Chapter IV: Part 4

CASE 20.--Margarethe T--, aet. 16, has hypermetropia 2 D. in the right eye, V. 5/6, in the left the ophthalmoscope shows with an otherwise normal condition a higher degree of hypermetropia, with + 6.5 D., V. 1/18, with + 10 D. No. 3.0 is read. No spectacles have been used until now; for the past few years school tasks have been performed with a certain effort, only during the last year the asthenopia has increased. Squint is not present, and with prisms as well as with the stereoscope (by the use of objects, whose size corresponds to the defective sight on the left side) binocular fusion can be proved.

The case is the same as regards divergent strabismus.

CASE 21.--Mr. H--, aet. 28, has myopia 6 D., V. 6/9 in the right eye; the left eye has always been weak sighted, emmetropia is detected with the ophthalmoscope, with normal fundus, V. 1/18. No squint, binocular fusion can be proved with prisms.

CASE 22.--Mr. B--, aet. 47, has hypermetropia 5 D., V. 5/9 in the right eye. Left eye with + 5 D., V. 1/18 (a few letters of 12 also were recognised at 1 m.). It seems, however, that the patient is not able exactly to indicate the position of the retinal images of his left eye, he does not know, as he expresses himself, "whether the letters stand here or there." Patient observed the defective sight long ago; the ophthalmoscopic condition is normal. Patient really comes on account of his son, aged 7-1/2, in whom hypermetropia of 3.5 dioptres is detected with the ophthalmoscope, right eye with + 3.5 V. 5/9. Left eye has convergent squint, V. 1/36, No. 3.0 is read with + 6.5 D.

The hereditary tendency is seen also in the following case:

CASE 23.--Mrs. S--, aet. about 46, on the left H. 4 D., V. 5/18 to 5/12, has used no spectacles until now, and reads No. 0.75 without glasses at about 15 cm. R. with + 4 D., V. 1/18, with + 6.5 D. large letters of No. 5.0 are recognised.

Two sons, present at the same time, are hypermetropic. One has in either eye V. 1/4, the other a slighter degree of congenital amblyopia.

CASE 24.--Johanna L--, aet. 4, came under treatment for a congenital fibroma covered with hair, about the size of a cherry-stone, situated on the outer corneal margin of the left eye, which was removed. Three years later, when the child had learnt to read, emmetropia and full visual acuteness was observed in the right eye, with the left No. 4.0 only is read with difficulty. The ophthalmoscope shows a slight degree of irregular astigmatism of the cornea, which in no way explains the defective vision; the image of the fundus is perfectly clear and quite normal.

CASE 25 afforded me a not altogether pleasant surprise. Martin M--, aet. 58, has matured cataract in the right eye, with perfectly satisfactory light reflex, proper projection, &c. On the left progressive cloudiness of the lens has begun. The course of operation and cure were regular in every respect, but the power of vision finally was so small that with a clear pupillary area, and otherwise normal condition, only single words of No. 3.0 were recognised with difficulty at 10 to 15 cm. with convex 20 D. For the first time the patient remembers that he noticed the defective sight in his right eye at the age of sixteen, and was for this exempt from army service. The operation performed later on the left eye procured satisfactory vision.

C. Visual acuteness of less than 1/36 12 cases.

Determination of refraction of the better eye is given in 6 cases, and showed twice emmetropia, twice slight myopia, twice hypermetropia. I only possess an exact ophthalmoscopic determination of the condition of the defective-sighted eye in one instance with H. 2.5 D.

This group is of special interest in that it represents the extreme degrees of congenital amblyopia, and, on the other hand, because it contains 5 cases of children under 10 years of age.

CASE 26.--Constanze von M--, aet. 9-1/2. Defective vision on the left side had been noticed long before by the child's parents. On May 1, 1879, emmetropia was observed in right eye, V. 5/12 to 5/9. No. 0.4 is read at 15 cm. On the left, only movements of the hand are seen, fingers cannot be counted even when close to the eye; the visual field is good, that is, on moving the hand in the periphery of the visual field the child sees "something" without being able to state what it is. Reaction of the pupils as rapid and equal as usual. The ophthalmoscopic condition (even with dilated pupils) is perfectly normal. All tests for simulation were of course applied.

On account of the importance of the case, I suggested another examination a year and a half later, on the 22nd December, 1880, which showed precisely the same result as the former one--optic disc, macula lutea, &c., perfectly normal, the ophthalmoscopic determination of the refraction shows H. 2.5 D.

The child's father also possesses in the left eye a slight degree of congenital defective sight, observed for many years, with normal ophthalmoscopic condition; No. 0.5 is read with + 6.5 D. at 10 cm.

CASE 27.--Tina S--, aet. 6. The defective sight of the left eye had been remarked some months previously; report on July 16th, 1878: R. full visual acuteness, L. movements of the hand are scarcely visible. The child cannot count fingers. Normal ophthalmoscopic condition. Eserine and separate use were prescribed. On September 9th, 1878, fingers were counted with the left eye at 1.5 m., single words of No. 4.0 were recognised, No. 3.5 with convex 6.5 D., but always with oscillating fixation. The improvement in the child's statements may be referred to the fact that she had meanwhile learnt to form right conclusions from the very imperfect sensual impressions of her left eye.

CASE 28.--Frank J--, aet. 10. Left eye. V. 10/50 to 10/40, No. 1-1/2 Snellen is read at 4 inches. On the right, nystagmus on fixation, fingers are counted at 5-6 feet. The ophthalmoscopic condition is normal. A sister of the boy squints.

CASE 29.--Ernest G--, aet. 8, has slight nebulae on both corneae. On the left V. 15/40. On the right, fingers are counted at 4 inches with visual axis deviating inwards.

CASE 30.--I operated on Moritz L-- for congenital cataract before he was a year old in 1869 by means of a needle operation. In June, 1877, a thin ophthalmoscopically transparent secondary cataract appeared in both eyes; on the left, with convex 12 D. V. 3/24 to 3/18, with convex 16 D. No. 0.4 is read at 10 cm. On the right, with convex 12 D., fingers are counted with difficulty at about 1 m., with inward deviation of visual axis.

CASE 31 is also worthy of note. Carl H--, aet. 22, shows quite a number of congenital anomalies on the left side of the face, harelip, deformed nostril and a skin defect on the inner corner of the eyelid. There is a congenital dermoid growth of the size of half a pea situated on the inner lower corneal margin. A slight irregularity in the curve of the cornea near the dermoid is detected with the ophthalmoscope; the fundus of the eye is perfectly normal. Fingers are not counted further off than a metre with visual axis deviating inwards. The right eye is emmetropic (perhaps slightly hypermetropic), and has full visual acuteness. There is no squint.

It is customary to "explain" these cases of monocular amblyopia by previously existing squint, and one is quite satisfied if by the examination of patients it is only possible to prove that they have occasionally squinted, although the advocates of the amblyopia ex anopsia disallow the presence of the same under these conditions, that is, in periodic squint. Of course a theory which cannot exist without the assertion that occasional alternation suffices to hinder the development of defective vision caused by disuse, cannot possibly hold periodic squint to be the cause of it. Certainly permanent squint may also disappear, but this much I have been able to determine, that this seldom happens before the twelfth year of life, and one may surely reckon that children in whom permanent squint is developed at the usual early period of life, still squint at the age of ten years. Cases 24 and 26 to 30 can under no circumstances be explained by previous squint, notwithstanding that they represent the extremest degrees of amblyopia, but the question is undoubtedly that of congenital defective vision; moreover I have excluded from the statistics of congenital amblyopia all cases in which the previous presence of squint could even be supposed.

A table of the cases above described with reference to the defective condition is interesting; when a determination of refraction existed for the weak eye I have given it, and when this was not the case I have stated that of the better eye, thus it is seen that among 85 cases in which the refraction was determined, hypermetropia (including hypermetropic astigmatism) was present in 39. Hypermetropia was found then in 47 per cent of all the cases. The percentage would probably be higher, if all weak-sighted eyes had been examined from the beginning as to their state of refraction, but as I only learnt to know the relation between hypermetropia and the higher degrees of congenital amblyopia from my statistics, I did not take notice of this relation when investigating individual cases.

How does congenital amblyopia now stand in relation to that disturbance of vision which we observe in squint? I see no difference; whether squint is present or not, the form of defective vision is precisely the same, and nothing happens in the combination with squint which could not also be proved without it. The relation to hypermetropia, which is proved with congenital amblyopia, also appears in squint.

A collective table of cases of convergent and divergent squint included in the statistics (pp. 19 and 47) shows:

(_a_) In myopia, emmetropia, and doubtful hypermetropia,
with convergent and divergent squint together
329 cases. Among them:
Visual acuteness to 1/7 239
" less than 1/7 to V. 1/12 19
" " 1/12 to V. 1/36 46
" " 1/36 25
Defective sight of higher degree than 1/7, 27.3 per
cent.

(_b_) In hypermetropia 1 to 3 D., including the few cases
of hypermetropia with divergent squint, 177 cases.
Among them:
Visual acuteness to 1/7 121
" less than 1/7 to V. 1/12 17
" " 1/12 to V. 1/36 27
" " 1/36 12
Defective sight then, 31.6 per cent.

(_c_) In hypermetropia 3 D. and more, 70 cases with convergent
squint, with:
Vision to 1/7 39
V. < 1/7 to V. 1/12 8
V. < 1/12 to V. 1/36 14
V. < 1/36 9
Defective sight then, 44.2 per cent.

This regular increase of defective sight with the increase of the hypermetropia can be no mere accident, and speaks strongly for the identity of defective vision in squint with congenital amblyopia. Were defective vision caused by the squint the various states of refraction would show no difference in the percentage of defective vision.

Further, the circumstance is worthy of remark that among 198 cases of periodic squint (convergent and divergent) which are applicable for the statistics of visual acuteness--

170 possess V. to 1/7.
16 " V. < 1/7 to V. 1/12.
9 " V. < 1/12 to V. 1/36.
3 " V. < 1/36.
14.2 per cent. then of defective vision of considerable degree.

That defective sight on the whole plays an influential part as a cause of squint is doubted by no one, indeed we see blind eyes lapse into squint as soon as the conditions necessary to it are supplied by the muscles. Of all the prevailing causes present defective vision will be the more decisive in proportion as it is of high degree; for the motive which despite the presence of favouring circumstances can prevent the real occurrence of squint, binocular vision, becomes less efficacious as the defective vision becomes more considerable. As binocular fusion takes place frequently in periodic squint, for a time at least, that is as long as proper fixation lasts, one can understand that periodic squint exists chiefly in cases where the visual faculty of both eyes is good. Even the highest degrees of congenital amblyopia are not excluded, for periodic squint appears where the faculty of binocular fusion has been completely lost. Further, that considerable congenital defective sight is more frequent with than without squint, may be accounted for quite simply by the fact that, in extreme degrees of it, binocular fusion cannot be learnt at all, while in the lesser degrees it is more easily forgotten again.

If defective vision is undoubtedly one of the causes of squint, we must seek for the grounds upon which it has been taken to be a consequence of squint, and described as amblyopia ex anopsia. I will not inquire to whom the honour of this invention belongs. I do not want to write a history of mistakes but only to examine the basis of the views now current. The most complete record of the same may be found in the well-known journal on the 'Cure of Eye Diseases,' vol. v, p. 1011. Leber, who does not seem to recognise the existence of congenital amblyopia, has shown quite a special predilection for amblyopia ex anopsia.

Amblyopia from want of use, which formerly included all possible disturbances to vision, great and small, is now only accepted in two cases, for squint and congenital cataract, if the latter is not operated on very early in the first or second year of life.

The fact is simply this, that in congenital cataract even the most successful operation is frequently deceiving as to its issue without ophthalmoscopic report; this is the more disagreeable as the most exact reflection test before the operation fails to prove the existence of this defective sight. But does it follow from this, that congenital cataract has induced defective sight from want of use? We find the same defective vision also in congenital defective development of the transparent lenses (so-called luxation of the lens). On the whole, we often find several congenital defects in the same individual. The very circumstance that the cataract is congenital makes it probable that the defective sight is so also, or are we to take congenital cataract as being a guarantee against congenital amblyopia?

Von Graefe, who first considered this defective sight to be congenital, designated it in his later lectures as originating from want of use, probably in order to advise the earliest possible performance of an operation. There is no mention of his having brought forward evidence for this assertion; that the great master himself said it was enough, and the host of believers felt themselves to be the happy possessors of a new dogma.

A number of children appeared in my practice, in whom congenital cataract was needled by von Graefe in the first or second year of life with recovery of transparent media, who showed, however, the extremest degrees of defective vision when they were sufficiently intelligent to have their vision tested. Whoever is interested in this can find a number of such cases in the Royal Institution for the Blind at Steglitz, which I am accustomed to visit several times a year by request of the committee. On p. 91 I have related a case of monocular congenital defective sight in congenital cataract of both eyes.

Everywhere then the principle holds good, that whoever makes an assertion must be prepared to verify it; amblyopia from non-use is denoted as an inherited trouble, and still not a single observation exists which furnishes proof that an eye of previously ascertained good visual acuteness has become amblyopic in consequence of disuse, a fact I drew attention to ten years ago. Leber replies to this, he remembers "to have seen patients with complete amblyopia in the squinting eye, who stated that its visual faculty had been found to be good during an examination instituted years before." Is this intended as an observation? By that I mean is it a proof of facts, for the trustworthiness of which he holds himself responsible: in the handling of scientific questions I do not place the least reliance on the dim recollections of unnamed individuals. Even in personally conducted examinations we must be on our guard to avoid mistakes, and now we are confronted with mere recollections of tests of vision!

By means of the above observations the theory that "the peculiar variety of monocular amblyopia which is so frequent in monocular squint is hardly observed without squint" is sufficiently disproved.

Leber seeks to enfeeble Alfred Graefe's statement that the presence of extremely defective vision may sometimes be proved at a very early age, in children who have only squinted a short time (the rapid development of amblyopia in consequence of the squint really appears incredible), by the assertion "that just at the earliest age, when the activity of the optic nerve is not yet sufficiently strengthened by use, the conditions for producing amblyopia from non-use are most favorable with complete exclusion of one eye," but complete exclusion of the squinting eye does not take place even in extremely defective sight, as can easily be seen by the mirror test (p. 66) I described fourteen years ago. Which activities of the optic nerve apparatus are strengthened then by use? Perhaps visual acuteness? The physiological conditions of this are only to be sought in the anatomical structure, and the physiological arrangements of the retina or the visual organs, which cannot be changed much by use. What we can learn from the visual act relates solely to the conclusions which we are able to draw from sensual impressions; but visual acuteness, _i. e._ the faculty for the recognition of distinct points, is an anatomical, physiological gift, and not a thing to be acquired.

The opposing observation, that squint, even of monolateral character dating from earliest childhood, continued to the middle and later years of life, can still exist with very good visual faculty, may easily be explained by alternation from time to time. If that is so indeed, if squint begins during the presence of good visual acuteness, and nothing further is necessary to its maintenance than alternation from time to time, why should defective vision from non-use ever be developed? With good visual faculty on both sides alternations also occur from time to time.

Still more convincing are those cases which are numerous where the visual acuteness of the squinting eye only amounts to about 1/7 to 1/12, and where, on this account, there is no alternation. Were this defective sight acquired through non-use it must of necessity be progressive; it must exist in proportion to the duration of the squint. A moderate experience will suffice to show that this is not the case. And further, defective sight must continue progressive even after removal of the squint by operation, for by the operation nothing is changed in the relations of the binocular vision present in squint, which are dismissed with the one word, "suppression," by the advocates of defective vision from non-use.

Moreover, suppression may exist for years without the slightest disadvantage to the visual faculty.

CASE 32.--In November, 1873, I operated on Fritz F-- for a slight divergent squint of the left eye. Slight hypermetropia was present on both sides, and nearly full visual acuteness. In October, 1880, perfectly normal position of the eyes showed itself with the same visual acuity and emmetropia in both eyes; at the same time, however, the boy affirmed that when reading he could never see with his left eye but only with the right; in reality only the right visual field was perceived in the stereoscope.

The second reason brought forward is, that the variety of amblyopia from non-use is quite a peculiar one; "it consists of a functional disturbance of those parts of the retina whose images belong to the common V. F., and are suppressed in squint in order to render vision distinct--the macula and the temporal and only a part of the nasal halves of the retina." Does this hold good for all cases of amblyopia in squint, or do those cases only belong to amblyopia from non-use where excentric fixation takes place with an inward deviating visual axis? It would be difficult to draw the line. I have seen a case in which the squinting eye possessed a visual acuteness of 5/36 together with excentric fixation and nystagmus; however, I attach no value to isolated cases. We frequently find excentric fixation with a visual acuteness of 1/12 to 1/36. Further, those cases cannot possibly be regarded as results of squint, which possess unsteady oscillating fixation or rapidly trembling nystagmus, which occurs as soon as the squinting eye fixes. But this conclusion is false, even for the excentric fixation with visual axis deviating inwards; if it were right the angle at which the eye deviates inwards on fixation in convergent squint would always be greater than the squint angle. Those cases are, of course, more remarkable where this is not the case; however, on close investigation those cases are more frequent where the angle of deviation is about the same size or smaller than the squint angle, and is fixed with a part of the retina which undoubtedly belongs to the common visual field.

On p. 91 I have described two cases of excentric fixation in children who had never squinted, and it is only necessary to take a little trouble to repeat the mirror test which I described, to be convinced that squinting eyes have not lost the power "of using those parts of the retina," even if they are amblyopic to an extreme degree; without the slightest doubt the reflection is perceived as soon as it falls on the retina.

Value is attached to the improvement produced by the separate use of the squinting eye. According to my experience no higher visual acuity can be attained by use of the amblyopic eye, than that which is best detected by the aid of eserine in the first examination, if it is only carried out thoroughly enough. No doubt if we proceed otherwise, and rest content with whatever statements the patient likes to make, without giving ourselves any more trouble, we may expect the most superficial diagnoses to show the most astonishing therapeutic results, as, indeed, often happens. And now, talking of strychnine injections! When two celebrated ophthalmologists occupy themselves simultaneously with the therapeutics of strychnine, one of whom obtains the most astonishing results in atrophic troubles of the optic nerves, but, on the other hand, obtains no real improvement in "amblyopia from non-use," while the other can show brilliant success in the last-named form of defective vision, and, on the other hand, none in atrophy of the optic nerves, we may perhaps conclude that both are right, if even really on the negative side, and that the circumstances are the same in the tests of vision. Again, we must examine more closely some of the cases, in which strychnine injections showed a brilliant result. (Anyone interested in the original work can read up the 'Vienna Weekly Medical News' for the year 1873.)

"1. Wilhelm H--, a strong healthy boy, aet. 12, complains of defective vision. Right eye has nothing abnormal in its outward appearance, and just as little in the fundus. V. 16/100, H. 2.5 D., Snellen IV-I/II; is the smallest type he reads at 3 to 7 inches. With + 10, I-I/II is read at 4 to 6 inches. Left eye V. 16/70. H. 2.75 D. II-I smallest type legible at 3 to 12 inches. With + 4 D. I-I/II is read at 4 to 6 inches. On March 14th, 1872, first injection of strychnine with 0.002 gr. in the temples. An hour later V. of right eye 16/70, left unchanged. On March 23rd, 1872, after one injection daily, V. of each eye is 16/50."

Patient shows then in the right eye visual acuity 16/100, with manifest hypermetropia 2.5 D.; in all probability the total hypermetropia really present was higher, and was scarcely corrected by means of convex 4 D. If the patient now reads No. I-I/II Snellen with + 4 D. at 6 inches, this proves a visual acuity of 1/3 during the first investigation before the strychnine injection, and shows that the estimate of 16/100 was inaccurate. At the close of the treatment, only a visual acuity of 16/50 (almost exactly 1/3) is specified for distance. The result seems to me, then, to be this, that the patient during repeated examinations has gradually learned to make more accurate statements, indeed, with a boy twelve years old one can scarcely expect it to be otherwise.

"4. Paul A--, aet. 18, was operated on ten years ago for internal squint of the right eye, and dismissed with + 2 D. for distance, and + 6.6 D. for near use. He now complains of decrease of his visual acuity. The eyes are normal externally and internally. Hyperopic formation in a high degree. Right eye V. 1/20, with and without convex glasses, without glass only VIII-I/II with difficulty, with + 6 V-I/II the smallest. Left eye appears emmetropic, but is decidedly hyperopic. V. 5/4. Glasses are rejected; I-I/II is read fluently at 6 to 12 inches. After one injection the right eye recognises III-I/II with + 6, after the second II-I/II, after the eighteenth I-I/II with difficulty. The visual acuity, however, remains at 1/20, and is not changed after six months, although latterly patient daily practised with + 3 D."

Visual acuity of 1/20 suffices to read III-I/II at 2.5 inches, II-I/II at 1.5 inches, and I-I/II at about 1 inch; clear, retinal images are then scarcely obtainable, but we know what hypermetropes can do in that case; besides this, if the patient is examined for weeks by Snellen's method, he may get so far as to realise fairly well "the strange fate of that man" of I-I/II, despite larger diffusion circles; in any case vision remained at 1/20, despite strychnine and separate use.

In extremely defective vision little importance should be paid to the fact of slight diversity in the statements, as where visual acuity amounts only to about 1/36, or where fingers are counted at a distance of 1 to 2 metres, it is quite immaterial, as far as the usefulness of the eyes is concerned, whether fingers are counted at a half or a whole metre, and we ought never to forget that all conclusions which we draw from the state of the visual acuity, are unreliable in proportion as the latter is lowered. Indeed, on repeated examination of such cases we frequently find considerable fluctuation in the statements of the patients, therefore we ought not to expect accurate statements for very inexact sensual impressions.

By separate use, even in extremely defective vision, no improvement in visual acuteness is developed, but only a more complete acquirement of the power of deducing right conclusions from imperfect sensual impressions. That which has been most unscientifically designated as "suppression of diffusion circles," depends solely on this method of use. As with indistinct retinal images so with facial impressions which are insufficient, one can never learn to recognise larger objects aright.

We must never forget that vision is a conclusive act acquired by practice; whoever sees well with one eye, and is weak sighted with the other, acquires this end only for the sensual impressions of the better eye, and must first collect experience for the defective eye, before he can use it.

Leber has recently joined those cases which are described as blindness through blepharospasm, to amblyopia from disuse. First, I wish to observe that blepharospasm is not a necessary cause; I have seen the same disturbance of vision follow severe double blenorrhoea, which destroyed one eye but left the other uninjured. These children are always of an age which renders any trial of vision impossible, and we are therefore obliged to draw conclusions as to visual power from the movements of the body. If children move as though they were blind, it need not necessarily follow that they are so in the common meaning of the word. The art of vision is a difficult one, the acquisition of which begins with the earliest days of life; we do not call every person blind who does not see what is before his eyes, because he does not understand how to see it. A child who has only imperfectly learnt the conclusive act of vision, and forgotten it again during a continued disuse of both eyes, will not know how to use perfect visual acuity, and will move like a blind person till he again learns to estimate the relations between his retinal images and the things of the material world, which happens in a very short time.

After this digression let us turn again to amblyopia from disuse, and to the last trump which is played for it. "Those cases are very remarkable where an immediate improvement occurs after tenotomy in amblyopia of high degree, which according to this is certainly produced and maintained by the squint." As proof a case is cited by Knapp, who describes it in the following words:--"The improvement in visual power varied very much. In many cases it was indefinable, in others very pronounced; for example, in one case, where it was very great before the operation, only No. 16 Jaeger could be read at 1 inch, while after it No. 2 was read at 8 to 9 inches."

And we are to believe wonders on the strength of this scanty communication! It is an every-day experience that a person who squints, who has just asserted his inability to read the largest type, immediately afterwards reads smaller and the smallest type, and it would at least first have to be determined that all endeavours to produce a better visual result before tenotomy were unsuccessful; but as the communication stands, the conclusion as to the effect of tenotomy is quite a superficial _post hoc ergo propter hoc_. Moreover, I had this case in view when I spoke on this matter in the first edition of my 'Handbook:'--"The frequently repeated assertion that a considerable improvement of vision may occur as a direct result of tenotomy, is so little in accordance with all the laws of physiology, that inquiries must be instituted _ad hoc_, and carried out with the most perfect exactitude. Only trials of vision which are carefully carried out and repeated several times before the operation, and which have regard to visual acuteness for distance as well as for near objects, the latter indeed by the aid of convex glasses or Calabar extract, can be recognised as proving anything in face of such a perfectly improbable assertion. In the course of examinations so instituted I have not myself found that tenotomy exercises any direct influence on visual acuity."

I would not have given so much space to this explanation had not a principle been in question. The occurrence of amblyopia as a result of non-use has been deductively constructed and is not inductively proved by observation. It is just an article of faith, and in science we cannot rely on such things; we must not depart from the inductive method.

ON THE CURE OF SQUINT.

Therapeutic investigations have their safest and most instructive basis in observation of the course of a disease as it appears without complications, and with no unusual symptoms; we can only arrive at a certain decision as to the extent of our therapeutics when we know exactly what will happen without skilled assistance. When squint is once present it is seldom complicated by fresh symptoms; on the other hand, spontaneous cures unquestionably take place. We must certainly not rely simply on the statements of patients themselves. On p. 1 we have seen what mistakes occur, even when it is a question of whether squint is present or not. How little such vague statements are worth is seen by the fact, that the question as to the direction of the previous squint very seldom finds a satisfactory answer; as a rule it is impossible to determine whether periodic or permanent squint has been present.

If we undertake the task of converting the statements of patients as to previous squint into observations, in order to confirm the statements from the objective material, we must first prove whether the squint cannot by some means be still produced (by excluding the eye or by raising or lowering the eyes). Thus the condition of binocular vision offers us valuable guides. If we find that binocular fusion does not exist with available power of vision on both sides, but that the same conditions of sight appear in the eyes as we have learnt to attribute to squint, there is no reason for doubting the statements about a previously existing squint. It is otherwise in those cases of extreme amblyopia where normal binocular vision is never expected, or at least cannot be proved on account of the enormous difference between the two eyes.

If we discover the existence of normal binocular fusion, squint may nevertheless have been present at a former time, for in many cases, of periodic squint particularly, the habit of binocular fusion is never quite lost.

That squint can disappear of itself is unquestionable; how often this happens it is difficult to say. The fact that in ophthalmic practice we see many more squinting children than adults is best explained by this,--that squinting children are brought to us by their parents, while adults who still squint have usually given up any desire for a cosmetic improvement, and only come under treatment accidentally or on account of other ailments; lastly, a considerable number of cases are cured by operation. If the squint has disappeared we only discover by accident that it was ever present. The fact of its previous existence may usually be determined by other signs more positive than mere statements from memory; with reference, however, to the age at which the spontaneous cure takes place we are left to depend almost entirely on the patient's statement. As far as I have been able to determine, the period from the ninth or tenth up to the sixteenth year seems to offer the most favorable conditions.

We rarely have an opportunity of watching the disappearance of squint, 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.