« AnteriorContinuar »
T-ions were known to the ancient writers, but have been revived only within these few years, it is difficult, and sometimes impossible, to distinguish it. Jiichter, Wenzel, and Scarpa, who have written so largely upon cataract, and have published cases of its varieties on which they have operated, have not recorded any instance of this remarkable species: in which the posterior part of the capsule is alone affected with opacity, while the anterior part of that membrane, and the crystalline lens, remain perfectly transparent. In this country, at least, there is reason to believe, that it was practically very little known previous to the publication of my work on Cataract, &c. in 1812, in which a case of this kind is detailed at length, in a gentleman who had been blind eighteen years,' seven of which he had been under the care of an eminent svnd experienced oculist, who considered and treated the disease as Gntta Serena.'—pp.6—8,
We have no doubt of the correctness of this statement, so far as relates to our own country, and concede to Sir William Adams the merit of having first practically called the attention of the English profession to this peculiar species of cataract, though the quotation we have just made from Plenck is a sufficient proof that the disease had been long known, and its seat distinctly laid down by writers on the continent.
It was formerly supposed, by one or two writers, that the crystalline humour has no proper capsule, and that the only membrane which invests it is a duplicature, or anterior and posterior extension of the membrane which incloses the vitreous humour, and which is commonly described by the name of tunica aranea, or membrana hyaloidea; but it had altogether escaped our attention that this anatomical mistake, as we must still venture to call it, had been unaccountably revived within the last five years by a distinguished surgeon of this metropolis, in a passage copied by the present writer, and plausibly asserted to be little more than a transcript from Anthony Maitre*Jan's Traite des Maladies de I'OeiL It is not necessary to enter into the subject: the anatomy of the eye is too well known in the present day to render the point for a moment questionable; and if it were not, the cloud of authorities brought forward by Sir William Adams, in proof that the lens has a tunica propria, and that the species of cataract before us is seated in the posterior part of that tunic, would impel us to banish all . hesitation whatever.
But we mention the fact for two reasons. First, because an error upon this subject is of great importance in a practical point of view; and secondly, if the position could be sustained for a moment, that the investing membrane of the lens is nothing more than an extension of the investing membrane of the vitreous humour, no writer has hitherto explained the proper meaning of the term eataract, as technically employed, or the real nature and extent of
VOl. Xviii. No. xxxv. l the
the disease it indicates; since, instead of being limited, as we believe it has been by every one, to an opacity of the lenticular chamber, or its delicate walls, it would run indefinitely into the walls and chamber of another and very distinct portion of the eye-ball, and, consequently, confound diseases that have hitherto been held altogether discrepant and dissociate.
The cause of cataract—we mean that of the crystalline lens—has never hitherto been satisfactorily explained. It was at one time supposed to be most frequently a result of inflammation. Our author abandons this principle upon every occasion, and adopts its opposite—that of debility of the minute vessels of the lens: in other words, we are now to read atony instead of entony as its origin. 'Indeed, it is a matter of doubt with me, whether the body of the lens is, under any circumstance, capable of taking on inflammation, although, both from disease and accident, the capsule is susceptible ot it in a high degree: and I think it more probable, when opacity of the lens results from a blow upon the eye, without the capsule being ruptured, that it originates from the derangement produced in the minute vessels of the lens, which occasions the want of a sufficient supply of blood, rather than an excess of it.
'This hypothesis (for such it must be considered) seems strengthened, by the manner in which cataract is supposed to occur in old persons, in whom the minute order of vessels, in common with those of every other part of the system, becoming obliterated, probably produces an opacity of the lens, from the want of nourishment, which, in consequence, being no longer influenced by the circulation of the blood, loses its vitality, and becomes opake.':—p. 29.
This explanation is ingenious; yet as a cataract of the capsule produced avowedly by inflammation, in many instances extends to the body of the lens, it does not account for the means by which such extension is produced. In this case, the action seems to be one and the same—simple and continuous.. But upon the hypothesis before us we are to suppose two opposite actions—excess of irritability operating on the capsule, and deficiency of irritability upon the lens; to contemplate the one as the cause of the other, and both these opposite actions as productive of a common result. The progress of the disease is accurately sketched in the following passage:—
'The first symptom of the approach of cataract is marked by a slight obscurity of vision, as if the patient was looking through a cloud, light smoke, or dirty glass, which is frequently accompanied with the appearance of black specks, cobwebs, flies, &c. flitting before his eye. At first, there is so small a change in the appearance of the crystalline lens, that no person, by examining that body, would be led to suspect the approach of cataract, as the dullness of vision perceived by the patient, I believe generally, if not always, precedes any observable thange in the transparency of the lens, which frequently renders it
exceedingly difficult to determine between the first approaches of gutta serena, and of cataract. Shortly afterwards the pupil loses its beautiful jet black colour, and assumes a turbid appearance, which muddiness increases by degrees, until at last the lens becomes entirely opake, and of a white, yellow, or dark colour, constituting what is called a.mature, or ripe cataract.
'During the whole of the advance of the cataract, unless it be complicated with any other state of disease, the natural functions of the iris are preserved, and no pain whatever is felt in the eye, or head. So little conscious, indeed, is the patient of the existence of cataract, when it attacks but one eye at a time, that he is frequently ignorant of the loss of sight in it, until, by accidentally covering the other, he finds himself wholly dark; or, from being unable to judge accurately of distances, he spills his wine in attempting to pour it into a small glass, or cannot, with certainty, snuff a candle, and is hence induced to examine his eyes separately. In one instance which I saw at Exeter, where cataract was produced by a blow from a bush, the wife of the patient soon after observed a whiteness of the pupil, which she did not mention to her husband, lest it should alarm him; and it was upwards of three •weeks before he knew himself to be blind, in one eye, by accidentally putting his hand over the other.
'The disease generally commences at first in one eye, and, by the time it has made any considerable progress, the other eye becomes affected. This, however, is not always the case, as I have known ten, or fourteen years, to intervene between the production of cataract in one eye, and the subsequent formation of it in the other. There is an equal degree of uncertamty, in the period of time, required for the complete formation of cataracts. I have known them completely formed (and when not arising, apparently, from any particular exciting cause) in the short space of three months, whereas, in other instances, if I may credit the patients' statement, they had been gradually losing their sight for upwards of ten years. The usual length of time is between one and three years, which embraces the period when the obscurity of vision first commences, until the cataract is completely formed. When, however, the cataract is produced by accidents, or arises from the application of any particular exciting cause, it will sometimes form in an almost incredibly short space of time.
'Richter mentions the case of a forester, who, labouring under the gout, had his feet exposed to a great degree of cold during the night: the gout suddenly retroceded in consequence, and he was entirely deprived of his sight the same night. He adds, "I saw him next morning, and found a complete pearly-coloured cataract. Eschenbach relates a similar case."
'Tartra, in his excellent Thesis on Cataract, mentions a case, related by Fabrice de Hilden, of a lady about fifty years of age, who, having wept a great deal for the loss of a relation, became blind from cataracts in one night, without pain or inflammation.
'He also mentions, that he was informed by Weidmann, a celebrated surgeon of Mayence, of a case of cataract, which suddenly
l 2 formed
formed in the eye of a man on his quitting a feast very much intoxicated. Tenon states, that he had seen a lady with two cataracts, which were completely formed in one day. He also relates the case of a potter, who, going into his pottery while it was heated, came out with two perfect cataracts.'
All these cases import great irritative action, and suggest inflammation rather than atony as the cause. Indeed we can hardly conceive how the latter could produce so sudden an influence: and it is observed by our author himself immediately afterwards, that, 'when cataract results from age, or is produced by any other natural cause, the progress of the disease is much more slow.' We mean not, however, to say that local debility does not induce cataract, but only that it is not the sole inductive principle; and that cataract, like gangrene, and a variety of other diseases, may proceed from either extreme. It is very probable, indeed, as our author observes, 'that cataract in old persons, or those in whom the animal powers, according to the course of nature, are suffering by slow decay, is occasioned by an obliteration of the vessels that nourish the crystalline lens.'—p. 48.
It is not very surprizing that a dexterous and successful operator should be forward in recommending, even from the first, a recourse to chirurgical rather than to medical treatment. We do not differ from our author in the main, but we think that he allows somewhat too little to the possibility of benefit from any plan of medical treatment that is either now known, or may be hit upon hereafter. The subject, however, is well put in the following passage:
'By whatever process the disorder may be produced, it is obvious, that it is not likely to be easily within the reach of medical treatment; and the almost uniform failure of general, and local remedies, leaves no other resource for the patient than an operation.
'It will be granted to me, without much hesitation, that no solid body, in any part of the system, admits of being removed by the absorbents, without first undergoing solution. A supposition to the contrary, involves the absurdity of believing, that the finest and most delicate series of vessels of the body, whose largest trunks are with difficulty made visible by dissection, and whose smaller tubes are not cognizable to the senses, and can only be proved to exist by analogical reasoning, should possess the mechanical power of abrading the solid substance of bone. The power of these vessels in absorbing fluids is undeniable; and it is equally certain, that portions of exfoliated bone are removed by them, and carried into the general system; but their structure shews the impossibility of their exercising a sufficient force, for this purpose, upon solid substances; it is, therefore, more than probable that solution takes place as a preliminary process to absorption. This reasoning applies with equal force to the absorption of solid cataracts, for, in proportion to the comparative size of the absorbent vessels, which the lens and capsule possess, the resistance will be equal to that which is
offered by bone to absorbent vessels of a larger size, in other parts of the body. One necessary step, therefore, to the removal of a solid, lenticular cataract, is, first of all, to effect its solution.
'To accomplish this, completely within its capsule, and without the solvent agency of the aqueous humour, must be admitted to be beyond the power of any internal, or external remedies.'—pp. 48, 49.
Now we cannot categorically consent to any such admission, although we are not, at present, acquainted with any medicine, or course of medicines which, whether generally or locally applied, will decidedly operate in removing the opacity. We object to the argument.
The cataract, or opaque lens, is here contemplated as a dead or inert body, surrounded by a living substance. It should first, however, have been proved that it is a dead or inert body. But granting that it is so, are we to suppose no other set of vessels at work to carry off this obstruction than the absorbents? We admit that in every case of this kind a solution of the dead matter, and consequently a solvent medium, is necessary: and in all common cases, even where a dead piece of bone is to be removed, we fmd this, or think we find it, in the new and correspondent action of the contiguous secernents thus keeping pace with the new action of the absorbents, and pouring forth a secretion that, being applied to the surface of the dead matter, dissolves, not indeed the whole substance at once, so as to convert it into a mass of pus, or of any other fluid, but only that part of it with which it is in immediate contact, and which hereby becomes fitted for absorption, and is absorbed accordingly. And as the same double and harmonious action is continued upon every fresh surface of the dend matter that thus becomes exposed, the whole is at length carried off, and a cavity produced where before was solid substance.
This reasoning, which is meant to embrace and exemplify the doctrine of Mr. John Hunter upon the general subject before us, applies to the opaque lens contemplated as a dead or inert substance alone. But it is not necessary thus to contemplate it in every case of lenticular opacity; for it is possible, and indeed probable, that, in many instances, it becomes nebulous from the secretion of a morbid and non-transparent fluid by its own minute secernents; and, in such cases, a return of the diseased vessels to their wonted healthy action is all that is necessary to remove the opacity, and consequently to carry off the cataract.
Whether there actually exist, in the wide region of therapeutics, any description of medicines capable of exciting this return of healthy action, or of stimulating the surrounding systems of secernents and absorbents to a removal of the entire lens when absolutely dead or inert, is a question altogether distinct from
h 3 the