Clinical gonioscopy is just over 100 years old. During those 100 years, some remarkable scientists and astute clinicians have played roles in the development of this important examination technique. This review will summarize the development of gonioscopy. The illustrations, rather than being of the people who advanced the field, will concentrate on the angle images that they produced.
Gonioscopy is considered to have two “fathers,” and the primacy of the two innovators is dependent on the views of the authors. Dellaporta1 wrote a delightful and detailed history of gonioscopy that included many charming personal anecdotes. Dellaporta focused on the contributions of Trantas, with whom he shares a Greek heritage. Other accounts focus on Salzmann, who was the first to study the optics behind gonioscopy and the first to use a lens to view the angle. In their textbook, Gorin and Posner2 say that Salzmann “will always be revered by ophthalmologists as the father of gonioscopy.” This review will consider both “fathers” chronologically.
Gonioscopy is required to view the iridocorneal angle, because light from the angle reflects back into the anterior chamber at the tear-air interface (Fig. 1). This is because of the total internal reflection—just as in a fiberoptic cable. The only circumstances in which the angle can be seen without special manipulation are in cases of keratoglobus where the light from the angle strikes the cornea at an angle perpendicular enough to escape. This is very rare.
To view the iridocorneal angle, one needs to overcome total internal reflection in some way. We do this today with a variety of lenses, but the first gonioscopy was performed with an ophthalmoscope and indentation. The first person to examine the iridocorneal angle in a living human was the Greek ophthalmologist Alexios Trantas3 in 1898. Trantas was in private practice. He was an outstanding observer—for example, he first identified the conjunctival infiltrates in vernal conjunctivitis that bear his name (Trantas dots). Trantas was able to see the angle using a direct ophthalmoscope while indenting the sclera with his finger (Fig. 2).3 He was actually more interested in viewing the ciliary body, ora serrata, and anterior retina. His view of the iridocorneal angle was a fortunate accident. In 1900, he described the appearance of a cyclodialysis cleft in a patient with an iridodialysis (his view was made easier by the iridodialysis, because the iris was not in the way).1 He later presented remarkably detailed drawings of the angle (Fig. 3).4 His descriptions of the angle were an afterthought, included in an appendix of an article describing the retrociliary region.4 It was Trantas who coined the term “gonioscopy,” meaning “observation of the angle,” in his native Greek.1
Maximilian Salzmann was a brilliant ophthalmologist who, upon graduating from college at age 15, went on to contribute in all aspects of eye research. He was also skilled in languages, mathematics, geology, and botany. Salzmann was a gifted painter whose paintings were used in many textbooks of his time.5 His own textbook, The Anatomy and Histology of the Human Eyeball in the Normal State, was a classic in German and was translated into English. Salzmann was unaware of the work of Trantas, because the descriptions of gonioscopy in the articles of Trantas' did not appear in the titles or abstracts.1 He first recognized the concept of total internal reflection.6 He also determined that total internal reflection could be overcome with a highly convex lens (Fig. 4). Salzmann was the first to view the angle through a contact lens and, in 1915, published an article with excellent drawings of the angle obtained by means of a Fick contact lens (a lens designed to treat keratoconus).7 He was not satisfied with the view through the Fick lens and, so, had Zeiss build him a lens with a smaller radius of curvature.2 Although Trantas was the first to see the angle, Salzmann was the first to really study the angle. Salzmann stressed the importance of gonioscopic examination in the fellow eye of patients who had suffered an attack of acute glaucoma.2 He recognized that the development of synechiae in the angle did not always lead to increased intraocular pressure.2 Salzmann was also the first to describe blood in Schlemm's canal.1 Salzmann produced wonderful drawings of the iridocorneal angle (Figs. 5 and 6).6,7 Through the courtesy of S. Karger AG, Basel, all of Salzmann's gonioscopy paintings are reproduced at: http://gonioscopy.org/salzmann/salzmann.html.
Mizuo examined the inferior angle in patients by everting the lower lid and filling the cul-de-sac with saline. The saline meniscus acted like a contact lens.8 He described this technique in 1914. Elschnig had verbally reported to Salzmann the same technique using the patient's own tears.2,7 The technique was difficult to perform because the saline “lens” was lost whenever the patient blinked.8
Many events occurred around 1920 that brought gonioscopy into clinical relevance. Zeiss developed the modern slitlamp at about this time, which permitted significant advances in gonioscopy. In 1920, Curran9 published his landmark article that recognized that angle-closure glaucoma was caused by forward bulging of the iris and that surgical iridectomy (which had been used indiscriminately for glaucoma) would only work for angle closure cases. He recognized that the iridectomy worked by reestablishing flow from the posterior to anterior chambers, not by uncovering the trabecular meshwork. In 1919, Koeppe10 used the Zeiss slitlamp to examine the angle with his newly developed direct contact lens, which was thicker and more convex than the lenses used by Salzmann. Gonioscopy was performed with the patient seated at the slitlamp. A knotted bandage rested on a central depression in the lens to secure it to the patient. This technique was effective only for evaluating the nasal and temporal portions of the angle. The Koeppe lens and modifications of the Koeppe lens (Barkan, Swan-Jacobs, etc.) are still used today for direct gonioscopy.
In 1925, Manuel Uribe Troncoso11 developed a selfilluminating monocular gonioscope that permitted examination of all parts of the angle. The handheld device combined the examining oculars with an illumination system. He also improved on the Koeppe lens by using polymethylmethacrylate instead of glass.2 In 1942, he created a handheld stereoscopic gonioscope.
In 1927, Thorburn first photographed the angle in a case of angle closure brought on by mydriatics and subsequently reversed by physostigmine. He also observed that the majority of his patients with glaucoma had open angles.12
Barkan et al.13 used a binocular slitlamp suspended from the ceiling and a handheld illuminator to view the angle through a Koeppe lens. His technique had the advantage of bright illumination and sufficient magnification. The flexibility of the ceiling-mounted handheld slitlamp enabled the entirety of the angle to be evaluated with the Koeppe lens in a supine patient. Barkan's apparatus brought gonioscopy into practical clinical application.
Barkan14,15 was also the first to describe goniotomy under direct visualization for primary congenital glaucoma. Before Barkan, goniotomy had been performed without visualizing the angle. He developed a special variation of the Koeppe lens in which one side was flattened to permit passage of the knife through the temporal cornea. Barkan felt that the eyes of children with congenital glaucoma had a membrane covering the iridocorneal angle (Barkan's membrane) because of the glistening appearance of the angles of babies with glaucoma.16 It is now recognized that there is no Barkan's membrane, simply compressed trabecular beams.17
Clinical use of direct gonioscopy is now limited to the operating room for examining babies under general anesthesia and for performing angle surgery. Direct gonioscopy is required for some surgical techniques such as for goniotomy for infantile glaucoma angle and for the Trabectome for open-angle glaucoma. Direct gonioscopy is rarely used in the clinic because it is inconvenient. The patient needs to be supine in a special room with a ceiling-mounted counterbalanced slitlamp. Any examination technique that is inconvenient is less likely to be performed. The Van Herick estimation of angle depth was developed because it was not practical to perform direct gonioscopy on every patient, and it was helpful to have a means of identifying worrisomely narrow angles at the slitlamp. To quote Van Herick et al.,18 “In the routine examination of nonglaucomatous patients, it is impractical to perform gonioscopy; it is only done of the angles are thought to be narrow.” In 2010, indirect gonioscopy is easy and convenient enough that the Van Herick technique should simply be an adjunct to gonioscopy.
Modern indirect gonioscopy was introduced in 1938 with the Goldmann mirrored contact lens.19 The Goldmann lens uses a mirror to redirect the light from the iridocorneal angle, so that it is visible to the examiner viewing through a slitlamp (Fig. 7). Goldmann was another polymath whose name is familiar because of the gonioscopy lens, tonometer, and perimeter that bear his name. His contributions to the understanding of the eye in health and disease were too numerous to list here.20 With the Goldmann lens at a slitlamp, one could readily examine the entire angle using the readily available slitlamp, rather than a separate apparatus. Gonioscopy was no longer reserved for those with suspiciously narrow angles on slitlamp examination. The Allen lens, developed a few years later, used totally refractive prisms rather than a mirror.21 This was later modified into the Allen-Thorpe gonioprism, which had four prisms and permitted most of the angle to be viewed without rotation of the lens (Fig. 8).22 The Allen-Thorpe lens had flanges that held it in place allowing the examiner time and free hands to make detailed drawings of the findings. Four-mirrored lenses, such as the Zeiss, Posner, Sussman, and Volk G-4 lenses, are commonly used today. Unlike the Goldmann lens, these lenses do not require a methylcellulose coupling solution. The remarkable angle paintings of Lee Allen were created with the Allen-Thorpe lens (Figs. 9 and 10). Many of the Lee Allen's paintings are included in the Color Atlas of Gonioscopy,23,24 and all of his gonioscopy paintings are available at: http://gonioscopy.org/leeAllenPaintings.html.
There have been no major developments in lens design over the last several decades. There have been modifications to the Goldmann and Allen-Thorpe/Zeiss lenses. Variations of the Goldmann lens include lenses with one to four mirrors. In the three-mirror lens, two of the mirrors are for viewing the peripheral retina. Other Goldmann-style lenses (such as the Ritch lens) are specially designed and coated with antireflective material for the delivery of laser energy. Others have mirrors that magnify slightly. The Zeiss style lenses are now available in plastic or glass with mirrors that are less fragile than the original Zeiss lens. These are available with handles (e.g., Posner and Volk G-4 with optional handle) or without handles (e.g., Sussman and Volk G-4), and there is even a six-mirror version (Volk G-6). However, the recent changes in gonioscopy lenses have been evolutionary, not revolutionary.
A major advance in gonioscopy technique was the introduction of the technique of indentation gonioscopy. First taught by Drs. Becker and Moses at Washington University with a handheld Zeiss goniolens, it was refined by using the Zeiss lens on an Unger handle by Max Forbes in 1966.25 Indentation gonioscopy requires the use of a gonioscopy lens with an area of contact smaller than the cornea (e.g., Zeiss, Posner, Sussman, Volk G-4, etc.). By using one of these lenses, the examiner pushes against the cornea, which drives the lens-iris diaphragm posteriorly. This permits the examiner to determine whether areas of angle closure are because of apposition or synechiae. Indentation gonioscopy can also reveal a peripheral iris hump in plateau iris syndrome. Lenses with large areas of contact (such as the Goldmann lens) are not ideal for this.
The first system to grade the angle was that of Gradle and Sugar26 in 1940. They used an Ulbrich drum mounted on the slitlamp to measure the chamber depth in millimeters—not something that could be practically used in the clinic. Scheie27 developed a grading system based on the visible structures. The Scheie system was opposite of our current systems. In the Scheie system, there was a category called “Wide” followed by grade I, which was slightly narrowed through grade IV, which was completely closed. Today, some still use a system in which they describe the visible structure such as “open to the ciliary body face” etc. Importantly, Scheie introduced a scale of grading the pigmentation of the posterior trabecular meshwork (from none to grade IV) that is used today.
The most widely used systems nowadays are the Shaffer and Spaeth systems. The Shaffer28 grading technique was described in his 1962 textbook. Shaffer determined an angle width in degrees (e.g., grade 1 ≤10° and grade 4 = 35–45°). It has the advantage of being widely recognized and easy to understand. A disadvantage is that it provides only angular width information and tells nothing about the iris shape or the level at which the iris inserts.
Spaeth29 modified the Shaffer system to provide information regarding the level of iris insertion (on a scale of A to E, with A being anterior to Schwalbe's line and E being extremely deep into the ciliary body), the angle of iris approach (in degrees), and the configuration of the iris (b for bowed forward, f for flat, c for concave, and p for plateau). To this, one adds the angle pigmentation. For example, the Spaeth system would grade the angle in the Lee Allen painting in Fig. 9 to be D45f, with 2+ pigmentation. The Spaeth system also permits information on indentation gonioscopy findings. This system is somewhat harder to learn but provides much more information than any other alphanumeric grading system.
Textbooks of Gonioscopy
In 1947, Troncoso published a comprehensive 306-page textbook entitled Gonioscopy. The text contains comparative anatomy and gonioscopy as well as beautifully illustrated descriptions of the angle in health and disease. Many of the illustrations were painted by Emil G. Bethke (Fig. 11). Interestingly, Bethke had been a medical illustrator at the University of Iowa where he roomed with a fellow artist, E. Lee Allen. When Bethke left the University, Lee Allen became the artist for the Department of Ophthalmology and developed a life-long interest in gonioscopy (see Figs. 8 to 10). Since Troncoso's book, there have been a handful of gonioscopy texts and atlases; the most important of which are included in Table 1.
Shaffer's Stereoscopic Manual of Gonioscopy is a wonderful resource, now out of print.28 His book includes beautiful drawings by Joan Esperson and three-dimensional photographs viewed through a View-Master. Kimura's Color Atlas of Gonioscopy has beautiful photographs of the angle.30 Kimura's atlas was out of print when my book of the same name was published in 1994.23
Because gonioscopy is a dynamic examination, it may be best taught with video, instead of still images. I created a webpage to teach gonioscopy (www.gonioscopy.org). The site is free and is not industry supported. It includes detailed descriptions of basic and advanced examination techniques as well as hundreds of video examples of pathology.
There are new ways to evaluate the iridocorneal angle, such as ultrasound biomicroscopy and optical coherence tomography. These techniques can describe the width of the angle and perhaps the risk of developing angle closure. They are excellent tools, but they cannot replace gonioscopy, which tells us so much more than whether the angle is open or closed. We are fortunate—through the efforts of Trantas, Salzmann, Zeiss, Barkan, Goldmann, Allen, and others—to be able to actually look at the dysfunctional meshwork rather than having to rely on imaging.
Wallace L. M. Alward
Department of Ophthalmology
University of Iowa Carver College of Medicine
200 Hawkins Drive
Iowa City, Iowa 52242
e-mail: [email protected]
1. Dellaporta A. Historical notes on gonioscopy. Surv Ophthalmol 1975;20:137–49.
2. Gorin G, Posner A. Slit Lamp Gonioscopy, 3rd ed. Baltimore, MD: Williams & Wilkins; 1967.
3. Trantas A. Ophtalmoscopie de la region ciliaire et retrociliaire. Arch Ophtalmol (Paris) 1907;27:581–606.
4. Trantas A. L'ophtalmoscopie de l'angle irido-corneen. Arch Ophtalmol (Paris) 1918;36:257–76.
5. Sugar HS, Foster CC. Maximilian Salzmann. Ophthalmic pioneer and artist. Surv Ophthalmol 1981;26:28–30.
6. Salzmann M. Die Ophthalmoskopie der Kammberbucht. Z Augenheilk 1914;31:1–19.
7. Salzmann M. Nachtrag zu ophthalmoskopie der kammerbucht. Z Augenheilk 1915;34:160–2.
8. Mizuo. Ein Verfahren zur Besichtigung der Kammberbucht. Klin Monatsbl Augenheilkd 1914;52:561.
9. Curran EJ. A new operation for glaucoma involving a new principle in the etiology and treatment of chronic primary glaucoma. Arch Ophthalmol 1920;49:131–55.
10. Koeppe L. Die mikroskopie des lebenden Kammerwinkels im fokalen Lichte der Gullstrandschen Nernstspaltlampe. Albrecht von Graefes Arch Klin Ophthalmol 1919;101:48–66.
11. Troncoso MU. Gonioscopy with the Electric Ophthalmoscope. New York, NY: New York Academy of Medicine; 1921.
12. Thorburn T. A gonioscopical study of anterior peripheral synechiae in primary glaucoma. Svenska Läkaresällskapets Handligar 1927;53:252–91.
13. Barkan O, Boyle SF, Maisler S. On the genesis of glaucoma. An improved method based on slit lamp microscopy of the angle of the anterior chamber. Am J Ophthalmol 1936;19:209–15.
14. Barkan O. Glaucoma: classification, causes, and surgical control. Results of microgonioscopic research. Am J Ophthalmol 1938;21:1099–117.
15. Barkan O. Recent advances in the surgery of chronic glaucoma. Am J Ophthalmol 1937;20:1237–45.
16. Barkan O. Pathogenesis of congenital glaucoma: gonioscopic and anatomic observation of the angle of the anterior chamber in the normal eye and in congenital glaucoma. Am J Ophthalmol 1955;40:1–11.
17. Anderson DR. The development of the trabecular meshwork and its abnormality in primary infantile glaucoma. Trans Am Ophthalmol Soc 1981;79:458–85.
18. Van Herick W, Shaffer RN, Schwartz A. Estimation of width of angle of anterior chamber. Incidence and significance of the narrow angle. Am J Ophthalmol 1969;68:626–9.
19. Goldmann H. Zur Technik der Spaltlampenmikroskopie. Ophthalmologica 1938;96:90–7.
20. Fankhauser F. Hans Goldmann. Ophthalmic Surg 1994;25:8–12.
L, O'Brien CS. Gonioscopy simplified by a contact prism. Arch Ophthalmol 1945;34:413–4.
L, Braley AE, Thorpe HE. An improved gonioscopic contact prism. AMA Arch Ophthalmol 1954;51:451–5.
23. Alward WL. Color Atlas of Gonioscopy. London: Wolfe; 1994.
24. Alward WL, Longmuir RA. Color Atlas of Gonioscopy, 2nd ed. San Francisco, CA: American Academy of Ophthalmology; 2008.
25. Forbes M. Gonioscopy with corneal indentation. A method for distinguishing between appositional closure and synechial closure. Arch Ophthalmol 1966;76:488–92.
26. Gradle HS, Sugar HS. Concerning the anterior chamber angle. III. A clinical method of goniometry. Am J Ophthalmol 1940;23:1135–9.
27. Scheie HG. Width and pigmentation of the angle of the anterior chamber; a system of grading by gonioscopy. AMA Arch Ophthalmol 1957;58:510–2.
28. Shaffer RN. Stereoscopic Manual of Gonioscopy. St. Louis, MO: Mosby; 1962.
29. Spaeth GL. The normal development of the human anterior chamber angle: a new system of grading. Trans Ophthalmol Soc UK 1971;91:709–39.
30. Kimura R. Color Atlas of Gonioscopy. Tokyo: Igaku Shorin Ltd.; 1974.
31. Salzmann M. Die Ophthalmoskopie der Kammerbucht. Z Augenheilkd 1915;34:26–49.
32. Troncoso MU. Gonioscopy. Philadelphia, PA: FA Davis; 1947.