Chapter V: The Pathological Anatomy of Couched Eyes (2)

It is not easy to obtain a view of these exudates in section, but nevertheless they appear in a considerable number of the microscopic specimens, and their character is always the same; they consist of more or less structureless masses with blood-cells and leucocytes imbedded in their substance. In fact, they would seem to be identical with the membrane spoken of by Straub as harbouring the leucocytes which gave rise to dust-like and other opacities of the vitreous in his experimental cases. At a later stage, or perhaps in cases where the inflammation has been of a more plastic character, a distinct fibrillation of the exudate can be seen, and there may even be evidence of a definite fibrous tissue formation. If we confine our attention for the moment to those eyeballs in which the exuded mass is devoid of structure in the anterior portion of the cone, we shall find that, on tracing it back toward the apex by which it is attached to the optic nerve, it becomes more highly organised and more richly cellular, whilst fibrillation and fibrous tissue formation make their appearance. The same thing, though in a lesser degree, may be observed in the neighbourhood of the ciliary body, doubtless due to the presence of a plastic exudate derived from that structure.

An examination (Pl. VI., Fig. 38) of the optic nerve and of the exudate attached to it reveals the following features: (1) The nerve head is congested, and its vessels stand out in prominent relief. (2) There is a considerable effusion of leucocytes in the neighbourhood of these vessels. (3) A mass of exudate fills up and projects from the optic nerve cup, whether this latter is physiological or glaucomatous. This mass is clearly contracting, and thereby pulling on the tissue which lines the edges of the cup. (4) Along the centre of the projecting exudate are to be seen (_a_) an abundance of mononuclear cells; (_b_) the commencement of a fibrous tissue formation; and (_c_) a new formation of bloodvessels.

The appearances above enumerated would indicate that we have to do with an inflammation of the optic nerve, which had been induced by chemotaxic substances brought thither along Stilling’s canal. Such an idea is not a new one. It was suggested by Straub in order to explain the optic neuritis he found in his two cases of experimental inoculations of the ciliary body, and it also enjoys provisionally the support of Fuchs’s[3] authority. The idea that part of the lymph of the eye passes backward along a passage corresponding to the central hyaloid canal is not generally accepted, and rests largely on inference from the observation of pathological specimens. It would be difficult, however, for anyone who has carefully studied this series to doubt that such a flow exists; it is, of course, not suggested that any large percentage of the lymph travels in this direction.

[3] Fuchs: “Textbook of Ophthalmology,” Duane, fourth edition. 1911, p. 16.

A confirmation of these views is obtained if we refer to the three eyeballs in which the organisation of the cone of exudate into the vitreous has attained the highest development. We notice in these how extremely far this process of organisation has been carried in the apex of the cone, where it is represented as a well-defined opaque cord (Pl. VI., Fig. 39; and Pl. III., Fig. 17). In one of the three a fibrous band, presumably the remains of the canal of Stilling, is clearly seen, whilst in the two others the existence of this structure is at least indicated. It is possible that in the first-named a congenital peculiarity exaggerated the distinctness of the appearance.

=The Retina.=

Detachment of the retina occurred in 38 of the 54 globes (70·38 per cent.), and was absent in 16 (29·62 per cent.). It was partial and ill-marked in 5 (9·25 per cent.), extensive in 9 (16·68 per cent.), and complete in 24 (44·44 per cent.). The ocular tension was above normal in 11 out of the 16, which presented no detachment, but in only 6 out of the remaining 38; it was below the normal in 13 of the 24 globes with complete detachment, and above it in 3 of them. In the very great majority of the eyes the detachment of the retina was undoubtedly due to traction from within. The sequence of events is plain from a study of the whole series.

At the operation there was an infection of the coats of the eye, and also of the vitreous chamber from without; this led to the formation of inflammatory material within the vitreous chamber; adhesions took place between these new-formed membranes and the retina; finally the shrinkage of the organising inflammatory material tore the retina from its bed. Every step of the process can be traced either in microscopic sections or in the naked-eye specimens. The earliest possible stage is seen under the microscope in sections of an eyeball (No. 37), where in the neighbourhood of the ora serrata the shrinkage of the exudate within the vitreous chamber has just begun to lift the retina from its bed. The individual points of attachment between the inflammatory membrane and the retina are beautifully illustrated. The ultimate stage of the process is to be found in those cases in which the retina is not merely totally detached, but has shrunk posteriorly into a stick-like form (Pl. III., Fig. 19, and Pl. IV., Fig. 25), whilst it opens out anteriorly into a mass in which the iris, the ciliary body, the lens, the remains of the vitreous, and the retina are inextricably matted and tangled. When sections of such specimens are examined under the microscope, their leading feature is the evidence of severe plastic iridocyclitis, with the formation of abundant cicatricial tissue, which mats all the parts together and severely distorts the normal anatomical arrangement. The retina is dragged forward from the neighbourhood of the ora serrata over the ciliary body, whilst elsewhere it is thrown into abundant folds and completely separated from its normal attachments. A pseudo-cystic condition is thus produced, the apparent cysts being formed by the elaborate folding of the membrane (Pl. III., Fig. 19, and Pl. V., Fig. 31). These may be small and slit-like, or may be large and round, so simulating the appearance of true cysts. In front of the retinal mass, lens fragments and capsule are seen in a number of the specimens entangled in the scar-tissue. As has already been said, all grades can be traced, from the slightest detachments up to those we have just been describing. The greater or less degree of separation of the retina met with in the different globes is doubtless in part a question of time, but it is also, and probably to a much larger extent, one of the character and grade of the inflammatory process excited in the eyeball. The more plastic the type of inflammation and the more intense the process is, the greater will be the measure of ultimate cicatrisation, always provided that the inflammation is not intense enough to result in suppuration.

There are several different ways in which the exudate which forms within the vitreous chamber may be placed in a favourable position for the production of retinal detachment.

1. The first of these is illustrated by each of those globes (Nos. 44 and 72) in which the site of a wound of the retina forms the point of connection between that membrane and the inflammatory exudate lying in the vitreous cavity (Pl. V., Fig. 30). The traumatic infection of the retina served to attach the vitreous exudate to its walls, and thus paved the way for the separation of the membrane. In one of these cases (No. 44) a longitudinal fold was detached, whilst in the other (No. 72) the detachment was broad and shallow.

2. In the second method also, it is necessary to postulate an infection of the retina before that membrane could have contracted adhesions, either localised or widespread, to the neighbouring vitreous exudate. Once, however, the virus was planted within the hyaloid chamber, it probably diffused itself widely, and by means of chemotaxis set up an inflammation of the retina; evidences of such a retinitis abound in many of the specimens. Attachments between the vitreous exudate and the retina having been thus formed, the contraction of the former would naturally lead to the separation of the latter from its choroidal bed.

3. In a few of the globes the contracting membrane is merely an infiltration and thickening of the anterior layer of the hyaloid. It is well known that the vitreous body is, under normal conditions, more firmly attached to the retina in the neighbourhood of the ora serrata than it is elsewhere; it is therefore obvious that an inflammatory contracting membrane in the anterior part of the vitreous will pull throughout its whole circumference on the retina in its neighbourhood, effecting a detachment over a very wide area (Pl. III., Fig. 20). This is just what we see happening in the globes we are now discussing.

4. In a number of the specimens it can be clearly seen that the bands, which drag upon the retina, radiate from the remains of lens masses, which are themselves encased in inflammatory tissue, and are bound thereby to the iris and ciliary body in their neighbourhood. Such bands appear in some cases to lie in the substance of the retina itself (Pl. IV., Fig. 24); in others they are situate in the vitreous and present the form of membranous sheets, separated from the subjacent retina only by narrow spaces, and finding attachment to it in the neighbourhood of the equator (Nos. 117 and 170). The characteristic of these cases would appear to be that the dislocated lens is in them the principal focus of sepsis within the eye. The point is of interest, since some of them, at least, represent ruptured Morgagnian cataracts; for there is reason to believe, on clinical grounds, that the liberation of Morgagnian fluid within the eye is, sometimes at least, productive of considerable irritation to the surrounding parts.

There are two globes in the collection in which the exudate within the hyaloid cavity, converted into organised fibrous tissue, is obviously tearing the retina from its bed in the course of its contraction. A very interesting feature of these eyeballs is that in each of them an opaque band which strongly suggests Stilling’s canal can be traced forward from the optic nerve head (Pl. VI., Fig. 39).

In many of the specimens an abundant subretinal exudate is present. In the long-standing ones, with complete detachment of the retina, this effusion fills up the whole of the space between the retina and the choroid. When the latter membrane is also detached, a further exudate of similar appearance is seen between it and the sclera. Owing to the action of the formalin, the very firm coagulation of the long-standing effusions gives the eyes a solid and very characteristic appearance (Pl. III., Fig. 19); the half-globes look like sections of marbles made of fissured and clouded glass. In earlier cases the effused mass is much less firm, but is whiter and more opaque, with a tendency to present a flocculent appearance. The question that naturally presents itself is, whether these effusions were the cause or the result of the retinal detachment. The presence of the inflammatory exudate within the vitreous, with which we have already dealt, provides such a satisfactory explanation of the detachments of the retina throughout this series, that it seems unlikely that the effusions in question, whether subretinal or subchoroidal, play any causative part whatever.

We must place in quite a different category the cases, four in number, in which the effused fluid consisted of blood. The source of the hæmorrhage in these cases is different from that which is met with when the pressure within an eye is suddenly reduced by the operative opening of the globe. In the latter case it is the large choroidal vessels which give way, and the hæmorrhage is subchoroidal, whereas in the four cases under review the bleeding was subretinal in one (No. 157), into the vitreous chamber alone in one (Pl. VII., Fig. 40), and into both the vitreous chamber and the subretinal space in two. The hæmorrhage into the vitreous chamber was probably due to injury to the retinal vessels by the coucher’s instrument, though it is possible that blood may have found its way through the retinal cut from choroidal vessels divided at the time. The subretinal probably escaped from the severed branches of the smaller choroidal vessels. The fact that in no case was a large subchoroidal hæmorrhage present would indicate that the large choroidal vessels were tough enough to escape injury, being probably pushed aside by the comparatively blunt instrument the coucher used. In one eyeball (No. 157) large cholesterine crystals were seen shining on the cut surface of the sanguineous mass. A similar phenomenon was observed in the case of one of the albuminous effusions above spoken of.

It remains to deal with a rare cause of detachment of the retina or of the retina and choroid--viz., the application of direct violence at the time of operation. This is best exemplified in the two globes in which the cataract was thrust through and behind the retina, by the coucher’s instrument, at the time of operation (Pl. IV., Fig. 22). It is also beautifully illustrated by specimen No. 72, in which the retina and choroid were carried in front of the coucher’s instrument before the latter succeeded in perforating them (Pl. V., Fig. 30). The dislocation thus produced proved permanent.

=Dots on the Retina.=--A striking feature of the series of specimens before us is the presence of numerous dots on the retina. These are to be seen in 16 cases, and doubtfully in a seventeenth. In at least one other, similar dots are present on the choroid and on the posterior surface of the iris (Pl. V., Fig. 28). We therefore find this peculiar appearance in one case in every three; but this is far from representing what is probably its real relative frequency, for in 24 of the globes the retina was totally detached, and it was therefore impossible to say whether there were dots present on it or not. If we put these 24 to one side, we find that the dots were certainly present in 16 out of 30--that is, in well over 50 per cent. If we include the other 2 cases above alluded to, the figure rises to 60 per cent.

In some of the specimens the dots are so large that they could scarcely be missed under a careful naked-eye examination (Pl. III., Fig. 18), whilst in others they were only discovered when highly magnified photographs of the eyeballs were thrown on a screen (Pl. III., Fig. 17). They could, however, be found easily with a loupe once their presence was known. The variation in different specimens was not confined to size; some of the dots were white, others were a pale grey, and a few were bright and shiny. Again, some of them appeared much more sharply defined than others.

It was at first thought that manifestations so distinct under slight magnification would yield very definite appearances under the microscope; but, on the contrary, much difficulty has been experienced in deciding the nature of the changes which have given rise to this phenomenon.

One of the first points noticed was that the dots were found almost exclusively in long-standing cases. This of itself would appear to indicate that their cause was to be sought in some degenerative process; but a closer analysis of the histories revealed a probable fallacy in such an argument, since a number of the eyes had had good vision for a long period after operation, and had eventually succumbed to a fresh inflammatory invasion, or possibly to a more severe recrudescence of a septic condition implanted at the time of operation.

On examination of a number of specimens, three distinct appearances have been found, any one of which might presumably account for the dots seen with the naked eye.

1. In some of the globes a proliferative retinitis can be found along certain of the vessels (Pl. VII., Fig. 41). These consist in section of masses of mononuclear leucocytes surrounding the vessel wall, and tending to make their way to the inner surface of the retina. It might be thought that such a change would produce lines rather than dots, and that those lines would run along the course of the vessels; but there are two features which make this doubtful: (_a_) Even under the same field some of the vessels appear quite healthy on section, whilst others show distinct masses of proliferation; and (_b_) along the course of a vessel cut obliquely one may find the proliferative exudate confined to one part of its course, the rest being comparatively free.

2. In the neighbourhood of some of the inflamed retinal vessels above spoken of, one finds on the surface of the retina what appear to be free collections of mononuclear cells (Pl. VII., Fig. 42). These are apparently of the same nature as the dots described by Straub on the posterior surface of the cornea and in the vitreous body. It will be remembered that he attributed them to chemotaxic action. It would appear not improbable that the same explanation holds for these retinal dots. It is of interest that, though they occur in cases of long standing, the history of a subsequent inflammation, destructive to vision is of a much later, and indeed, of a comparatively recent date. The presence of such exudative masses would then be easily explained.

3. The grouping of these dots varies considerably in different specimens, but does not lend much colour to the idea that they are vascular in origin, for in some at least of the eyes they certainly do not follow the course of the vessels. On the other hand, in a few of the eyeballs there is a massing of these dots in the neighbourhood of the ora serrata, which is in itself suggestive of a degenerative process, since this is the area of lowest circulatory activity, inasmuch as this region is supplied by the ultimate twigs of the retinal vessels. This observation gathers interest from the fact that in quite a number of these specimens it is possible to demonstrate the presence of small cysts in the walls of the retina (Pl. VII., Fig. 43). These cysts are produced by the coalescence of œdematous spaces in degenerative areas. All stages of the process can be traced in different specimens of the series before us. Such cysts are only likely to be met with in long-standing cases in which the degenerative processes have had time for full play.

Inasmuch as these retinal dots are found in the cases in which the retina is still in its normal position, it would seem probable that a careful clinical search should reveal their presence in living eyes now that their existence is established pathologically. It is a point which should repay the study of surgeons who are practising where couching is commonly resorted to, and especially in India.

PLATE VII

Fig. 40: Specimen No. 240.--The original cavity of the vitreous is represented by a mass of blood-clot, surrounded by the walls of the totally detached retina. The subretinal exudate is firm and abundant. The iris and ciliary body, the lens remnants, and the anterior part of the retina are matted together in a dense mass of cicatricial tissue.

Fig. 41: Specimen No. 175.--This shows a proliferative dot in the retina. R, retina; SCL, sclera; CH, choroid; D, mass of leucocytes surrounding vessel wall.

Fig. 42: Specimen No. 37.--A collection of leucocytes lying on the inner surface of the retina, superficial to its limiting membrane, and projecting freely into the vitreous. In the substance of the retina can be seen the section of a vessel surrounded by a mass of leucocytes.

Fig. 43: Specimen No. 111.--Small cysts in the retina, which would probably have coalesced before long to form a larger one.

Fig. 44: Specimen No. 111.--A whole-section of the eye already shown in Fig. 34. The condition of l’iris bombé is well marked, the pupillary edges being adherent to an inflammatory mass formed of the capsule and the anterior layers of the hyaloid matted together. Notice the large cysts occupying the central area of the detached retina, with the macula lutea showing in its inner wall.

Fig. 45: Specimen No. 131.--A large Morgagnian lens in its capsule was adherent to the iris base, the ciliary body, and the neighbouring retina over a wide area. The capsule ruptured during the transit of the specimen from India. Note the thickened white dots upon it; they are characteristic of Morgagnian cataract. The large brown nucleus, which escaped when the capsule burst, now lies free in the cavity of the eye; notice the “bite” out of its edge. The optic disc was deeply cupped, and the angle of the anterior chamber was widely obliterated, the chamber itself being very shallow.

Fig. 40 (No. 240).--Left eye, lower half.

Fig. 41 (No. 175).--Microscopic section, low power.

Fig. 42 (No. 37).--Microscopic section, high power.

Fig. 43 (No. 111).--Cysts in retina. Microscopic section, high power.

Fig. 44 (No. 111).--Left eye, whole section.

Fig. 45 (No. 131).--Left eye, lower half.]

=Macroscopic Cysts of the Retina.=--It remains to speak of larger cysts of the retina which can be recognised by the naked eye. It has already been mentioned that, in those cases in which this membrane has been found to be tightly folded on itself, a pseudo-cystic condition is thereby produced; the cavities of these false cysts are merely shut-off portions of the original vitreous chamber. Of a quite different nature are the true cysts of the retina, three examples of which are to be found in this collection. In one (Pl. II., Fig. 12) a narrow slit-like cyst is seen in the outer layers of the detached retina at its lower part. In the second, a whole-section of the globe shows a large cyst occupying the central region, the macular area forming a portion of its wall (Pl. VII., Fig. 44). Lastly, in the third a large round cyst can be seen to the temporal side. A point of interest in connection with this specimen is that it shows both true and false retinal cysts (Pl. III., Fig. 19, and Pl. V., Fig. 31).

=The Choroid.=

It remains to add a few words to what has already been said about this membrane. The great majority of the changes we have found in it are, clearly, to be attributed to the effects either of hypertony or of hypotony of the eye; they do not, therefore, differ from similar appearances found under the same conditions generally.

Compared with detachments of the retina, those of the choroid are rare in this series. In one instance, already mentioned, the two membranes had been displaced together by the instrument used in couching (Pl. V., Fig. 30). In another, in which severe inflammation had occurred, the retina and choroid had adhered to each other, and had been detached as one sheet by the contraction of an exudate, which lay in the neighbourhood of the iris and ciliary body and in the front part of the vitreous cavity. In a number of other globes, in which the tension was low, the ciliary body and the anterior portion of the choroid were found separated from the sclera as far back as the line where the anterior segment of the latter coat was drawn over the posterior in the manner pointed out by Treacher Collins in his work on Hypotony (Trans. of the O.S. of the U.K., 1917).

In the previous chapter we have spoken of an appearance commonly seen in successfully couched eyes--viz., an unusual distinctness of the large vessels of the choroid in the ophthalmoscopic picture. It is necessary to insist that in such cases the vessels are not sclerosed; they are seen with unusual distinctness simply because the pigment which usually hides them from view has disappeared. What is more, a careful study of a number of these cases has created a strong impression that the deficiency in pigmentation affects both the pigmentary layer of the retina and also the pigment of the choroid. The absence of the former lays bare what lies behind it; the absence of the latter is inferred from the general appearance of pseudo-albinism. These findings are the more noteworthy by reason of their contrast to the usual deep pigmentation of the Indian eye. Some of our specimens throw light on this phenomenon, for we observe in them two changes: (1) The pigmentary layer of the retina is irregularly thinned and altered, and at some points its pigment can be seen migrating into the choroid; (2) the choroidal pigment itself is extensively altered in an irregular manner, being heaped up in some areas and thinned in others. It is necessary to remember that, inasmuch as our specimens are wholly obtained from the coucher’s failures, whilst the interesting appearance we are discussing is best seen in his successes, we cannot expect very definite results from our pathological material, since the changes we desire to study are there overlaid and obscured by those of pathological processes, such as hypertony, hypotony, and inflammation.

=Glaucoma.=

It has long been known that couching is frequently followed by secondary glaucoma. In the present series of 54 globes, 19 of them showed evidence of high intra-ocular pressure. This figure must not, however, be taken as a reliable index of the numerical frequency of glaucoma as a complication of the operation. On the one hand, we must remember that the present series deals with the failures only, and that a large number of eyes are met with clinically in which the lens is floating free in the vitreous chamber without any sign that the intra-ocular tension is raised. Again, the cases which go on to suppuration, and which are very numerous, are excluded from the present series owing to the fact that all such were eviscerated in order to avoid the risk of intracranial sepsis. This obviously diminishes the total number of globes under consideration, and thereby raises the apparent percentage of other conditions, such as glaucoma. On the other hand, it would be a mistake to suppose that out of these 54 globes only 19 had suffered from secondary glaucoma, for in 24 of them a complete detachment of the retina had covered up any evidence which may at some time have existed of the presence of increased intra-ocular pressure, though the conditions still found in some of them make it more than probable that the globes were formerly glaucomatous. In any case, it leaves us with the fact that, out of 30 eyeballs which were available for accurate examination, no less than 19 were glaucomatous. In 17 of the 19 the angle of the anterior chamber was extensively closed, and in 3 of these the chamber was so shallow as almost to be reduced to a potential slit. The remaining 2 are thus accounted for: In one the angle was open save for a small marginal adhesion, and there was free communication between the aqueous and vitreous chambers; unfortunately, the specimen was almost spoilt in sectioning it for the microscope; in the second, a Morgagnian lens was impacted in and had blocked the angle of the anterior chamber.

Returning to the 17 cases in which the angle of the chamber was closed, and to certain other eyeballs in which it seemed probable that glaucoma had at some time been present, we found that in every one of them one or other of the accepted causes of secondary glaucoma was revealed when looked for; in some, more than one such cause was discoverable. We shall content ourselves with enumerating these factors.

A corneal fistula, with evidence of past anterior staphyloma, was present in one; here the cause of the glaucoma was evidently the closure of the filtering angle, which resulted from the anterior synechia; in one there was a capsulo-corneal synechia (Pl. IV., Fig. 24), and in another a retino-corneal synechia (Pl. IV., Fig. 25); in 5 the ciliary body was involved in the scar; in 6 the dislocated lens pressed extensively on the iris base (Pl. VII., Fig. 45); in 3 the lenses, tilted at right angles to their normal position, pressed the anterior hyaloid membrane severely back on the side of the dislocation, whilst causing the vitreous to bulge the iris forward into the anterior chamber on the opposite side; in 5 the pupil was blocked, and in 3 of these l’iris bombé was present; in 2 the anterior layers of the hyaloid were so thickened by inflammatory exudate as to suggest that there was an abnormal obstruction to the passage of fluid across the membrane; in one a marked thickening of the lens capsule in the form of an after-cataract may possibly have provided an obstruction to the forward passage of fluid from the vitreous; lastly, there is one globe in which glaucoma had probably been present before the operation, if one may judge from the history of the case and from the violent hæmorrhage which followed the couching.

It has been suggested that one of the causes of glaucoma after this operation is an advance of the front part of the vitreous body owing to a rupture of the anterior layers of the hyaloid during the operation. Without in any way denying that the suggestion may be a valid one in certain cases, the impression gained from a study of this series is that we need look no farther than the well-recognised causes of secondary glaucoma. We have only to remember that the trauma inflicted is extensive and various, and that a greater or less degree of sepsis accompanies every couching in the hands of its Indian exponents.