Surgical Techniques in Ophthalmology: Glaucoma Surgery Ashok Garg, Boris Malyugin, Bojan Pajic, Tanuj Dada, Jorge L Alio, Jerome Jean Bovet, Roberto G Carassa, André Mermoud, Jes N Mortensen, Shlomo Melamed, Ehud I Assia, Ahmad K Khalil, CS Dhull, Gabor B Scharioth, Gabriel Simon
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Surgical Techniques in Glaucoma

Surgical Management of Congenital and Developmental GlaucomasChapter 1

Ahmad K Khalil
(Egypt)
Management of EODG is a challenging responsibility, which starts with early detection, and offering optimum surgical intervention and then going on for a life long follow up. The prognosis in this disease is related to the time of its initial presentation, initial surgical intervention, degree of optic nerve damage and later visual rehabilitation.
Early detection helps in avoiding harmful rise of IOP and possibly increases the success rate of surgery. Public awareness programs should include educating parents on presenting symptoms of EODG. A prompt thorough examination under general anesthesia, in the operating theatre to have the advantage of examination by the operating microscope, should be carried out. EODG is an ophthalmic emergency the surgeon should be ready for surgery that may be needed.
Surgery is the first line of therapy for EODG for the following reasons: 1) Since this type of glaucoma results from abnormal anatomical development of the anterior chamber angle, anatomical or surgical correction is recommended. 2) Accumulated experience shows the effectiveness of surgery. 3) It is difficult to determine the effectiveness of medical therapy in infants and children because the procedure is complicated and may require anesthesia. The long-term effectiveness and compli-cations of different anti-glaucoma drugs have not been well studied.
 
SURGICAL MANAGEMENT
Trabeculotomy and goniotomy remain the first line surgical procedures for EODG. A surgeon anticipating to manage these cases should be familiar with either technique. Goniotomy and trabeculotomy act to enhance aqueous outflow by cutting through the trabecular meshwork, which is the main site for resistance for aqueous outflow in these eyes. The rates of successful IOP control with these procedures are relatively high and the incidence and severity of intra-operative and postoperative complications are small in comparison with all other procedures. There is no effect on ciliary body function and aqueous humor production as with cycloablative procedures. They invite much less tissue reaction and fibrosis which very often compromise the surgical outcome. The absence of external aqueous filtration precludes delayed filtering bleb-related complications, such as infection, hypotony, and leaks. Although augmentation of trabeculectomy with mitomycin-C can enhance the IOP reduction, its late-onset complications should limit the use of this technique. There is no need for implantation of artificial devices as with aqueous shunts, thereby eliminating complications such as ocular motility dysfunction and corneal decompensation.
 
Trabeculectomy
The decision to perform this procedure must be made carefully because in infants and children, filtering bleb formation may be difficult despite intraoperative use of antimetabolites. Even after filtering blebs are successfully formed, the patients may be exposed to the risk of post-surgical infections for the rest of their life. It has a success 2rate at around 70% with and wihthout mitomycin-C (MMC). The use of MMC leads to a lower intraocular pressure level, but also leads to a greater incidence of resultant hypotony maculopathy. Late bleb-related ocular infection does occur in children after trabeculectomy with MMC and is characterized by abrupt onset, bleb infiltration, and rapid progression. Leading to significant late visual loss. This modality, therefore, should be reserved for recurrent cases in which other modalities have failed. When done, a fornix-based technique and posterior application of MMC can decrease the occurrence of thin blebs and should decrease the risk of infection. The addition of trabeculectomy, deep sclerectomy to trabeculotomy looks to be a handsome synergism and has been advocated by some authors.
 
Deep Sclerectomy
Deep sclerectomy lowered the pressure below 16 mm Hg in 56% of EODG eyes. Although deep sclerectomy may reduce the IOP in patients with refractory EODG, there is a specific risk profile associated with it and all eyes are ultimately classified as failures. Deep sclerectomy leaves the trabecular beams, which are the main site for resistance to outflow in EODG.
 
Aqueous Shunt Implantation
Aqueous shunt implantation offers a significantly greater chance of successful glaucoma control in the first 2 years of life, compared with trabeculectomy with MMC. However, the enhanced success with aqueous shunt devices is associated with a higher likelihood of postoperative complications requiring surgical revision, most commonly tube repositioning. They can probably used as a last resort in refractory cases with multiple previous surgeries and compromised angle structures.
 
GONIOTOMY VERSUS TRABECULOTOMY
Trabeculotomy and goniotomy seem to be in some ways equivalent, and both are particularly successful in previously unoperated cases of EODG. Goniotomy, however, does not have a good success rate when done below 1 month or over 2 years of age. It is usually associated with a relatively high rate of recurrence, and multiple goniotomies are needed to achieve a success rate similar to that of trabeculotomy. Trabeculotomy is probably a more demanding technique with which it may be more difficult to achieve a technically perfect procedure than it is with goniotomy. Even with goniotomy advocates, trabeculotomy is generally preferred in children over the age of three years, in situations where corneal clouding prevents adequate visualization of the trabecular meshwork, and in patients with aniridia.
Trabeculotomy was first introduced late in the sixties and early seventies. The idea is to approach the canal of Schlemm from outside the eye (ab-externo), introduce specially designed probes into them, and rotating these into the Anterior chamber. In doing so the inner wall of the canal, the trabeculum; usually offering the most resistance to aqueous outflow in these eyes, and any associated developmental anomaly, are severed. In eyes with no previous surgical intervention, it is possible to probe the canal of Schlemm along the full length of the trabeculotome in virtually all cases. The often acclaimed branching canal is not met surgically that often. A 360 degrees trabeculotomy was suggested, but added to its possible technical difficulties, it is commonly followed by extreme hypotony. Indeed the current 120 degrees technique of trabeculotomy provides sufficient controlled pressure lowering.
Goniotomy involves the creation of a superficial incision into uveal TM, allowing the iris root to move posteriorly and presumably relieving the mechanical obstruction to aqueous outflow. This procedure is performed under direct visualization through a gonioscopic contact lens and the operating microscope. There have been some reports on endoscopic goniotomy overcoming the inherent drawback of difficult visibility caused by corneal cloudiness with no much later reports about further results.
Trabeculotomy is my first choice for surgery in all cases of EODG, regardless any previous surgery, as long as there is a sound non-scarred 120 degrees of limbic circumference. A properly performed trabeculotomy gives good results in most of these eyes. Bad prognostic signs include; eyes with corneal diameter 14.5 or more, advanced congenital cases, and multiple previous surgeries.
Several techniques have been described for performing trabeculotomy. I describe here my technique which I have been using systematically for the past 12 years.
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Fig. 1: A previously non-operated eye; trabeculotomy is performed at the 12 o'clock position
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Fig. 2: A scarred superior limbus caused by previous trabeculectomy. A successful trabeculotomy was performed in the nasal limbus (right side of the picture)
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Fig. 1.3: Different curvatures trabeculotomy probes. Each set suits its equivalent corneal diameter and limbal curvature. Being without a handle renders them mechanically weak enough not to force a false intra-scleral passage, yet very sensitive to the appropriate limbal curvature, and strong enough to do their job in severing the delicate trabecular meshwork. On the other hand, this light-weightness renders the probes much more difficult for handling and maneuvering. As with any surgical difficulty, this can be overcome by practice
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Figs 4A to D: (A and B) Diagrammatic representation of the layout of surgery; surgery is usually carried out at the 12 o'clock position, unless this site is jeopardized by previous surgery, in which case a lateral (or even inferior) approach can be used. Trabeculotomy probes are introduced into both sides of the cut ends of Schlemm's canal. Both probes should be introduced before rotating the first probe to reduce the difficulty of inserting the second probe in a collapsed canal. (C and D) Probes are then rotated, one after another into the anterior chamber. In doing so, the trabecular meshwork is cut along the length of the probes connecting the Schlemm's canal directly to the anterior chamber
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Fig. 5: A 6-0 corneal traction (arrow) helps to expose the surgical field. A limbal based conjunctival incision is made 6–8 mm from the limbus. Two 8-0 retraction sutures are taken in the limbal side of the conjunctival incision. These not only retract the conjunctiva, but they also exert gentle traction on the globe, further helping exposure in these usually large globes in small palpebral fissures
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Fig. 6: A superficial scleral flap similar to that done during trabeculectomy is made
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Fig. 7: Intra-scleral dissection is carried out well into the clear cornea. Position of the canal is so variable in buphthalmic eyes
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Fig. 8: A radial incision is started, gradually deepening over the presumed location of the canal of Schlemm. This differs greatly between adult and infant eyes, and still there is considerable variation in its location among newborn-infant eyes with different globe sizes. Though it is not a rule of thumb, it is usually located more posteriorly in larger globes. In very large eyes, it can often be found well underneath the (white of sclera)
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Fig. 9: The radial incision is very gradually deepened, extending anteriorly or posteriorly if the need arises, till the canal is reached. Opening of the canal is recognized by one or more of the following;
  • -gentle egress of aqueous; a gush or an efflux of aqueous denotes opening the anterior chamber rather than the canal.
  • -direct (dry) visualization of the canal; most commonly in stretched out buphthalmic eyes. This is usually associated afterwards by the exudation of aqueous.
  • -rarely; in congested eyes, egress of blood from the canal site can be the main sign of its opening
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Fig. 10: Direct (dry) visualization of the canal
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Fig. 11: Gentle egress of aqueous is a good indication of opening the canal
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Fig. 12: A (gush) of aqueous during dissection signifies opening the AC rather than the canal. Finding the canal becomes more demanding, but should be tried
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Fig. 13: The lip of the radial incision is held by the non-dominant hand, while the trabeculotomy probe is held by the dominant hand and gently directed towards the cut end of the canal
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Fig. 14: The probe is gently introduced into the canal; the lip of the incision is released. Depending on the depth of dissected scleral flap, the internal probe can usually be visualized in its tight path in the canal (arrows). The external probe is always there to assess the conformity of the trabeculotome to the limbic circumference, and that it has not gone astray. A correctly places trabeculotome only moves along its axis. If correctly placed, it should not rotate. It is a blunt pin in a conforming tube!
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Fig. 15: Gentle knocking on the back of the trabeculotome safely guides it along its path to its full length in the canal of Schlemm. There should be minimal resistance; significant resistance means either the probe is in the wrong place or if the probe is surely in the canal, that the probe curvature is not the ideal one for the eye
A smooth passage blocked in the middle of the way can occur if the probe hits a scarred limbic area caused by a previous surgery. In primary trabeculotomy, this is very rare. In over 120 eyes I have performed in 2002 and 2003, I have encountered this in only 2 eyes!
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Figs 16 and 17: The same is repeated with the second probe
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Fig. 18: Pulling the conjunctiva occasionally is necessary to assess the conformity of the outer probe to the limbic circumference
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Fig. 19: The 2 probes nicely in place; the outer probes are parallel to the limbus. They are not freely mobile either anteriorly into the AC, or posteriorly into the supra-ciliary space
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Fig. 20: An example of an extremely stretched-out slit like canal in a case with advanced buphthalmos. Despite the apparent difference in the level of right and left trabeculotomes, both are correctly in the canal (the tube is a bit loose!). Note the relation of the outer probes to the limbal circumference, and the visibility of the inner probes anterior to the scleral white
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Fig. 21: The outer probe betrays a faulty insertion into the supra-ciliary space; the trabeculotome is freely mobile antero-posteriorly. This has to be removed completely, and re-inserted carefully. (temporal secondary trabeculotomy in an eye with previous trabeculectomy at 12 o'clock position)
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Fig. 22: Same case of previous figure after proper insertion of the trabeculotome
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Fig. 23: Faulty insertion into the AC, aqueous gushes to the surgical field, and the probe is freely mobile anteriorly
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Fig. 24: Same as previous after proper insertion
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Figs 25 and 26: The trabecular meshwork to be cut during trabeculotomy is a soft structure. Cutting it does not involve any force. On rotating the trabeculotome into the AC, the tip makes the first cut, and appearance in the AC (arrows), then follows the rest of the internal probe (inset). This tactile lag between appearance of only the tip first, with no limbal or corneal distortion, and then the rest of the probe (Khalil's sign), is an important sign of success. The need for force, with corneal or limbal distortion (Fig. 8) simply means that the trabeculotome is not properly placed. On the other hand, if rotation meets no resistance at all, with simultaneous appearance of the whole length of the internal probe in the AC means that it was lodged in the anterior chamber angle rather than in the canal
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Fig. 27: After rotating of the full length of the probe into the AC, the probe is gently withdrawn, paying care not to touch the iris-lens. This is especially important with the second probe when the anterior chamber gets shallower
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Fig. 28: Corneal wrinkles on rotating the trabeculotome imply its faulty insertion in scleral lamellae or into the supra-ciliary space
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Figs 29 and 30: Hyphema on rotating the trabeculotome is not uncommon. It is usually self limited, and absorbed by the second post-operative day. Injection of air into the AC helps to control a more active bleeding
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Fig. 31: Scleral flap is closed tightly by interrupted 10/0 monofilament
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Figs 32 and 33: The conjunctiva is then closed by running 8/0 vicryl
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Figs 34 and 35: (Optional addition) In the rare event of inability to locate the canal, the procedure can be easily converted to a trabeculectomy