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

Annex

Trabeculectomy

Purpose of Trabeculectomy

Trabeculectomy has been a great success in the history of glaucoma surgery. It has replaced all the fistulizing operations done until then and is accepted worldwide.

John Cairns made the first trials in 1967 in Cambridge. In 1968 [69], he published the surgical technique for the first time.

Barkan [70] was the first to introduce the term “trabeculectomy.” Explaining its goniotomy, he said that, depending on the case, it could be called trabeculotomy or ab externo trabeculectomy.

About the same time, Vasco-Posadas [71] described a similar surgery that he called protected filtering. A little later, Fronimopoulos and Christakis [72], Watson and Barnett [73], Nesterov et al. [74], and Krasnov [75] published modifications to Cairns’s original technique. The purpose of this surgery is to remove an approximately 4×2-mm piece of trabecular meshwork, including the spur, the Schlemm canal, the Schwalbe line, and juxtacanalicular meshwork to make way for the aqueous humor to flow out freely through the Schlemm canal, “without subconjunctival drainage of the aqueous humour,” as Cairns said. However, in most cases, a good filtering bleb is formed.

Surgical Technique Steps

Conjunctival Flap

A limbusor fornix-based conjunctival flap is formed.

Coagulation of the Vessels

At the insertion of the Tenon capsule, 3 or 4 mm behind the limbus, there are small vessels that have to be coagulated along the entire edge of the insertion of this capsule. We perform the coagulation with equipment made by MIRA (Uxbridge, MA, USA), which uses bipolar microdiathermy with two electrodes in the point itself. This equipment was recommended to us by Dr. Alvarado and we particularly recommend it. Its point is very fine, and the intensity of the coagulation can be regulated in great detail. It can be used for coagulating the major arterial circle of the iris, the blood vessels of the ciliary body band, etc. Dr. Alvarado states that, by preventing hemorrhage at this level, not only is

blood flow interrupted, but also activator hormone escape is stopped, which causes intense scarring, which, when there is a filtering bleb, leads to surgical failure. Dr. Alvarado, personal communication, conducted a study on wound scarring in general and wound scarring occurring in glaucoma after fistulizing operations such as this, and divided them into three stages: the first includes the surgical trauma and necrosis with hemorrhage. The second produces fibrovascular scarring through the fibroblasts, macrophages, and the formation of new vessels. The third stage occurs when scarring stops and the tissue oxygenates normally. He therefore provided recommendations so that the healing process takes place and is not modified, leading to limited fibrous scarring of the bleb in its environment, fibrosis, and reduction of the bleb until it flattens and disappears. To prevent all this, he advises not cutting the conjunctival and Tenon blood vessels, a rapid cauterizing of the vessels, and finally, attempting to obtain the vascular part of the operated tissues to return to the presurgical state as soon as possible.

He then goes on to dissect the conjunctiva and sclera Tenon with scissors until he reaches the insertion of the upper rectus. A strabismus hook with a hole can be passed, as we described earlier, or a loop can be passed directly on the upper rectus before the incision. In this way, the eye remains well fixed for the maneuvers that follow, which are much more delicate and precise.

Dissection of the Scleral Flap

Figure 15.77 shows that before starting the scleral flap, a needle with an 8-0 Biosorb suture is passed in the corneal part of the sclerocorneal limbus to fix the eye. After dissecting the conjunctival flap, the dissection of the scleral flap is begun, which is a rectangle with one side 5 mm long, parallel to the limbus, and two vertical incisions joining it to the limbus.

Excision of the Trabeculectomy Piece

After dissecting the scleral flap (Fig. 15.78a), two incisions are made perpendicular to the limbus (1, 2), which are 0.5 mm inside the incisions of the primitive scleral flap. While doing this, it is helpful to use transillumination of the Minsky maneuver (Fig. 15.78b, d) to locate the anatomic elements that are to be excised.

It is very important to respect these measurements to obtain a good trabeculectomy piece. On the left of Fig. 15.79, the correct dimensions can be seen, and on the right, what should not be done.

Figure 15.80 shows the third incision that joins the two perpendicular incisions (1, 2). It should be noted carefully that it goes 0.5 mm beyond the perpendicular incisions. This is most important because the surgeon can thus take the trabeculectomy piece with small forceps.

Incision 3 is deepened until the anterior chamber is opened and, using angled Vannas scissors made by Storz or Katena, the incision is completed. The last two cuts correspond to the segment passing the vertical incisions.

At this point, so that the iris does not come into the incision, it is necessary to empty the anterior chamber.

This is done by introducing a delicate iris spatula in the anterior chamber parallel to the iris and rotating it 90° so that it opens the sides of the incision. The aqueous humor comes out and, in order to empty the chamber completely, triangular sponges should be placed over the incision to absorb it. This maneuver has to be repeated several times; once the chamber is completely emptied, the iris does not prolapse. Then the two vertical incisions are completed until they reach the vertex of the angle.

Figure 15.81a shows the flap to be removed, which has the Schlemm canal in its center, 15.81b shows the iridectomy, 15.81c, the trabeculectomy piece removed.

Iridectomy

If the iris tends to introduce itself into the wound, the anterior chamber is emptied again with the spatula, before going on to perform the iridectomy. We then use forceps that are not overly fine-toothed to take all the layers of the iris, for example, the Hoskin #22. In this way, the iris is taken with the left hand, pulling gently; the surgeon sees the pupil stretch, without the sphincter coming out through the trabeculectomy, and with De Wecker scissors, held between the index finger and thumb of the right hand, performs the iris cut. If a round iridectomy is desired, the blades of the scissors must be parallel to the limbus; if a triangular iridectomy is planned, they must be perpendicular to it. For the latter maneuver, a Barraquer model specially

designed for the microscope is very useful, in which the cutting blades form a 90° angle with the body of the scissors.

After performing the iridectomy, we instill 1% sterilized atropine on the wound itself. The iridectomy is cleaned so that no iris remains stuck in the wound, deforming the pupil. An iris spatula, no longer than 1–2 mm, is introduced gently from right to left in the anterior chamber, in the ends of the incision, taking care not to touch the crystalline lens.

Figure 15.82 shows that the iridectomy must not be made very peripheral, as the major arterial circle of the iris passes there and, if cut, will cause a profuse hemorrhage. The cut in that part of the trabeculectomy piece to be removed must pass the scleral spur. It contains the scleral spur, the Schlemm canal, and the Schwalbe line.

Fig. 15.82 a Drawing of the iridectomy. b Photograph, the iridectomy must not be very peripheral as the major arterial circle of the iris passes there, and if cut it will cause a profuse

hemorrhage. c Photograph of the cutting of the iridectomy. d The incision of the trabeculectomy piece to be extracted must pass the scleral spur. e,f see next page

Suture of the Scleral Flap and the Conjunctiva

The scleral flap is folded back, putting it in its place, and two stitches are made with 10-0 nylon suture in its ends. Nylon is used to avoid the granulomas that we saw when we used virgin silk, which, in the case of a filtering bleb, can limit it and make the operation fail. If the conjunctival flap is fornix-based, we put two virgin

silk stitches at 9 and 3 o’ clock, in such a way that the conjunctiva covers the entire limbus and overlaps the cornea 1 mm. If it is a limbus-based flap, we carefully make separate silk stitches that take the conjunctiva and the Tenon capsule as well as each lip of the wound. A continuous suture can be made with cross-stitching in its ends so that it does not loosen. Figure 15.83 shows the most important surgical instruments used.

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Contents

Percentage of Trabeculotomy and Combined Surgery

in the Study Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

We have analyzed the postoperative anatomical and functional outcome in a sample of 138 patients with pediatric glaucoma. These cases were divided into three groups:

1.Congenital glaucomas operated once (glaucoma was almost reversed with a single procedure: trabeculotomy).

2.Congenital refractory glaucomas (one or more reoperations were required).

Percentage of Trabeculotomy

and Combined Surgery in the Study Group

In 98 cases (70%), we performed trabeculotomy and in 38 cases (30%) combined surgery, Other authors have done the procedure in the same proportions, for example: Meyer et al. [1]. Their frequency in 37 cases was trabeculotomy, 62%, and combined surgery, 38%.

-The number of cases studied was:

-Trabeculotomy: 90 patients (70.3%); Combined surgery: 38 patients (29.7%).

-Follow-up lasted:

- In trabeculotomy: 12–40 years after surgery; In combined surgery: 7–35 years after surgery.

A number of parameters were studied before and after -surgery:

Intraocular pressure (IOP) in a single spot check at 9 a.m., with applanation) (Table 16.1);

Table 16.1 Intraocular pressure before and after surgery: spot check pressure and diurnal pressure curve

After surgery the daily pressure curve was normal -in all cases.

Daily pressure curve with applanation, in bed at 6, 9, 12, 15, and 18 o’ clock: after surgery (Chap. 15[45,

-46]);

Median (M) and standard deviation: variability (V), normal M, not more than 19 mmHg, V not more

-than 2.1 mmHg;

Axial length: measured with echometry (Fig. 16.1,

-Table 16.2);

-Refraction after surgery (Fig. 16.2, Table 16.3);

-Visual acuity (Fig. 16.3, Table 16.4);

Correlation between axial length and visual acuity

-(Fig. 16.4);

-Optic nerve; Visual field.

The last two parameters are studied in Chaps. 17 and 18.