«FUCHS'S EPITHELTAL DYSTROPHY OF THE CORNEA* BY J. H. DOGGART London BEGINNERS in any branch of medicine are often accused of being too ready to ...»
Brit. J. Ophthal. (1957) 41, 533.
FUCHS'S EPITHELTAL DYSTROPHY OF THE CORNEA*
J. H. DOGGART
BEGINNERS in any branch of medicine are often accused of being too ready
to diagnose rare diseases among patients afflicted with the common things.
Bearing in mind, as we always should, that common diseases are often
manifested non-typically, we must look with initial suspicion at any evidence
pointing to a rarity. We know, for instance, that appendicitis can simulate all manner of recondite abdominal lesions, and that pneumonia emerging in bizarre forms may bewilder all but the most astute clinicians; and of course we have comparable pitfalls in ophthalmology. Nevertheless, I will not apologize for speaking about a rare condition. On the contrary, I want to emphasize the importance of Fuchs's corneal dystrophy. This disease is often missed, often enters into differential diagnosis, and it has been repeatedly confused with glaucoma. Therefore statistical tables concerning the relative frequency of eye diseases necessarily fail to convey the full significance of Fuchs's dystrophy in everyday clinical practice.
The main features of this malady are now well established. It affects both eyes, although one may be implicated earlier than the other, as obtains in so many bilateral diseases. Most of the victims are elderly, and women outnumber men in nearly all the recorded series. First the endothelium is attacked, then the epithelium, and finally the comeal substance. Failing vision is the cardinal symptom, and the causation remains obscure. Before we proceed to more detailed description, it will be convenient to recall the pioneer work upon this subject.
BRIEF REVIEW OF THE LITERATUREFuchs's original account of epithelial dystrophy (Fuchs, 1910) is a locus classicus in ophthalmic literature. There we find most lucidly marshalled all the essential points except those endothelial changes which were not recognizable until slit-lamp microscopy had been evolved. Fuchs describes the loss of corneal sensation, the development of epithelial vesicles spreading from the centre to the periphery of the cornea, and the subsequent invasion of the substantia propria. His paper is based upon thirteen elderly patients, nine of them women, set forth in detail.
Although Fuchs did not possess that apparatus which enables us to scrutinize the living corneal endothelium, he was able to foreshadow that an endothelial defect might be responsible for this strange clinical entity. In his Bowman lecture delivered eight years earlier (Fuchs, 1902), he had already made brief mention of a * Received for publication March 21, 1957. This communication is based on a paper delivered at the Spring 1957 Congress of the Gill Memorial Hospital, Roanoke, Virginia, U.S.A.
J. H. DOGGART strange condition simulating glaucoma in the corneae of elderly patients; and he speculated concerning the possibility of an endothelial change as the primary lesion.
Those remarks, if they are read in conjunction with his 1910 paper, clearly show that Fuchs was already on the track of his now famous dystrophy, but he did not follow up this brilliant guess about the endothelium. The only fragment of cornea which he could secure for histological investigation was a disc consisting only of the superficial layers. Even a whole-thickness corneal section would probably have failed to display the endothelial changes after exposure to the chemical processes of fixation.
Kraupa (1920) was the first to publish a description of the endothelial changes which are now known to precede those of the epithelium in Fuchs's so-called epithelial dystrophy. It will be recalled that Gullstrand (1911) demonstrated his slit lamp in Heidelberg at the International Congress, just a year after the publication of Fuchs's classical paper. During the ensuing years, in the face of shortages and distractions created by the 1914-18 war, various improvements were wrought in Gullstrand's lamp. Kraupa made good use of these devices, and reached the correct conclusion that the endothelium is the first layer to be implicated in this disease. At the same time Vogt was scrutinizing the endothelial changes in Fuchs's dystrophy, though his observations were not published until the year after Kraupa's paper had appeared. Vogt (1921) gave, as might be expected, a beautifully vivid description, likening the altered endothelium to powdered bronze dusted upon the back of the cornea.
Vogt's powdered bronze phenomenon is essentially due to disintegration of the cells composing the endothelial mosaic, which are displayed by slit-lamp microscopy of the posterior corneal surface in the zone of specular reflection. In a minority of cases, endothelial disintegration is not the first sign produced by Fuchs's dystrophy. Instead, we may find large apparent holes in the endothelium of the axial region. Similar but smaller "holes" have been proved to consist of localized backward bulges of Descemet's membrane into the anterior chamber. Naturally the endothelium at the back of each bulge is thrown out of focus in relation to the rest of the endothelial sheet, and so we get the illusion of "holes". The same structural explanation holds good for the larger, axial "holes" occasionally found in early Fuchs's dystrophy. In this context it is interesting to recall the contribution of Graves (1924). Graves had assembled some bilateral cases of these multiple endothelial warts in elderly people, some of whom displayed epithelial vesicles; and he came to realize, when his paper was nearly completed, that he was dealing not with a new entity but with instances of Fuchs's dystrophy. Within the next year or two Friedenwald and Friedenwald (1925), Gifford (1925), and Sallmann (1926) all produced work to confirm that the endothelium is the first layer to be involved. Further striking testimony was supplied by Paufique (1951), who noted that attempts to relieve the victims by a superficial lamellar graft were foiled by transudation of aqueous through the abnormally permeable endothelium; but the question of surgical treatment will be considered later.
AETIOLOGY In the last quarter of a century I have been able to see at least a hundred instances of Fuchs's dystrophy, some of whom have been other people's
FUCHS'S EPITHELIAL D YSTROPHY OF THE CORNEApatients sent for a second opinion. Of the 64 coming direotly under my care, 49 (73 per cent.) have been women, and fifteen (27 per cent.) men. In Fuchs's original but shorter series, the relative percentages were similar, viz. 69 for women, 31 for men. I know of no substantial collection of cases in which the females do not greatly outnumber the males, and it is now generally agreed that Fuchs's dystrophy is commoner in women than in men, although this aspect of the aetiology has not so far thrown any light upon the causation.
The next aetiological point to be considered is the age at onset. Among the first five patients I saw, the average age was 69 years. Some of them showed a late stage of the disease, and must already have been affected for years. Since then I have several times discovered early Fuchs's dystrophy during routine examination of patients not producing any symptoms.
Therefore some reduction must be made from the average age of observed victims if we want to estimate the true average age at onset. Even after due allowance was made for this consideration, I was led to conclude that the disease was rare before the age of 60 years, and I never saw a single instance in a patient less than 50 years old until 12 years ago, when to my astonishment I found the whole fully-delineated picture in both eyes of a 36-year-old woman. Since then I have been able to see Fuchs's dystrophy in a further six patients under 40 years old. The youngest was a 34-year-old man free from symptoms, and 2 years later he had still experienced no difficulty, although the physical signs were certainly more pronounced. I often wonder whether the second world war has shattered a lot of our longestablished conceptions about aetiology. For example, most of us used to suppose that the older generation virtually monopolized basal-celled carcinoma of the eyelids, but since 1939 I have seen it in a number of patients less than 30 years old. We can still regard Fuchs's dystrophy mainly as a disease of old people, but it can no longer be ruled out as a possible explanation for visual failure in the lower age groups.
Having said that Fuchs's dystrophy is commoner in old than in young people, and that females are more susceptible than males, we arrive at the clouds of speculation if we continue to discuss aetiology. Treacher Colfins (1907) described changes in the corneal epithelium associated with myxoedema and responding to the administration of thyroid extract, but this treatment fails to disperse Fuchs's dystrophy; and indeed these corneal lesions exhibit many points of difference from each other. Dystrophy of the corneal epithelium has also been found in cases of myotonia atrophica, but no particular systemic disease is typically linked with Fuchs's dystrophy;
nor can Fuchs's corneal changes be dismissed as a manifestation of premature senility. Juler (1930) reported the disease in two. sisters, but I know no other authentic example of familial incidence. No special climatic, occupational, or racial factors have been identified.
J. H. DOGGART SYMPTOMS Fuchs's dystrophy, like most other bilateral diseases, may attack one eye sooner than the other, so that the earliest possible symptom is slight disturbance of vision in one eye. Sooner or later both eyes will become defective, but the march of disability may be exceedingly slow, and symptoms tend at first to be variable or even intermittent. Near objects look more blurred than distant ones, and many of the patients find that their sight improves as the day goes on.
When we recall the corresponding structural changes in the cornea we can perhaps account for this fluctuation. The endothelial changes, although they prepare the way for subsequent seepage of aqueous into the substance, do not of themselves obscure vision. Epithelial vesiculation, which becomes evident soon afterwards, is responsible for the blurring. Now it does not seem far-fetched to suppose that repeated blinks might temporarily clear the cornea by flattening the vesicles upon its epithelium. That supposition is borne out by clinical facts. Among several patients who had felt improvement in their sight as the day progressed, I was able to note that the signs as well as the symptoms were less obtrusive in the afternoon than in the morning.
Evidently the eyelids as they move over the cornea with each blink produce an effect comparable with that of a light roller upon a piece of carefully clipped turf, so long as the vesicles remain small and delicate. As time goes on the epithelium coarsens, and changes develop in the corneal substance, so that vision remains bad all through the day.
Many of the patients suffering from Fuchs's dystrophy complain of seeing coloured rings around lights, a symptom which immediately raises the question of congestive glaucoma. It has been known for a long time that glaucomatous "haloes" are not the specific result of raised intra-ocular pressure. Epithelial vesicles, whatever may be their origin, can split white light into the colours of the Newtonian spectrum; and such vesicles can occur in a number of non-glaucomatous diseases, including Fuchs's dystrophy..
Nevertheless the word "halo" continues to bias many ophthalmologists almost irrevocably towards a diagnosis of glaucoma. They see an elderly patient complaining of "haloes" and failing vision. Digital estimation of the intra-ocular pressure is notoriously uncertain. Even tonometry is far from precise. When once the mind has prematurely leapt to a diagnosis, rationalization can easily fill any gaps there may be in the evidence; and so it is not surprising that the literature contains numerous instances of people being wrongly subjected to drainage operations when they were in fact victims of Fuchs's dystrophy.
PHYSICAL SIGNSAlthough the earliest signs of this disease are located in the endothelium, a large majority of the patients already show epithelial changes by the time
FUCHS'S EPITHELIAL DYSTROPHY OF THE CORNEAthat a diagnosis can be made. Early endothelial changes in Fuchs's dystrophy do not disturb vision, and remain undetected unless the patient happens to come under slit-lamp scrutiny. Not uncommonly, however, we see the disease limited to the endothelium in a second and less affected eye, when the other and earlier affected eye shows epithelial signs as well.
The commonest endothelial change is disintegration of the cells, so that, when we focus on the posterior surface of the cornea in the zone of specular reflection, there is no golden mosaic. The normal tessellation is replaced by those amorphous red-pepper granules which Vogt likened to powdered bronze. One source of fallacy must, however, be borne in mind. Slitlamp examination of elderly people nearly always reveals upon the hind surface of the cornea a few granules of iris pigment. Even in younger subjects we may discover similar particles aggregated into a Krukenberg's spindle; but this phenomenon should not be confused with endothelial dystrophy. Granules scattered by the iris pigment are never so abundant as to hide the whole of the endothelial sheet; and if we focus the posterior surface of the cornea in the zone of specular reflection away from the densest granular clumps, then we shall readily identify the mosaic pattern.
A minority of sufferers from Fuchs's dystrophy at first display large axial gaps in their endothelial tessellation. These apparent holes are, as we have already seen, due to localized backward bulges of Descemet's membrane together with the corresponding portion of endothelium. Although they do not directly impair the visual acuity, such interruptions in the endothelial mosaic are important in that they foreshadow more serious changes.
Sooner or later the aforementioned endothelial disintegration will be evident, and by that time epithelial signs may have emerged.