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

ND:Yag Laser Goniopuncture

In 20% of cases, YAG goniopuncture was required after surgery when the IOP in the follow-up reached values greater than 18 mmHg so that the anterior chamber would communicate with the scleral lake. The beam is focused on the trabecular Descemet membrane with a power of 2–3.5 mJ; however, sometimes higher power, 4–5 mJ, is required, but it should be kept in mind that

a power above 4 mJ may cause small hemorrhages, which can be stopped by pressing the lens firmly against the eye. A total of five to 20 shots should be made at the Schwalbe line, as well as above and below it (Fig. 15.61). In 85% of late congenital glaucoma cases, the IOP is well-regulated and its progression is stopped. Figure 15.61b shows the most important surgical instruments used in this surgery.

Fig. 15.61 a Nd:Yag laser goniopuncture. On the left, the right place to perform goniopuncture: at the Schwalbe line, in the posterior corneal surface and in the trabecular meshwork. On the right, there is a goniophotograph shows the Schwalbe line,

the scleral spur, and blood coming from the Schlemm canal, after goniopuncture. b 1 15° Diamond blade, 2, NPDS spatula, 3 NPDS diamond blade, 4 NPDS uproofing blade, 5 Mermoud forceps, 6 ophthalmy microdiathermy (MIRA)

Valve Devices in Congenital Glaucomas

Introduction

The first to construct a valve was Molteno [63]. His basic idea was not only to insert a tube in the anterior chamber to extract the aqueous humor, but also to create a broad surface for its reabsorption, located in the equatorial zone of the eye at the level of the rectus muscles. The plate was made of acrylic material 8.5 mm in diameter, with an acrylic tube through which the aqueous humor flows into the sub-Tenon space. A series of valves with different designs then appeared, such as those of Brooks et al. [64], Lim et al. [65], Coleman et al. [66], Ahmed, personal communication, Krupin [67], Mermoud [68], etc.

We will discuss the indications, contraindications, surgical technique, intraand postsurgical complications, results, and the authors’ experience in valve implants for congenital glaucomas.

Indications

Implanting a valve will never be the first operation in a congenital glaucoma. It will be inserted as a first surgery only in cases of congenital aniridia. Trabeculotomies and combined operations (trabeculotomy with trabeculectomy in a single session) will always be

performed. All the other congenital glaucomas, such as those associated with ocular, or ocular and somatic malformations, etc., will be treated in the same way. Two or more trabeculotomies and combined operations will be made before indicating a valve implant as the last resort.

Types of Implants

Valve devices can be divided into limited and unlimited devices: the former have mechanisms that at least partially prevent prolonged hypotony after surgery, while the latter lack this mechanism and may lead to the complication more frequently.

Even though the manufacturer, New World Medical, Inc. (Rancho Cucamonga, CA, USA), has a special pediatric model (FP8), we prefer to insert the valve model S3 made of polypropylene, designed for adults, in children with refractory congenital glaucoma, because we have never had any allergic reactions and above all because in all cases the eye of a child with congenital glaucoma is larger than that of an adult.

The most commonly used state-approved valve in our area is the Ahmed valve (Fig. 15.62). Until now we have used the Ahmed valve for adults in its classic version and not the silicone pediatric valve.

Child or adolescent eyes are generally phakic, and it should be remembered that, in many cases, these eyes, being type II refractory glaucomas, are myopic, with a

substantial increase in their axial length and therefore with thinner walls and a much thinner sclera than in the adult. It should also be mentioned that eyes in children will grow with time, and this should also be taken into account. This is why the surgical technique varies from the technique routinely used with older patients. It involves a change in the location of the tube in the anterior chamber and a change in the technique used to cover the tube.

The implant technique retains some points used in adults: for example, the preferred locations will be, in this order: temporal superior, nasal superior, temporal inferior, and nasal inferior.

In adults, there are three ways of situating Ahmed valve tubes so that they do not extrude: below a scleral flap fashioned within the patient’s own sclera, guided by a needle through an intrascleral tunnel, or covered with a patch of donor sclera.

In congenital glaucoma cases, scleral thinning can at times even lead to zones of real scleromalacia; therefore the technique of choice is to cover with a donor patch of sclera, so as not to use the patient’s own sclera, which would only lead to greater thinning.

The tube in the anterior chamber should be slightly longer than is usual in adults. This is because the eye

is going to continue growing naturally, and if the glaucoma should decompensate, it may grow even more. We have even seen cases where the tube comes out of the anterior chamber because of normal eye growth. Leaving a long section inside the anterior chamber thus prevents this complication.

Lastly, since these eyes are in general phakic, the tube is not usually located radially to the pupil, but paracentrally and peripherally (Fig. 15.63), which means that the tube should be placed parallel to the pupil, leaving it completely outside the pupil area, without pointing toward it. This prevents the point of the tube from touching the lens, thus preventing cataract formation in children, who are more prone to injury than adults.

The surgical steps are the following:

1.Opening of the conjunctiva;

2.Scleral flap;

3.Puncture of the anterior chamber with a 26-gauge needle;

4.Insertion of the valve;

5.Fixation of the valve with two sutures;

6.Cutting of the tube;

7.Introduction of the tube;

8.Suture of the tube at 1.5 mm outside the scleral flap.

Fig. 15.67 a The moment of making the paracentesis in a parapupillary direction and not radial to the pupillary axis; injecting light viscoelastic in the anterior chamber. b Introduction of the tube in the anterior chamber, checking where the point

Fig. 15.68 a The first stitch to fix the donor scleral patch. b The conjunctival closing with absorbable 8-0 silk suture. c After testing the bleb with physiological solution, on the right can be

is, its relation with the visual axis and its anteroposterior positioning, confirming that it is not in contact with the iris or the cornea. c A nylon stitch is made to fix it in the episclera

seen the final position of the tube in the anterior chamber. The lower temporal filtering corresponds to the injection of gentamicin and corticoids

Postsurgical Biomicroscopy in Valve Implants

As we have mentioned, implanting the tube is rather different than in adults. The tube must remain in a parapupillary position, above the iris and not radial to the visual axis. In the anteroposterior direction, it should also be situated between the cornea and the iris, leaving a space between the tube and these structures. Lastly, as far as possible, its intrachamber portion

should be somewhat longer than usual for later growth of the ocular globe, with the bevel, as in other cases, toward the front.

It is also important during check-ups to see how the bleb maintains its shape, without seeing the edge of the valve body. When the conjunctiva surrounds the valve and shows its edge, it is because the bleb has formed a cyst and is not filtering properly (Fig. 15.69, 15.70, 15.71).

Fig. 15.71a–c The valve implant in congenital glaucoma with posterior pseudophakia is shown on the left; in the center, the correct location of the tube in the anterior chamber as ob-

served with gonioscopy. On the right, the usual position used in adults, in which it reaches the pupil border, almost radially in a pseudophakic eye

The most common complications in valve implants in young people are the appearance of inflammatory granulomas, traumatic extrusion, spontaneous extrusion, corneal decompensation from the tube touching the endothelium, cataract produced by the tube touching the crystalline lens, the tube leaving the anterior chamber because of the growth of the ocular globe, unregulated normal IOP for the child’s age, loosening of the valve body from its original placement, and cyst formation of the valve body by the Tenon capsule.

Other less frequent complications are blebitis and endophthalmitis. Even though valve implants tend to have fewer infections than perforating surgery, these have been described. It should be made clear that, as has already been shown, the use of antimetabolites associated with the valve implant does not increase their hypotensive efficacy, and so they should not be used in this surgery.

Even though we have much greater experience in trabeculectomy and trabeculotomy, in cases in which we have decided to use valve implants, pressures have nearly always been between the 10 and 15 mmHg that a newborn requires. Mean IOPs achieved were 14.5 ± 5 mmHg, so that in 40% of the cases, medication was needed to help to regulate ocular pressure correctly. It should be clarified here that in general these were reoperations for the second, third, or fourth time (see Figs. 15.72, 15.73, 15.74, 15.75, 15.76).

Fig. 15.72a,b The spontaneous extrusion of an Ahmed valve implant with a loosening of the valve body (nylon point near the limbus) can be seen on the left. The increase in the section of the tube in the anterior chamber can also be seen, result-

ing from inward movement of the implant. An inflammatory granuloma can be seen on the right that obliged the removal of the valve implant

Clinical History No. 1

This boy, first seen in 1965 at the age of 3 months, has been followed up for over 40 years (Figs. 15.72, 15.73). Another ophthalmologist performed two goniotomies without results.

Conclusion of Clinical History No.1

Congenital glaucoma operated for the first time at the age of one, then later on, two times at the right eye and four times at the left eye. Plus surgery for retinal detachment in the right eye and Ahmed valve in the left eye, and finally cataract surgery in both eyes. At the age of 40 years good visual field and a visual accuity of 20/20 in both eyes.

This is a good example of how the ophthalmologist must not be descoraged, and has to reoperate when necessary. This young man supports today his mother and is on the way of becomming a well known writer.