The History of Glaucoma
Peter C. Kronfeld
The history of the diseases categorized today under the term “glaucoma” may be divided into three major periods. The first is the early period from approximately 400 BC to approximately 1600 AD; during this time, “glaucoma” was used to refer to a general group of blinding ocular diseases without the distinctions that historians now can recognize. During the middle period from the beginning of the 17th century to the middle of the 19th century the cardinal signs of glaucoma, singly and in combination, began to emerge clearly in published texts. The third period extends from the time of the introduction of the ophthalmoscope (1854) to the present.
400 BC TO 1600 AD
As a diagnosis by physicians, glaucoma is first mentioned in Hippocrates’ Aphorisms; thereafter the term appears in most early medical texts, but with only the smallest bits of information regarding the types of diseases thus diagnosed. All that can safely be deduced from the writings of the early period is that the term was applied to afflictions of the elderly in which some abnormality (probably a change in color) could be recognized in the pupillary area; attacks of severe pain due to overdistention of the ocular coats could be associated with this change. The inevitable outcome was total blindness.
1600 TO 1854
Glaucoma in the adult or elderly patient became more distinct with the emergence of four characteristics: (1) the consistent failure of cataract operations to improve vision, (2) the clinical appearance of eyes in terminal stages of the disease, (3) a specific history indicating self-limited forerunners of the severe disease, and (4) the elevated intraocular pressure.
The anatomic site of cataracts was not clearly established until the anatomic findings of Brisseau (1707) and the introduction of the process of lens extraction by Daviel (1752). This led to a search for the site of glaucoma in other structures of the eye and to concentration on clinical signs that could be helpful in distinguishing between cataract and glaucoma. Since a majority of the eyes in which the diagnosis of glaucoma was made in the 18th century were in an advanced stage of visual loss and iris atrophy after one or several acute attacks or after a prolonged chronic course, the clinical picture was dominated by congestion (varicosities) of the anterior ciliary veins, a dilated, poorly reacting pupil, and a varying degree of nuclear lens opacity. On examination with the light sources of that period, a greenish reflex could often be obtained; since this seemed to point to the real location of the disease, it became a prominent sign listed in the literature of the 181h and early 191h centuries.
The fact that the clinical features of advanced glaucoma were occasionally preceded by attacks of blurred vision that recurred with a high degree of uniformity was first recorded in St. Yves’ “Treatise of the Diseases of the Eyes” (1741) and was described in more detail by Weller (1826).
Elevation of the intraocular pressure as a distinct sign of ocular disease, recognizable by undue resistance of the eyeball to indentation by the physician’s finger, was first clearly mentioned in the “Breviary” of the itinerant English oculist Banister (1626). In 1738 an equally clear reference to hardness of the eye appeared in the independent writings of Johann Platner, professor of anatomy, surgery, and therapeutics at the University of Leipzig. As a distinct clinical symptom, hardness of the eyeball was apparently generally known and accepted in the 1820s, as one may judge from the almost simultaneous but independent texts by Demours of France (1818), Guthrie of England (1823), and Weller of Germany (1826).
Between 1830 and 1854 William Mackenzie (1) exerted a great influence on European and American ophthalmology through his personal teaching and through his textbook. He distinguished between acute and chronic glaucoma and gave a detailed description of the course of the latter from a stage 1 characterized just by a greenish hue reflected from the pupil to a stage 6 in which the eyeball, after perforation of a corneal ulcer in absolute glaucoma, has become atrophic.
Mackenzie was well aware of the abnormal hardness of the glaucomatous eye from the second stage on; also, he apparently was the first to recommend a form of posterior sclerotomy to relieve the abnormal hardness.
For a more detailed review of the second period one may refer to the introduction to the section Glaucoma and Hypotony in Duke-Elder’s System of Ophthalmology (2).
1854 TO THE PRESENT
Eduard Jaeger, the son and grandson of distinguished Austrian ophthalmologists, was the first investigator to place a description and a picture of the ophthalmoscopic appearance of the glaucomatous disc in the literature. He was misled by the relative depth clues provided by monocular indirect ophthalmoscopy and described (and depicted) the glaucomatous disc as a swelling of the papillary tissues with respect to the surrounding retina (3).
Just a few months later, Albrecht von Graefe also placed himself on record as having observed a prominence of the papilla in glaucoma (4). His original description of the glaucomatous disc included a detailed account of the phenomenon of pulsation of the retinal arteries in the glaucomatous eye; this phenomenon became a reliable and, at the time, clinically useful indicator of elevated intraocular pressure. The ring-shaped zone around the “swollen” disc was officially named “halo glaucomatosus.” The matter of the apparently swollen disc was cleared up by observations in von Graefe’s clinic. In a rabbit with a congenital fundus anomaly, ie, a coloboma of uvea and of optic nerve, different examiners could not agree from ophthalmoscopic examinations whether certain parts of the eyeground were elevated or depressed. The anatomic examination revealed tissue defects, ie, depressions. This prompted an analysis of the optics of monocular indirect ophthalmoscopy by Adolf Weber (5), one of von Graefe’s assistants, who in his later life made significant contributions to the understanding of the mechanism of glaucoma. His analysis of monocular indirect ophthalmoscopy revealed several factors, partly optic and partly perceptual, that could cause misinterpretations of relative depth in the fundus.
The corrected ophthalmoscopic observation of a depression of the disc was promptly confirmed by pathologic findings and was interpreted as the effect of elevated pressure, ie, as “pressure excavation.” This had a profound effect on von Graefe’s thinking and made him examine all known symptoms of glaucoma in the light of their possible relationship to elevated pressure. This analysis led him to regard the elevation of intraocular pressure not as just a symptom but as the “essence” of glaucoma.
THE GLAUCOMAS AT VON GRAEFE’S CLINIC
One type of glaucoma seen at von Graefe’s clinic was the acute or inflammatory glaucoma which in 70% of the cases began with self-limited prodromal attacks of misty vision with the patient seeing rainbows around candle flames. The attacks increased in length, severity, and frequency until the real disease suddenly erupted in the form of an acute attack of inflammation and severe reduction of vision. Temporary remission with some recovery of vision could occur spontaneously or in response to treatment consisting of antiphlogistics, opiates in large doses, and paracentesis. During the remissions the affected eye lent itself to more penetrating examination than was possible at the height of the attack. From close observation of all phases of the disease, von Graefe arrived at the concept that acute glaucoma was a choroiditis or an iridochoroiditis with diffuse impregnation of vitreous and aqueous with exudative material which caused the rise in pressure through an increase in volume.
The second type of glaucoma seen was the chronic glaucoma in which the prodromal attacks, without any signs of congestion, swelling, or irritation, gradually lengthened and finally fused into a chronic state of dilatation of the anterior ciliary veins, shallowness of the anterior chamber, atrophy of the iris, reduction in vision, glaucomatous cupping, and arterial pulsation in the fundus.
For the third type of case in which the anterior segment remained normal and only the excavation of the optic nerve paralleled the gradual deterioration of vision, von Graefe (6) coined and for several years used the term “amaurosis with excavation of the optic nerve,” placing it outside the group of glaucomatous diseases.
To complete his classification of glaucomas, von Graefe used the designation “glaucomatous diseases” for disorders or diseases which secondarily lapse into glaucomatous states and which thereby may result in blindness; only in his last communication (1869) did he introduce the terms “primary glaucoma” and “secondary glaucoma.”
In 1861, von Graefe (7) declared that the exclusion of the amaurosis with optic nerve excavation from the glaucomas was an error of his, the correction of which he credited to his friend Donders of Utrecht, who had found the palpable tension in many of the eyes with so-called amaurosis with optic nerve excavation to be perceptibly above normal. Donders suggested the name “glaucoma simplex,” meaning the typical glaucoma without complications. For the glaucomas with other manifestations, particularly in the anterior segment, Donders proposed the term “glaucoma with ophthalmia.” He attributed the common cause of all glaucomas, ie, the elevated pressure, to hypersecretion of intraocular fluid due to irritation of secretory nerves.
Von Graefe had also recognized slight degrees of ocular hypertension in some of his cases of amaurosis with optic nerve excavation. He therefore accepted Donders’ term “glaucoma simplex” for that entire group; of course, he was unable to foresee that posterity (at first Schnabel [8]) would reinstate his amaurosis with optic nerve excavation, implying that it was an optic nerve disease unrelated to elevated intraocular pressure.
Von Graefe held on to the concept of some form of inflammation as the primary cause of the rise in pressure and to “inflammatory” as a designation for the glaucomas that showed signs of inflammation connected with the rise in pressure. The term “inflammatory” was retained by some schools of ophthalmology until the clinical discovery of the angle-closure mechanism in the 20th century; there were early dissenters who suggested alternate terms, such as “irritative” (de Wecker [9]), “congestive” (Hansen-Grut), and, much later, “uncompensated” (Elschnig). In the literature of Great Britain the preferred terms were “acute,” “subacute,” and “chronic” glaucoma.
GLAUCOMATOUS OPTIC NERVE DISEASE
The anatomic counterpart to the ophthalmoscopically observed depression of the disc was first described by the German anatomist Heinrich Mueller in the late 1850s (10) and was interpreted as having been produced by abnormally increased vitreous pressure acting upon the lamina and forcing it to recede. To account for the atrophy of optic nerve fibers, Mueller and his followers assumed that the receding lamina had taken the entire papilla with it, placing the nerve fibers on a steadily increasing stretch or pressing them against the sharp edge of the excavation.
When subsequent pathologic studies confirmed the displacement of the lamina in some glaucomatous eyes but not in others, the assumption of preexistent physiologic differences in the laminar resistance to pressure was added to the basic pressure hypothesis. In this form the concept gained wide acceptance, but doubts about its general applicability were voiced early and gradually built up as new ophthalmoscopic and pathologic facets of glaucoma were revealed.
In the 1890s an eloquent champion for an alternate theory emerged in the person of the Austrian ophthalmologist Isidor Schnabel (1842–1908) (8), who was the first to describe in detail the nerve fiber breakdown with the formation of cavities as a characteristic of the glaucomatous process in the optic nerve. In Schnabel’s pathologic material this cavernous atrophy appeared to be the earliest sign; in some eyes, for a long time this was the only glaucomatous change. In later stages the atrophy affected all portions of the optic nerve up to the entrance of the central vessels.
Schnabel interpreted retroplacement of the lamina as its dropping or sinking into large retrolaminar caverns. In his opinion, cavernous atrophy was the glaucomatous atrophy. From its histologic characteristics and its initial selectiveness, ie, not involving the supporting elements of the nerve, Schnabel saw the mechanism of the glaucomatous optic nerve disease in a process of imbibition of pathologic fluid from the vitreous by the nerve fibers, a process independent of the intraocular pressure.
Schnabel’s findings were partly confirmed and partly refuted by subsequent investigators. Differences in material and technology account for most of the divergence of opinions.
One other view regarding the nature of the glaucomatous optic nerve disease was voiced early (Priestley Smith [11]):
The truth of the matter appears to be that the glaucomatous cup is not a purely mechanical result of exalted pressure, but is in part at least, an atrophic condition which, though primarily due to pressure, includes vascular changes and impaired nutrition in the area of the disc and around its margin which require a considerable time for their full development.
The notion that the rise in pressure may cause damage to the tissues of the disc through its influence on blood circulation can be traced from Priestley Smith’s original wording to the present.
MECHANISM OF OCULAR HYPERTENSION
The elevation of the intraocular pressure, recognized in the mid-1850s as the essence of glaucoma, was attributed to excessive formation of intraocular fluid or “hypersecretion,” the cause of which was assumed to be either a form of choroiditis (von Graefe) or a secretory neurosis (Donders).
Basic science at the time did not provide a clear concept of the mechanisms involved in the buildup of pressure within the eye. The systematic experimental study of the fluid exchange of the eye began with the work of the German anatomist Schwalbe in the 1860s. Searching for lymphatics in the anterior segment of the eye, Schwalbe (12) made the observation that when certain dyes are injected into the anterior chamber in aqueous solution or suspension, they promptly appear in veins on the surface of the globe. He concluded that the anterior chamber was a lymphatic space in open communication with anterior ciliary veins.
His view was contested by Theodor Leber (13), whose dye injections into the anterior chamber of the eye of a rabbit indicated a discriminating border structure. This stimulated a number of anatomic studies of the structures of the chamber angle in animals and in man by Schwalbe and others and further anterior chamber cannulation studies by Leber and his co-workers. Thus Leber discovered the normal outflow from the fresh enucleated mammalian eye, which he interpreted as filtration through the trabecular meshwork and as flow from there into anterior ciliary veins as well as vortex veins. The rate of outflow was, in principle, proportional to the perfusion pressure, except during an initial period, when the perfusion fluid took up the space occupied in the living eye by blood.
Leber actually determined filtration coefficients, the forerunners of today’s coefficients of aqueous outflow. Since this outflow was from fresh enucleated eyes at the pressures prevailing in the living eye, Leber reasoned that the same process of outflow must also take place in the normal living eye. To maintain a stable in vivo pressure, the steady loss of fluid must be compensated for by steady formation of an equal amount of fluid, which Leber believed could also take place through a process of filtration. Thus, the filtration theory of aqueous formation and elimination was born. In a few human eyes enucleated in far-advanced stages of glaucoma, Leber found very low filtration coefficients which indicated abnormal resistance to aqueous outflow (14). This finding fitted in well with the first detailed pathologic report on the condition of the chamber angle in far-advanced glaucoma (15): “The most important finding in genuine glaucoma is the circular adhesion of the iris periphery to the periphery of the cornea or the obliteration of the space of Fontana.”*
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