ocular muscles in the perform- 
ance of their duties, may expel the fluid from the gland in 
inordinate quantities. 
Certain marked facial expressions and certain attitudes 
are characteristic, though not by any means constant in 
hyperphoria. Certain patients affected with this anomaly 
when looking indifferently, the eyes not specially directed 
to any object, will often present an appearance of moderate 
strabismus, more frequently diverging than converging. One 
of the eyes may even be observed to swing outward and 
then inward, giving a certain unsettled expression to the 
countenance. If, with even these strong indications of 
ocular deviations, tests for equilibrium are made, the result 
may be that either slight or even no evidence of lateral 
vicious tendency will be found. Involuntary convulsive 
contractions of the muscles of the face, giving rise to 
habitual distortion, constitute an important indication in 
some instances, of the efforts which are being made to 
overcome the effects of hyperphoria. 
The habitual spasmodic closure of the lids of one eye 
should always direct the oculist’s attention to the relations 
of the visual axes in the horizontal line. An effect upon the 
physiognomy not unfrequently observed is a rigid stare, 
the eyes being opened very wide, and all the facial muscles 
being apparently in a state of tension ; associated with this 
peculiarity there is sometimes observed a tendency to snap 
the lids together forcibly and almost spasmodically. 
The characteristic attitude of the head is even more strik- 
ing and much more frequently observed. The head is 
carried toward the. shoulder, usually to the side correspond- 
ing to the eye which tends below the other. This appears 168 
George T. Stevens. 
at first thought to be quite inconsistent with the demands 
for relief. But when we remember that the object seen by 
the upward tending eye appears lower, and that seen by the 
downward tending eye appears higher, than the other, it be- 
comes evident that by carrying the head toward the lowest 
tending eye the images of the two eyes are brought more 
directly into the horizontal line. In a certain proportion of 
these cases the contraction of the muscles of the neck be- 
comes permanent, demanding for relief tenotomy of the 
tendons of the sterno-mastoid muscle ; but in much greater 
number the muscles of the neck will regain their equilibrium 
either speedily or after some time, when once the vicious 
ocular tendency is removed. 
This peculiar carriage of the head is much more common 
than would be supposed by one who has not specially inves- 
tigated the subject. To a close observer familiar with the 
fact, the false relations of the eye muscles is very often 
reached even before any of the technical ocular tests are 
made. Graefe spoke of the turning of the face to one side 
in cases of “ insufficiency of the interni,” in order to obtain 
relief to the lateral muscles or to assist in the mental exclu- 
sion of one image. The attitude of carrying the head toward 
one of the shoulders in hyperphoria is even more character- 
istic and much more common, and in this case serves to per- 
mit of more easy fusion by raising one image and depressing 
the other. As has been observed above, correction of the 
deviating tendency of the eyes is followed by an habitual 
erect carriage of the head. 
The more remote results of hyperphoria are those common 
to anomalies of the ocular muscles, but with certain special 
characteristics. Neuralgia, neurasthenia, insomnia, chorea, 
and epilepsy are among the manifestations of this condi- 
tion. Much more than esophoria or exophoria is hyper- 
phoria inducive of vertigo and epilepsy. The nervous dis- 
turbance arising from this cause is more perplexing, both 
from the difficulty in overcoming it by ordinary effort, and 
from the complications arising from it in respect to the con- 
verging and diverging efforts, than moderate grades of 
deviating tendencies in the lateral direction, Hence, The Anomalies of the Ocular Muscles. 
169 
nervous phenomena of a higher intensity are liable to 
result from this condition. The constitutional effects 
of hyperphoria are well shown in the following illustra- 
tion : 
This case was seen and treated at the Willard Asylum for 
the Insane. It is proper to remark that this institution is 
not designed for acute cases, or those in which there exists 
a reasonable prospect of recovery. It is a home for incura- 
bles, and the case here reported was one of chronic epilep- 
tic mania belonging to that class. The history is given as 
it was furnished by Dr. P. M. Wise, the superintendent, 
and Dr. H. E. Allison, the physician under whose immediate 
charge the patient was. 
M. L., female, aged thirty-six. Insanity commenced seven 
years previous to the present record, but the patient has been 
subject to epilepsy for an unknown period, certainly longer than 
the period of insanity. About once a month she is taken with a 
series of epileptic seizures, varying from three to eight or more, 
and at these times is liable to become greatly excited, the degree 
of excitement depending apparently upon the number of convul- 
sions. A period of great exaltation and frenzy follows, during 
which she is furious, sings wildly, and shouts at the top of her 
voice, and is exceedingly destructive and violent. The paroxysm 
may last several weeks. When it has subsided, she becomes or- 
derly, neat, and industrious, and usually continues so until another 
series of convulsions occurs. 
She was first seen by me July 31, 1886. Examination of the 
eyes showed hyperopia of moderate degree and right hyperphoria 
40 (prism). Glasses for the correction of the hyperopia were fur- 
nished, and tenotomy of the right superior rectus was made, fol- 
lowed within a few days by a similar operation upon the left inferior 
rectus. This final operation was made August 22d. Bromides, 
which had been previously freely administered, were withdrawn 
July 31st. August 26th, four days after the last operation, a 
period of moderate excitement, very much less pronounced than 
usual, commenced, which lasted until Sept. 12th. On Jan. 2, 
1887, five months from the beginning of the ocular treatment, Dr. 
Allison wrote concerning Miss L. : “ She has not, thus far, had 
any attack of maniacal frenzy, and only one attack (that which is 
above mentioned) of excitement, which was not great. She says George T. Stevens. 
170 
she has not had any convulsions. . . . She is very much 
improved, and feels very grateful.” 
A single other instance will suffice here to illustrate the 
constitutional effects of hyperphoria : 
A lady gave me the following history of her physical condition : 
She had been subject to asthenopia, severe headaches, vertigo, 
and backache during all her life, and had hardly experienced any 
relief during her waking hours. Fifteen years before my acquaint- 
ance with her she had been insane, and had been taken to an 
insane asylum, from which she was removed after a period of 
nearly one year, but only to return. She was not free from illu- 
sions for nine years. With the restoration of reason a new form 
of nervous manifestation was exhibited. Habitual and frequent 
paroxysms of vomiting have now continued during several years. 
The paroxysm commences by seeing every thing in confusion, 
followed by an indescribable nervous sensation in the back, and 
finally by violent retching and vomiting, which is greatly intensi- 
fied when the lady opens her eyes. The paroxysms continue 
from two or three days to several weeks ; the last attack lasted 
six weeks. 
She was found to have right hyperphoria 50. She was fur- 
nished for a time with prismatic glasses, which established a 
nominal correction of hyperphoria, and after a few weeks 
tenotomy of the superior rectus of the right eye was made. The 
paroxysms of vomiting did not return, the lady was relieved of 
the distressing pain in the head, and soon after the tenotomy she 
expressed herself as feeling in every way better than she had done 
during the past twenty years. The lady was not seen during sev- 
eral months, but when finally she did present herself, she com- 
plained of suffering again from symptoms of asthenopia, but no 
more from the general nervous condition. Hyperphoria of 20 
was found still to exist, which could not be discovered soon after 
the operation was made. Another tenotomy has since been made, 
which has been followed by relief to the asthenopic symptoms. 
It will be seen that attending this muscular anomaly, 
headaches, pain in the back, vertigo, insanity, and habitual 
vomiting constitute prominent features which followed this 
lady from infancy; one form of trouble succeeding another, 
and possibly replacing it for a time, but from some mani- 
festation of which she was never free until she was relieved The Anomalies of the Ocular Muscles. 
171 
from the necessity of a most difficult and perplexing ocular 
adjustment. With this release came relief from the whole 
train of nervous symptoms. 
Treatment of Hyperphoria. 
The treatment of hyperphoria is tenotomy. If the pa- 
tient is unwilling to submit to a radical relief, or if the sur- 
geon hesitates to perform the operation, if complicating 
circumstances render such an operation inadvisable, other 
means may be resorted to. The use of a prism, with its 
base up or down, is indicated under such circumstances. 
Let it be remembered that while glasses are of inestimable 
value, they are still inconvenient and often extremely so ; 
that with the best art of the optician, glasses detract from 
the symmetry and expression of the face, a fact of much 
importance to females at least ; and finally, that in the con- 
ditions of muscular deviations, they neither cure nor afford 
as complete temporary relief as a removal of the actual 
defect. Indeed, it is not uncommon for one having hyper- 
phoria of i° or 2° to suffer much pain in or about the eyes 
while wearing a correcting prism, but to experience almost 
immediate and complete relief from all the symptoms 
caused by the mal-adjustment of the eyes, as soon as ten- 
otomy is performed. Glasses are like crutches, desirable 
when defects which render them useful cannot be removed. 
A special disadvantage of a very weak prismatic glass is 
the fact that it reflects a false image of every strongly illu- 
minated object, seen at some distance, just above or just 
below the true image. This false image is often extremely 
annoying. 
The daily exercise, continued through two or three weeks, 
of overcoming prisms placed vertically before the eyes 
alternately, with the bases in the same direction or before 
the same eye with the prism reversed, may tend to give the 
muscles greater vigor, and hence to enhance their ability to 
endure the difficulty. The duration of the exercise should 
not exceed three to five minutes at a time. 
If tenotomy is performed, the surgeon must choose be- 
tween relieving the tension of the superior rectus of one or 172 
George T. Stevens. 
the inferior rectus of the other eye. If it is evident that 
the defect can be located in one or the other muscle, of 
course his treatment should be directed accordingly. This 
is possible in a very considerable proportion of cases. The 
appearance of the eyes, when the patient’s view is directed 
indifferently in space, will often aid in forming a correct 
judgment. The fact that, ametropia being corrected, the 
vision of one eye is less than that of the other, is a strong 
indication that this is the deviating eye. 
If it is impossible, as in a certain proportion of instances 
it appears to be, to determine to which of the eyes the 
anomalous tendency is to be attributed, we are left to select 
upon more general principles the one to be subjected to the 
tenotomy. The inferior recti are those which possess the 
greatest power, and therefore a slight advantage taken from 
one of these in favor of the weaker muscle will, other cir- 
cumstances being equal, cause, if possible, less change in 
the motile functions of the muscles than in the opposite 
case. If the hyperphoria is of considerable grade, it is 
better, unless there are very positive indications that the 
fault lies in a special muscle, to gain the relief by relaxing 
both the superior rectus of one eye and the inferior of the 
other. By this procedure, no practical restriction results 
to the movements of either eye in the vertical direction. 
The method of performing tenotomy in these cases of 
deviating tendencies less than strabismus, has been de- 
scribed by me some years since.' Since that time I have 
found it advisable to modify the procedure somewhat, ren- 
dering the operation more simple and the results more 
satisfactory. As now performed, the eyelids being retract- 
ed, a fold of the conjunctiva is seized by a fine but rather 
rigid pair of mouse-tooth forceps, parallel with the course of 
the muscle and exactly over its insertion. With a pair of 
small narrow-bladed scissors, having blunt but very perfectly 
cutting points, a transverse incision is then made through 
the membrane, exactly corresponding to the line of inser- 
tion of the tendon. The conjunctival opening thus made 
1 “ Irritation oculo-nevrale ” : Memoire de l’Acd. Royale de Med., Belgium, 
1883. The Anomalies of the Ocular Muscles. 
173 
should not exceed in extent one fourth of an inch. With 
the forceps now pressing the outer cut edge of the con- 
junctiva slightly backward toward the course of the 
tendon, the latter is seized behind but very near its inser- 
tion. The distance may depend upon the freedom with 
which the intended section of the tendon is to be made. 
But in hyperphoria or in slight relaxations of the lateral 
muscles, a distance barely sufficient to allow a small part of 
the tendon to be raised from the sclera is all that should be 
allowed. Making some tension now with the forceps, the 
points of the scissors are directed against the central por- 
tion of the tendinous insertion and toward the sclera, when 
a small opening is made dividing the centre of the tendi- 
nous expansion exactly on the sclera. The small opening 
is now to be enlarged by careful snips of the scissors toward 
each border, keeping more carefully on the sclera as the 
border of the tendon is approached. As the section of the 
tendon is carried toward the borders, the outer blade of the 
scissors passes beneath the conjunctiva. If the relaxation 
of the tendon is to be slight, the extreme outer fibres of the 
tendon are to be preserved untouched ; but if a considerable 
effect is desired, these fibres can be entirely severed, pro- 
vided that the reflection of the capsule of Tenon upon the 
tendon is not disturbed. By means of the capsule acting as 
an auxiliary attachment, the tendon is held in position, but 
is allowed to fall back slightly while maintaining its rela- 
tion to the eyeball. In this respect, and in preserving the 
outer tendinous fibres, this operation differs radically from 
the ordinary operation for strabismus, and from any opera- 
tion which has been proposed for so-called “ partial tenot- 
omy ” of the recti muscles. 
The judgment of the operator must determine the extent 
to which the division should be carried, but should it be 
found that too little has been accomplished, the section can 
be extended. In doing this, the use of a very fine hook 
may be advisable. For this purpose a hook very much 
smaller and more delicate than the ordinary tenotomy 
hook should be employed. Its rounded point is carried 
under the remaining border of the tendon with great care, 174 
George T. Stevens. 
to prevent hemorrhage or unnecessary disturbance of the 
connective tissues ; the extension being made toward one 
and then toward the other border, as the demand for further 
relaxation may require. When the remaining band of fibres 
is made tense by the hook it is slightly elevated from the 
sclera, when the fine-pointed scissors are introduced be- 
neath the conjunctiva, and the necessary extension of the 
wound is made with extreme caution not to divide the cap- 
sular attachment. The conjunctival suture should in no 
case be employed. 
All bandaging of the eye or covers of any description are 
not only needless but mischievous. Indeed, if permitted to 
digress from the subject at issue, I would express my un- 
qualified disapproval of bandages in nearly all operations 
about the eyes. During many years I have abstained 
almost entirely from the use of bandages in ophthalmic 
surgery, and know of no reason to regret this course. 
Bandages are promoters of heat, filth, and septicism. They 
have no possible advantage, and should, I believe, go out of 
fashion in ■ ophthalmic operations. My own patients are 
permitted to return at once from the operating-room to 
their homes without regard to weather or the distance to be 
travelled. Many of them return on the day of the operation 
to their ordinary business. 
In respect to the results of tenotomy for hyperphoria 
there would appear to be nothing in the range of surgery 
more satisfactory or certain. My first operations for the 
correction of a tendency of the visual lines to deviate in the 
vertical direction, and in which no vertical strabismus ex- 
isted, were made in 1875. Very many were made in each 
succeeding year, but it was not, however, until during the 
past two years that the operation in my hands became as 
uniformly successful as could be desired. Now, with the 
procedure which has been described above, there is a great 
measure of certainty of success. During the year 1886 I 
performed tenotomy for the relief of hyperphoria one hun- 
dred and nine times in eighty-eight cases. The result in 
nearly every instance was, when the patient was last ex- 
amined, a relief either partial or complete to the hyper- The Anomalies of the Ocular Muscles. 
175 
phoria. In some instances in which, soon after tenotomy, 
no hyperphoria could be discovered, a partial return to the 
original condition has been found, and quite possibly this 
may be true of some who have not been seen since within 
a month or two of the operations. Of those in which a par- 
tial but incomplete relief to the hyperphoria has been ac- 
complished, some are still under observation for treatment. 
Among these are two cases in which tenotomy of both ex- 
terni has been performed by prominent oculists, in each 
instance leaving the patient with homonymous diplopia and 
pronounced hyperphoria, unless, in one instance, the verti- 
cal deviation should be regarded as an original vertical 
strabismus. In both instances nearly complete correction 
has been accomplished, and there seems no doubt that in 
the end equilibrium in all respects will be established. 
Of the cases which have been stated to be correct when 
last seen, it may be repeated that it is possible that, at a 
future time, hyperphoria of a certain degree may become 
manifest. This happens in a proportion of cases after some 
weeks or months, and it is not safe to assume that no hyper- 
phoria exists until many months after the operation. 
In respect to the results of treatment of hyperphoria it is 
my purpose only to say here that the relief in uncompli- 
cated cases is of the most marked, not to say surprising, 
character. Many patients who, from this cause, have suf- 
fered from distressing affections during many years recover, 
when this source of irritation is removed, with astonishing 
rapidity. 
With little admiration for the practice of introducing 
slight modifications of well-known instruments as new de- 
signs, I think it reasonable, when the old instruments are 
evidently unsuited to new operations, to suggest such 
changes as will adapt them to the new conditions. It is in 
this spirit that I venture to describe such modifications of 
familiar instruments as I have found best suited to the 
operation for the relief of the ocular muscles as it has been 
described in this article. 
The scissors have narrow yet strong blades, cutting per- 
fectly at the points, which are blunt, in order that they may 176 
George T. Stevens. 
not endanger the sclera. The blade is scarcely wider at the 
distance of half an inch from the point than at the point. 
This form permits the narrow blade to be insinuated be- 
tween the conjunctiva and the insertion of the tendon with 
the least possible disturbance. I have found much diffi- 
culty in having scissors of this description made which, 
with the very narrow blades, should possess sufficient 
strength and perfect cutting qualities at the points. After 
several trials, Messrs. Meyrowitz Brothers have succeeded 
in producing an instrument combining these requirements. 
The toothed forceps are so constructed as to combine 
much strength with delicacy at the working extremity. 
The branches are one fourth of an inch broad at their 
widest part, and taper but slightly until within one half 
inch from the toothed extremity, where they are suddenly 
contracted to a very narrow shaft, as fine as the most deli- 
cate iris forceps. 
The hook is also quite delicate. From the stem, an inch 
in length, the hook extends by a short curve, at nearly a 
right angle, to the distance of three sixteenths of an inch. 
It is rounded and slightly probe-pointed at its extremity. 
I he diameter of the hook and of the principal part of the 
stem is a little less than 0.5 mm, or of the size of No. 25 of 
Brown & Sharp’s wire gauge. G. P. PUTNAMS SONS, PRINTERS 
NEW YORK