still I have observed two cases in which a permanent convergent squint
disappeared after about a year. In both cases the squint had arisen in
young people (of eight and nineteen years of age) in the course of
irido-choroiditis which terminated in blindness, and disappeared with
the sight. The fixing eye was emmetropic in one case, in the other the
condition of error could not be determined owing to nebulae of the
cornea.
We more frequently see periodic squint disappear.
CASE 33.--M--, a boy aet. 10, was first examined by me in April, 1873;
the right eye has hypermetropia 4.5 D., and almost full visual
acuteness, the left has convergent squint, and recognises No. 6-1/2
(Snellen) with convex 10 D.; V. = 1/18 at 1 metre. (The boy's father
also squints with the left eye, which is amblyopic to a high degree (V.
= 1/36), right eye has emmetropia, and full visual acuteness). The
prescribed spectacles (convex, 4.5 D.) were used for working, but not
continually; still three years later, in 1877, the deviation was
considerably less and only occurred occasionally. In March, 1880,
nothing more was seen of the squint, only slight convergence still
recurred on excluding the left eye. Patient now wears convex 4.5 D.
constantly.
On account of the importance which the disappearance of squint possesses
in hypermetropia I will describe a few more cases which belong here.
CASE 34.--Mrs. B--, aet. 32, has on the left H. 1.5 D., V. 5/9; on the
right H. 1.5 D., V. 5/12, binocular vision (H. =.75 D., V. = 5/6 to
5/9). Asthenopic troubles are the cause of her present complaint. She
says she squinted with the right eye as a child till her eighth or ninth
year; the present position of the eyes is quite normal; ordinary type is
read at the usual distance with normal fixation without glasses.
Particularly keen fixation is rarely followed by squint, which may be
produced by excluding the right eye; the latter then deviates about 5
mm. inwards and slightly upwards; the secondary deviation of the left
eye is rather less. Only the left visual field is seen in the
stereoscope.
CASE 35.--Mrs. W--, aet. 31, has on the right H. 3.5 D., V. 5/9, on the
left V. = 1/16 with + 4 D., single words of No. 0.8 are read (mother and
aunt have also congenital weak sight in this eye). Position and movement
of the eyes are perfectly normal, exclusion of the left eye is followed
by slight relative divergence. In answer to my question whether she had
not previously squinted, patient replied that she did not know, it had
always been a matter of dispute in her family; as, however, only the
right visual field was seen in the stereoscope, we may be sure that
squint had been present and that binocular fusion had been lost in
consequence.
CASE 36.--Mrs. G--, aet. 49, report in March, 1876: On the right H. 3 D.,
V. 10/10, on the left H. 4 D., V. 10/40; a previously existing squint
had disappeared of itself; the position of the eyes appears perfectly
normal, but binocular fusion is not present; with red glass before one
eye and a prism deviating in a vertical direction before the other,
patient does not see double, but first with one eye and then with the
other. The squint as well as its disappearance occurred however, at a
time when it would have been regarded as an error to allow children to
use convex glasses.
CASE 37.--Miss H--, governess, aet. about 30, came under treatment for
asthenopic disorders; on both sides hypermetropia 2.5 D., visual
acuteness 5/18. She owns to have squinted as a child,--it had often been
remarked when she was at school. The squint gradually disappeared, but
still occurred sometimes on keen fixation. The usual position of the
eyes appears perfectly normal, and gives no suspicion of squint;
convergence occurs on exclusion, sometimes with downward deviation of
the right eye. With the aid of a red glass changing fixation is easily
produced even without prisms, but never diplopia. At first only the left
visual field was seen with the stereoscope; then the right on exclusion
of the left eye; never both at the same time. According to this the
condition of binocular vision speaks entirely for the fact, that squint
had existed long enough to prevent the development of a normal binocular
visual act, and the squint had disappeared without the help of convex
glasses in spite of the hypermetropia.
CASE 38.--Bertha W--, aet. 18, reads with the naked eye on the right No.
0.75 at 10 cm., on the left only 1.75 at the same distance;
hypermetropia of 6 D. is detected with the ophthalmoscope, with + 5.5
the visual acuteness of the right eye amounts at 1 metre to 1/9 (if the
test-letters had contained No. 8 or 7.5, that would probably have been
recognised also), on the left with + 5.5 D., V. = 1/12, with + 6 D. No.
0.8 is read with difficulty. Patient admits to have squinted as a child;
no squint is present now; binocular fusion can be detected with prisms
and she only squints now and then on the left side to assist vision,
with which, patient states without being questioned, diplopia is
combined. Spectacles have not been used till now.
I could cite several more such cases, but they would prove no more than
these. At any rate the fact is settled that squint can disappear
spontaneously, and without the aid of convex glasses even in high
degrees of hypermetropia.
Wecker's announcement that "this spontaneous cure goes hand in hand with
the progressive decrease of the accommodation, and depends on the fact
that the squinter, on the strength of this progressive decrease,
renounces more and more the aid which he finds in the increased
convergence during the act of accommodation," only proves to how great
an extent one may be prejudiced by theories. A limitation of the
accommodation must necessarily increase the claims which are made on it,
and can only afford inducement for calling forth all the help possible
to support the accommodation.
The fact that squint spontaneously disappears after normal binocular
fusion is completely and permanently lost, and in individuals who
accommodate without the occurrence of a too strong convergence,
notwithstanding their hypermetropia and without the help of the
controlling influence of binocular single vision, seems to me quite
irreconcilable with Donders' theory. Every motive for the same,
hypermetropia, difference of refraction, monocular defective vision,
&c., may not only be present without the occurrence of squint, they do
not even prevent the spontaneous recurrence of a squint already cured.
Of course I will not affirm that the causes made so prominent by Donders
exercise no influence on the origin of squint, but will only emphasize
the fact, that other causes exist which possess a greater influence, and
which we can find only in the ocular muscles.
We have no experience as to whether this spontaneous cure occurs in
myopia with divergent squint. This is not to be wondered at, as
hypermetropia is present in the great majority of cases of squint, and
the observations as to spontaneous cure are also rare in these. But I
can vouch for one case where a slight absolute divergent squint, with
crossed diplopia, which I treated shortly after its origin in a youthful
myope, with prismatic spectacles, soon disappeared, and remained
permanently cured.
The inclination to preponderance of the interni appears to be peculiar
to youth, while later on circumstances change in favour of the externi,
and that seems to me the chief ground for the spontaneous cure of
convergent squint. The cure is not always complete; deviation still
occurs on exclusion, or on particularly keen fixation; sometimes,
however, also under conditions which can only be put down to a change in
the elastic tensions of the muscles. The following is an interesting
illustration of this:
CASE 39.--Miss S--, aet. 20, states that she squinted frequently as a
child from her fifth to her tenth year; the squint gradually
disappeared, but returned again from time to time during the last half
year without apparent cause. The examination showed normal position of
the eyes, slight convergence only on exclusion. Visual acuteness on the
right 5/6, with atropine ophthalmoscopic and functional emmetropia, the
visual acuteness is lowered to 5/12 by convex 1 D.; on the left
hypermetropia 7 D., visual acuteness 5/18; the same degree of
hypermetropia is found with the ophthalmoscope.
Crossed diplopia with a difference in height is distinguished with the
aid of a red glass, the difference being corrected by a prism of 4 deg.,
with the base downwards before the right eye; a prism of 4 deg. with the
base inwards suffices to place the double images immediately above one
another. Spontaneous diplopia does not take place; only the right visual
field is seen in the stereoscope. As patient lived in Brandenburg and
only came to consult me occasionally I never had an opportunity of
seeing the squint till she decided to stay here for some time. It was
then seen that a peculiar oscillating deviation of the left eye of about
4 mm. inwards often occurred. As the previous spontaneous disappearance
of the squint and the crossed diplopia made one fear that tenotomy of
the internus might be followed by divergence, instillations were used in
order to make a more exact measurement of the deviation,--by this means
the condition was so improved in the course of a few weeks, that
deviation no longer occurred even on exclusion of the right eye.
The spontaneous cure of squint may, however, be quite complete; indeed I
have seen one case where convergent squint became divergent.
CASE 40.--A young lady, slightly over twenty years of age, showed on the
right M. .75 D., V = 10/10, on the left H. 1.5 D., V. 10/40 to 10/30,
and slight divergent squint on the left side. Crossed diplopia could be
produced with a red glass, tenotomy of the left abducens sufficed to
correct it. I had not concealed my doubts as to her statement that she
had previously squinted inwards, but they were quite dispelled by a
photograph taken about twelve years before, in which decided right
convergent squint could not be mistaken. There is something to be said
for the fact that it may have been a periodic squint, which occurred
during the taking of the picture, as the photographer would have taken
pains to hide a permanent squint in some way.
Conscious suppression of squint happens now and then, although very
rarely.
CASE 41.--Miss A. L--, aet. 27, is stated to have commenced to squint in
her first year, until at the age of eighteen she took pains to cure the
habit, and with perfect success as far as regards the position of the
eyes; the only disagreeable symptom was that she could no longer read
with the naked eye. Spectacles were therefore prescribed for her, convex
5 D., but even they did not quite remove the trouble in reading; it was
now a disagreeable, painful sensation to have recourse to squint in
order to see more clearly. It was easiest to read with greatly lowered
field of vision and with the help of a convex eyeglass as well as the
spectacles. During the examination I found on the right hypermetropia
5.5 D., visual acuteness 5/12 to 5/9, on the left with + 5.5 D., V =
1/12. With convex 6 D. No. 0.5 was read at 12 inches from the glass, but
not nearer, with normal fixation on both sides. The binocular near point
(if we may employ this expression in the absence of normal binocular
fusion) was considerably removed without the existence of paresis of the
accommodation, despite the over-correction of the hypermetropia. It was
rather a question of the same disposition of the relative amplitude of
accommodation as I have previously described in a similar case. By
methodical practice of binocular vision, I had taught an intelligent boy
to fix binocularly, not only for distance, but also for near objects,
but here again the relative amplitude for accommodation was diminished,
so that with correct binocular fixation he could only read with convex
glasses, which greatly over-corrected the hypermetropia. Finally, the
normal amplitude of accommodation was restored by tenotomy of the left
internal rectus, and when I saw the patient twelve years later I was
able to satisfy myself that both were perfectly preserved. In the case
of Miss L--, I believed I ought to give up all thoughts of an operation;
the position of the eyes could not be improved, convex 5.5 D. eyeglass
perfectly sufficed for distance, and convex 7 D. spectacles for reading.
It seemed to me senseless to perform tenotomy merely to enable her to
use the same glass for distance and for near objects, without any
possibility of a cosmetic improvement. Moreover the condition of
binocular vision quite confirmed the statements as to the previous
squint. Diplopia could only be produced now and then with the help of
prisms and red glass, at first the right visual field only was seen in
the stereoscope, on closer observation also the left, but without
binocular fusion.
Besides, the proved decrease of the relative power of accommodation in
both these cases, marked by a voluntary suppression of the squint, does
not appear in those cases where squint disappears of itself, the state
of the accommodation, therefore, shows nothing unusual.
The spontaneous cure of squint teaches us two important facts, firstly,
that the conditions of tension of the ocular muscles may change in the
course of time, and secondly, that normal binocular fusion of the
retinal images is not necessary for a correct position of the eyes;
neither the spontaneous nor the operative cure of squint presupposes the
presence or the restoration of a normal binocular fusion. If this were
the case the operation for squint would not be of much use.
Observation of these cases further teaches, that treatment with convex
glasses has prospects of success, particularly in periodic squint with
hypermetropia, if squint can disappear spontaneously even without
correction of the hypermetropia. At the same time, however, it appears
that we need not form hasty conclusions about it. Periodic squint
frequently arises during the earliest years of life, and everyone
(perhaps with the exception of a few ophthalmologists) will at once
reject the idea of allowing children of two to three years old to wear
spectacles; constant wearing of spectacles even by older children seems
to me not to be without risk as long as there is any chance of their
falling when running, playing, &c., in which case the eyes as well as
the spectacles would be in danger. As a rule I only order children to
wear convex spectacles when they are distinctly indicated, and then only
during sedentary occupations, when working and eating. Of course,
exceptions may be made according to the individuality of the child, and
the care with which it is looked after at home.
We are more rarely able to remove permanent convergent squint by means
of convex glasses than the periodic form; that it is possible, however,
I should like to show by an account of a patient, who offers, besides,
other interesting peculiarities.
CASE 42.--Marie S--, aet. 6, came under treatment on November 28th, 1878,
for recent superficial marginal keratitis of the left eye, which was
treated first with atropine; a few days later slight blepharitis
appeared also. On December 9th, atropine was discontinued; on the 14th,
the position of the eyes was still quite normal; on the 19th, permanent
convergent squint of the left eye was present. Squint had never been
observed in the child before. Double images were voluntarily announced
without my having inquired for them, they were homonymous and moved
further apart at both sides of the visual field. On December 28th, the
squint still remained the same, the double images were, however,
scarcely noticed by the child, so quickly do the relations of the
corresponding points of the retina change even in the sixth year. Both
eyes were atropinised for the better determination of the error, when a
slight degree of hypermetropia was shown by the ophthalmoscope, at most
1.5 D.; certainly a higher degree was specified when the vision was
tested, namely, on the right H. 2.5 D., V. = 5/12 to 5/9, on the left H.
1.75 D., V. = 5/18, probably, however, the objective determination was
more exact than the child's statements. If a child of six knows its
letters and figures sufficiently well to undergo a visual test, that is
as much as we can expect; in any case, however, the forms of the
letters and figures which we use for the visual test are not easy to
children, and the more objective the way in which the child comprehends
the examination, the less it perplexes itself by guesses, but only names
the letters which it really distinctly recognises, the less deficient
are the reports as to the visual acuteness; the proportionately larger
retinal images are still recognised, even if they are no longer quite
distinct, but consist of diffusion circles as a result of
over-correction of the hypermetropia. That these observations were right
for the case in point, is seen by the fact that eight days later, after
the effects of the atropine had passed off, the child could see better
with the naked eyes than with convex glasses, and that finally, when it
had become accustomed to the forms of the letters and figures employed,
V. = 5/9 was announced on the right, and V. = 5/12 on the left.
Mydriasis by atropine had no influence whatever on the squint,
therefore, on December 31st, convex spectacles 2 D. were prescribed for
permanent use. On January 4th, the linear deviation still amounted to 4
mm.; on January 15th, convergence was no longer discernible for
distance, with red glass double images occurred at once; on January
21st, no squint was present, and binocular fusion was again restored;
prisms immediately caused double images, the facultative divergence was
= 0. I thought it prudent to order the spectacles to be worn till the
middle of March, when they were discontinued; squint has not appeared
since then.
In this case it is impossible to determine what really induced the
squint, certainly not the slight hypermetropia, for the child had
already learnt to read without squinting, and was spared any exertion at
the time when the squint arose. Neither can we look for the cause in the
inflammatory condition for which the child first came under treatment,
this was as good as removed before the squint began and no exciting
condition worth naming was present. Moreover, most cases of squint
arise without directly assignable causes. It seems to me unquestionable
that the permanent use of convex glasses made the pathological relation
between accommodation and convergence normal, before it had firmly
established itself, and before the muscular relations were definitely
changed, and that the squint was really thus cured. But if the child had
not been under treatment I should scarcely have seen the squint so soon
after its first occurrence, and most cases of squint arise at an age
which forbids the permanent wearing of spectacles.
If permanent squint has already existed for a long time, nothing can be
hoped for from the use of convex glasses; for the conditions of the
muscles are then so much changed, that they are no longer influenced by
such weak physiological powers. I have been able to convince myself in
the case of several squinting persons, who conscientiously wore the
spectacles prescribed for them elsewhere, that the squint was concealed
by this means; that may suffice in some cases, but if it is a question
of young girls we may well ask, which is to be preferred for appearance
sake, squint or spectacles.
Tenotomy effects essentially a cosmetic improvement--its object is to
restore the correct position of the eyes by equalising the elastic
muscular tensions. The means at our disposal are, the simple separation
of the tendon of the too-tense muscle from the sclerotic, the
distribution of the operation between both eyes, and finally, increasing
the strength of the antagonist by moving forwards its insertion.
The method of tenotomy as I carry it out is as follows: The conjunctiva
is seized with fine forceps exactly over the insertion of the muscle to
be divided, and the fold thus raised cut into with the smallest possible
wound. Provided we operate on the right spot we enter this opening with
the forceps and immediately seize the tendon close to its insertion on
the sclerotic, which is drawn forwards, as was the conjunctiva, and
loosened with flat, curved scissors, the points of which must be rounded
off. The incision must only be large enough to allow a small hook with a
knob to be inserted through it and behind the insertion of the tendon,
which is now lifted up and divided with fine pointed scissors close to
its insertion into the sclerotic. It is important to make sure that a
few threads coming off from the tendon at the ends of the insertion do
not remain uncut; we can only consider the operation to be complete when
the hook, carried behind the edge of the insertion made clearly visible
by the foregoing proceeding, slides up to the margin of the cornea
without any interruption.
The method of performing advancement is as follows: An incision is made
in the conjunctiva over the tendon of the muscle to be brought forward
and just at the outer bend of the latter, then loosened together with
the subconjunctival tissue to the corneal margin; it is desirable to
carry out this loosening close to the sclerotic, as the flap of the
conjunctiva thus formed must afford sufficient support to the muscle to
be brought forward. Then the capsule of Tenon is cut into at one edge of
the insertion, a flat, curved, blunt hook without a knob is carried
between muscle and sclerotic, and out again at the other edge of the
insertion. We must be careful to get the muscle as clean as possible on
the hook in the whole width of its insertion, that is without the
capsule of Tenon, for the suture put in ought only to enclose the
muscle, without at the same time dragging the capsule of Tenon. For the
suture I always use fine catgut which is provided at both ends with
curved needles; needles of slightly different form may be chosen in
order that the threads may be easily distinguished from one another. A
needle is carried behind the hook from each thread, one through the
upper, the other through the lower edge of the muscle, between it and
the sclerotic, then the thread is tied in a knot on the muscle to make
sure that it does not slip back through the loop of the thread after
its separation from the sclerotic. Then the threads are knotted on the
muscle, and the insertion is separated from the sclerotic. As the edge
of the insertion is now exposed we can see how the land lies, and can
carry the threads exactly in the direction of the muscle under the
conjunctiva to the corneal margin, where they are passed through, and
ends tied in a knot. By this means the muscle is drawn forwards
precisely in its normal direction and stretched tighter. The wound in
the conjunctiva is closed by a suture.
It is desirable to slightly stretch the muscle that is to be brought
forward in both the above operations while the eye is rolled towards the
opposite side with forceps. Further, as I always operate under
chloroform, I dispense with the usual test of the immediate effect of
the operation; such tests have no value before the effects of the
narcotic have completely disappeared, and one must be sure in the way
above described that no single fibres are left undivided. I lay special
stress on the fact that the operation is so performed, that it is able
to bring about the desired mechanical effect.
The immediate mechanical effects of simple tenotomy may be easily
deduced; the divided muscle retracts as far as its elasticity and its
relations with the surrounding tissues permit. With reference to the
internal and external rectus with which strabotomy specially has to do,
those relations come principally under observation which the front part
of the muscle enters into with the conjunctival tissues; the greater the
extent to which we loosen these relations, the farther the muscle can
retract. If it is a question of obtaining a greater effect, I am
accustomed to loosen the subconjunctival tissue at the front part of the
muscle behind the lachrymal caruncle to a greater extent--this offers
the additional advantage that the distorting sinking in of the caruncle
is avoided.