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.
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.
PLATE VII.
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]).