Redmond Smith

A new technique for opening the canal of Schlemm. Preliminary report.

THERE are many reasons for supposing that a perfect goniotomy would be a successful operation for several types of glaucoma, and Barkan (1936) tried it in some cases of chronic simple glaucoma. Apparently his results were not satisfactory, since he gave up this technique for this type of case, and recent histological evidence presented by Maumenee (1959) suggests that goniotomy in practice is not quite the same as goniotomy in theory. The ciliary body and scleral spur are probably maximally affected and it is doubtful whether the trabecular meshwork is efficiently divided. If this could be done, especially if it could be effected without bleeding, and if the obstruction to outflow of the aqueous humour did lie in the trabecular meshwork (a point about which there is still no certainty), then a new and hopeful type of glaucoma surgery would have been initiated. Prompted by earlier experience of the injection of the canal of Schlemm in the Department of Pathology at the Institute of Ophthalmology, a series of experiments has recently been carried out at the Western Ophthalmic Hospital, London (St. Marys Hospital). Using cadaver human eyes, a technique has been devised by means of which access is gained to the canal of Schlemm by an ab externo approach, and the canal is then opened into the anterior chamber over a wide area, almost half the circumference of the limbus. Following the experiments on cadaver eyes a similar operation was performed on a living subject immediately before removal of the eye for malignant melanoma of the choroid, and it is this operation which is now described.

ANATOMICAL STUDIES OF THE TRABECULAR MESHWORK OF THE NORMAL HUMAN EYE

IN recent years increasing evidence has been obtained of an abnormal resistance to aqueous outflow in eyes affected with chronic simple glaucoma; it now appears essential to determine to what extent this may be attributable to structural changes and at which particular site or sites in the drainage area the impediment is located. In this problem, consideration of the trabecular meshwork is clearly of primary importance, but a true assessment of morbid anatomical changes and their distinction from appearances due to artefact can be based only upon an accurate knowledge of normal structure. Although many anatomical studies of the trabecular meshwork are available both in. papers and textbooks, they are frequently deficient in detail and differ from each other in important respects. As a preliminary to future work on pathological material, we have therefore thought it necessary to sununarize existing knowledge and to carry out, by old and new methods, a further anatomical study of this region.

Anatomical study of Schlemm's canal and aqueous veins by means of neoprene casts. III. Arterial relations of Schlemm's canal.

IN previous studies of this region (Ashton 1951, 1952), it has been shown that the canal of Schlemm and its efferent connections may be clearly demonstrated by Neoprene latex casts, prepared by direct injection of the canal followed by enzyme digestion of the ocular tissues. Over 200 casts have now been studied by this technique and while the preparations in the main confirm the anatomical accounts of earlier workers, who used serial sections or injections of ink and gelatin followed by clearing, they have the advantage of showing the exact anatomy of the canal in its entirety and in a stereoscopic way that can be readily appreciated. The study has revealed some minor but important deviations from the classical descriptions and these will be discussed in a subsequent communication dealing in detail with the structure and connections of the canal itself. It is the purpose of this paper to describe the arterial relationships of Schlemms canal as observed in cast preparations. The vessels involved are the anterior ciliary and the long posterior ciliary arteries which originate indirectly from the ophthalmic artery and meet again at the major circle of the iris, the anterior having pursued a mainly extraocular and the posterior a mainly intra-ocular course. According to the classical description of Leber (1903), anterior ciliary arteries run forward on the tendons of the rectus muscles; there are usually two on each of the recti, except the lateral on which there is only one. Uncommonly one of the arteries may be derived from the vessels in the eyelid. As the vessels approach the limbus, they divide and subdivide into smaller and smaller branches. The larger divisions pass into the eye through perforating scleral channels to join the arterial circle of the iris. The smallest remain in the episclera and pass forward to the limbus, where they loop backward to contribute to the anterior conjunctival arteries, while others dip down through the sclera to reach the deeper parts of the corneal limbus immediately external to the canal, or extend more deeply towards the canal itself. The further destination of these latter arterial twigs is a matter of great interest and considerable controversy. According to Maggiore (1917) and Dvorak-Theobald (1934) they tend to run in a circular fashion, accompanying the canal to form an incomplete arterial circle in close association with it, so close, in fact, that they may cause irregularities in the canal wall; indeed, Wolff (1945) has depicted a small artery apparently lying within its lumen.

BLOOD IN THE CANAL OF SCHLEMM

THE APPEARANCE of blood in the canal of Schlemm was described by Salzmann (1914) and has been reported since by many workers. It has been suggested, furthermore, that this gonioscopical appearance is seen less commonly in glaucomatous as compared with normal eyes (Kronfeld, McGarry, and Smith, 1942; Frangois, 1948). Ascher and Spurgeon (1949) interpreted this as a sign of a relative obstruction in the depths of the sclera, since a blood ,regurgitation into the aqueous veins is said to occur more commonly in glaucomatous eyes. Hobbs (1950) cast doubt, however, on the validity of the evidence that blood was less commonly seen in the canal in glaucoma, and it was therefore decided to investigate this problem by Hobbss method.

Reading test in glaucoma.

ALAN HIGGITT AND REDMOND SMITH From the Glaucoma Clinic, Institute of Ophthalmology, University of London Director of Research: Sir Stewart Duke-Elder LITTLE attention has been paid to the effect of reading on the tension of the glaucomatous eye. The first brief reference to the subject is by Gradle (1931): The reading test is still less likely to be positive (than the water-drinking test), but is of very definite value when it is so. The patient is told to concentrate upon any form of reading, preferably fine print at a close range, and the tension is then measured after forty-five minutes. When positive the increase in tension will seldom be more than 10-15 mm. Hg. Several authors (Duke-Elder, 1940; Sugar, 1951) quote this paper but give no data of their own on the matter.

Ophthalmomyiasis in England.

Case Report.-A male, aged 34, a motor fitter, attended the casualty department at the Moorfields, Westminster and Central Eye Hospital, on the afternoon of August 6, 1950, complaining of pain in the right eye. The pain had started one hour before, just as he was bending over the luggage boot of his car, when he had felt a sensation like a drop of water falling into the eye. There was no previous history of eye disease, and he had not been overseas since 1945. Examination: VA, R and L, 6/6. Left eye appeared normal. Right eye showed mild conjunctival injection, profuse lacrimation, and considerable chemosis, especially of the lower fornix. The conjunctival sac was infested with larvae. There were about twenty present, white in colour, about one mm. long by j mm. wide, flattened, with a black head-end and actively motile.

Gonioscopic Studies in Congestive Glaucoma

SINCE narrow-angle glaucoma was described by Barkan (1938), conflicting opinions have been expressed as to the correctness of his views. Barkan postulated, and many authors have since agreed with him, that the rise in intra-ocular pressure in the condition usually known as congestive glaucoma, is due to mechanical obstruction to the outflow of aqueous at the filtration angle of the anterior chamber by the apposition of the periphery of the iris to the corneo-scleral trabeculaeorto the cornea just anteriorly(Sugar, 1941; Haas and Scheie, 1952; Chandler, 1952). These authors believe that the anatomical configuration of the eye predisposes to this event and do not admit that the pre-existing shallowness of the anterior chamber has a dynamic pathological cause. Moreover, Rosengren (1950) has produced evidence to show that the depth of the anterior chamber in patients with congestive glaucoma does not vary appreciably if measurements are made before, during, or after an acute attack. Priestley-Smith (1883) showed that the lens increases in size with age, and Tornquist (1953) in a careful study, presented convincingevidence that shallowness of the anterior chamber per se may be an inherited characteristic. He also showed that the depth of the anterior chamber in relatives of persons known to have congestive glaucoma tends to be significantly less than in that of the general population. Although the relationship may not be precise, it is the opinion ofthe present author, as the result of gonioscopic studies, that shallowness of the anterior chamber is associated with a narrow filtration angle. There appear to be three schools of thought regarding the mechanism of the rise in intra-ocular pressure in congestive glaucoma. The adherents of the narrow-angle theory are of the opinion that the actual closure of the filtration angle is the result of some physiological event which only produces a pathological result (the rise in intra-ocular pressure) because ofthe pre-existing anatomical condition of narrowness of the angle. Various suggestions have been made as to the exact mechanism involved; Chandler (1952) and Haas and Scheie (1952) postulated a slight peripheral ballooning ofthe basal portion of the iris caused by a relatively higher hydrostatic pressure in the posterior chamber over that in the anterior chamber, the so-called physiological iris bomb6. Barkan in his original paper suggested a bunching of the base of the iris due to pupillary dilatation, and Sugar quoted a number of factors which

A POSSIBLE AETIOLOGY FOR GLAUCOMA IN NEGROES

CHRONIC simple glaucoma is a syndrome well established in ophthalmic practice, but its aetiology is still unknown. Fundamentally this must be related to the question of how the intra-ocular pressure is maintained at a constant level. The many theories which have been advanced to explain the cause of this disease fall into two groups postulating either a hypersecretion ofaqueous humour or an obstruction to its drainage. The latter concept has assumed pride of place ever since Leber (1873) discovered the preferential channel of drainage of the aqueous humour at the angle of the anterior chamber. This was confirmed by Priestley Smith (1891), who stressed that obstruction at the angle of the anterior chamber was primarily responsible for raised tension. This simple mechanical concept was challenged by Duke-Elder (1926), who felt that the obstruction was only an adjuvant factor and that the essential disease process was a vascular disturbance resulting in a state of congestion and stasis of the uveal circulation. Recently a large volume of work has accumulated on the anatomy and physiology of the drainage of aqueous humour from the angle of the anterior chamber, and various sites of obstruction have been suggested, so that the mechanical hypothesis is slowly gaining ground. Sugar (1957) summarized the immediate cause of ocular hypertension as being either vasoconstriction or sclerosis at the outlets of Schlemms canal, or increased resistance within the trabecular meshwork itself. In considering the importance of the episcleral and aqueous veins in the drainage mechanism, Thomassen (1948) showed that changes in the pressure of episcleral blood veins anticipated changes in the intra-ocular pressure in glaucomatous eyes, and that this was a constant finding. He further concluded that, because the pressure in the aqueous veins is proportional to the intra-ocular pressure, the same relationship must exist between these veins and the episcleral blood veins; therefore, when the intra-ocular pressure is in an increasing phase, the pressure in the blood veins will be high in proportion to the aqueous veins, and the outflow through the latter will accordingly be hampered. This idea was confirmed

Equatorial Cataract after Corneo-Scleral Trephining

THE occurrence of cataract in association with glaucoma presents a therapeutic problem of some magnitude which has attracted a good deal of attention in recent years (Samuels, 1947; Sourdille, 1950; Chandler, 1949;, Fran9ois, 1947; Williamson-Noble, 1953). The difficulties of treatment are not made less by the uncertainty which still exists as to the role played by the glaucomatous process and its treatment in the genesis of the lens opacity. Since the utility of corfieo-scleral trephining was first established after its introduction by Elliot in the early 20th century, the cause of the cataract which may be seen post-operatively in some cases has been a subject of speculation. Elliot (1914) was not convinced that the cataract was due to the operative interference, and although, as experience with the operation has become world-wide, the contrary view has found its advocates, the general opinion appears still to be in agreement with his, provided that direct operative damage to the lens has not taken place (Duke-Elder, 1940; Spaeth, 1941; Arruga, 1952). The association of delayed reformation of the anterior chamber with post-trephine cataract is, however, generally familiar, and this post-operative complication has been assigned a major place in the causation of the lens opacity by Duke-Elder (1940) and by Williamson-Noble (1953). The purpose of this paper is to present four cases which showed lens changes after trephining, and in which the clinical features can be fairly clearly interpreted in the light of the gonioscopic picture of the site of the operation. This distinguishes them as a type of post-trephine cataract not previously described, and permits the formulation of a possible hypothesis to account for them.

Chandler and Grant's Glaucoma

It is difficult to target the group of readers who would most benefit from this excellent little pocket book of ophthalmology colour pictures. Pocket diary size and 83 pages, it is one of a series of such guides. It consists of a selection of colour photographs, and a few diagrams, of ophthalmological conditions. Almost all the photographs are of high quality and the corneal conditions are especially well depicted, with the exception of pterygium, which is an atypical example. The illustration of buphthalmos is also unsatisfactory, as it shows a rather distant view of an established case with a totally scarred cornea, and the glaucoma disc photograph is somewhat blurred. Each photograph has an enlarged caption, but of course this cannot be regarded as a text; therefore written information is necessarily slight. Although not comprehensive, this guide has a good range of conditions well illustrated, and the pictures of squint are especially useful. Probably the most effective readership for this book would be informed physicians and general practitioners, for it is an easily carried little ready reference volume.