Elements of Surgery

by Robert Liston

It is too true, that the hopes of a cure, after the extirpation of the eyeball for malignant disease, are defeated by the prior existence of a similar affection within the cranium. In the majority of cases, death has occurred from tumours of greater or less extent, along the course of the optic nerve, or their tract: behind the commissure, and extending to the optic lobes and even cerebellum.

[STRABISMUS.

Strabismus, or squint, as it is vulgarly designated, may be defined to be an aberration from the natural direction of the optic axes, by which the consent between the eyes is destroyed, and vision more or less impaired. The resulting deformity varies in different cases, from the slightest possible cast to the most disagreeable obliquity. The affected organ may be turned inwards or outwards, upwards or downwards, according to the muscle upon the derangement of which the squint depends. When the eye is directed inwards, it constitutes what is called convergent strabismus; if, on the other hand, it inclines outwards it is said to be divergent. The upward and downward obliquities have not received any particular names. As might be supposed, these different forms of strabismus do not occur with equal frequency. On the contrary, two of them are so rare that I have not yet met with an instance, though I have examined the eyes of a very considerable number of persons labouring under this infirmity. These two forms are the upward and downward, both of which, but especially the latter, are so seldom witnessed that their occurrence may well be doubted, except as the result of external violence.

The most common variety of strabismus by far is the convergent, in which the eye is directed inwards, or inwards and upwards. Of 536 cases collected from various sources by a writer in the Philadelphia Medical Examiner, 506 were of this description, a proportion which fully accords with my own but more limited observation. The degree of obliquity may be very moderate, or so great that when the person looks directly forwards with the sound eye the cornea of the other shall be almost entirely concealed at the inner canthus. It is worthy of remark, that in this form of the lesion, at least so far as my own experience goes, the organ rarely, if ever, inclines downwards, but nearly constantly somewhat in the opposite direction.

Next in point of frequency is the divergent form, which, however, is comparatively rare. Of 866 cases reported in the work above alluded to, it was noticed only forty-four times; and thus far I have myself seen only three or four examples of it. The eye in this variety of strabismus is seldom drawn out very far, nor is it so apt to be attended with the same amount of upward obliquity as the convergent.

It seems to be the general sentiment of writers on strabismus, that, in the great majority of cases, only one organ is affected. Thus, in the article in the Philadelphia Examiner, before adverted to, it is stated that the distortion occurred 459 times in one eye, and only 47 times in both. Dr. Dix, of Boston, in a small treatise on strabismus, makes a similar remark. Of 50 cases which fell under his notice, the lesion is said to have been limited to one eye in 36. Now I am convinced from a good deal of experience that nothing can be more unfounded than this opinion, which is to be deprecated the more because it is calculated to lead to very serious errors in practice. I unhesitatingly assert, that in nearly all instances, at least of convergent squint, both organs are implicated, though not in an equal degree. Usually—perhaps always—one is more affected than the other, which the patient, therefore, regards as his good eye, as it is the one which he constantly employs in viewing objects. Nor is it surprising that this should be the case, when we recollect the remarkable sympathy existing between these structures, and the fact that when one eye is diseased the other is very liable to take on morbid action also. Amaurosis of one eye is very often followed by a similar malady of the other, and the same is true of cataract and some other affections. In the natural state there is a perfect agreement between the optic axes, produced by the harmonious action of the straight muscles, but when this consent is destroyed, as it is in strabismus, the eyes lose their parallelism, and the distortion in question is the consequence.

As was previously intimated, one eye is commonly more affected than the other, and this, if I mistake not, will be found to be the left, though it is impossible, in the existing state of the science, to indicate the proportion. Mr. Lucas thinks that the proportion in favour of the left eye is as three to two; Dr. Phillips of Liège, on the other hand, maintains that the right organ is more frequently involved than the other. It rarely happens that both eyes become deranged simultaneously; on the contrary, one generally squints first, and after a while the lesion begins in the other, the interval being probably very short.

Whether strabismus occurs with equal frequency in both sexes, is still an unsettled question. Of thirty-two cases on which I have operated, only five were females, whereas in the fifty cases published by Dr. Dix, of Boston, only nineteen were males, thus exhibiting a most remarkable disparity in reference to this point. The difference, if any, is perhaps not great either way, and, as it is of no practical importance, it need not be pursued any farther here.

The exciting causes of this affection are numerous and diversified. One of the most frequent is imitation. Nearly one-seventh of all the cases that occur are probably induced in this manner. Hence our schoolrooms may be regarded as a fruitful source of mischief, one cross-eyed child being often the cause of strabismus in many others, merely from that habit of imitation to which the young are so much addicted. Ophthalmia, by whatever cause induced, is another, and that a very common source of this distortion. I have seen repeated instances of this kind, and many others are mentioned by authors. Convulsions, eruptive diseases, such as measles and scarlet fever, hooping-cough, derangement of the digestive organs, injury on the eye, and difficult dentition, may all be enumerated as so many causes of the lesion in question. Frequently it arises without any assignable reason, and when the individual is in the most perfect health. Occasionally it is congenital, or, what is more probable, makes its appearance within a few days after birth.

It is supposed that strabismus is occasionally hereditary. This is doubtful; for if we sometimes meet with cross-eyed children whose parents, one or both, are similarly affected, it by no means proves that the distortion was transmitted to them in the manner of certain maladies. It only shows a coincidence, which may be explained, in most instances, on the assumption that the children have acquired the obliquity by imitation, or by some other cause, not that it was entailed upon them previously to birth. In the same manner we may satisfactorily account for the existence of strabismus in several members of the same family, of which a remarkable instance has recently come under my own observation. Of three brothers, one has three children affected with it, another two, and a third one. The parents have all sound eyes, and so have the uncles and aunts, except one, on whom I operated successfully several months ago. Last autumn I operated for cataract on three children belonging to a gentleman from Mississippi, who informed me he had six others at home, of whom three were affected with strabismus. Both parents, as well as their immediate relatives, are free from the affection.