viscocanalostomy procedure because it prevents the polymerization of fibrinogen (present in blood) to fibrin by suppressing antithrombin III. It also acts as a physical barrier to fibrinogen migration.22,26 If fibrinogen is able to polymerize into fibrin, then fibroblastic proliferation can occur. This can result in closure of the ostia into Schlemm’s canal.22,26 Healon GV lasts approximately 6 days in the subscleral reservoir,26 Healon5 lasts 2 weeks,26 and the reticulated hyalonic implant of Sourdille’s lasts 4 months.28 It will be interesting to see whether Healon5, the reticulated hyaluronic implant, or a combination of the two will be preferred in the future for viscocanalostomy.

Trabeculectomy

When intraocular bleeding occurs during a trabeculectomy it can usually be stopped by applying a fine-tipped cautery to the bleeding source (usually the iris root or the ciliary body). It is important to stop intraocular bleeding. If there is postoperative hypotony, the bleeding in the AC will continue, threatening the surgical result. If intraocular bleeding cannot be stopped, extra removable sutures should be employed to close the flap. This will create an initial tight closure with minimal aqueous egress and adequate IOP to internally tamponade bleeding. The removable sutures can then be removed in the first week postoperatively. Always remember to stop miotics; aspirin and other oral NSAIDs except the COX-2 inhibitors Coumadin, Plavix, and Ticlid; and vitamin E before surgery according to the guidelines stated at the beginning of this chapter.

BROKEN CAPSULE WITH

VITREOUS LOSS

If the anterior capsulorrhexis is not continuous during the performance of a combined phacoglaucoma procedure, a posterior extension and capsular tear may occur. If this happens, it is important to remove all lens fragments, cortex, and any vitreous according to the principles outlined in Chapters 18 and 19. This is necessary to minimize postoperative inflammation, which may cause increased scarring and failure of the glaucoma procedure. If vitreous is present in the anterior chamber postoperatively, it may block or form anterior synechiae to Descemet’s window in NPTS or to the sclerectomy in trabeculectomy surgery. In this case, an additional surgical intervention with anterior vitrectomy and lysis of vitreous bands may be required. Sometimes vitreous bands can be lysed with the YAG laser. However, this frequently requires high energy and a large number of pulses. This can increase the inflammation in the anterior chamber with a resultant increased risk of failure

of the glaucoma procedure. Subconjunctival DepoMedrol or Kenalog (triamcinolone 20 to 40 mg) should be routinely given after combined phacoglaucoma procedures, but especially after cases in which more inflammation is anticipated.

If the anterior capsular rim is intact, and a posterior capsular rent cannot be converted into a continuous tear by capsulorrhexis, then a posterior chamber IOL should be placed in the ciliary sulcus. If the diameter of the anterior capsulotomy is smaller than that of the IOL optic, the optic of the IOL should be captured within the anterior capsule. This ensures a snug fit between the edge of the capsulorrhexis and the posterior edge of the optic and makes herniation of vitreous into the AC unlikely. Additionally, it also stabilizes the lens implant, making anterior displacement of the lens less likely if postoperative hypotony occurs. The haptics of a posterior chamber lens placed in the ciliary sulcus should be orientated in a meridian perpendicular to the meridian of the glaucoma operation. This will prevent iris from being pushed anteriorly at the site of Descemet’s window (in NPTS) or the sclerectomy (in a trabeculectomy), thereby reducing the chance for synechiae. If there is an anterior capsular rent in conjunction with an intact posterior capsule, a posterior chamber (PC) IOL can usually be gently placed in the capsular bag. If both the anterior and posterior capsules have been damaged to a significant degree, then a suture fixated PC IOL in the ciliary sulcus or an AC IOL is sometimes necessary. If either a ciliary sulcus suture fixated PC IOL or an AC IOL is used, it is best to place the haptics away from Descemet’s window (in NPTS) or the sclerectomy (in trabeculectomy). This will help to minimize inflammation in the immediate area of the Descemet’s window or the sclerectomy and will make the occurrence of peripheral anterior synechiae, with subsequent failure of the glaucoma procedure, less likely.

DESCEMET’S DETACHMENT

NPTS

Descemet’s detachment can occur in the viscocanalostomy operation either when the ostia of Schlemm’s canal are being injected with sodium hyaluronate too forcefully, or after the superficial flap has been sutured, while additional sodium hyaluronate is injected beneath the flap. The cleavage plane between Descemet’s membrane and the rest of the corneal stroma is already established when the Descemet’s window is created. If too much pressure is applied to Descemet’s window by aggressive injection of sodium hyaluronate beneath the superficial flap, a viscodissection of the potential space between Descemet’s membrane and the rest of

the corneal stroma is created. A low intraoperative IOP (single digit) in all probability also contributes to a Descemet’s detachment. An IOP in the teens, prior to infusing additional sodium hyaluronate, will help prevent this dilemma. Additionally, careful observation of the limbal area immediately over the Descemet’s window for any change in appearance that would indicate a Descemet’s detachment is prudent. If a detachment starts to occur, remove some of the viscoelastic from the subscleral space. If the detachment does not invade the visual axis, no corrective measures are required. If the detachment is extensive, a corrective measure such as injecting viscoelastic, air, or sulfur hexafluoride gas (SF6) into the anterior chamber as well as suturing may be necessary. The technique is outlined in Chapter 23.

RUPTURE OF SCHLEMM’S

CANAL/TRABECULAR MESHWORK

WITH HEALON GV OR HEALON5

This complication can occur if the sodium hyaluronate is injected too forcefully into the ostia of Schlemm’s canal during a viscocanalostomy. In this event the flow of viscoelastic material into the anterior chamber can usually be visualized. Sometimes this is accompanied by a small amount of bleeding. In essence, when this occurs, a trabeculotomy has been created. No remedial intervention is indicated. To prevent rupture of Schlemm’s canal/trabecular meshwork and a possible Descemet’s detachment, it is important to apply smooth, steady pressure, rather than forceful intermittent pressure, to the plunger of the viscoelastic cannula. After a rupture has taken place, Descemet’s window should be created, the deep flap transected, and the superficial flap should be closed as normal.

If the canal is ruptured, the patient should be started on pilocarpine 2%, one drop q.i.d., followed each time in 10 minutes by a drop of 10% phenylephrine, for about 3 to 4 weeks. As mentioned previously, this makes the iris taut and therefore peripheral anterior synechiae are less likely to develop. Having a rupture in Schlemm’s canal increases the likelihood of failure of the viscocanalostomy operation. This is because the clotting cascade is set into motion when the canal is damaged and scarring is more likely to result.26

NPTS DIFFICULTY IN IDENTIFYING THE

OSTIA OF SCHLEMM’S CANAL

Even when Schlemm’s canal is unroofed according to plan, it can sometimes be difficult to identify the ostia. This occurs because the ostia appear as slits rather than wide open pipelines. Usually the ostia

can be identified by gently walking the Grieshaber cannula along the wall of the scleral bed. The cannula will eventually enter the ostia. Then, by injecting BSS through the cannula, if the ostia are correctly cannulated, blanching of the superficial aqueous veins is usually observed. A small amount of bleeding from the ostia may also be recognized due to episcleral venous pressure. This serves as an additional landmark for correct identification. Once the ostia are correctly identified, the injection of the sodium hyaluronate may proceed. During the injection occasionally it is possible to see small clumps of sodium hyaluronate passing through the aqueous veins. This is reassuring that the ostia have been correctly cannulated.

POSTOPERATIVE COMPLICATIONS

HYPHEMA

The incidence of hyphema is definitely higher with trabeculectomy compared to NPTS. This is because an intact Descemet’s window functions as a barrier to blood entering the anterior chamber. Also, bleeding frequently occurs from the root of the iris/ciliary body after an iridectomy has been performed. Because an iridectomy is not normally performed in NPTS, the risk of hyphema is lessened. To further reduce the risk of hyphema, all drugs with anticoagulant properties should be discontinued, prior to surgery, according to the guidelines outlined at the beginning of this chapter.

If a hyphema does occur during the postoperative period, it is usually a self-limited event that does not require surgical intervention. Hypotony will generally contribute to anterior chamber hemorrhage and may prolong its course. A large hyphema (>50% of the AC volume) that does not show any evidence of clearing within a 4- to 5-day period may require surgical intervention. An elevated IOP may make intervention more urgent. Under these circumstances, an AC washout should be considered, because failure to do so can result in the formation of anterior synechiae that may block either the sclerectomy (in a trabeculectomy) or Descemet’s window (in NPTS). In either case the result may be failure of the glaucoma operation. Fibrin in the AC may also cause an occluded pupil (pupillary membrane), a secluded pupil, or localized posterior synechiae that may cause pupillary distortion. It is prudent to increase the frequency of topical steroids to every 2 hours while awake as well as to use topical steroid ointment at bedtime to suppress the additional inflammation caused by the blood in the AC. Short-acting cycloplegic agents are indicated to prevent iris synechiae and if the AC becomes shallow. In this oc-

currence they help to pull the iris/lens diaphragm posteriorly. Routine usage of cycloplegic agents makes the peripheral iris “bunch up” in the angle and may promote the formation of peripheral anterior synechiae. Miotic agents are to be avoided because they cause vascular congestion and can cause additional bleeding.

When an AC washout is performed, it is best done with a bimanual irrigation and aspiration technique through two clear corneal incisions. The longer a hyphema is present, the more likely it will become consolidated into a clot that requires a larger surgical incision for clot removal rather than simple irrigation and aspiration. If additional bleeding occurs at the time of the AC washout, the original operative site may need to be explored. The bleeding site may require direct cautery with a fine-tipped cautery instrument. Because hyphemas are more likely to occur in eyes with postoperative hypotony, it is imperative to end the surgery with an adequately pressurized eye. A pressure around 10 should serve this purpose.

SHALLOW ANTERIOR

CHAMBER-HYPOTONY

Hypotony is defined as an IOP below the normal range; therefore, the term is vague. Some eyes may tolerate an IOP lower than 6 mm Hg without sustaining visual loss. Deleterious effects on the eye are common at an IOP less than 6 mm Hg (3 standard deviations from the mean).36 Therefore, for this discussion, hypotony will be considered to be an IOP less than 6 mm Hg. This is more common after trabeculectomy surgery and unlikely after NPTS. Hypotony occurs commonly after filtering surgery as the result of excessive aqueous outflow beneath the scleral flap. It may persist if the episcleral fibroblastic response is limited. Other causes of excessive aqueous outflow in the early postoperative period include a conjunctival wound leak or buttonhole, and rarely a cyclodialysis cleft. Occasionally hypotony can occur weeks to months after the trabeculectomy surgery, due to a spontaneous breakdown of an ischemic bleb. The use of antimetabolites, especially mitomycin-C, has increased the incidence of hypotony. This is due to the decreased fibroblastic response and the increased presence of ischemic blebs caused by these drugs. Other factors that contribute to postoperative hypotony cause decreased aqueous production. These are surgically induced inflammation (uveitis), ciliochoroidal detachment (suprachoroidal effusion), retinal detachment or use of aqueous suppressants (systemic effect of topical mediation in the contralateral eye or from oral carbonic anhydrase inhibitors [CAIs] or beta-blockers).

To prevent hypotony after trabeculectomy surgery, it is necessary to create a properly proportioned flap and sclerectomy as well as suture the scleral flap tightly enough to allow only a small, steady trickle of aqueous beneath the flap. It is usually easier to either laser a flap suture, or release an externalized releasable suture, to lower a mildly elevated postoperative IOP, than it is to raise a low IOP by various techniques (autologous blood injection, trabeculectomy revision with additional flap suture placement). This author attempts to leave the early postoperative IOP in the 10 to 15 mm Hg range and then if a lower target IOP is desired, after the first week postoperatively, the release of externalized releasable flap sutures is performed. The use of externalized releasable sutures has several advantages over Hoskins’ and Migliazzo’s37 laser suture lysis technique. First, a thick Tenon’s fascia or subconjunctival hemorrhage may make laser suture lysis impossible but it does not hinder the release of externalized releasable sutures. Second, if an ophthalmologist does not have an argon laser in the office, an impromptu trip to use a hospital laser may be obviated by using externalized releasable sutures. These sutures are easily releasable at a slit lamp with the use of a superblade and jeweler’s forceps.

If hypotony does occur in the immediate postoperative period after a trabeculectomy, the severity of the hypotony and the clinical findings determine the course of action. If the IOP is below 6 mm Hg and the anterior chamber is deep, observation is usually adequate. If the IOP rises and becomes stable, no additional treatment is necessary. If, however, hypotony persists and anterior chamber shallowing recurs, reassessment is necessary. In a phakic eye, if corneal lenticular touch occurs, immediate reformation of the anterior chamber is indicated because failure to do so will certainly result in a cataract. This may be performed by injecting, at the slit lamp or in the operating room, a viscoelastic, preferably a dispursive type such as Viscoat, through the preexisting paracentesis incision. Unfortunately, viscoelastic injection usually provides only brief reformation of the AC. Unless the underlying cause of the hypotony is repaired, chamber shallowing will typically recurs. Therefore, revision of the trabeculectomy by adding sutures to the scleral flap, or suturing of the conjunctivae, is required to diminish the aqueous egress.

In combined phacotrabeculectomy with PC IOL implantation, this author has found that AC shallowing is usually less severe and better tolerated by the eye than the AC shallowing seen in phakic patients with hypotony. Therefore, a longer observation period may be possible in pseudophakes than after trabeculectomy in phakic patients.

Early postoperative hypotony, in the presence of an intact conjunctival wound, as a rule indicates that

aqueous egress from the sclerectomy is too copious. If AC shallowing is present without corneal-lenticu- lar touch, medical management with a cycloplegic agent (hyoscine 0.25%, homatropine 2% or 5% q.d.) may be tried for several days up to 1 week. Topical steroid usage should be decreased to minimize inhibition of wound healing. Also, the patient should be instructed to restrict activity. Specifically, bending, lifting, and Valsalva-positive conditions (e.g., vigorous coughing, nose blowing, sneezing, or constipation) should be avoided. This is crucial if the patient is at risk for suprachoroidal hemorrhage (e.g., aphakic, status postvitrectomy, or elderly individuals with very high preoperative IOP).38

If no improvement in chamber depth or IOP occurs, the use of pressure patching39,40 with aqueous suppressants,40 a large bandage contact lens,41 a Simmon’s shell,42 or a symblepharon ring43 may be tried prior to proceeding with a trabeculectomy revision.

CONJUNCTIVAL LEAK

In the presence of hypotony the conjunctiva should always be examined with a Seidel test, using either 2% fluorescein solution or a moistened fluorescein strip, to establish if a bleb leak or a buttonhole exists. Because aqueous may percolate intermittently through a bleb leak in a hypotonous eye, it may be necessary to watch for 30 seconds to a minute, or to apply light pressure to the globe, to see aqueous leakage. A bleb leak, whether early or late, or a small buttonhole, will occasionally heal with pressure patching39,40 in combination with aqueous suppressants40 (oral or topical carbonic anhydrase inhibitors plus a beta-blocker). Bandage contact lenses,41 which now come in diameters up to 24 mm, may also promote healing.

Another conservative technique is the use of cyanoacrylate tissue glue44,45 in conjunction with a bandage contact lens or collagen shield. When using this technique it is important to place only one or two drops of glue with the wooden end of a cottontipped applicator or a plastic micropipette onto as dry a conjunctival surface as possible. A bandage contact lens must be placed. This will prevent patient discomfort due to foreign body sensation, as well as prevent the lid from disrupting the glue.

Fibrin tissue glue, a mixture of fibrinogen and thrombin that induces the formation of a clot, may also be used to seal an early or late bleb or buttonhole leak.38 Fibrin glue is available commercially (Tisseel, Immuno AG Industriestr, Vienna, Austria) although this is not FDA approved.46 This commercial fibrin glue has the disadvantage of being prepared from pooled plasma and thus has the risk of transmitting blood-borne pathogens.47 Although difficult to do, it can be prepared from the patient’s

blood (autologous fibrin tissue glue).38 The autologous fibrin glue preparation requires the use of a centrifuge, several reagents, and a warming unit, which makes it cumbersome to prepare in the average ophthalmologist’s office. The use of fibrin tissue glue has some advantages over the use of cyanoacrylate glue, including (1) a nonirritant nature making bandage contact lens use unnecessary, (2) the ability to be applied and held to a moist surface, (3) the promotion of healing by providing a fibrin scaffold, and

(4) the ability of the glue to dissolve on its own.38 Autologous blood injection under the conjunctiva

has been used not only to decrease the size of an overfiltering bleb48 but also, unsuccessfully, to stop a bleb leak.38

Other therapeutic modalities that may be tried to heal leaking bleb include the Simmon’s shell,42 symblepharon rings,43 chemical irritant therapy46,49 with 0.25 to 1.0% silver nitrate or 50 to 100% trichloroacetic acid, argon laser,50 thermal neodymium (Nd): YAG laser,51 and cryopexy.52

If the use of one or more of these conservative techniques does not result in closure of a bleb leak or a buttonhole, definitive surgical repair should be attempted.

For an early bleb leak or conjunctival buttonhole, especially if the conjunctival defect is gaping, suturing of the conjunctiva can and should be performed because the tissue has not yet become thin and ischemic. As mentioned previously, 8-0 or 9-0 Vicryl on a blood vessel needle is advantageous when suturing conjunctiva to conjunctiva. The vascular needle will minimize the size of the suture holes in the conjunctiva. If suturing conjunctiva to either cornea or sclera, a small cutting needle (Ethicon VAS 100–4) will be needed.

For a late bleb leak, direct suturing of the conjunctiva is frequently not possible due to its friable nature. Therefore, sliding conjunctival flaps39,53,54 or free conjunctival autografts55,56 have to be used. The fresh conjunctiva can be placed directly over the ischemic and thin-walled bleb and sutured to the cornea anteriorly and to Tenon’s fascia posterior to the bleb. The epithelium on the ischemic bleb and the limbus should be removed as much as possible to promote adhesion between the fresh conjunctiva and the preexisting filtering bleb. This will also prevent formation of epithelial inclusion cysts. In addition, scleral patch grafts57 and corneal grafts58 have been used to close chronically leaking blebs. Surgical revision of a leaky bleb may result in decreased bleb function and higher IOP.

SUPRACHOROIDAL EFFUSION

If postoperative hypotony is severe, and/or persists for an extended period of time, suprachoroidal ef-