Thursday, December 28, 2006

Section 10-C: Treatment of congenital glaucoma

Unlike adult glaucoma, the initial treatment for congenital glaucoma is often surgical. A “drainage angle surgery” is often recommended for congenital glaucoma. The most common surgical procedures for congenital glaucoma are goniotomy and trabeculotomy. While they are considered to have similar rates of success (80-90%), some surgeons prefer one technique over the other. One advantage of trabeculotomy over goniotomy is that a clear cornea is not necessary to perform the procedure, while a reasonably clear cornea is necessary for goniotomy. The goniotomy surgery involves entering the anterior chamber with a sharp goniotomy knife and making an opening incision through the abnormally developed trabecular meshwork to allow greater outflow of the aqueous fluid and thereby, lower the IOP (Figure 10-5). Often 120 degrees (out of 360 degrees total) of the trabecular meshwork can be treated with goniotomy in a single setting. Trabeculotomy surgery involves making an external incision and identifying the Schlemm’s canal from the outside, inserting a fine instrument into the Schlemm’s canal, and breaking through the trabecular meshwork to increase the aqueous outflow (Figure 10-6). Typically, 120-140 degrees of trabecular meshwork can be treated by trabeculotomy in a single surgery. If one surgical technique is unsuccessful in decreasing the IOP, the other technique can be utilized in a fresh area of the trabecular meshwork (the area not previously operated upon) to increase the success of the surgery. Even after initial control of the intraocular pressure is established with surgery, a periodic monitoring is necessary to ensure the IOP doesn’t increase again and the glaucoma go out of control.

Figure 10-5. Goniotomy
Figure 10-5. Goniotomy. A fine surgical knife is used to open the drainage angle (trabecular meshwork) in order to lower the intraocular pressure.

Figure 10-6. Trabeculotomy
Figure 10-6. Trabeculotomy. A trabeculotome instrument is used to open the drainage angle (trabecular meshwork) in order to lower the intraocular pressure.

Medications can be used as an adjunct therapy either before or after the surgical treatment. Medications may be utilized temporarily after the diagnosis until surgery can be performed. If the initial surgery fails to completely control the IOP, topical medications can be used to bring the glaucoma under control. The systemic side effects of topical medications are greater in infants than in adults because of the smaller body mass. Because of potential systemic side effects, the first line of medications that are commonly employed is the topical carbonic anhydrase inhibitors (CAI, see Chapter 7). After the CAI, the next choices are topical prostaglandin analogs or beta-blockers (Chapter 7). The prostaglandin analogs appear to be safe in children; however, there are no long-term data on the safety of these medications in children. Topical beta-blockers should be used with caution in children because of the well-known systemic side effects (Chapter 7). Finally, topical alpha-2 agonist (brimonidine, Chapter 7) should be AVOIDED in infants because it’s been associated with severe respiratory depression (breathing difficulty).

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