The purpose of this chapter is to outline a therapeutic and surgical approach to the management of congenital and pediatric glaucoma. This chapter does not substitute for experience in handling these sometimes complicated surgical problems. Because the initial surgery for these problems is often the procedure that has the highest likelihood of success, and because the infant or child faces the prospect of a lifetime of impaired vision should the surgery be unsuccessful, the management of these patients is best left to those experienced with these procedures. The postoperative management of congenital glaucoma in reality lasts a decade or more (with periodic examinations under anesthesia, amblyopia therapy, contact lens fittings, and so forth). These complicated problems should be managed using a team approach for the patient's benefit.

In infants less than 3 or 4 months of age, it is usually possible to perform tonometry using either a hand-held Goldmann applanation tonometer or an electronic tonometer, the Tono-Pen (Mentor Ophthalmics, Norwell, MA). The Schiøtz tonometer is relatively inaccurate when used to measure the intraocular pressure (IOP) of an infant eye and should be used only to gauge a general range of IOP. The young infant should be swaddled and held in its mother's arms while the eyelids are gently pried apart to perform tonometry. The Tono-Pen device, which has a very small (about 2 mm) measuring surface, is well suited to the small intrapalpebral fissures of an infant⁵ and can measure IOP without placing undue pressure on the lids; the use of a lid speculum can often be avoided. The observer's head does not need to be right next to the patient's, which can alarm some children. The Tono-Pen has been found to be accurate compared with both cannulated cadaver eyes and Goldmann tonometry,^6,7 but no studies exist to assess its accuracy in infant eyes.

The office measurement of an IOP much greater than 20 mmHg in a calm, resting infant is suspicious for glaucoma when other signs and symptoms suggest the disease,⁸ as is an asymmetry of more than 5 mmHg in suspected unilateral or asymmetric cases. IOP measurements taken when the child is crying usually cannot be interpreted, because a nonglaucomatous infant can have an IOP in the forties or fifties when crying vigorously and squeezing the eyes shut.

Funduscopy is at the heart of the diagnosis of congenital glaucoma. It can be greatly facilitated by using a Richardson or Koeppe (Ocular Instruments, Bellevue, WA) diagnostic infant gonioscopy lens that has no central depression. These lenses permit good visualization of the disc, even through a small pupil.

When the diagnosis of glaucoma is strongly suspected on the basis of the office evaluation, an examination under anesthesia should be recommended to the child's parents. Once the diagnosis is firmly established, the parents will be in a state of shock, unwilling to believe that their young child has a potentially blinding eye disease. The ophthalmologist should devote a significant amount of time to the counseling and education of the child's parents regarding the diagnostic and surgical plan that will be recommended. It must be emphasized to the parents at the outset that although the surgery is usually highly successful, a decade or more of follow-up will be necessary. Frequent examinations under anesthesia, amblyopia therapy, and other interventions are part of this long follow-up care, particularly in early childhood. Because some of the infantile and pediatric glaucomas represent genetic diseases,^9–11 with subsequent siblings at increased risk for the disease, appropriate counseling by a clinical geneticist familiar with ophthalmic disease should be arranged.

Congenital and pediatric glaucomas are ophthalmic emergencies, and in most cases an examination under anesthesia and probable surgery should be scheduled within 24 to 72 hours of the initial diagnosis. When for logistical or medical reasons this proves impossible, the IOP can be lowered somewhat using aqueous suppressant medications. Topical β-adrenergic antagonists can often be safely used on an every-12-hour dosage schedule, but because the potential for systemic side effects is increased in a small infant, the lowest dose should be used initially, and the infant must be carefully monitored.^12–14 Carbonic anhydrase inhibitors can also be used. Acetazolamide can be administered parenterally or orally (5 to 10 mg/kg every 6 hours). For outpatient use, the pharmacist will usually find it easiest to compound an elixir based on the parenteral powder; as much as 500 mg can be made up in 5 ml of strongly flavored elixir, but 250 mg/5 ml is more palatable. The elixir is stable for about 1 week at room temperature; refrigeration improves the taste but does not lengthen stability. In adults, the topical carbonic anhydrase inhibitors dorzolamide (Trusopt) and brinzolamide (Azopt) achieve IOP-lowering comparable to the systemic use of acetazolamide and additive to β-blockers; there are no published reports regarding their efficacy in infants, however.

The α₂-agonist brimonidine (Alphagan) should be avoided in infants. After several reports of near-fatal apnea in young infants after dosing with brimonidine, the US Food and Drug Administration ordered relabeling of the drug to indicate its contraindication in small children. Although similar problems have not been reported with apraclonidine (Iopidine), because it is in the same class of medications it too should probably not be used in young children.

Latanoprost (Xalatan), a prostaglandin F₂α analog, has proved extremely useful in the management of glaucoma in adults; in children, however, it appears less useful. Enyedi and coworkers¹⁵ found a clinically relevant IOP response in only a small portion of their patients, an experience mirrored in my practice. Altuna and colleagues¹⁶ found similar disappointing results in patients with glaucoma associated with Sturge-Weber syndrome.

Medical therapy of congenital glaucoma is not recommended for routine use and should be used only if an examination under anesthesia and surgery must be deferred. It is far better to proceed promptly with the definitive evaluation and treatment.

EXAMINATION UNDER ANESTHESIA

General anesthetics are known to have a potent effect on IOP in both normal and glaucomatous persons. The anesthesiologist responsible for administering the general anesthetic in these cases should be familiar with the issues involved and willing to work with the surgeon to obtain the most useful information possible during the crucial first few minutes of anesthesia.

Virtually all of the inhalational anesthetics are known to depress the IOP within minutes of administration.¹⁷ Ketamine HCl slowly elevates the IOP as deeper anesthesia is attained.^18,19 The benzodiazepines do not appear to have a significant effect on IOP when used in preoperative doses. Midazolam HCl (Versed) is often used as a preoperative sedative in children, and in many cases the child is sufficiently sedated with this medication to perform a quick IOP measurement before the administration of an inhalational general anesthetic. Such a measurement, with the child resting comfortably but not under the influence of the potent inhalational anesthetics, is probably the most accurate. If such a situation cannot be achieved, as in the case of a highly agitated infant or toddler, the anesthesiologist should be aware that it is preferable for the surgeon to measure the IOP as early as possible during the induction of general anesthesia (Fig. 2). At this point in the anesthetic induction, however, airway management is of paramount importance, and the surgeon must defer to the judgment of the anesthesiologist as to when measurements can safely be taken. In most cases, endotracheal intubation is appropriate.

Table 1 lists the information that should be obtained during an initial or follow-up examination under anesthesia. Once the initial IOP measurements are made, the surgeon should tell the anesthesiologist what will remain to be done during the rest of the examination if surgery is not planned. Portions of the examination that require a clear media, such as ophthalmoscopy, retinoscopy, and fundus photography, should be performed first, followed by axial length measurement, gonioscopy, and corneal diameter measurements.

TABLE 1. Essential Information for the Examination Under Anesthesia

  Intraocular pressure
  Optic nerve examination (drawing, cup-to-disc estimation, photography if possible)
  Fundus examination
  Cycloplegic retinoscopy
  Axial length determination
  Corneal diameter (horizontal and vertical)
  Gonioscopy

Preoperative dilation should be avoided if the iris and anterior chamber angle appearance will be important factors in making the initial diagnosis, or if corneal opacities prevent any view of the fundus. However, ophthalmoscopy, retinoscopy, and fundus photography are important parts of the initial and subsequent evaluations of a child with glaucoma, and preoperative dilation with a short-acting mydriatic should be performed before entering the operating room to avoid prolonging anesthesia while waiting for dilation. If necessary, intracameral acetylcholine can be instilled during surgery to constrict the pupil to allow safe intraocular maneuvers.

Funduscopy is essential, with both a direct and an indirect ophthalmoscope. The Richardson or Koeppe diagnostic gonioscopy lenses can be of great assistance (Fig. 3). The lens is placed, and then direct ophthalmoscopy is performed through the lens. After this, the periphery should be carefully evaluated with an indirect ophthalmoscope.

Fundus photography of the optic nerve allows the surgeon to document the extent of progression of the disease (Fig. 4). It is well known that the optic nerve cupping seen in congenital and juvenile glaucoma can to some extent reverse itself,^20–22 and this can be used in some cases to gauge the success of therapy. Similarly, axial length measurements by ultrasonic biometry can help establish the degree of disparity between the two eyes, particularly in unilateral cases.^23–25 In many cases the disparity decreases after successful therapy,²³ and thus a constant or increasing disparity between the two eyes may signal a worsening clinical situation. The Bio-Pen hand-held ultrasonic biometric ruler (see Fig. 2) is a portable device that can be brought to the operating room for intraoperative biometry; because it is similar in size, operation, and appearance to the Tono-Pen, it can also be used in the office setting in young children who have become accustomed to IOP measurements being taken with that device.

Gonioscopy is a mandatory part of the examination under anesthesia. It allows the surgeon to identify the underlying congenital or juvenile glaucoma diagnosis and permits appropriate surgical planning. The Koeppe gonioscopic lens, introduced in 1919,²⁶ has significant advantages over the Zeiss four-mirror or Goldmann three-mirror gonioprism. Chief among these is the ability to compare simultaneously the gonioscopic appearance of two eyes in the same patient (see Fig. 3). The surgeon should be familiar with the gonioscopic findings in primary congenital glaucoma as well as the various secondary glaucomas seen in childhood. Gonioscopic photography can help document the appearance of the anterior chamber angle before and after treatment.

The cornea should be measured both horizontally and vertically, and the presence or absence of Haab's striae or other corneal abnormalities should be noted. Enlargement of the corneal diameter over time is worrisome for progressive buphthalmos, and some clinicians believe these measurements to be more useful than axial length determinations.²⁷ In many cases, however, these measurements are difficult to make accurately or consistently because of uncertain landmarks at the corneoscleral limbus.

Cycloplegic retinoscopy during follow-up examinations (both under anesthesia and in the office) are used to monitor for progressive axial myopia²⁸ and to provide the spectacle correction to be used in conjunction with patching or other amblyopia therapy.

TABLE 2. Surgical Options in Surgery for Pediatric Glaucoma

In cases of primary infantile glaucoma, several studies have demonstrated that goniotomy ab interno and trabeculotomy ab externo are essentially comparable, with surgical success rates approaching 80% to 90%.^29–31 McPherson and Berry³⁰ found that with multiple operations, both procedures controlled IOP in most patients, but more operations were required after goniotomy. Goniotomy ab interno is a simple and elegant procedure, but it requires excellent visualization of the anterior chamber angle. Trabeculotomy ab externo is no less elegant and can be performed in virtually all cases. Both procedures have been made much safer during the past decade by the introduction of viscoelastic materials. The surgeon who anticipates performing a significant amount of congenital glaucoma surgery should be familiar with both techniques.

If the clinical situation permits the use of either approach, the surgeon's personal preference and logistical considerations should dictate the choice. A goniotomy is greatly facilitated by a surgical assistant who is familiar with the procedure and understands what the surgeon is trying to visualize and achieve. A trabeculotomy, however, can be performed with a scrub nurse as the only surgical assistant.

The choice of surgical approach in the case of secondary pediatric glaucomas is more complicated. As ophthalmologists have become more aggressive about treating congenital cataract in early infancy, perhaps the most common secondary glaucoma seen in children today is that associated with surgical aphakia.^32,33 In this form of glaucoma, both open-angle and secondary angle-closure variants are recognized; it is thought that both may be the result of chronic, low-grade inflammation caused by residual lens material. In these cases, the surgeon is confronted with the dual challenge of lowering the IOP and maintaining aphakic correction to prevent the development of amblyopia. Careful preoperative gonioscopy is mandatory to determine whether (and where) a goniotomy should be attempted or whether the peripheral anterior synechiae present will lend themselves to goniosynechialysis (performed in a manner similar to goniotomy). Trabeculotomy ab externo should be avoided if extensive, broad peripheral anterior synechiae are present. Lysis of these adhesions by the trabeculotome can be associated with significant intraocular bleeding and can result in a slowly clearing vitreous hemorrhage that can be profoundly amblyogenic. In such cases, the implantation of an aqueous drainage device can be considered as a primary procedure. As will be discussed below, even though guarded filtration surgery with antimetabolite use has a reasonable chance of success in lowering pressure, it should probably be avoided because of the problems associated with extended-wear contact lens use in the presence of a filtration bleb.

In cases of inflammatory glaucoma in children and young adults where significant peripheral anterior synechiae are absent, trabeculodialysis has proven to be useful in some hands,^34,35 with success rates of 50% to 60%. This approach is attractive because it avoids the creation of a filtering bleb prone to endophthalmitis in patients taking long-term topical steroids.

Another secondary glaucoma seen in children is that associated with Sturge-Weber syndrome. Glaucoma presenting with this and related syndromes (e.g., Klippel-Trenaunay-Weber syndrome) at or shortly after birth is usually associated with an angle appearance similar to that of primary infantile glaucoma. Later presentation of glaucoma in this group of syndromes is probably associated with a combination of abnormal angle structure and elevated episcleral venous pressure. A variety of surgical approaches have been used in the management of this glaucoma.^36–40 In my experience, trabeculotomy ab externo, performed inferiorly or laterally to preserve the superior conjunctiva for subsequent filtering surgery, has been successful in most cases presenting in infancy.

Congenital aniridia is another syndrome associated with glaucoma for which many procedures have been attempted, with varying success.^41,42 In this syndrome, true agenesis of the iris is rare; in most cases, a tiny, hypoplastic iris can be identified on gonioscopy.⁴³ Although angle surgery can be successful in cases presenting in infancy,⁴² it is common for this iris stump to rotate anteriorly, closing off what little open angle remains, leading to late failures. Chen and Walton⁴⁴ have reported promising results using goniotomy to prevent the development of glaucoma in these children. Their findings highlight the importance of periodic examinations under anesthesia and gonioscopy in children with aniridia to monitor them for the early gonioscopic, IOP, and nerve changes associated with glaucoma. Aqueous drainage devices have proven extremely helpful in these difficult cases, and I have found it useful in several cases to perform a staged implantation of a drainage device at the same time as angle surgery in eyes at high risk of failure of the primary surgery. The staged device can be introduced into the anterior chamber with a low risk of hypotony or choroidal hemorrhage if it is needed at a later time.

More unusual syndromes associated with glaucoma, including Peter's anomaly, sclerocornea, and microcornea, are handled on a case-by-case basis. The results of surgery for these problems are dismal, particularly in unilateral cases, but in bilateral cases it is difficult for the surgeon to stand back and do nothing. These eyes usually must be tackled using a team approach, often combining a penetrating keratoplasty with a cataract extraction, vitrectomy, and aqueous drainage device. Such an aggressive approach may provide the patient with some ambulatory vision.

GONIOTOMY AB INTERNO

When Otto Barkan introduced goniotomy ab interno in the late 1930s,^45–47 the management of congenital glaucoma was revolutionized. Until then an incurable disease, congenital glaucoma was among the leading causes for admission to schools for the blind. The basic principles of the procedure have changed little since it was first described, but goniotomy has been made safer and more successful with the introduction of better instrumentation, viscoelastics, and the operating microscope.

Excellent visualization of the anterior chamber angle is needed to perform the procedure safely and accurately. Mild corneal edema can sometimes be overcome by denuding the cornea of its epithelium, either by blunt scraping or by topical alcohol and glycerin. Unfortunately, corneal clarity often worsens during the course of surgery. If the surgeon anticipates that visualization may become a problem during surgery, or if large Haab's striae or other corneal opacities prevent adequate visualization of the anterior angle structures, a trabeculotomy ab externo should be performed instead.

When a goniotomy is planned, the anesthesiologist should be informed that the surgeon and assistant will be manipulating the patient's head back and forth during the procedure, and that the endotracheal tube should be secured with this in mind. I have found a Rae-style endotracheal tube to be particularly useful in this respect.

It is technically easiest to perform a goniotomy over the nasal 120 degrees of the anterior chamber angle, using a temporal approach. This is the usual site of an initial goniotomy. The patient's head is turned away from the surgeon approximately 45 degrees from vertical and is secured firmly in place (Fig. 5). If the surgeon uses an operating microscope rather than loupes, the microscope head should be tilted to permit adequate visualization of the nasal anterior chamber angle once the gonioscopic prism is placed on the eye.

The assistant, who is seated across from the surgeon or at the head of the table, grasps the eye at the 6 and 12 o'clock positions with toothed forceps to rotate the eye nasally or temporally at will. Bridle sutures are usually not necessary. The surgeon then creates a limbal stab incision through the cornea just anterior to the corneoscleral limbus and injects a viscoelastic substance into the anterior chamber to deepen it.

Various operative gonioscopic prisms are available. The Hoskins-Barkan operating gonioprism (Ocular Instruments, Bellevue, WA) permits excellent visualization of the anterior chamber angle while permitting the assistant to maintain excellent control of the eye and the surgeon to introduce the goniotomy knife through the stab incision that has already been created. The lens is placed on the eye with balanced salt solution as the gonioscopic coupling agent.

Various goniotomy knives are available to perform a goniotomy ab interno; a sharp knife with a slight bevel to the handle is preferable. The knives that permit irrigation can be more difficult to manipulate and are not preferred. Some surgeons find them helpful to prevent collapse of the anterior chamber; however, when goniotomy is properly performed with minimal distortion of the corneal wound, collapse of the anterior chamber should not be a problem. If necessary, the chamber can be well maintained using a viscoelastic material.

The stab incision should be made small enough that the anterior chamber remains formed during the procedure. The surgeon then advances the knife across the anterior chamber angle, taking great care to avoid the crystalline lens (Fig. 6). Anterior movement of the lens indicates that the stab incision is gaping, permitting egress of the anterior chamber fluids. The surgeon should assess whether the knife handle is distorting the stab incision or whether the incision is too large; it can be partially closed with a temporary suture.

The abnormal mesodermal tissue that creates the restriction to aqueous outflow in infantile glaucoma has an almost translucent appearance, blurring and distorting the anterior chamber angle anatomy. Most infants have light blue or very transparent iris stroma, making the landmarks somewhat difficult to identify; In infants with primary congenital glaucoma, the iris root usually has a scalloped, almost serrated anterior edge that provides an excellent landmark for the surgeon. The surgeon uses the goniotomy knife to place an incision at the anterior aspect of the middle third of the trabecular meshwork, behind Schwalbe's line, starting at a point 180 degrees away from the corneal incision and rotating either clockwise or counterclockwise as appropriate (see Fig. 6). The assistant can rotate the eye slightly to permit the surgeon to extend the goniotomy incision peripherally without distorting the corneal incision. The knife is then flipped 180 degrees and the goniotomy is completed in the opposite direction.

If the incision is placed too far anteriorly, the goniotomy will not function; placed too far posteriorly, the incision will incise only peripheral iris and iris root, causing a peripheral iridotomy, iridodialysis, or intraocular hemorrhage, making further surgery difficult at best. The surgeon should be able to visualize directly the iris root fall gently posteriorly as the abnormal mesodermal attachments are lysed. The goniotomy can be performed in this manner over approximately 120 degrees of nasal angle centered 180 degrees away from the corneal stab incision. A small amount of bleeding is common during a goniotomy, but the amount seen is usually less than occurs during a trabeculotomy.

At the conclusion of the procedure, any viscoelastic that remains in the eye that can be easily flushed from the eye and so removed. The corneal stab incision, although usually self-sealing, can be closed with a single 10-0 nylon suture. Subconjunctival injections of a steroid and antibiotic are at the discretion of the surgeon.

In some cases, a single goniotomy involving the nasal 120 degrees of the anterior chamber is not sufficient to control intraocular pressure, and a second goniotomy may be subsequently performed over the temporal or inferotemporal angle. This has raised the possibility that performing two simultaneous goniotomies might be advantageous. In a prospective, randomized study of infants with bilateral infantile glaucoma, Catalano and coworkers⁴⁸ found no significant difference between eyes that underwent a single goniotomy at initial surgery versus those that underwent two simultaneous procedures.

TRABECULOTOMY AB EXTERNO

Trabeculotomy ab externo was introduced in the 1960s^49–51 after it was recognized that an external approach was needed for cases of congenital glaucoma in which the cornea was too cloudy to permit the safe performance of a goniotomy ab interno. Like the goniotomy, trabeculotomy ab externo has benefited from the introduction of viscoelastics and the operating microscope, which have made the procedure highly successful and for all intents and purposes equivalent to goniotomy.

The child's head is prepared and draped in a manner similar to that for adult eye surgery. A superior rectus bridle suture is placed to depress and expose the superior limbal region. Rarely, a lateral canthotomy must be performed to provide adequate exposure in small or premature infants.

A limbal peritomy is performed straddling the 12 o'clock position (Fig. 7). A partial-thickness scleral flap (either rectangular or triangular) is then created in the 12 o'clock meridian in such a manner as to sit astride the corneoscleral junction (Fig. 8). The surgeon should be familiar with the three-dimensional anatomy of the limbal region and should recognize that Schlemm's canal will lie just below the transition from white scleral fibers to the blue corneal fibers. Using a microsurgical blade, the surgeon creates a radial incision measuring approximately 2 mm long that straddles the corneoscleral limbus. Carefully dissecting down layer by layer, Schlemm's canal is unroofed. Entry into Schlemm's canal can be confirmed by the egress of a small amount of aqueous humor without the shallowing of the anterior chamber; such a shallowing would indicate that the anterior chamber had been directly violated.

A short length of 6-0 black nylon suture material should be used to cannulate Schlemm's canal. The cut end of the suture can easily be smoothed by the application of heat from a disposable battery-operated cautery. The nylon suture must not be forcibly introduced into Schlemm's canal, lest a false passage be created. The suture will pass easily if Schlemm's canal is correctly cannulated, and intraoperative gonioscopy with either a Koeppe lens (Fig. 9) or a Zeiss four-mirror gonioprism (Fig. 10) can be used.

Once Schlemm's canal is correctly identified and cannulated in both a clockwise and counterclockwise manner, a trabeculotome with the appropriate curvature for the particular eye is chosen. The lower probe of the trabeculotome is then introduced into the previously identified opening into Schlemm's canal. It is then passed along Schlemm's canal in a curvilinear fashion, using the upper probe as a guide to confirm the location of the lower one (Fig. 11), making certain that the trabeculotome is oriented in such a way that on its rotation the trabeculotome will rupture Schlemm's canal internally and the probe will pass parallel to the iris and not impinge on the crystalline lens (Figs. 12 and 13).

This maneuver is usually associated with a small amount of bleeding and egress of aqueous humor from the base of the trabeculotome probe. Care should be taken to avoid distorting the incision so that the anterior chamber does not collapse. If it does, it may be necessary to place some viscoelastic in the anterior chamber so that this maneuver can be carried out in the opposite direction without risk to the crystalline lens.

Once the trabeculotomy has been performed on either side of the incision, the overlying scleral flap can be closed with one or more 10-0 nylon sutures. The overlying conjunctiva is then tacked over the scleral flap with a fine absorbable suture. Subconjunctival injections of steroid and antibiotic are at the discretion of the surgeon.

Trabeculotomy carried out in this manner will open the angle over almost 180 degrees, straddling the incision at the 12 o'clock position. Another technique of performing a trabeculotomy ab externo over 360 degrees has recently been described,⁵² using a nylon suture to cannulate the entire circumference of Schlemm's canal (Figs. 14 and 15). This technique has two significant advantages: no metallic instruments are introduced into the anterior chamber, reducing the chance of lens damage, and the entire anterior chamber angle is treated, eliminating the need for additional angle surgery if the primary surgery fails. Unlike goniotomy,⁴⁸ the question of whether a complete 360-degree trabeculotomy is superior to 180 degrees has not been resolved.

GUARDED FILTRATION PROCEDURES (TRABECULECTOMY)

Although guarded filtration procedures (trabeculectomy) have become the mainstay of glaucoma surgery in adults, their use in infantile and pediatric glaucoma is limited. The exuberant healing response of infants and children greatly reduces the success rate of filtration surgery in this patient population, and it is difficult to defend guarded filtration as a primary procedure when the success rates for trabeculotomy and goniotomy approach 90%.

The recent introduction of antimetabolites such as 5-fluorouracil^53–55 and in particular mitomycin-C⁵⁶ has given the surgeon additional tools to control this exuberant healing response and may very well allow the glaucoma surgeon to achieve the success rates seen in the adult population. Nonetheless, guarded filtration is a procedure fraught with problems in the pediatric age group.

The filtration bleb that develops after a guarded filtration procedure in which antimetabolites have been used is usually thin and cystic and prone to infection.⁵⁷ One recent study of the adult population estimated the risk of a repeat hospital admission for filtration bleb infection or endophthalmitis to be up to 1.2%.⁵⁸ In the pediatric age group, this level of risk is probably unacceptable. Al-Hazmi and colleagues⁵⁹ performed either trabeculectomy or combined trabeculotomy/trabeculectomy in 254 eyes of 180 pediatric patients. They reported complications including cystic blebs, bleb leaks, flat anterior chamber, and cataract and found that children younger than 2 years had fewer complications but higher failure rates. Complications increased with time after surgery, and they cautioned that because bleb thinning increases with time after surgery, additional problems could be anticipated with longer follow-up. This mirrors the findings and conclusions of Beck and colleagues,⁶⁰ who found trabeculectomy generally effective in older children but also cautioned that late-onset bleb-related endophthalmitis would become a substantial risk in this population.

Azuara-Blanco and coworkers⁶¹ described a series of 21 pediatric patients undergoing mitomycin C-augmented trabeculectomy; they reported reasonable short-term success in phakic patients but no success in aphakic eyes. Freedman and colleagues⁶² found that although guarded filtration procedures with mitomycin C, 5-fluorouracil, and postoperative suture lysis were viable in older children, the addition of these adjunctive measures did not provide any convincing improvement in the success of the procedures in pediatric patients and may have increased the complication rate.

A guarded filtration procedure can be considered if two or more attempts at angle surgery (e.g., trabeculotomy or goniotomy) have been unsuccessful. If significant buphthalmos is present, the surgeon must be particularly cautious when developing the partial-thickness scleral flap because the sclera in these eyes is extremely thin. The use of adjunctive antimetabolites probably increases the success rate of these procedures, albeit at the cost of higher long-term complication rates. The surgeon should take into consideration the social situation of the child. If it is unlikely that the parent or responsible guardian will take action at the earliest sign of a bleb infection or endophthalmitis, filtering surgery is inadvisable.

Guarded filtration procedures should probably be avoided altogether in cases of childhood glaucoma associated with surgical aphakia. The need for extended-wear contact lenses for aphakic correction and the prevention of amblyopia raise the risk of devastating endophthalmitis to an unacceptably high level if a filtration bleb is present, particularly given the poor hygiene of toddlers and young children. In general, a guarded filtration procedure should be considered in the older child in whom juvenile glaucoma presents anew, or in whom prior angle surgery has failed.

GLAUCOMA DRAINAGE DEVICES

The introduction of the Molteno implant in the early 1970s represented a new and promising option for eyes in which conventional angle surgery had failed.⁶³ The Molteno implant and similar devices have saved many eyes that were otherwise destined to become blind and painful.

These procedures involve the placement of a small-caliber silicone drainage tube into the anterior chamber or, in the case of an aphakic, vitrectomized eye, into the posterior chamber through the pars plana. This tube is connected to an external bleb-maintaining device that is designed to create and maintain a potential space between the sclera and conjunctiva. Aqueous filtration then occurs through the surface of this bleb. Studies in primate eyes⁶⁴ have demonstrated that the degree of pressure-lowering effect is roughly proportional to the surface area of this external potential space.

Each of the glaucoma implants has taken a different approach in terms of the design of the external portion of the device. The Molteno implant (IOP, Inc, Costa Mesa, CA) uses an acrylic disc that is sutured to the sclera in the equatorial region. The Baerveldt glaucoma implant (Pharmacia & Upjohn, Peapack, NJ) uses a flexible Silastic rubber device shaped to conform to the surface of the globe to maintain a bleb around the equatorial region of the eye. This device is available in three sizes (250, 350, and 425 mm²) and can be implanted in a single quadrant. A 350-mm² implant with a right-angled bend in the silicone tube has recently been marketed for use in conjunction with pars plana vitrectomy;⁶⁵ I have found this device useful in aphakic eyes undergoing a complete vitrectomy and removal of residual lens material. The smaller 250-mm² implant is well suited to pediatric cases, although when an eye comes to undergo such a procedure it has often grown to almost adult size or larger, permitting the implantation of a larger device.

One of the many technical challenges in drainage implant surgery is the avoidance of profound postoperative hypotony and its attendant complications. The Ahmed Valve Implant (New World Medical, Inc, Rancho Cucamonga, CA) uses a Silastic valve to prevent early postoperative hypotony. Englert and colleagues⁶⁶ reported promising results in a series of pediatric cases. For devices without a valve, the silicone tube portion is usually occluded in a temporary manner by using an absorbable suture such as 8-0 polyglactin (Vicryl). Techniques for the temporary occlusion of the tube that require later lysis by the argon laser or surgical manipulation are impractical for children. In all cases, the tube must be covered with donor sclera or other appropriate material to prevent its erosion and externalization through the conjunctiva.^67,68 Although in adults some surgeons place the tube in the bed of a partial-thickness scleral flap, this technique should be avoided in infants and children; the sclera of a buphthalmic eye is extremely thin, and erosion of a silicone tube into or out of the eye through the thinned scleral tissue has been reported.^69,70

If the tube is placed into the anterior chamber, care must be taken to avoid impinging the crystalline lens, because a cataract is likely to develop. The long-term safety and efficacy of these devices are not known at present, but some have been in place in adult patients for almost two decades. The placement of these devices should not be avoided in children for these reasons, but the parent or responsible adult must be advised of the many unknown aspects of these procedures.

Among the currently available aqueous drainage devices, glaucoma surgeons have the longest experience in the congenital and juvenile glaucomas with the Molteno implant.^71–73 The Baerveldt implant has several attractive aspects to its design: a large surface area for aqueous filtration can be created in a single quadrant, and the soft, pliable nature of the implant facilitates its introduction in the tight surroundings of the pediatric orbit. Reports of strabismus associated with the Baerveldt implant,⁷⁴ presumably related to the large equatorial filtration bleb the device creates, may limit its usefulness in eyes with good visual potential, but strabismus has been reported with the other aqueous drainage devices,^75,76 and it remains to be seen whether this implant has more problems than the others in this regard. The fenestrated version of the Baerveldt device, which prevents the filtration bleb from growing too large, may partially solve this problem.

CYCLODESTRUCTIVE PROCEDURES

Long a mainstay of therapy when conventional incisional surgery has failed, cyclodestructive procedures have usually been perceived as procedures of last resort because of the high incidence of phthysis bulbi thought to be associated with cyclocryotherapy. Wagle and colleagues⁷⁷ found that cyclocryotherapy yielded a success rate of 66% at 6 months, dropping to 44% at longer follow-up. The main complication encountered was phthysis, particularly in eyes with aniridia.

The introduction of other modalities of ciliary body ablation, namely Nd:YAG and infrared wavelength diode lasers, promises to give the surgeon more control over the amount of ciliary body that is ablated at each sitting. At present, it appears that laser cyclophotocoagulation, whether by contact or noncontact techniques, produces a lower rate of phthysis bulbi than cyclocryotherapy. Bock and coworkers⁷⁸ found diode laser cyclophotocoagulation to be a useful treatment in pediatric cases, although many of the patients required retreatment. No prospective, randomized clinical study has been performed comparing the two modalities, and it is unlikely that one will ever be performed. Because of the pain associated with cyclodestructive procedures, they are usually performed under general anesthesia in the pediatric age group. I find it useful to place a long-acting retrobulbar block with bupivacaine (Marcaine) while the child is asleep to control postoperative pain, along with a subconjunctival injection of triamcinolone (Kenalog) to provide corticosteroid coverage during the early postoperative period. In general, these procedures are reserved for eyes with poor visual potential.

The patient should be examined during the first 24 hours after surgery and the IOP measured if possible. If a significant amount of viscoelastic was left in the eye, the IOP can be as high or higher than the preoperative level; it may be necessary to prescribe aqueous suppressant medication for several days until the viscoelastic has cleared the eye. In most cases, any viscoelastic or blood that was present in the eye at the conclusion of the surgery will have cleared within the first 24 hours.

Although in a small infant it may be possible to assess the IOP accurately in the office a few days or weeks after the surgery, it is advisable to perform a complete examination under anesthesia some 4 to 6 weeks after the initial surgery to gauge the success of the procedure more formally and to document the status of the eye. In particular, an examination under anesthesia will permit the ophthalmologist to perform a careful cycloplegic refraction and obtain color fundus photographs of the optic disc that will serve as a baseline for future examinations.

In some cases, the administration of chloral hydrate syrup (25 to 50 mg/kg) in the office can facilitate the performance of many if not all of the aspects of an examination under anesthesia outlined above.⁷⁹ Although chloral hydrate sedation is quite safe, the drug should be administered only in a setting where equipment and trained staff are available for emergency airway management in the case of respiratory distress.

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