T H E MECHANISM O F OCCLUSION OF T H E "SINUS CAMERULARIS" IN UVEITIS*

ARCHIMEDE BUSACCA, M.D. Säo Paulo, Brazil

Since the anatomic designation, angulus camerae anterioris (translated by Lauber as Kammerbucht) conveys a faulty conception of the normal findings, I have for many years substituted the term sinus for angulus in my writings on gonioscopy, but to my regret this change in nomenclature has not been generally adopted. The periphery of the anterior chamber is composed of the root of the iris and the scierai trabecula joined by the slightly curved aspect of the ciliary body of variable extent. In gonioscopy the ciliary body often appears almost perpendicular to the sclerocorneal wall (fig. 6).

The root of the iris, the anterior surface of the ciliary body and the scierai trabecula constitute a sinus, the sinus camerulans, not an angulus camerularis. An angular forma­tion occurs only pathologically as the result of iris adhesions to the scierai trabecula or to the posterior surface of the cornea incident to pathologic changes affecting the ciliary body to be discussed later. When the ciliary body is eliminated from participation in the periphery of the anterior chamber by adhe­sions between the inner and outer walls of the sinus camerularis, the outcome is an irido-corneal angle or an irido-trabecular angle (figs. 7 and 8) .

In gonioscopy a precise image of the sinus camerularis is obtained through optical-sec­tion examination. It is necessary to study in detail how the corneoscleral profile and the iridic profile are connected by the ciliary pro­file. The corneoscleral profile line extends to the scierai spur, is curved regularly and shows no functional modifications gonio­scopically observable. The ciliary profile line exhibits marked individual differences that depend on the distance between the scierai

* Submitted to THE JOURNAL in French. Transla­tion by James E. Lebensohn, M.D., Chicago, Illinois.

spur and the insertion of the root of the iris (compare figs. 2 and 5) . Functional changes likewise occur. With contraction or relaxa­tion of the ciliary muscle, its deeper portion is respectively nearer or farther from the scierai spur as becomes evident after the in­stillation of eserine or atropine. Noticeable individual variations of the iridic profile line depend on the length and conformation of the root of the iris, the contractive status of the dilator muscle and the contractive status of the ciliary muscle, especially of the fibers that, coming from it, terminate in the proximal part of the dilator muscle (fig. 3-f ) (Busacca1).

Corroborative details are illustrated in the histologie sections (figs. 1 to 6) . These re­veal that the surface of the ciliary band of the sinus camerularis consists of a thin con­nective-tissue layer that covers the ciliary muscle and sends septa between the muscle bundles. This layer displays trabeculae, not unlike those of the scierai trabecula, repre­senting a residue of the embryonic pectinate ligament (figs. 3, 4 and S-g) to which I gave the name "trabeculo-connective lamella" (Busacca2) ; it is visible gonioscopically (Troncoso3) and has an extremely important role in the pathology of the sinus camerularis.

Gonioscopic and pathologic investigations have convinced me that the mechanism effect­ing closure of the sinus camerularis is differ­ent from that usually assumed. I shall begin by describing a case of healed severe chorio-retinitis in which I observed certain gonio­scopic alterations in the lower part of the sinus camerularis. Schwalbe's ring and the scierai spur were quite visible. The neat bundled structure of the scierai trabecula was besprinkled with numerous pigment granula­tions. Two small spherules of pigment were deposited at the scierai spur, and just poste­rior to it were two large masses of pigment.

383

384 ARCHIMEDE BUSACCA

Fig. 1 (Busacca). Histologie section of a narrow sinus camerularis. Truly angular; its bottom formed for the most part by iris and a very narrow ciliary band. Gonioscopy: Narrow sinus but well seen; ciliary band invisible since the iris root, inserted slightly posterior to scierai spur, covers it almost com­pletely. (a) Schwalbe's ring, (b) Schlemm's canal, (c) Scierai spur, (d) Last iris torus, (e) Limit of iris tissue.

These were fragments of the pupillary pig­ment-fringe, resulting from rupture of pos­terior synechiae, that had fallen in the in­ferior part of the sinus camerularis and had become adherent to the surface of the ciliary band through organized exudate. Some goniosynechiae were present.

After a lapse of time an intense exacerba­tion of the uveitis ensued. The two large masses of pigment behind the scierai spur

were no longer seen gonioscopically. Schwalbe's ring was visible in its entire extent. The scierai spur was partly hidden by a peripheral torus of iris* that had been

* In the French manuscript, Basacca refers to the last bourrelet, signifying the iris ridge after the last furrow, termed in German Irisrolle. In the apparent absence of an English technical equivalent, Busacca proposed the apt word torus.

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Fig. 3 (Busacca). Histologie section of a sinus camerularis of moderate amplitude. Profile of sinus is semi-elliptical ; ciliary band is slightly elevated and partly covered by basal band of iris processes ; very large iris root. Gonioscopy: Scierai spur distinct; ciliary band appears narrow, being partially hidden by iridic tissue; root of iris very long, (a) Schwalbe's ring, (b) Schlemm's canal, (c) Scierai spur. (d) Last iris torus, (e) Limit of iris tissue, (f) Ciliary muscular fibers to dilator muscle, (g) Tra-beculoconnective lamella.

THE "STNUS CAMERULARIS" IN UVEITIS 385

Fig. 2 (Busacca). Histologie section of a narrow sinus ciliary band and root of iris almost nonexistent. Gomoscopy: scierai trabecula is very near the root of the iris; the iris camerularis; last iris torus opposite Schlemm's canal; blood (b) Schlemm's canal, (c) Scierai spur, (d) Last iris torus. Schlemm's canal, (g) Trabeculoconnective lamella.

camerularis. Definitely angular with low Sinus camerularis is narrow because the

barely participates in formation of sinus in Schlemm's canal, (a) Schwalbe's ring. (e) Limit of iris tissue, (f) Emissary of

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Fig. 4 (Busacca). Histologie section of normal sinus camerularis of moderate amplitude. Profile of sinus rounded; high ciliary band; iris root almost nonexistent. Gomoscopy: Sinus of good width; last iris torus near bottom and opposite Schlemm's canal, and so hides part of the sinus from view, (a) Schwalbe's ring, (b) Schlemm's canal, (c) Scierai spur, (d) Last iris torus, (e) Limit of iris tissue. (f) Scierai trabecula extended into cornea, (g) Trabeculoconnective lamella.

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Fig. S (Busacca). Histologie section of a large sinus camerularis. Profile of sinus rounded; high ciliary band; long iris root. Gonioscopy: Sinus camerularis large; long iris root (seen behind last iris

THE "SINUS CAMERULARIS" IN UVEITIS 387

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b c Fig. 6 (Busacca). Histologie section of a large sinus camerularis. Sinus rounded; ciliary band quite

high; iris root short and thin. Gonioscopy: Large sinus; high ciliary band with surface overrun by a copious iridic trabecula; last iris torus, very slim and near bottom of sinus, does not interfere with its inspection, (a) Schwalbe's ring, (b) Schlemm's canal, (c) Scierai spur, (d) Last iris torus, (e) Limit of iris tissue.

displaced distally and nearer to the outer wall of the sinus camerularis. Because of this dis­placement most of the ciliary band could not be seen. The scierai trabecula, infiltrated and hidden by exudate, had a whitish color.

To elucidate these findings I examined histologically cases of posttraumatic uveitis in varied phases of evolution with the follow­ing results:

In Figure 7 is seen distinctly the boundary between the very pigmented proximal ex­

tremity of Henle's membrane* and the trabeculoconnective lamella. The ciliary mus­cle is extremely edematous and its most anterior bundles are displaced to a posi-

* The eponymic term, Henle's limiting membrane, commonly used in French ophthalmic writing, re­fers to the anterior layer of the iridic stroma in contact with the aqueous humor and resulting from a dense network of cells intensely pigmented in dark eyes (Redslob in Traité d'Ophtal., Paris, Masson, 1939, p. 522.) This is the Grenzschicht of Fuchs.

torus) participates in forming bottom of sinus; some iridic processes run over surface of trabeculo­connective lamella, (a) Schwalbe's ring, (b) Schlemm's canal, (c) Scierai spur, (d) Last iris torus. (e) Limit of iris tissue, (g) Trabeculoconnective lamella.

388 ARCHIMEDE BUSACCA

tion perpendicular to the midportion of Schlemm's canal. The edema has swollen the trabeculoconnective lamella (in which mi­nute cavities are observable) and also the root of the iris. As a result of the edema the posterior layers of the iris and the proximal border of the iris dilator muscle—on which can be seen the insertion of muscular fibers arising from the "apex" of the ciliary proc­esses—are displaced distally. The alterations affecting the anterior portion of the ciliary body have changed the position of the trabec­uloconnective lamella, which, swollen by

edema, has partly filled the cavity of the sinus camerularis.

Figure 8 is informative about conditions in the final phase of the inflammatory process. At f, the extremity of depigmented Henle's membrane (reflecting postinflammatory atrophy of the iris) forms a goniosynechial column. At g are seen muscular fibers pass­ing from the "apex" of the ciliary processes to the dilator muscle and (s) marks the posi­tion of the bottom of the sinus camerularis. The space between f, s and g is filled with infiltrated loose tissue in which there are

Fig. 7 (Busacca). Histologie section of occlusion of sinus camerularis by a coalescent goniosynechia in a cicatrized perforating injury of cornea. Sinus camerularis is transformed to an acute angle because of insertion of Henle's membrane of iris into the scierai trabecula (f). Between the iris insertion and the ciliary muscle, the deformed cavity of the sinus is filled with very loose connective tissue derived from the trabeculoconnective lamella, the position of which is now parallel to the external surface of the sinus. The entire area shows a slight diffuse infiltration. The "apex" of the ciliary processes has stretched forward and the anterior extremity of the muscle fans out to the scierai spur. Gonioscopy: Sinus distorted to an acute angle by the coalescent goniosynechia, by which the scierai spur is hidden, (a) Schwalbe's ring. (b) Schlemm's canal, (c) Scierai spur, (f) Limit of iris tissue (pigmented Henle's membrane).

THE "SINUS CAMERULARIS" IN UVEITIS 389

Fig. 8 (Busacca). Histologie section of the sinus camerularis occluded by coalescent and columned goniosynechiae. The scierai trabecula is densely infiltrated and covered by a thin coat of exudate. The infiltrated iris is swollen by marked edema and exudate, reflected from its two layers of ectoderm. The iris root and the trabeculoconnective lamella are significantly altered. A cone-shaped elevation of the extremity of Henle's membrane (f) adheres to the scierai trabecula, behind which is the cavity of the sinus camerularis. The changed position of the trabeculoconnective lamella has altered this cavity and apparently has lengthened the iris root. Considering the position of the radial muscle in relation to the longitudinal muscle, the bottom of the sinus should be at about (s). In (g) are the fibers that run in­ternal to the trabeculoconnective lamella to join the dilator muscle (compare Figure 3). The tissue be­tween (f) and (s) belongs to the trabeculoconnective lamella which, sequential to advancement of the ciliary body, rotation of the "apex" of the ciliary processes and edema, assumes a position parallel to the external wall of the sinus to which it is adherent. Gonioscopy: Sinus narrow and angular, with goniosynechiae of various degrees, behind which is a grayish zone, (a) Schwalbe's ring, (b) Schlemm's canal, (c) Scierai spur, (f) Columned goniosynechiae. (g) Muscular fibers internal to trabeculoconnective lamella, (s) Posterior extremity of original cavity of sinus camerularis.

little cavities. This loose tissue is derived from both the inflamed deeper layers of the iris root and the trabeculoconnective lamella. The latter reaches the external wall of the sinus camerularis with which it coalesces to form a large goniosynechia. In this case, as in that previously described, the sinus cam­erularis becomes closed and the periphery of the chamber is converted into an iridotra-becular angle.

C O M M E N T

These histopathologic observations war­rant the following interpretation of the changes affecting the ciliary body in uveitis

that eventuate in closure of the sinus cam­erularis. The increased volume of the ciliary body, caused by inflammatory edema, would tend to be directed toward the vitreous cav­ity because of the rigidity of the scierai wall. But the contraction of the muscle of Müller, provoked by the inflammatory process (as evidenced by cyclitic myopia in most cases of uveit is) , displaces the mass of the ciliary body distally so that its anterior extremity oversteps the level of the scierai spur, thus taking a position never encountered in the normal eye.

A further effect is rotation of the tra­beculoconnective lamella from its normal al-

390 ARCHIMEDE BUSACCA

most perpendicular position to a forward and outward tilting so that it approaches the scierai trabecula while swollen by edema and infiltration. The surface of the edematous iris is in continuity with that of the trabeculo-connective lamella ; the boundary between the two is denoted by the pigmentation of iridic tissue, especially when Henle's membrane is heavily pigmented. The degree of elevation of the ciliary band determines to what extent the trabeculoconnective lamella contacts the external wall of the sinus camerularis. The exudate on the two contiguous layers or­ganizes to form goniosynechiae that close the sinus camerularis definitively.

The phases of the process, shown schemat-

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ically in Figure 9-A, B and C, illustrate the thesis that, sequential to the swelling of the ciliary body in uveitis, the edematous, infil­trated trabeculoconnective lamella is pushed against the external wall of the sinus cam­erularis and closes it. The seclusion is ex­tended by the concomitant displacement of the swollen root of the iris. The probability of a similar mechanism in acute glaucoma is suggested by my gonioscopic observations and the histopathologic evidence of others (for example, Figure 175 in Fuchs' Text­book of Ophthalmology, third French Edi­tion).

The glaucoma that follows the dislocation of the crystalline lens into the anterior cham-

Fig. 9 (Busacca). Diagrams. (A) Appearance of the upper part of a normal

sinus camerularis as examined gonioscopically. The anterior extremity of the ciliary muscle is perpen­dicular to the scierai spur and the trabeculoconnec­tive lamella is almost perpendicular to the external wall of the sinus.

(B) Uveitis of moderate intensity. Note the swelling of the ciliary processes, forward displace­ment of the ciliary muscle, edema and displacement of the "apex" of the ciliary processes and of the iris root and the rotation of the trabeculoconnective lamella toward the sclerocorneal wall, with forma­tion of columned goniosynechiae between it and the external wall of the sinus camerularis.

(C) Very severe uveitis. The phenomena just de­scribed are aggravated. The anterior extremity of the ciliary muscle is perpendicular at the anterior portion of Schlemm's canal. The trabeculoconnec­tive lamella, swollen and infiltrated, is adherent to the external wall of the sinus where it forms a coalescent goniosynechia. The proximal extremity of Henle's membrane, normally inserted within the trabeculoconnective lamella (see Diagram A), ap­proaches or is in contact with the external wall of the sinus to which it may adhere, (a) Iris, (b) Tra­beculoconnective lamella, (c) "Apex" of ciliary processes, (d) Ciliary muscle, (h) Sclera. (m) Cornea, (s) Schlemm's canal.

THE "SINUS CAMERULARIS" IN UVEITIS 391

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Fig. 10 (Busacca). Histologie section of the sinus camerularis in dislocation of the lens into the anterior chamber with secondary glaucoma. The sinus is large and filled with exudate, coagulated by fixation. The border of the lens has no contact with the periphery of the sinus camerularis. The scierai trabecula is infiltrated and Schlemm's canal contains blood. The iris is atrophie. The muscle bundles of the ciliary body are fanned out by edema and the entire muscular mass is displaced forward; its anterior extremity is in the plane passing through the anterior extremity of Schlemm's canal. The fringes of the ciliary processes, displaying intense edema and vascular engorgement, are displaced forward also and toward the vitreous cavity. The trabeculoconnective lamella is atrophie and the ciliary muscle's bundles form the bottom of the sinus camerularis. Gonioscopy: Not possible, (a) Schwalbe's ring, (b) Schlemm's canal, (c) Scierai spur, (e) Limit of iris tissue.

ber is not provoked by the edge of the lens corking the sinus camerularis, as is generally asserted. As illustrated in Figure 10, the principal changes affect the ciliary body and are fundamentally identical with those de­scribed in uveitis, namely an intense edema

of the ciliary body and ciliary processes with distal displacement of the muscular mass. Figure 10 demonstrates that the sinus is open and definitely separated from the border of the crystalline lens.

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R E F E R E N C E S

1. Busacca, A.: La physiologie du muscle ciliarie étudiée par la gonioscopie. Ann. ocul., 188:1-18, 19SS. 2. : Éléments de Gonioscopie. Säo Paulo, Rossolillo, 1945. 3. Troncoso, U.: A Treatise on Gonioscopy. Philadelphia, F. A. Davis, 1947.