SOME OF THE CAUSES OF FAILURE 
IN 
Operations for the Correction of Squint. 
Read before the Kentucky State Medical June 25, 1885. 
[Reprinted from the Philadelphia Medical Times, of September 5, 1885.] 
BY DUDLEY S. RKYNOF±>S, M.D., 
Professor of General Pathology, Hygiene, and Diseases of the Eye and //frl 
Hospital College of Medicine, Louisville. 
i 
In order that we may be in a position to advance in the studyoTflTC' 
best means of relief for persistent squint, it is first necessary that we 
should clearly comprehend its nature, as well as the predisposing and 
exciting causes. 
In 1862, Donders gave the first hint at the real causes of convergent 
and divergent squint. Before that time, however, central lesions of 
the nervous system, traumatism, and habit were regarded as the most 
common causes; while sudden fright, and the attempt to imitate a person 
already affected, were counted as occasional causes. 
Graefe was quick to apply the optical principle suggested by Don- 
ders. Others took up the subject, and, in 1864, when Donders wrote 
his great work on the anomalies of accommodation and refraction for 
the New Sydenham Society of London, he presented to the world a 
clear and well-nigh complete analysis of all the varying forms of squint, 
demonstrating the causes, both predisposing and exciting, and showing 
wherein Dieffenbach’s already universally-adopted tenotomy had not 
been attended with that degree of success necessary to establish it as a 
universally-justifiable surgical procedure. What Graefe regarded as 
lost physiological sensibility through psychical exclusion, Mooren had 
already correctly interpreted as deficient refraction. Strangely enough, 
however, Mooren did not establish the relations which abnormal re- 
fracting power sustains to the accommodative function. 2 
Alfred Graefe, as early as 1858, reported a case wherein the con- 
ditions of accommodation were recognized as tending to cause a devia- 
tion of the right eye ; yet, farther on in his paper, he makes the strange 
announcement that the squint, though coexistent and intimately con- 
nected with the deficient accommodative power, was completely inde- 
pendent of the existing state of the accommodation. 
We may say that all cases of persistent squint are independent of the 
existing state of accommodation, because, the squint being already 
established, the eyes must continue the exercise of an amount of 
accommodative power sufficient to compensate as far as possible for 
the error of refraction. 
To be more plain, the world now recognizes in all cases of squint, 
whether convergent, divergent, sursumvergent, or deorsumvergent, a 
certain relation to the acuity of vision, depending upon irreconcilable 
obstacles to the harmonious fixing of the two eyes upon a single object. 
The focusing power and the accommodative power are not the 
same; yet, they are intimately associated with each other, and any dis- 
turbance in their normal relations may create the predisposing cause of 
some form of squint. Active accommodation implies the power of 
harmonious convergence of the optical axes of the two eyes, and a 
normal power of fixation. The fixing power will depend, mainly, 
upon the state of the perception, while the converging power will 
depend upon the normal state of the recti muscles, and this state, in 
turn, of course is dependent upon normal nerve and blood-supply, as 
well as constitutional vigor. Central nerve-lesions may, by disturbing 
motor branches, create spasm in the muscle, or paresis; the pressure 
of morbid growths may exercise a similar power; impairment of the 
power of perception in the retina, or of the power of transmission in 
the optic nerve, or of the sensorium, will prevent fixation of the eye 
upon an object, and thus tend to produce squint. Opacities of the 
cornea, occlusion of the pupil, or displacements of the pupil, opacities 
of the lens or its capsule, diseases of the vitreous humor, all tend 
to predispose the eye to squint. 
It is easily understood, therefore, why, in many cases, tenotomy 
can not be relied upon as a remedy for squint. I have long been im- 
pressed with the difficulties attending this means of correcting squint, 
and I am persuaded that the first step, in all cases, should be directed 
toward the correction of errors of refraction—first to the acuity of 
vision, and subsequently to the inharmonious muscular action. 
If the subject of squint have hypermetropia, which means insufficient 
power of refraction in the eyes, it will be observed at first that the 3 
subject, on looking at near objects, approaches too closely, and 
develops a squint by overtaxing the converging power of the eyes, and 
the squinting, at first, will be observed to come on with general cerebral 
excitement, followed, in most cases, by severe headache and general 
neurotic phenomena. If the subject have no organic defect, other than 
the insufficient power of refraction, the squint may be corrected by 
suspending the patient’s accommodative power and correcting the error 
of refraction. If organic change of structure has already occurred in 
the recti muscles, this must be corrected by tenotomy carefully done, 
the error of refraction being, at the same time, overcome by the use of 
suitable glasses. I have many times observed in young persons a per- 
fectly satisfactory tenotomy accompanied by the use of lenses to correct 
the error of refraction mislead the patient, who, for a time having 
regained a vigorous accommodative power, laid the glasses aside, and 
gradually the eye having the least acuity of perception deviated 
outward. 
Dr. Hermann Scheffler and Giraud-Teulon have demonstrated 
clearly the importance of muscular co-ordination of the eyes which 
have not nearly or exactly equal perceptive power. Since the acuity 
of perception always depends upon normal refraction, we must under- 
stand that eyes naturally endowed with normal perception may, in 
those who have congenital errors of refraction, never both be called 
into activity at the same time, and, by habitual use of one eye, the per- 
ception of the unused eye gradually fades as the child grows, and, after 
mature growth of the individual, this can never be regained. It is, 
therefore, obviously important to correct squint as soon as possible 
after it has become manifest. 
The tendency to squinting is often observed for weeks, and some- 
times months, before the deformity is established. During this period 
little or no excuse may, in the present state of our knowledge, be 
allowed for neglecting to determine the refraction of the eyes. The 
aversion to spectacles can not weigh against the dangers to physical 
comfort of a person deprived of the use of one eye, with the horrible 
countenance which squinting produces. 
Many a child, the subject of some trivial error of refraction, has 
been denied the opportunity of educational qualifications for a brilliant 
and useful career in life because ignorant parents, and equally ignorant 
family physicians, have said: “This child, whose nervous system is 
abnormally excited, and who suffers headaches, and who, at times, 
exhibits vertigo with nausea after prolonged attempts at study, must not 
be permitted to continue his studies; the brain is over-sensitive, the 4 
blood-vessels supplying the outer structures of the eye are flushed'; 
there is danger of brain-disease. Further attendance at school must 
not be permitted.” 
This state permitted to go uncorrected, however, will, when the 
child grows older, if the mind be active, lead in many cases to spasm at 
first, and subsequently to structural changes in one or more recti 
muscles; and this is squint. 
Now, five minutes’ attention to the state of refraction in the eyes 
will disclose the cause of all these disturbances. Suspend the accom- 
modative power, and a test of refraction not only determines the neces- 
sity for the glasses, but, at the same time, the acuity of vision and 
the character of glasses necessary. 
With the involuntary accommodation of the emmetropic eye, no 
cerebral excitement beyond that which accompanies the idea suggested 
by what the eye sees will occur. In all cases of defective refraction, 
there must be added to the normal accommodative power a certain 
tension of mind in the attempt to see with sufficient clearness to trace 
the object in view. This antagonizes the power of thought, retards 
the consentaneous exercise of the faculties of reason, and one eye 
is sacrificed in the attempt to see where great strain is required to 
maintain fixation of the eyes upon the object. On the other hand, 
persons who have but one eye gradually become educated into the 
habit of dispensing with that power of the mind which discriminates 
angles, distances, and comparative size of objects. It robs the mind 
of its best faculty in all logical processes of thought. Children 
educated in the use of one eye must have remarkable intellectual 
endowments to enable them to acquire any profound degree of original 
reasoning power. 
Claudius Ptolemy’s first book on astronomy was devoted to an ex- 
planation of the causes and uses of single vision with two eyes. In all 
accurate visual exercise there must be constantly present before the 
mind a single point in the projected field, and this necessarily depends 
on the position of the eyes and the direction of the visual line. In eyes 
having defective refracting power, the projected point of the field 
of vision must correspond to identical points in the retinae of the two 
eyes. If the image is not formed in identical portions of the retinae, the 
two eyes can not see singly, and it is a strain upon the mind, as well as 
the eye, to overcome the confusion which this condition produces. 
Whatever may be said concerning the influence of constitutional dis- 
eases or of traumatism in the development of squint, this mental strain 
necessary under the attempted exclusion of inharmonious images so 5 
irritates the sensorium as at times to disturb and limit the powers 
of thought. All errors of refraction do not lead to squint, however, 
nor even to the formation of images in eccentric portions of the retime ; 
but they do lead to the necessity for abnormal intensity of mental pro- 
cesses, and bring on headaches, with the accompanying depression of 
spirits, disturbed sleep, and impaired appetite, producing malnutri- 
tion, which, when fully established, constitute the sum of that group of 
neurotic phenomena now described as neurasthenia. With this founda- 
tion, drawn from actual observation, do you wonder that merely sur- 
gical procedures often fail to produce permanent correction of the 
squinting eye ? 
In the haste to dispatch the business in hand, to say nothing of the 
obliging disposition one feels toward the other patients who are waiting 
in the reception room, is it surprising that one should, at times, neglect 
some important detail in the preliminary examination of the eyes of the 
patient who has come for the radical cure of squint? A little intro- 
spection may be as useful for the doctor as it is wholesome to the 
Christian. The study of the causes of failure may lead to their elimina- 
tion, and thus broaden our sphere of usefulness. I find it convenient 
to make frequent reference to the little case-books in which I have 
carefully kept the record of all cases of errors of refraction which 
I have attempted to correct, since March, 1877. This often serves to 
point the way in searching for the cause of failure. 
Soelberg Wells expressed a glowing truth in the statement that the 
first effects of an operation for the correction of squint are seldom 
permanent. A little inquiry as to the reason for this robs ocular tenot- 
omy of all its simplicity, and consigns it to a place high in the list of 
the more grave and serious operations in surgery. True, any mere tyro 
may cut a tendon, and cut it well; but it takes an ophthalmic surgeon, 
well trained in the study of the anomalies of refraction and accommo- 
dation, to estimate the character of a tenotomy which shall perma- 
nently establish the necessary conditions for the exercise of binocular 
vision. I am persuaded that tenotomy, unaccompanied by correction 
of existing errors of refraction, should never be done in persons under 
thirty years of age, and then only in such as have lost the sight in one 
eye. To correct the squinting of a blind eye is, in fact, a very simple 
proceeding; but where it concerns the establishment of a harmonious 
exercise of the visual power of both eyes it is a serious business, and 
should always be done with deliberation. The mechanical devices are 
not numerous, nor difficult to apply, provided, always, the optical 
properties of the eye are first inquired into. 6 
To recapitulate briefly : Failures in attempts to correct squinting are 
to be attributed to neglect on the part of the surgeon to rectify, at the 
same time, deficiencies in the refractive and accommodative powers of 
the eye; neglect of the patient to observe the rules laid down for this 
purpose ; and, more rarely perhaps, to bungling and unskillful execu- 
tion of the tenotomy. It is a great mistake to suppose the eye operated 
upon for the correction of squint should be excluded from the light, or 
bound up as one would bind a breach of continuity in the skin, and it 
is a mistake of greater import still to permit such exercise of the visual 
power as attempting to see near objects. 
With the newly-discovered anaesthetic, cocaine, general anaesthesia 
is no longer to be thought of in operating on strabismus. The opera- 
tion being done with as small an opening in the conjunctiva as will con- 
veniently admit the points of the scissors, the eyes should at once be 
bathed in cold water, which always proves grateful to the sensibilities 
of the patient, and tne glasses, which have been previously devised for 
the correction of the error of refraction in each eye separately, should 
then be put on, to be removed at such intervals as maybe desirable for 
bathing the eyes to soothe the irritation from the wounds. The ac- 
commodative power should be kept suspended by the use of a mild 
mydriatic, just sufficient for that purpose, until complete recovery from 
the operation. 
It will be found that few persons, indeed, are able to make regular 
and continuous use of the eyes within a month after such an operation ; 
it should in all cases be allowed, not only for the firm attachment of the 
cut tendon to its new position upon the surface of the eyeball, but for 
the complete absorption of the provisional callus or plastic effusion 
which nature provides for the cementing of the cut tendon to the scleral 
surface. If the eyes be used too early, permanent impairment of mus- 
cular function may be developed thereby, and the result of an other- 
wise perfect operation materially altered. All eyes that tend to squint 
should be treated upon the first discovery of the defect. In this way 
many may be corrected without operation. After the squint is confirmed, 
operative procedures should not be delayed, because the unused eye of 
a child always loses acuity of perception from the lack of use or natural 
exercise of the vision. Slight impairment of the perceptive function 
may, if treated before the mature growth of the individual, be in a 
great measure corrected; but the dimness of sight due to lack of use 
in an eye that squints can, in an adult, rarely be improved, and never 
wholly overcome. It is hardly necessary to say that the tendons should 
always be divided close upon the surface of the sclerotica. The scis- 7 
HPT which this ma\ be done should have thin and narrow blades. 
gjgjgg||Pj|)m ts being so smoothly rounded as to prevent pricking or wound 
am of the structures with which they may incidentally be 
ptv into contact. The hook used for lifting the muscle should be 
T small and of delicate pattern. It should be angular, rather than 
curved. Finally, the patient should be cautioned not to exercise the 
muscles of the eyes for the amusement of inquisitive people, nor to 
encourage comments about the apparent results of the operation, before 
complete recovery is established.