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

Pathology of the Specimens of the First

(Trabeculectomy) Technique and the Second

(Modified Kozlov) Technique

Figure 15.35 shows semiserial cuts of the pathological anatomy of a trabeculectomy piece. Figure 15.36a shows the same section as Fig. 15.35c, showing that as well as the pathological mesodermal remnants, the anterior face of the ciliary body is centripetally displaced. This displacement is also sketched in Fig. 15.39b.

We will now look at what surface electron microscopy discovers in trabeculectomy pieces. On the left of Fig. 15.37a, a normal trabecular meshwork can be seen with the trabeculae, the intertrabecular spaces, and the red blood cells passing freely through these spaces. Each trabecula is approximately 6 or 7 µm thick, and each round granule of pigment, 1–1.5 µm. Two granules can be seen in the upper trabecula below the red blood cell on the right. the Barkan membrane can be seen in b, occupying the intertrabecular spaces with

some small holes. The persistence of the Barkan membrane can also be seen in c and in d.

Figure 15.38 is from a specimen obtained from a combined operation of a 2-month-old child with refractory congenital glaucoma. In Fig. 15.38a, the complete specimen of the trabeculectomy can be seen at low magnification. The zone between Fig. 15.38b–d shows the Schlemm canal opened by the trabeculotome. This zone can be seen with greater amplification in Fig. 15.38c. The black square adjacent to this zone that can be seen in Fig. 15.38a is considerably magnified in Fig. 15.38b and d.

Figure 15.39 shows the surface optical microscopy technique (Dr. Zarate’s method), taken from a series corresponding to the optical image. The section becomes transparent as in an inclusion process. When it is dehydrated, it is examined with the microscope with an eosin background stain. The pathological mesodermal tissue is seen with ramifications reaching the rear face of the cornea (Fig. 15.40).

Fig.15.35 a Hematoxylin eosin stain (×40). A mesh of diffuse mesodermal remnants can be seen occupying the pretrabecular and trabecular region, ending below the ciliary muscle, which is displaced forward. b The same case as in the previous figure. Semiserial cuts. PAS stain (×40). The Descemet membrane (PAS-positive) stands out, reaching the point of the trabecular meshwork. The diffuse mesodermal remnants are dyed more weakly than in the Descemet membrane. c Semise-

rial cuts. Masson Trichrome stain (×40). With this technique, it is possible to clearly recognize the anomalous position of the ciliary muscle, situated above the filtration zone and the Schlemm canal. d Semiserial cuts in the same case. Gomori reticulin stain (×40). The diffuse mesodermal remnants are stained black with this technique because of its wealth of reticular fibers. The reticular fibers surrounding the fibers of the ciliary muscle are also stained

Fig. 15.37a–d Scanning electron microscopy. a Normal trabecular meshwork can be seen with the trabeculae, the intertrabecular spaces, and the red globules passing freely through these spaces. Each trabecula is some 6 or 7 µm thick, and each round

granule of pigment, 1–1.5 µm. Two granules can be seen in the upper trabecula below the red blood cells on the right. b–d The Barkan membrane occupying the intertrabecular spaces with some small holes and blocking the passage of red cells

Fig. 15.38a–d From a specimen obtained from a combined operation of a 2-month-old child with refractory congenital glaucoma. a The complete specimen of the trabeculectomy can be seen at low magnification. The zone between b, c, and d

shows the Schlemm canal opened by the trabeculotome. This zone can be seen with greater amplification in c. The black square adjacent to this zone that can be seen in a is considerably magnified in b and d

Fig. 15.39 The surface optical microscopy technique (Dr. Zarate’s method), taken from a series corresponding to the optical image. The section becomes transparent as in an inclusion process. When it is dehydrated, it is examined with the

microscope with an eosin background stain. The pathological mesodermal tissue is seen with ramifications reaching the rear face of the cornea

Nonpenetrating Deep Sclerectomy for Late Congenital Glaucoma

Background

It was Krasnov [48, 49] who originally proposed the removal of the external wall of the Schlemm canal and coined the word sinusotomy for the procedure by which he removed the external wall of the Schlemm canal from 10 to 8 o’ clock over 120°; the inner wall of the Schlemm canal was left untouched and then the conjunctiva was closed. Alkseev [50], proposed removing the endothelium of the inner wall of the Schlemm canal and of the juxtacanalicular tissue in sinusotomy in order to increase the permeability of the inner wall of the chamber angle.

Zimmerman et al. [51] introduced nonpenetrating trabeculectomy; Fyodorov et al. [52, 53] proposed deep sclerectomy and later together with Kozlov and others (1989), nonpenetrating deep sclerectomy; Kozlov et al. [47] perfected the method with the addition of a cylindrical collagen implant and later developed laser goniopuncture, methods that were further developed by Kozlov and Kozlova [54] and by Kozlov and Kozlova and Kozlova et al. [55, 56]. In Kozlov’s technique, in addition to the resection of the external wall of the Schlemm canal, the inner wall of the Schlemm canal with the endothelium, together with the juxtacanalicular tissue and external corneoscleral trabecular meshwork are removed. In 1991, Arenas Archila [57] proposed trabeculotomy ab externo, by which the same tissues were removed, after removal of the external wall of the Schlemm canal, but using a microtrephine working at a speed of 800 rpm. In 1999, Stegman et al. [58] reported their results with viscocanalostomy in black African patients. Sourdille et al. [59] used a triangular

reticulated hyaluronic acid implant of the same size as that of the second triangular scleral flap. We have successfully tested this technique, which, as it is currently known, is also successfully used by Demailly et al. [60]. Moreover, a very complete book has been published recently by Mermoud and Shaarawy [61], who has extensive experience in nonpenetrating surgery.

The main advantage of nonpenetrating deep sclerectomy (NPDS) lies with the high percentage of cases in which it prevents the three most severe complications of trabeculectomy: flat chamber, hyphema, and choroidal detachment. Furthermore, since neither anterior chamber opening nor iridectomy or atropine instillation into the anterior chamber are required, the postoperative period is short, with the patient preserving the preoperative visual acuity, in contrast to our experience with trabeculectomy, which has a difficult postoperative course, independently of the success of the procedure.

Moreover, the mild postoperative period, as well as the low percentage of complications, has encouraged surgeons to safely recommend this technique as early as in the preperimetric period, when damage to the optic nerve has already occurred and pharmacotherapy has failed to regulate IOP, though visual acuity and visual field are still normal. This technique is thus quite close to the ideal therapy for the prevention of serious anatomic and functional damage caused by the disease. We perform this technique only in late congenital glaucoma (see Chap. 20).

Nonpenetrating Deep Sclerectomy:

Anatomical Landmarks

Figures 15.41, 15.42, 15.43, and 15.44 illustrate the anatomical landmarks.

Fig. 15.41 Resistance on the conventional outflow pathway, which was removed by trabeculectomy (vertical red line). With NPDS (vertical green line) we removed the external wall of the Schlemm canal with collectors upon removing the triangular flap. Removal of the internal tissues includes internal wall of the Schlemm canal, the juxtacanalicular tissue, the external

part of the corneoscleral trabecular meshwork. The internal part of the corneoscleral trabecular meshwork and the uveal trabecular meshwork, which, together with the Descemet membrane form the trabecular Descemet membrane, remain unmoved

Fig. 15.43 In NPDS, the external wall of the Schlemm canal is removed with the second triangular scleral flap and with the Mermoud forceps, a membrane comprising the inner wall of the Schlemm canal, the juxtacanalicular tissue, and the external part of the corneoscleral trabecular meshwork is also removed. The tissues that are left in their place are the trabec-

Fig. 15.44 Chamber angle sections of the chamber angle. 5 Ciliary muscle, 6 ciliary body, 7 sclera, 8 limbus, 9 scleral septum and Schwalbe line, 11 iris, 12 cornea, 13 Schlemm canal, 14 lens gonioscopic image, S. SPUR scleral spur, TR trabecular meshwork, TRSHL trabecular meshwork of the Schlemm canal, LSCHW, Schwalbe line, CB ciliary body band, LRI last fold of the iris, I PR iris process. Optical cut, 1 profile line at the posterior corneal surface, 2 profile line at the anterior corneal surface, 3 profile line at the anterior iris surface

ular Descemet membrane, made up of the internal part of the corneoscleral meshwork and the uveal meshwork. As stated by Dr. Mermoud, this membrane is strong enough to support the anterior chamber and also permeable enough to improve aqueous humor outflow with the consequent intraocular pressure reduction

Nonpenetrating Deep Sclerectomy:

Surgical Technique

After retrobulbar anesthesia with 2–4 ml of a solution of Xylocaine 4%, the conjunctiva and the Tenon capsule are opened at the upper fornix or at the limbus. With the sclera thus exposed, careful hemostasis is performed using a bipolar cautery manufactured by MIRA (MIRA Western Surgical Specialties, Uxbridge, MA, USA). A nylon suture is placed on the cornea 1 mm from the limbus, at 12 o’ clock, to move the eye.

Step 1

A rectangular one-third scleral thickness limbal-based scleral flap, the same as that created for trabeculectomy, is dissected. One side of this rectangle, 5 mm in length, is parallel to the limbus, while another one is perpendicular to it and 6 mm long. Anteriorly, the scleral flap is dissected closer to the cornea than usual in trabeculectomy procedures. Corneal lamellae are dissected along 1.5 mm (Fig. 15.45).

Fig. 15.45 The dissection has been correctly performed if three clear areas are visualized. Dark area (limbal area); blue area 2 (more posterior), with its anterior limit corresponding to the Schwalbe line, and its posterior limit, to the scleral spur and the open the Schlemm canal; white-grayish area 3 (behind the

blue area), triangular, made up of scleral tissue and covering the external surface of the ciliary muscle. On the right side of this figure the correspondence of the surgical appearance of the three areas with the anatomical elements of the chamber angle can be seen

Step 2

A second limbal-based triangular scleral flap is then created by penetrating 1.5 mm into the corneal tissue. A useful landmark step for this dissection, which must be performed carefully, is the orientation of the scleral fibers, which, although arranged in multiple directions at the scleral level, behind this flap become neatly parallel and circular at the level of the scleral spur, thus adopting a more whitish and nacreous appearance. Aqueous humor percolation at this stage, with the anterior chamber closed, when the dissection goes from

the scleral spur toward the cornea, indicates that the incision is placed in the proper plane. The triangular flap containing the external wall of the Schlemm canal, including its endothelium, is then resected. Anteriorly, the dissection should be made down to the deep corneal lamellae so that only the corneal endothelium remains. The Descemet membrane and a small layer of corneal lamellae are left. The dissection plane can generally be easily created at this final stage by pulling the vertex of the triangular flap toward the cornea with a clamp (Fig. 15.46). Figure 15. 47 shows the pathological anatomy of the external wall of the Schlemm canal.