Surgery is the preferred, definitive treatment of most cases of PCG; medications have limited long-term value. Although medication can better control IOP in other forms of pediatric glaucoma, a high percentage of these cases also eventually require surgery. Goniotomy and ab externo trabeculotomy are the procedures of choice for the treatment of PCG. Either procedure is appropriate if the cornea is clear. If the cornea is cloudy, poor visualization of the target structures makes goniotomy difficult to perform; trabeculotomy is preferred in these eyes because it is more easily performed. Angle surgery has a high success rate in children with PCG; the highest success rates have been observed in children diagnosed between 3 and 12 months of age.
Angle surgery may also be used to treat other forms of pediatric glaucoma, including glaucoma following congenital cataract surgery, glaucoma associated with aniridia, A-R syndrome, and SWS; however, the success rates are lower. Trabeculectomy and glaucoma tube shunt surgery should be reserved for congenital glaucoma cases in which goniotomy or trabeculotomy has failed or for cases in which angle surgery is not appropriate. Cyclodestruction is necessary in some intractable cases, but because of the risk of phthisis bulbi, it should be avoided if possible.
Glaucoma surgery in children poses unique difficulties. For example, in PCG, the anatomical landmarks are distorted in the buphthalmic eye, and the thin sclera presents additional difficulties during trabeculotomy and trabeculectomy. The surgeon performing glaucoma surgery in pediatric patients should be experienced in handling these challenges and able to provide the necessary environment for evaluating these patients postoperatively. Additional surgery is often required, so the surgeon should also develop a long-term plan in order to keep surgical options available for the future and to minimize the risk of visual compromise.
The decision to proceed with angle surgery is often made during an EUA; ideally, if glaucoma is diagnosed, angle surgery is performed during the same anesthesia session in order to minimize the number of general anesthesia exposures for the child. If both eyes have uncontrolled glaucoma it is the standard of care to perform bilateral surgery in the same session. If angle surgery is anticipated, it is best not to dilate the eye during the EUA in order to protect the lens during the surgical procedure.
In a goniotomy, the angle is visualized with a surgical gonioscopic contact lens, a needle or appropriate blade is passed across the anterior chamber, and a superficial incision is made in the trabecular meshwork (Video 11-1, Fig 14-11). As mentioned, a clear cornea is required in order to visualize the angle.
Courtesy of Ken K. Nischal, MD.
Go to www.aao.org/bcscvideo_section10 to access all videos in Section 10.
In an ab externo trabeculotomy, Schlemm canal is cannulated from an external approach, and the trabecular meshwork is opened by breaking through Schlemm canal into the anterior chamber. The procedure begins with creation of a conjunctival flap, beneath which a partial-thickness scleral flap is created, similar to a trabeculectomy. Beneath that partial-thickness scleral flap, the surgeon identifies Schlemm canal, either by creating a radial incision into the scleral-corneal junction or by dissecting a deep scleral flap and noting the canal at the edges of this flap. Alternatively, the surgeon can identify the canal edges after unroofing the Schlemm canal by creating a single deep scleral flap. The surgeon inserts a rigid instrument (trabeculotome) into Schlemm canal and then rotates it into the anterior chamber (Fig 15-11), tearing the trabecular meshwork (Video 11-2). Alternatively, a 6-0 polypropylene suture or a fiber-optic microcatheter can be fed through Schlemm canal for its entire 360° circumference and pulled tautly into the anterior chamber (Video 11-3). There are other commercially available devices to perform an ab interno trabeculotomy. When performing a trabeculotomy, the surgeon must take care to avoid creating a false passage and entering the subretinal or suprachoroidal space.
Figure 11-14 Illustration of a goniotomy incision as seen through a surgical contact lens.
(Illustration courtesy of Mark Miller.)
Figure 11-15 Trabeculotomy. A, Illustration of the probe as it is gently passed along Schlemm canal, with little resistance for 6–10 mm. B, By rotating the probe internally (arrow), the surgeon ruptures the trabecular meshwork and the probe appears in the anterior chamber with minimal bleeding. C, photograph of the trabeculotome used in ab externo trabeculotomy allows the surgeon to open the angle over 1 quadrant.
(Parts A and B reproduced and modified with permission from Kolker AE, Hetherington J, eds. Becker-Shaffer’s Diagnosis and Therapy of the Glaucomas. 5th ed. Mosby; 1983. Part C courtesy of JoAnn A. Giaconi, MD.)
VIDEO 11-2 Trabeculotomy over 1 quadrant.
Courtesy of Young Kwon, MD, PhD.
VIDEO 11-3 Trabeculotomy over 360°.
Courtesy of JoAnn A. Giaconi, MD.
Many surgeons inject viscoelastic into the anterior chamber at the start of goniotomy and trabeculotomy in order to prevent collapse of the chamber and to tamponade bleeding intraoperatively. To prevent a postoperative spike in IOP, thorough removal of the viscoelastic at the end of the procedure is necessary.
The success rates of these 2 angle surgeries are similar, but each procedure has its advantages (Table 11-12) and disadvantages. Complications associated with these procedures include hyphema, infection, iris damage, lens damage, and uveitis. Descemet membrane may be stripped during a trabeculotomy.
Table 11-12 Comparison of the Advantages of Goniotomy and Trabeculotomy
Angle surgery has a success rate of 70%–80% in infants presenting with PCG between 3 and 12 months of age; this success rate includes repeated angle procedures, which are common for this disease. Trabeculectomy or tube shunt surgery should be considered after 2 or more angle surgeries fail to control the IOP or when adjunctive medical therapy is inadequate.
Trabeculectomy and tube shunt surgery
If angle surgery is not successful, the surgeon must take several factors into account when deciding between trabeculectomy and tube shunt surgery as the next procedure. Trabeculectomy has a low success rate in children younger than 2 years and in aphakic eyes. Failure rates are high without the use of antifibrotics, but serious risks of bleb leaks and bleb infections are associated with the use of these agents. Due to the risk of blebitis and endophthalmitis, mitomycin C (MMC)–augmented trabeculectomy should be performed with caution in pediatric patients who are too young to understand good hygiene, which is necessary to minimize the risk of infection.
Tube shunt surgery is useful for lowering IOP, has higher success rates in children compared to trabeculectomy, and is associated with a lower risk of bleb-related infections. Success rates vary with different tube shunts, diagnoses, and patient ages. Complications include anterior migration of the tube with resultant corneal damage, tube blockage, tube erosion, infection, cataract, motility disturbances, bleb encapsulation with elevated IOP, and pupil distortion. In small eyes, the surgeon must ensure the posterior aspect of the drainage device plate does not compress the optic nerve. IOPs are usually higher after implantation of these devices than after successful trabeculectomy, and most children need to continue using topical ocular hypotensive medications, as is the case for adults.
In children, cyclodestruction (discussed in Chapter 13) is reserved for cases refractory to other surgical and medical treatments. When these procedures are performed in pediatric patients, general anesthesia is required. The rate of complications is lower with cyclodestructive laser procedures than with cyclocryotherapy. A disadvantage of cyclodestructive procedures is the difficulty in titrating the results. Another disadvantage is the risk of serious complications—which include hypotony, uveitis, retinal detachment, phthisis bulbi, and blindness. The most common cyclodestructive modalities currently used are transscleral and endoscopic cyclophotocoagulation (ECP) with the diode laser. ECP is particularly useful in eyes with distorted anterior segment anatomy and in eyes with prior unsuccessful transscleral cyclophotocoagulation. Either procedure can be very useful for providing additional IOP lowering after tube shunt surgery.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.