eye towards it as far as its own elastic tension and the powers still
present on the other side permit. The improvement in position which we
strive to obtain is brought about by the elastic power of the
antagonist, and not by the tenotomy itself, and it is seen by this then,
that the term strabotomy simply, does not quite express the
circumstances of the case. Tenotomy is nothing more than the means for
procuring a preponderance of the elastic power of the antagonist,
therefore the effect attainable on the position of the eye does not
depend solely on the division of the muscle, but to a great extent on
the elasticity of the antagonist, and may be nullified at once, if the
antagonist does not perform what we expect from it, and that may happen
without our being able to foresee it. For example:
CASE 43.--Julie B--, aet. 21, is stated to have squinted inwards since
her third year, principally with the right eye, but with occasional
alternation. The deviation amounts to 5 mm., the outward movement of
both eyes is perfectly normal. Hypermetropia 2 D., visual acuteness 5/18
on both sides. Ophthalmoscopically with atropine the same degree of
hypermetropia. Tenotomy of both interni on March 7th, 1879. On March
14th, deviation 5 mm., just as before. Then renewed division of the
internal rectus and shortening of the external rectus of the right eye;
but still the result was insufficient. Therefore, on March 21st, the
left eye was dealt with in the same way. By this means a normal position
of the eye was obtained, which was perfectly preserved when I saw the
patient again a year and a half later. Everything led me to suppose
beforehand that simple tenotomy of both internal recti would perfectly
suffice to remove the squint, yet it was of no use, but had to be
supplemented by shortening both external recti. In such cases I would
not advise repeated tenotomies, but for the correction of the
insufficient result as soon as possible by advancement of the
antagonist.
Advancement very frequently gives us an opportunity of seeing with our
own eyes the insufficiency of the antagonist and its faulty anatomical
development. We may suppose this to be the case if the mobility towards
the side of the antagonist is faulty, however that is no proof;
considerable insufficiency may co-exist with perfectly normal mobility.
If limitation of movement is present, to which insufficiency of the
antagonist may be assigned as the cause, or if it is desirable to obtain
the greatest possible result by means of an operation on the squinting
eye, we must combine tenotomy of the deviating muscle with advancement
of the antagonist. The same is stretched tighter, and rolls the eye more
strongly to its side, and we can regulate the degree of shortening of
the muscle, by the distance behind the insertion at which we place the
threads in the muscle, also by the distance from the corneal margin at
which we place our anterior sutures, although the rapidly increasing
ductility of the conjunctiva makes it desirable that we should not go
far from the corneal margin.
The exact rules for the application of the methods of operation differ
according to the nature of the case under consideration. If we
contemplate first the largest group, that of the ordinary permanent
convergent squint, the choice of the method is principally determined by
the average degree of deviation, the condition of error, and the visual
power, lastly by the mobility, particularly the outward movement of the
eyes. If the visual power of both eyes is nearly the same, or if the
squinting eye possesses such a visual acuteness that it can be used in
fixation, it is advisable as a rule to arrange the relations of the
muscles as equally as possible in both eyes--simple division of the
internal recti is therefore, as a rule, to be performed in both eyes.
If, on the other hand, the vision of the squinting eye is in a high
degree defective, so that only the better one is used, it is generally
advisable to confine the operation as far as possible to the squinting
eye; in that case, tenotomy of the internal rectus and advancement of
the external rectus is usually indicated in the squinting eye, and
frequently suffices.
Deviations which are so slight, that the careful division of both
interni without loosening the conjunctiva at the front part of the
muscle makes us fear an excessive result, are seldom the subject of
operative treatment; if the deviation is slight but still a
disfigurement, if it amounts to 3 to 4 mm., distribution between both
eyes is suitable, because, when the squinting eye possesses requisite
visual acuteness it is put into fixation more frequently after the
operation than before. Under these circumstances, if the operation is
confined to the squinting eye, and a sufficient result is thereby
obtained, as soon as this eye is used for fixation a remarkable
secondary deviation of the other eye occurs, which is not the case if
the tensions of the muscles have been balanced by an operation on both
sides.
A deviation of 5 to 6 mm. may usually be balanced by means of simple
double tenotomy if the conjunctiva is considerably loosened behind the
caruncle; not unfrequently, however, we must be careful to strengthen
the result by means of the after-treatment. Commonly, during the first
twenty-four hours, the result appears to be quite satisfactory, whilst
on the second or third day troublesome convergence again sets in. By
practice of the outward movement we then usually obtain at once a
perceptible improvement of the position. Both eyes are repeatedly turned
as far as possible to the right and left, by which means is obtained on
the one hand, exercise of the external recti, on the other, increase of
the effect of the tenotomy of the internal recti. I order these
exercises to be begun on the day after the operation.
Besides this, however, in the relation between accommodation and
convergence of the visual axes there is a very essential cause which is
able to lessen the immediate effect of the operation. Persons who squint
inwards, even if emmetropic, have the habit of combining accommodation
for near objects with excessive convergence of the visual axes, thus
the immediate effect of the operation is diminished as soon as they
begin to use their eyes again. This happens, not by a lessening of the
effect of the tenotomy, which could, indeed, only be increased by
exertion of the internal recti, but in that sufficient time is not given
for the external rectus to regain its normal elastic tension. Nothing is
changed at first by the operation in the customary relation between
accommodation and innervation of the internal recti--it is a question,
then, of avoiding every exertion of the accommodation for some time, in
order that no inducement for strong convergence should be given. I am
accustomed, therefore, even in the case of emmetropes, to paralyse the
accommodation by means of atropine twenty-four hours after the
operation, and to remove the far-point by convex glasses to about 0.70
m.; the spectacles must, of course, be worn constantly, for only by that
means can we be sure that they are always used for near objects. After a
few weeks the spectacles are discontinued, first for distance, then for
near objects also. This after-treatment is not necessary under all
circumstances; but I have repeatedly assured myself that an originally
sufficient result which perceptibly diminished after a few days, could
by this means be restored and permanently maintained even in emmetropes.
In the case of hypermetropes, we more often meet with the same
experience; in permanent convergent squint it is by no means necessary
to neutralise the hypermetropia permanently after the operation, but it
happens here more often than in emmetropia, that a perfectly good
immediate effect is lost within the first week after the operation, and
can be restored again by permanently wearing the correcting convex
glasses. In such cases also, I am accustomed after a few months to
discontinue the spectacles for distance as an experiment, while they are
still used for working.
Simple tenotomy of both internal recti does not, as a rule, suffice for
deviations of more than 7 mm.; therefore, even if both eyes possess good
visual power, we must still decide on tenotomy of both internal recti
together with advancement of the external rectus of the squinting eye,
or anticipate repeated tenotomies of the internal recti, or seek to
obtain the greatest possible effect by means of slight modification of
the method of procedure.
Provided that the muscle was completely divided, and sufficiently
loosened from the conjunctiva during the first operation, a repetition
of the tenotomy can only aim at an increase of the effect if the elastic
tension of the antagonist has improved in the meantime. I very rarely
therefore carry out repeated tenotomies; it seems to me much more
desirable to obtain a sufficient result at one operation whenever that
is possible.
In some cases where there is a deviation of 7 to 9 mm., the effect of
the tenotomy may be increased by inducing a strong divergence
immediately after the tenotomy of the internal recti, which is
maintained for 6 to 8 hours. For this a thread is passed through the
conjunctiva at the outer edge of the cornea about 4 mm. above the
horizontal meridian, and out again about 2 mm. below the horizontal
meridian, then from below upwards in the same way, so that the
conjunctiva is contained in a loop. The needle is then passed through
the external canthus from the conjunctival surface and fastened by tying
it over a roll of paper. This procedure is only to be recommended in
exceptional cases; a greater effect on the internal recti is thus
obtained, while with reference to the position the result depends on the
elastic tension of the external rectus just as in simple tenotomy.
If the squinting eye has only an unavailable visual acuteness, a
combination of tenotomy of the internal rectus with shortening of the
external rectus is the best procedure. As a rule, simple tenotomy of the
internal rectus of the squinting eye is of very little use in such
cases, as the abducens, weakened by continual extension and wanting
practice, places too slight an opposing power in the balance. The chief
effect of the operation then devolves on the other solely available eye,
which is not a desirable circumstance, and is also frequently
insufficient. On the other hand, the combination of tenotomy of the
internal rectus with advancement of the external rectus enables us
successfully to change the opposing muscular tensions. As a rule, the
operation may be confined to the squinting, weak-sighted eye, as that
suffices to obtain a correction of 5 to 6 mm.
If the result is seen to be insufficient, it may be supplemented by
tenotomy of the internal rectus of the other eye; in the case of
deviations of more than 7 mm. it is advisable to divide the operation
between the eyes in this way.
The suture has a special use in so-called artificial strabismus; that
is, in those cases where convergent is converted into divergent squint
through unskilful treatment, or where tenotomy of the abducens,
performed on account of "insufficiency of the internal recti," is
followed by convergent strabismus. I have not found confirmation of the
fear expressed by Arlt, that the method proposed by me could be scarcely
practicable if it is a case of the advancement of a muscle too far
forward, and I have corrected a large number of such cases in other
practices. It is seldom profitable to take up things in which others
have been unsuccessful, but it bring its own reward in the case of
artificial squint.
Periodic convergent squint offers a less certain ground for the
operation. The change between normal position and a very considerable
squint gives rise to the fear that an operation which would be able to
remove the convergence might finally induce divergent strabismus. This
fear is certainly not groundless, but at the same time it must be
remembered that, with the exception perhaps of a few cases of clearly
accommodative deviation, elastic preponderance of the internal recti or
insufficiency of the external recti is generally the cause of periodic
squint also. I have frequently, in periodic squint, performed double
tenotomy of the internal recti with the slightest possible loosening of
the conjunctiva. I have also attempted to confine the operation to the
shortening of the external rectus without loosening the internal recti
and with success, but not frequently enough to be able to deliver a
certain opinion upon it.
In periodic squint, the first care must always be to determine the
condition of refraction, if possible with atropine, and to neutralise or
over-correct hypermetropia if present. If squint is absent during the
use of convex glasses, which happens frequently under these
circumstances, the operation offers no further advantages, as the
constant use of convex glasses afterwards can hardly be avoided. If the
periodic deviation continues to exist, the operation can be carried out
according to the above rules and so as to cause a slight effect.
The final result is usually attained after two to three weeks in
convergent squint; it is better to allow a slight degree of convergence
to exist, as divergence, however slight, existing at this time, brings
with it the fear of a gradual increase. It happens occasionally, that
after years, convergence asserts itself again; I have observed it in
spontaneous (see Case 39) as well as in operative cure of squint; still,
this is so unusual, that I should like to give an illustration of the
latter observation on account of its rarity.
CASE 44.--Hedw. von L--, aet 10, came under treatment in April, 1874, for
convergent squint on the left side which arose in her seventh year, with
occasional alternation. Emmetropia, determined with atropine on both
sides and good visual acuteness. Diplopia was present at the
commencement of the squint. Patient can only be rendered conscious of
double images by the help of a red glass and vertically deviating
prisms. Double tenotomy of the internal recti effected a normal
position, and at the end of December, 1874, the continuance of the same
could be proved as well as binocular fusion with prisms. At the
beginning of 1880, I was informed that from time to time periodic squint
had occurred with diplopia. In the middle of March, I had an opportunity
of seeing the young lady. Myopia 2 D. had meanwhile developed on both
sides, visual acuteness almost = 1. The position of the eyes was
perfectly good, slight convergence occurred during covering, homonymous
double images with a red glass which, at a distance of 5 m., were joined
by a prism of 8 deg.; stereoscopic fusion was not perfectly certain. A true
squint could not be proved. On April 3rd, as patient stopped for a few
hours on her journey through, a striking convergent squint of the left
eye was seen. The deviation amounted to 4 to 5 mm. Single vision existed
at a distance of 15 to 20 cm., then homonymous double images appeared,
which did not correspond to the objective deviation; the double images
were however corrected by a prism of 6 deg. (base outwards) for an object 5
m. distant.
We cannot conclude the consideration of the operative treatment of
convergent squint without once more returning to the relation between
the line of vision and the position of the cornea. The angle [Greek: a]
still deserves mention in a few thankful words--_hic mihi angulus
praeter omnes ridet_--it is a very useful guide in tenotomy. In tenotomy
we may count as gain the apparent divergence which it causes in
hypermetropes who do not squint. We obtain a perfect cosmetic result,
while a convergence, objectively determinable, but not otherwise easily
visible, continues to exist. It would be folly to exceed this; and for
cases where binocular fusion does not exist, and where diplopia is not
present, to wish to remove this covered convergence due to the angle
[Greek: a], the cosmetic result would be impaired by it.
Those cases where it is a question of uniting homonymous double images
are very instructive when considering tenotomy. Only when squint arises
after childhood (after the fifteenth year) does it cause troublesome
diplopia, this accords naturally with the laws of normal binocular
fusion learnt meanwhile. (On the other hand those cases, which sometimes
occur after tenotomy, with the double images in a position which does
not correspond to the normal physiological laws and which cannot
therefore be united by prisms, are naturally unsuitable for the
operative removal of diplopia.) Cases in which convergent squint is
followed by troublesome double images, appear, with the exception of the
hysterical form mentioned on p. 41, chiefly in myopia, more seldom in
emmetropia, and very rarely in hypermetropia; for if the conditions
contained in the ocular muscles are coincident with hypermetropia,
squint usually arises in the course of childhood, before normal
binocular vision has become a fixed habit.
As the cases here under consideration are not very common, I will relate
a few from which conclusions may be derived as to the effect of
tenotomy.
CASE 45.--Miss von B--, aet. 14, came under treatment on May 1st, 1875,
for diplopia, which made its appearance about a year previously.
Emmetropia and full visual acuteness exist on both sides. The double
images are homonymous and further apart on both sides of the visual
field. At first single vision existed only to about 0.75 m.; gradually,
however, the area of single vision was extended by practice of the
outward movement, supported by the use of prismatic spectacles, so that
after a year patient could see singly to a great distance. This
improvement was not maintained. At the beginning of 1879, diplopia was
again present to a troublesome degree, particularly on looking
downwards; on looking straight forwards the left eye showed a slight
convergent deviation, amounting at most to 2 mm. During various
examinations the distance of the double images was stated to be now
less, now greater, a prism of at least 5 deg., at most of 9 deg., was requisite
for correction. Diplopia was at once removed by tenotomy of the left
internal rectus, with very slight loosening of the conjunctiva, and has
not appeared since.
CASE 46.--Miss A--, aet. 17, suffered from diplopia for a few weeks, a
year and a half ago; for the last half year the diplopia is continuous,
and striking squint is stated to be sometimes present. Myopia 2 D. on
both sides, visual acuteness = 5/9. On fixation of an object about 4 m.
distant, the left eye deviates inwards at most 2 mm.; homonymous double
images, with a red glass and on correction of the myopia, which were
united by means of prism 14 deg. at a distance of 5 m., without red glass
(with retinal images alike on both sides) prism 8 deg. sufficed to unite
them. If a vertically deviating prism is held before one eye, the double
images stand just above one another when looking at an object 20 cm.
off, on nearer approach they are crossed. On May 3rd, 1879, tenotomy of
the left internal rectus with small conjunctival wound without loosening
of the conjunctiva, and union of the conjunctival wound by a suture. On
May 8th, single vision, also with correction of the myopia and with red
glass. Facultative divergence = 2 deg. On May 14th, with correction of the
myopia, there was still single vision for distance; however, with red
glass double images occurred again; and at the end of May the condition
of the double images was just the same as before the operation. On
vertical shifting of one visual field by a weak prism the double images
are brought into a vertical line by means of prism 16 deg., with the base
outwards. Therefore, on July 1st, the right internal rectus was also
divided, with small conjunctival wound without loosening of the
conjunctiva and without suture. The evening after the operation slight
divergence on covering. On July 24th, binocular single vision is
present; with red glass homonymous double images at 5 m., corrected by
prism 4 deg. This time the result was final; for in the middle of October,
three months after the operation, the report was exactly like the one of
July 24th above stated.
CASE 47.--Mrs. A--, aet. 33, has suffered for six months from alternating
convergent squint with diplopia, for a short time even a parallel
position is still possible. On the right myopia 4 D., V. = 6/12. On the
left myopia 4 D., V. 6/9. Single vision occurs to 22 cm., at a greater
distance homonymous double images, whose mutual distance remains the
same when looking to one side. On correction of the myopia a prism of at
least 32 deg. is necessary for the union of the double images for an object
at 4 m. Two days after tenotomy of the internal recti on both sides, the
facultative divergence amounted to 7 deg. (at 4 m.) on correction of the
myopia. Single vision was also present when looking strongly to one
side, and with differentiation of one retinal image by a red glass.
CASE 48.--Mr. B--, aet. 32, first observed the occurrence of diplopia at
the beginning of April, 1877. Myopia 6 D. is present in both eyes,
visual acuteness on the right 1/2, on the left rather more than 1/2
(5/9). The double images are homonymous and sometimes (not always) move
farther apart at the limits of the visual field. Patient could only
decide after two years, in July, 1879, on the operative treatment then
proposed. Diplopia continued to exist; single vision was only now and
then possible for a short time. On correction of the myopia (if one eye
is provided with a red glass) prism 12 deg. suffices for union of the double
images. If one visual field is moved in a vertical direction by a prism
of 5 deg. during the trial of convergence, prism 38 deg. is necessary in order
to equalize the lateral deviation of the double images, and to place
them perpendicularly above one another for an object 5 m. distant. On
July 14th, tenotomy of the internal rectus of the left eye; single
vision next day on correction of the myopia, prism 6 deg. is overcome by
divergence; if, however, double images are produced by a vertically
deviating prism of 5 deg. they immediately show homonymous lateral
deviation, which is corrected by prism 18 deg. at a distance of 5 m.
Two months after the operation the diplopia was certainly better, but by
no means removed; squint occurred periodically as before, so that
sometimes single vision was possible at 3 to 4 m., sometimes troublesome
diplopia was present.
During the test of convergence with prisms deviating in a vertical
direction, a prism of 38 deg. was necessary for the equalization of the
lateral deviation just as before the operation. Therefore in the middle
of October the internal rectus of the right eye was divided, and the
conjunctiva loosened as far as the caruncle. Three days afterwards
single vision, facultative divergence = prism 5 deg.; in the trial of
convergence, equalization by means of prism 8 deg. In the middle of
October, two months after the operation, diplopia had not appeared
again; facultative divergence = 0; homonymous double images are produced
by a red glass before one eye, slight convergent deviation on covering
it, which in the trial of convergence is equalized by prism 20 deg. The
preponderance of the interni was now so far lessened for the ordinary
use of the eyes, that permanent binocular single vision was possible.