Ординатура / Офтальмология / Английские материалы / The Glaucomas Volume 1 Pediatric Glaucomas_Sampaolesi, Zarate_2009

The gonioscopic image depends on the mirror used. The three-mirror lens (the curved mirror of this lens) can be used in children, since they do not have a recess in their chamber angle. This lens enables the observation mainly of the external wall of the chamber angle from the front. In adults, particularly if the chamber angle is narrow, the one-mirror lens should be used. With this lens, the fundus of the chamber angle and the iris wall can be seen from the front.

The different elements, mainly of the external wall, can be studied with the optical section. However, identification of the Schwalbe line is vital, even in the absence of other elements, such as pigment, which may be of assistance. This requires looking for the hookor Y-shaped (either in an upright or inverted position) image, depending on whether the upper or lower chamber angle is observed (12 or 6 o’ clock). The upper arms of the “Y” stand for the anterior and posterior corneal surface above the Schwalbe line, while its single lower line represents the profile line of the trabecular meshwork.

1.Rohen JW, Unger HH (1959) Zur Morphologie und Phatologie der Kammerbucht des Auges. Abhandlungen der Mainzer Akademie der Wissenschaften und Literatur Franz Steiner, Wiesbaden, pp 1–206

2.Busacca A (1964) Biomicroscopie et histopathologie de l‘oeil, Vol. 2. Schweizer Druck und Verlagshaus. Zurich, p 119

3.Roussel P, Fankhauser F (1983) Contact glass for use with high power lasers – geometrical and optical aspects. Solutions for the angle of the anterior chamber. Int Ophthalmol 6:183–190

4.Goldmann H (1954) Das Glaukom. In: AmslerM, Brückner A, Franceschetti A, Goldmann H, Streiff EB (eds) Lehrbuch der Augenheilkunde. Karger, Basel, p 398

The Normal Chamber Angle

The description of the chamber angle in children, as well as the graphics presented are based on the study of 76 gonioscopies performed in normal children of the following ages: three children under 1 month, 13 between 1 and 6 months, seven who were 1 year old, three 2 years, three 3 years, two 4 years, four 5 years, three 6 years, one 8 years, and one 10 years.

The chamber angle in children continues its development from birth to 2 years of age, when the gonioscopic appearance stabilizes. Nevertheless, there is still no chamber angle recess at this age, since this will appear at 4 or 5 years of age. Many normal chamber angles that have not completed their evolution have normal mesodermal remnants.

The Chamber Angle in Premature Children

The gonioscopic image of the eye of a premature child born at the 7th or 8th month of gestation is the same as the histological image shown by the sections of the normal chamber angle development taken from Seefelder and Wolfrum [1]. The gonioscopic image corresponding to this histology shows a flat anterior chamber, the bottom of which is covered with a gray band corresponding to the mesodermal remnants (see Chap. 8). Worst [2] has described this gonioscopy remarkably well.

When the Mesodermal Remnants

Have Reabsorbed

At this stage, the chamber angle shows at the external wall: the Schwalbe line, the scleral trabecular meshwork of a slightly darker gray color, where sometimes the Schlemm canal, the spur, in white, and the ciliary body, in an even darker gray color, can be seen by transparency. The base and root of the iris which can be seen at the internal wall (Fig. 12.1, I).

It is very important to know how to identify the appearance of the internal wall of the chamber angle in its periphery. If, as usually occurs, the superficial mesodermal layer of the iris is poorly developed, is unpigmented, and there are no opaque mesodermal remnants, the pigmentary layer of the iris at the periphery, dark gray in color, almost black, can be seen by transparency (Fig. 12.1, I, e) through triangular holes. Let us analyze this appearance in depth. Behind the dark gray ciliary body band, another lighter band can be seen (Fig. 12.1, I, b), the latter one is made up of iris tissue of a pinkish orange color. This tissue is located immediately above the iris’s major arterial circle, which is visible in some sites. The iris-radiated vessels emerge from this arterial circle. These vessels are surrounded by mesenchymal tissue (Fig. 12.1, I, c) (vascular pilars), which are the same color as the orange band described above. These vascular pillars form the sides of the black triangles.

The avascular iris cords, slightly lighter in color, are distinguished inside the triangular black areas (Fig. 12.1, I, d). This appearance of the internal wall of the chamber angle, at the areas corresponding to the base and root of the iris, is described in a figure exactly like ours by Eisler [3] and Kupfer [4]. The ciliary body band has a different development depending on age:

the older the child, the wider the band. The width of the ciliary body band depends on the development of the radial and circular portions of the ciliary muscle. It is also related to refraction.

When There Are Transparent

Mesodermal Remnants

The appearance described above changes: between the external and internal walls, the chamber angle is filled with mesodermal remnants, which give the chamber angle a more circular shape. The mesodermal remnants are sometimes covered with a gray band with a cellophane appearance (Barkan membrane). Worst [2] made a superb demonstration of this gonioscopy with contact lenses specially designed for this purpose. They are sometimes transparent and slightly pigmented. When it is in the reabsorption process, the Barkan membrane has holes. If all these elements filling the chamber angle are wholly transparent, the iris tissue extending until it ends above the ciliary body band can be seen beneath them and, at the base and root of the iris, the black triangular holes can also be seen. Barkan [5] and Lister [6] presented figures showing this clearly (Fig. 12.1, II, III).

When the Mesodermal Remnants

Are Opaque or Pigmented

When the mesodermal remnants are opaque or pigmented, they hide the structures of the chamber angle, which are located below it. The mesodermal remnants extend from the segment between the root and base of the iris and up to the external wall, though sometimes they reach the Schlemm canal or overlap it in tree-like terminations, which may be in direct contact with the scleral wall. Busacca agreed that the iris processes correspond to the mesodermal remnants (Fig. 12.1, IV): “A smooth, bright arch-shaped surface extends from the spur to the iris base and it becomes the chamber angle. This area of the chamber angle may have different appearances and this structure variety depends on the presence, the absence or the number of iris processes, which are the remnants of the pectinate ligament in animals, which is present in the ontogenic development of man” [7].

The dark triangular areas, corresponding to the base and root of the iris, are only visible at this part when both the mesodermal tissue and the Barkan membrane are transparent; but when these formations are opaque, they can only be seen at the level of the Barkan membrane insertion. When the mesodermal remnants are

Fig. 12.1 Variations of the normal chamber angle within the 1st year of age. Schw Schwalbe line, Sch Schlemm canal, Ssp scleral spur, Cbb ciliary body band, Ir iris root, a, b iris major arterial circle, c vascular pillars, d avascular pillars, e iris epithelial pigmentary layer. I chamber angle without Barkan membrane,

II persistence of Barkan membrane from a´ to b´, III persistence of Barkan membrane from aʹ to bʹ (Barkan membrane disappears during the development of the angle), IV iris processes

resorbed or missing, the maximum peripheral location these dark zones can reach is the iris root; they can never extend beyond the ciliary body since this is anatomically impossible.

In the chamber angle in normal children, the ciliary body band is generally present and this should always be kept in mind.

It is important to distinguish the base from the root of the iris [7]; the base corresponds to the termination level of the last circular fold of the iris (whose most elevated part is the Busacca iris crest line). Either the mesodermal remnants, when present, or the Barkan membrane, or both, end there. The iris root extends from the base to the ciliary body band. It is covered by mesodermal remnants and it develops after the tearing and resorption of the Barkan membrane and the mesodermal remnants. The entire length of the root is in part made up of the radial fibers of the ciliary muscle (Ivanoff muscle).

The fine slit and the profile lines of gonioscopic images are usually not used in gonioscopies on newborns. This accounts for the common mistake of believing that the vertex of the future chamber angle is located where the corneoscleral profile line joins with the mesodermal profile line, or at the attachment site of the iris profile line with the mesodermal profile line. None of these union points (corneomesodermal and mesodermal-iris) are the vertices of the future chamber angle. The mesodermal profile line is tangent to the corneoscleral and iris profile lines. The actual intersection point of the margins of the future chamber angle is the connection between the extension of the corneoscleral profile line and the iris profile line.

Since the optical section is rarely applied to the study of the chamber angle, its topography is generally

misinterpreted. It should be stressed that the chamber angle in a normal child has its fully developed gonioscopic elements: the Schwalbe line, the clearly visible ciliary body band, and, sometimes, mesodermal remnants undergoing a resorption process or slightly persistent. It should be remembered that in the root of the iris is the peripheral arterial circle of the iris (Fig. 12.2). The excellent description made by Busacca and Carvalho [7] of the mesodermal remnants and the systems making them up, is highly recommended. According to these authors, the mesodermal remnants are developed by three systems.

The reticular system is inside the mesodermal triangle (1, Fig. 12.3). This triangle is bounded to the front by an external longitudinal system of fibers (2, Fig. 12.3) making up the tendon of the Brücke muscle and extending from the Schwalbe line to the longitudinal muscle. Toward the back, it is bounded by the internal longitudinal system (3, Fig. 12.3). This system gives rise to the iris root, especially to the avascular part (radiated cords); it extends from the iris base up to the radiated fibers of the ciliary muscle (Ivanoff muscle) and it is the source of the future iris root. The triangle’s side, bounded by the anterior chamber, is made up of the Barkan membrane, known in gonioscopy as the mesodermal band. Remnants of the external longitudinal system will give rise to trabecular formations attached to the external wall of the chamber angle, which are later lined with the Henle layer and with pigment. Remnants of the reticular system will give rise to fibers extending from the iris base or from different points at the iris root, like a bridge on the chamber angle, and up to different heights of the external wall (spur, trabecular meshwork at the level of the Schlemm canal, Schwalbe’s line, etc.)

It is very important to know the direct and gonioscopic appearance of the iris of a normal child. Jerndal et al. [8] state that “the gonioscopic appearance of Barkan’s membrane and other goniodysgenetic signs have been a veritable apple of discord, and a number of authors have overlooked or denied the obvious angle maldevelopment in infantile congenital glaucomas.”

Figure 12.4 shows a front view of the eye of a newborn. The superficial mesodermal layer of the iris, the clear tissue that follows the pupil, has not developed to the periphery. Therefore, black triangles appear in the peripheral half of the iris, which correspond to its pigmentary layer. The radial sides of these black triangles are the so-called vascular pillars of the iris, which contain very fine red vessels. In the black triangles there are clearer, thin pillars, parallel to the vessels, corresponding to the avascular pillars of the iris.

Figure 12.5 shows normal chamber angles of newborn children. As Jerndal said, many writers do not

know this normal morphology: “Scheie (1968), wrote: I, on the other hand, place almost no diagnostic value on the gonioscopic appearance of the angle of the anterior chamber in infantile glaucoma. Although I do routine gonioscopy, in my opinion, the findings are so nebulous that I cannot distinguish between the angle in a normal eye and one with infantile glaucoma, unless the eyeball is enlarged or some other anomaly known to be associated with glaucoma is present, such as aniridia or Axenfeld’s syndrome.”

Some authors (Fig. 12.6) present drawings like these and say that they correspond to a chamber angle of congenital glaucoma, whereas it actually corresponds to a normal chamber angle in a normal child.

Figure 12.7 shows four goniophotographs of normal children, with the drawing of a normal chamber angle in a child in the upper right hand corner.

All the authors who have produced gonioscopy atlases made a drawing of the chamber angle in the child, as we have just shown, calling it a pathological image of the angle in congenital glaucoma, when it is really a normal chamber angle image in a normal child. This Fig. 12.8 is from a very good book: Color Atlas of Gonioscopy, by Wallace L.M. Alward [9] (Fig. 12.8).

Goldmann [10] had drawn the anomaly that presents in type II refractory congenital glaucoma, a perfect drawing by his own hand, in which these vessels and black triangles, in an apparent high insertion of the iris, are at the level of the Schwalbe line and do not permit any of the elements of the angle to be seen (Fig. 12.9).

Contact Lenses for Chamber Angle Examination in Children

For the examination of the chamber angle in newborns and infants up to 2 years of age, there are lenses specially designed by Haag Streit. Their diameter, at the surface that comes into contact with the eye is different from the diameter used for adults, i.e., they have a smaller diameter. There are two alternative lenses for children: one is 10-mm and the other 11-mm. However, recently, Rousell and Fankhauser developed a new contact lens for gonioscopy with greater resolution.

References

1.Seefelder R, Wolfrum C (1906) Zur Entwickliung der vorderen Kammer und des Kammerwinkels beim Menschen nebts Bemerkungen über ihre Entstehung bei Tieren. Arch Ophthalmol 63:430–451

2.Worst JGF (1966) The pathogenesis of congenital glaucoma. Royal Vangorcum Publishers, Assen Netherlands

3.Eisler P (1930) Die Anatomie des menschlicken Auges. In: Shiek F, Brückner A (eds) Shieck und Brückner’s Kurzes Handbuch der Ophthal I. Springer, Berlin

4.Kupfer C (1963) Gonioscopy in infants and children. In: Apt L (ed) Leonard’s diagnostic procedures in pediatric ophthalmology. Little Brown, London, pp 11–23

5.Barkan O (1936) The structure and functions of the angle of the anterior chamber and Schlemm’s canal. Arch Ophthal Chicago 15:101–110

6.Lister A (1960) Some aspects of congenital glaucoma. Trans Ophthal Soc UK 79:163–179

7.Busacca A, Carvalho C (1968) Osservazioni gonioscopiche sul glaucoma congenito. Atti del L Congresso della Societá Oftalmologica Italiana. Arte della Stampa, Roma, pp 64–68

8.Jerndal T, Hansson HA, d Hill A (1978) Goniodysgenesis. A new perspective on glaucoma. Scriptor, Copenhagen

9.Alward WLM (1994) Color Atlas of Gonioscopy (Illustrated by Lee Allen). Wolfe Medical, London

10.Goldmann H (1948) La gonioscopie. Jules François. Rapport sur les informations gonioscopiques, particulerement dans l’étude et le traitement du glaucome. Presenté à la Société Belge de Ophtalmologie. Librairie R. Fonteyn, Louvain, Belgium, p 73

Contents

Pathological Chamber Angle in Congenital Glaucomas 107

The Use of SL-OCT in Diagnosis

and Follow-Up of Congenital Glaucomas . . . . . . . . . . . . . 110

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Pathological Chamber Angle

in Congenital Glaucomas

The two types of pathological chamber angle in children are type I and type II. Type I (Fig. 13.1) has thin pathological mesodermal remnants that cover the ciliary band of the chamber angles and sometimes slender extensions reach the Schwalbe line. Type II (Fig. 13.1) chamber angles are identified by the presence of thick pathological mesodermal remnants with apparent high iris insertion with black triangles and pillars. In both types, it is impossible to distinguish the ciliary body band.