Surgery in the Chamber Angle

Many surgical procedures in glaucoma have the aim of improving outßow facility by different means. Only a few aim to reduce the production of aqueous humor. Some of them are more, some less and some minimally invasive.

Is gonioscopy of informational value before, during and/or after an operation? DeÞnitely, yes! You need to know about the anatomical status. Some of these procedures require an open chamber angle, and therefore they are preferably performed in combination with phacoemulsiÞcation of the lens.

10.1Filtration or Penetrating Surgery (Trabeculectomy)

After preparation of the conjunctiva, TenonÕs capsule and the scleral ßap, a tiny full-thickness part of the cornea, the trabecular meshwork and sclera is excised to create a bypass ßow below the TenonÐconjunctiva complex, called a Þltering bleb (Fig. 10.1). It is highly advisable to perform a peripheral iridectomy to avoid blockage of the new Þstula.

If the IOP is the same postoperatively as it was preoperatively, the anterior chamber is the same depth, there is no Þltering bleb and the pupil is possibly slightly distorted to the site of the scleral ßap, a gonioscopy should be done. One might Þnd the iris trapped in the Þstula, and no further outßow is possible (Figs. 10.2 and 10.3). Revision is mandatory.

Fig. 10.1 Opening of the scleral ßap shows the hole after excision of a tiny part of the sclera, cornea and the trabecular meshwork. To prevent occlusion of this hole by the iris a peripheral iridectomy has been performed, so the ciliary processes are visible

If the bleb is well functioning, the chamber angle shows a rectangular excision with a ßat and tiny slit between the sclera and the ßap (Fig. 10.4).

10.2Non-penetrating Surgery

10.2.1 Deep Sclerectomy

After preparation of the conjunctiva, TenonÕs capsule and the scleral ßap, a second, deep and a little bit smaller scleral ßap is created and excised.

Fig. 10.2 The iris is trapped in the excision site of the trabeculectomy. The running nylon suture of the conjunctiva/ TenonÕs capsule at the limbus is visible. Revision is mandatory because outßow through the Þstula is blocked. The patient had experienced a blunt trauma

Fig. 10.4 Excision site after trabeculectomy in the chamber angle including a part of the scleral spur and the posterior, pigmented trabecular meshwork. The bright white sclera of the inner wall of the scleral ßap is visible

Fig. 10.5 Rectangular DescemetÕs window (edges are marked by arrows) after resection of a deep scleral ßap (Courtesy A. Mermoud)

Fig. 10.3 Filtering bleb with running nylon suture at the limbus in the same eye as shown in Fig. 10.2. Note the slight distortion of the pupil towards the site of Þltration because of trapping of the peripheral iris

The preparation proceeds into the corneal tissue performing a ÒDescemetÕs window,Ó a clear rectangular area where aqueous humor should ÒpercolateÓ from the anterior chamber into the newly created reservoir between the sclera (Òscleral lakeÓ) and the conjunctiva, producing a Þltering bleb (Fig. 10.5). In gonioscopy, DescemetÕs window can be seen clearly. On gentle pressure with the contact lens DescemetÕs membrane and the endothelium will wave lake a sail in the wind.

10.2.2Viscocanalostomy

The Þrst steps are the same as in deep sclerectomy. After excision of the deep scleral ßap, the ostia of SchlemmÕs canal are widened with a viscoelastic agent (an ophthalmic viscosurgical device, OVD), doubling their diameter. Watertight closure of the scleral ßap avoids a Þltering bleb. Gonioscopy reveals the same as in deep sclerectomy.

10.2.3Viscotrabeculotomy

As in viscocanalostomy, the ostia of SchlemmÕs canal are widened, but afterwards speciÞc cannulas are introduced into the canal and injection