52.1  How Do I Perform Goniosurgery?

››Goniotomy is an important procedure for many children with glaucoma. Preoperative gonioscopy is important, as is careful attention to surgical instrumentation, surgical technique, and to postoperative care.

››Trabeculotomy is an alterative goniosurgical procedure that does not require a clear view of the angle.

››Hyphema may complicate goniosurgery during the immediate postoperative period.

››There are maneuvers to minimize the risk of a large hyphema.

››Whether to perform a trabeculectomy or glaucoma drainage device surgery is a multifactorial clinical decision that is not easily broken down into simple algorithms.

››Glaucoma drainage device surgery may be performed for most children of all ages, and it is relatively safe. Complications occur frequently and may relate to the drainage plate or to malposition of the drainage tube.

››Tube-shunt surgery for children is technically similar to the procedure for adults.

D. S. Walton

Massachusetts Eye and Ear Infirmary, Harvard Medical school, 2 Longfellow Place, Suite 201, Boston, MA 02114, USA e-mail: blacki@att.net

52.1.1  What Can I Do Technically

to Perform a Better Goniotomy?

The goniotomy procedure is elegantly simple and requires minimal equipment; however, preparation for this procedure is essential for its success. In the operating room, gonioscopic examination of the filtration angle prepares the surgeon for the upcoming procedure by redefining the target trabecular meshwork (TM) and by confidently assuring the presence of an adequate view of the angle for surgery. Of note, the view of the angle during surgery rarely equals the examination view qualitatively, something to take into account when planning for surgery.

The two most common causes of poor angle visualization in young children with glaucoma are diffuse epithelial edema and localized stromal edema associated with breaks in Descemet’s membrane. During the gonioscopic exam, the presence of epithelial edema can be quan­ tified by back focusing on the epithelium and noting the intensity of epithelial microcysts present in light reflected from the iris. Only the corneal opacification secondary to epithelial edema is corrected by removal of epithelium (stromal edema is not improved by this maneuver). When necessary the epithelium is carefully peeled off to create a clear window on the surgeon’s side of the cornea extending to the visual axis. This procedure is performed after selecting a meridian for knife entry that allows an optimal view to either side of any stroma opacity.

Preoperative preparation insures that suitable instrumentation for a goniotomy will be present (Table 52.1). Locking forceps, operating lenses of various sizes, and the goniotomy knife of the surgeon’s choice are essential. Forceps are used to grasp the rectus muscles through

Table 52.1  Goniotomy instruments and supplies Surgical instruments

 Loupe and head mounted light, or tilting surgical microscope

 Locking fixation forceps [3]

 Castroviejo forceps (0.3)

 Fine needle holder, jewelers forceps, infant lid speculum

 Operating gonioscopy lenses: small, medium, large

 Goniotomy knifes (e.g., B&L SP7-52233, Storz Instr Co,

St Louis, MI), or 25-gauge operating needles Medications and supplies

 Balanced saline

 Apraclonidine 0.5%

 Viscoelastic for anterior chamber deepening

 10-0 absorbable suture (Vicryl 448-G, Ethicon Inc, Somerville, NJ)

 70% isopropyl alcohol

 #15-BD blade

 30-gauge corneal irrigation needles

the conjunctiva in order to control eye position, and locking forceps are particularly helpful to prevent slippage off the rectus muscles. Operating lenses in various sizes are especially useful to have ready. For example, when performing the procedure on eyes with smaller corneas a smaller lens allows comfortable entry of the knife through clear peripheral cornea without dimpling of the cornea under the lens, which would impair one’s view of the angle. The goniotomy knife used must be in perfect condition. If dulled anterior chamber (AC) entry will be problematic and attempted incision of the TM will scrape and drag the tissue rather than incise it sharply. Use of a 25-gauge needle attached to a syringe in place of a gonio-knife has the advantages of permitting fluid injection into the AC should it shallow.

The goniotomy surgeon must plan entry into the AC on the meridian diametrically opposite the desired position of the planned goniotomy (Fig. 52.1). Once the knife has entered the AC, the globe may be rotated around the entry site (using the locking forceps grasping the recti muscles) in either direction to lengthen the incision in the TM both clockwise and counterclockwise of the initial TM contact. Incision of as many clock hours as comfortably possible should be performed. There is not good data in the literature examining success of goniotomy and clock-hours treated. When a nasal entry is desired, an entry site must be selected that allows rotation of the knife handle without encountering the patient’s nose.

I believe that AC blood reflux during the interval of hypotony following knife removal can be lessened by pretreating the adjacent limbus with 0.5% apraclonidine. A minimal amount of this topical medication should be administered to prevent excessive dosage

Fig. 52.1  The goniotomy procedure with globe held in position by fixation forceps

that might cause the pupil to dilate prior to goniotomy. Apraclondine may be administered again at the end of the case. Blood reflux is usually brief and promptly responds to reforming the AC and raising the eye pressure. It is helpful, however, to have a 1:16,000 mixture of epinephrine (1 cm3 of 1:1,000 epinephrine into a 15 cm3 bottle of balanced salt solution) prepared ahead of time to treat bleeding that is more persistent. This epinephrine mixture can be injected into the AC with an air bubble, which helps tamponade the bleeding until epinephrine has an opportunity to take effect.

Postoperatively it is very beneficial to instruct parents to keep the child’s head elevated at all times for 4 days to lessen the reflux of blood into the AC. Sleeping in a car seat can be very helpful to accomplish this posturing.

52.1.2  What Can I Do Technically to Perform a Better Trabeculotomy ?

The classic Harms trabeculotomy is an alternative goniosurgical procedure indicated for those glaucomas that have been reported to respond to goniosurgery. Trabeculotomy is performed using a standard operating microscope and does not require a clear view of the filtrationangle.Followingalimbalperitomy,Schlemm’s canal is unroofed with a radial groove under a scleral flap. Schlemm’s canal is then canalulated with a prolene suture or with trabeculotomy probes; a cleft into the AC from Schlemm’s canal is then created. It has been reported that Schlemm’s canal cannot be located in 11–15% of cases, so one must be prepared with an alternative plan if trabeculotomy cannot be performed successfully [1].