Summary
Trabeculotomy is another form of angle surgery that can be considered for the treatment of children with infantile glaucoma.
16 Trabeculotomy
16.1 Goals
Lower the intraocular pressure (IOP).
Decrease glaucoma medication usage.
16.2 Advantages
Although goniotomy is the preferred first-line procedure for primary infantile glaucoma, trabeculotomy is an alternative method of treatment when there is poor visibility of the angle.
16.3 Expectations
The results of trabeculotomy depend on patient selection, similar to goniotomy.
Best results are achieved with infantile primary congenital glaucoma.
A small hyphema is usually present at the conclusion of the procedure and may persist for 1 to 2 days.
16.4 Key Principles
Trabeculotomy is considered when there is poor visibility of the angle, impeding the ability to perform goniotomy.
16.5 Indications
Trabeculotomy may be used for the same types of glaucoma for which goniotomy is indicated.
The degree of difficulty of a trabeculotomy is not increased in the presence of corneal clouding to the same extent as a goniotomy.
Trabeculotomy is reserved for those cases when corneal clouding or opacification results in an inadequate view for a goniotomy.
16.6 Preoperative Preparation
Ensure that the required instruments and equipment are readily available for an uninterrupted presurgical examination under anesthesia and successful trabeculotomy (Table 16.1). Once the patient is under anesthesia, tonometry, corneal diameter measurements, gonioscopy, inspection of the cornea and irides with portable slit-lamp examination, and fundoscopy are performed first.
16.7 Operative Technique
The procedure is performed superotemporally or superonasally to avoid areas that may be needed for a trabeculectomy in the future.
A conjunctival peritomy is created with two relaxing incisions and dissected down to bare sclera. This is followed by the creation of a 3.5-mm triangular limbus-based scleral flap (Fig. 16.1) using a #57 Beaver blade or a scarifier.
Dissection of this flap is extended anteriorly toward the cornea until the darker limbal tissue is easily visualized at a depth of approximately one half of the scleral thickness.
An anterior chamber paracentesis wound is created with a paracentesis blade, either superonasally or superotemporally, depending on patient and surgeon positioning.
The paracentesis allows entry of a short, 30-gauge cannula for re-formation of the anterior chamber and should be of adequate length to be self-sealing.
A radial partial thickness incision is made with a paracentesis blade, initially partial thickness and under the scleral flap, from 1.0 mm anterior to 2.0 mm posterior to the limbal scleral junction (Fig. 16.2).
With continued dissection, the circumferential fibers of the scleral spur should become evident at the posterior third of the radial wound with less dense circumferential fibers found immediately over Schlemm’s canal (Fig. 16.3). The tissue making up the outer wall of Schlemm’s canal often appears dark green-black.
Successively deeper layers of sclera through the radial incision are dissected, eventually entering Schlemm’s canal through its outer wall.
Magnification should be increased at the surgeon’s discretion for final dissection into Schlemm’s canal.
Upon entry, blood or aqueous humor may appear.
A short length of 6–0 nylon suture may be held with fine forceps, such as jeweler’s forceps, and passed to the right and then to the left circumferentially to test for the presence of Schlemm’s canal.
Angled Vannas scissors are used to enlarge both sides of the entry into Schlemm’s canal by placing one blade of the scissors in Schlemm’s canal and cutting circumferentially to the right and then to the left of the radial incision.
A trabeculotome is then used to incise the trabecular meshwork (trabeculum) by placing the distal arm of the instrument into Schlemm’s canal, and using the proximal arm as a guide for the placement of the distal arm (Fig. 16.4). No resistance should be encountered with this maneuver.
Once the distal arm is in the canal, it is rotated into the anterior chamber over the surface of the iris to expose approximately three-fourths of the arm’s length in the anterior chamber; there should be no resistance to this rotation.
If the trabeculotome is rotated in a plane angulated posteriorly, the iris may be encountered. If it is rotated in a plane angulated anteriorly, resistance may be felt due to engagement of tissue approximating Schwalbe’s line.
Partial collapse of the anterior chamber may occur with the first rotation of the arm, requiring re-formation or deepening of the anterior chamber before the same maneuver is performed on the opposite side of the radial incision.
After the trabeculotome is used on both sides of the radial incision, the overlying triangular scleral flap is closed using 10–0 polyglactin suture to maintain the anterior chamber.
The conjunctival peritomy is then closed at the corners to the limbus with 9–0 polyglactin suture. The relaxing conjunctival incisions are closed with interrupted 10–0 polyglactin suture on a tapered needle. 1
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