Goniotomy, the classic initial angle surgery for congenital/infantile glaucoma, refers to the creation an internal cleft in trabecular tissue under direct visualization through the cornea in order to allow access of aqueous humor to Schlemn’s canal [16]. Typically this is performed using a specially-designed direct gonioscopic lens and gonitomy lens knife under the operating microscope with the patient’s head turned such the desired segment of angle to be treated is brought into view. A sector of the angle is typically treated, and the procedure can be repeated in another sector if needed. Because excellent visualization of the angle is needed, classic gonitomy cannot be performed in the setting of significant corneal scarring and/or haze. Visualization can sometimes be improved by removing corneal epithelium and/or a short course of oral carbonic anhydrase inhibitor; in addition, endoscopic gonitomy is an option in such situations [17-19]. Besides congenital/infantile and early developmental glaucoma, there is also a role for goniotomy in uveitic glaucoma of recent onset [20]. Western series of congenital/infantile and early developmental glaucoma generally report high success rates from single or multiple goniotomies, often over 90% [21-24]. However, the procedure is much less successful for cases with congenital onset or onset after 2 years old, reported as 30% in one large Western series when restricted to these ages [22]. Complications are typically related to intraoperative hyphema or intraoperative technique (e.g., iatrogenic crystalline lens trauma). An advantage of goniotomy over many other glaucoma surgical procedures is that it spares the conjunctiva, thus preserving un-operated conjunctiva for future surgical procedures. Although goniotomy is not a typical choice for aphakic glaucoma or open-angle juvenile glaucoma, some authors suggest its use for these diagnoses [25, 26]. In addition, it has also been suggested that there may be a role for prophylactic goniotomy in selected aniridia patients without glaucoma [27]. One report described the use of Q-switched neodymium:yttrium aluminium garnet (Nd:YAG) laser to perform photodisruptive goniotomy and avoid invasive intraocular surgery [28], but this has not been further studied.

External trabeculotomy [29] is classically the initial procedure of choice for congenital/infantile glaucoma with a scarred or hazy cornea that precludes goniotomy; such severe disease is more common in the Middle East and South Asia [30-32]. The only specialized instrument required for the procedure is the trabeculotome (Fig. 6); other needed instrumentation is standard for ophthalmic microsurgery. After the overlying conjunctiva is dissected, Schlemn’s canal is opened (either directly or underneath a scleral flap) and is cannulated with the trabeculotome. The trabeculotome is then rotated through the trabecular meshwork into the anterior chamber. Classically a sector of the angle is treated, and the procedure can be repeated in another sector if needed. Western series report success rates in primary congenital/infantile and early developmental glaucoma comparable to and sometimes higher than those for goniotomy [23, 24]. Although disease in the Middle East is often more severe and difficult to treat than in Western populations, trabeculotomy can be effective (Fig. 7); a major determinant of success is the degree of angle maldevelopment. One variation of the procedure involves use of a prolene suture rather than a trabeculotome in order to cannulate Schlemn’s canal x 360 degrees and perform a 360 degree “suture” trabeculectomy, with or without illuminated microcatheter guidance [33, 34]. Complications are typically related to intraoperative hyphema or intraoperative technique (e.g., iatrogenic crystalline lens trauma, iridodialysis). A disadvantage of trabeculotomy as compared to goniotomy is manipulation (and thus later scarring) of conjunctiva, which may make future glaucoma surgeries more difficult in the operated conjunctival quadrant.

Trabeculectomy, the creation of an opening into the anterior chamber under a superonasal or superotemporal scleral flap, is familiar to most ophthalmologists as a common treatment for glaucomas with a well-formed anterior chamber. Failure occurs more in children than in adults [35]. Because of the rapid and robust healing response of children [36], the antimetabolite mitomycin-C is often used during pediatric trabeculectomy although its use increases the potential for complications, particularly later-onset infection [37-41]. In selected cases, some authors use post-operative suture lysis and/or the antimetabolite 5-flourouracil to further modulate healing [42-44]. However, currently there are no prospective data comparing pediatric trabeculotomy with antimetabolite to pediatric trabeculo-tomy without antimetabolite. Factors correlated with trabe-culectomy bleb failure include age less than one year and aphakia [37, 42]. The literature suggests that fornix-based flaps are superior to limbus-based flaps in children [45]. This has been my experience as well; I have found noticeably better long-term blebs (more diffuse, less ischemic, less leakage) with fornix-based blebs (and diffusely posteriorly-applied mitomycin-C) (Fig. 8). Because of the possibility of late-onset blebitis/endophthalmitis [37-39], all families with children that have had trabeculectomies, particularly those done that have been done with antimetabolite, need to be aware that the child should be examined immediately if red eye develops in the operated eye. Late-onset blebitis following mitomycin-C use may be more common in children than in adults [37-39]; however, as mentioned above, how the conjunctiva is dissected and how mitomycin-C is applied is a factor in the incidence of this complication [45, 46]. Other complications following trabeculectomy in children are similar to those of adults, such as anterior chamber shallowing, bleb leak, hypotony, suprachoroidal hemorrhage, etc. Delayed suprachoroidal hemorrhage is a rare complication in children but potentially devastating and may be more likely following mitomyocin-C use [47]. Tra-beculectomy by an internal approach (using the Trabectome electrocautery system and avoiding a conjunctival incision) is a newer technique that has been used in adults and avoids complications associated with standard penetrating trab-eculectomy but to date has not been studied in children [48].

Combined trabeculotomy-trabeculectomy has been advocated as an initial procedure for severe congenital/infantile glaucoma [49-53]; however, as there are no prospective data demonstrating this combined procedure to be superior to either procedure alone some ophthalmologists use trabeculotomy alone [30, 54-57] or trabeculectomy alone [49, 54, 58-60] for such cases. The combined procedure can be done with [52] or without [53] mitomycin-C. Complications are similar to those of the individual procedures alone.

The anatomic goal of non-penetrating procedures such as deep sclerectomy and viscocanalostomy is to create an intrascleral space by removal of a deep scleral flap, the external wall of Schlemm's canal adjacent to trabecular meshwork, and external corneal stroma adjacent to Descemet's membrane. Aqueous humor then leaves the anterior chamber through the intact trabeculo-Descemet's membrane into the scleral space reservoir, from where it egresses into different pathways [61]. Deep sclerectomy has been used with varying degrees of success in developmental glaucoma [62, 63] and seems to be a good option for uveitic glaucoma [64]. Because it is a non-penetrating surgery the potential for complications is less; however, the procedure requires a certain degree of normal angle structure, requires a certain degree of surgical experience, and tends not to lower IOP as much as penetrating procedures. One recent study advocated combining deep sclerectomy with trabeculectomy for better results [65].

Glaucoma drainage devices are useful when angle surgery and trabeculectomy or deep sclerectomy are not good options and there is a relatively clear view of the anterior chamber [66]. The Ahmed glaucoma valve (New World Medical, Inc., Rancho Cucamonga, CA) is popular in pediatrics because of its theoretical valve mechanism and the availability of smaller flexible sizes [47, 67-71]. Adjunctive ocular anti-hypertensive drops are often still needed after device implantation for IOP control. Silicone seems to be a better tolerated material than polypropylene although plate encapsulation that affects pressure control can occur with either material [69]. Tube immediately posterior to the scleral entrance site needs to be covered with a material such as pericardium or sclera to prevent tube exposure through the conjunctiva. Some ophthalmologists apply mitomycin-C to the subconjunctival region where the the plate will be implanted in an attempt to prevent thick encapsulation that can affect pressure control; however, there is no evidence that its use in children improves outcomes while there is evidence that its use in children promotes failure or complication [47, 70]. In my experience when plate encapsulation occurs, surgically removing a portion of the encapsulation from the posterior plate can be useful. Tube retraction and anterior tube migration towards the cornea are recurrent problems in young children, the latter being particularly problematic as it can lead to exposure of the tube and infectious endophthalmitis (Fig. 9). Although one prospective study suggested Ahmed valve implantation can offer better IOP control than trabeculectomy in children less than 2 years old, approximately one-third of the implanted cases had post-operative anterior tube migration requiring intervention [72]. In our series, within 2 years post-operatively anterior tube migration occurred in 26% of eyes implanted with an Ahmed glaucoma valve before 2 years of age [71]. In my experience this complication can be minimized if care is taken to insert the tube parallel to and just anterior to the iris, just abutting the iris; at the same time I leave the tube slightly longer than would be done in adults in anticipation of some expected tube retraction. Delayed suprachoroidal hemorrhage is a rare complication following Ahmed glaucoma valve implantation in children but may be more likely following Ahmed valve implantation in pediatric aphakes [47]. Failure of the Ahmed glaucoma valve can be related to plate encapsulation as mentioned above, fibrous ingrowth [73], or, in aphakes, vitreous plugging the tube, which can occur months to years after the procedure even if anterior vitrectomy was done (Fig. 10). If a glaucoma drainage device is still functioning but further IOP control is needed despite adjunctive ocular anti-hypertensive medication, implanting a second device is an option [74]. Glaucoma drainage devices other than the Ahmed glaucoma valve have also been used successfully in children [72, 75-78]. However, newer smaller implantable glaucoma stents and shunts have not been evaluated in this patient population [79].

The major cyclodestructive procedures are cyclocryo-therapy and cyclophotocoagulation, with the former rarely used since the advent of the latter. Cyclophotocoagulation – typically external application by a diode laser – is a destructive procedure that historically is a procedure of last resort, although some authors advocate its earlier use [80]. Re-treatments are often necessary in children [80-83]. Reasons include because the ciliary epithelium of children can recover after treatment and also because the distorted anatomy of buphthalmic eyes can result in intended treatment not actually being applied to the ciliary body. Ultrasound guidance when external treatment is applied can be useful in cases of distorted anatomy [84]. Although external cyclophotocoagulation is non-incisional, post-operative complications such as phthisis, uveitis, and scleral thinning are possible, especially in buphthalmic eyes that have had multiple prior surgeries (Fig. 11) [81, 82]. Endo-scopic cyclophotocoagulation seems to be a more precise technique; however, it is invasive, requires experience with the endoscope, requires an unobstructed endoscopic view of the ciliary processes, and is usually not a good option in phakic eyes [85-88].