Anup K. Khatana, MD,
John S. Cohen, MD,
Robert H. Osher, MD
Contents
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History |
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Surgical Options in patients with Cataract and Glaucoma |
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Antimetabolites |
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Results Following Combined Surgery |
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Combined Surgery method |
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Conclusion |
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CHAPTER HIGHLIGHTS |
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History
The indications for combined surgery have evolved full circle during the past several decades. In the 1970s and early 1980s, cataract surgery alone was thought to have a beneficial effect on long-term glaucoma control.[1–3] Although the precise mechanism for this is not known, large incisions and large sutures often resulted in unintentional filtering blebs in some eyes and probable subclinical filtration in others, which had beneficial effects on intraocular pressure (IOP) in glaucoma eyes. Combined surgery at that time was technically more complex than present techniques and was associated with greater risks and limited success. To avoid the increased risks of this more complex surgery, patients often underwent staged surgery with performance of one procedure and then the other, resulting in a longer total period of rehabilitation.
In the 1980s, with newer techniques of extracapsular surgery and safer intraocular lenses (IOLs), cataract surgery was performed earlier with improved visual results. In the late 1980s and 1990s, more secure closure of surgical incisions and concern about the risks of postoperative IOP elevations prompted greater interest in combined cataract and glaucoma surgery.[4–8] Enthusiasm, however, was dampened with clinicians' belief that the more extensive combined procedure resulted in less filtration than trabeculectomy surgery when performed alone. With the ability to increase filtration after combined surgery by modifying wound healing with antimetabolite therapy, the indications became more liberal. Expectations increased that short- and long-term IOP control would be improved, many patients would be able to discontinue glaucoma medications altogether, and both cataract and glaucoma would be effectively managed with one surgical procedure. Several studies showed the benefits of this approach with minimal complications.[9–11] In time, however, it became evident that antimetabolite use was associated with a small but troubling incidence of complications such as leaking blebs, hypotony, “blebitis,” and endophthalmitis, which represented a significant contrast to the infrequent incidence of complications of cataract surgery alone. In addition, with the development of small-incision surgery, clear corneal incisions, foldable IOLs placed in the capsular bag, and improvements in techniques of anesthesia and virtually same-day rehabilitation, cataract surgery alone became much more desirable if it could be performed without risk of glaucoma damage from perioperative IOP elevation.
With the realization that IOP elevations were uncommon (although still possible) following the present minimally traumatic technique of phacoemulsification and IOL implantation, cataract surgery alone is becoming the procedure of choice in many patients with diagnoses of ocular hypertension, glaucoma suspect, and early-to-moderate glaucoma. Combined surgery may rarely be considered in eyes with diagnoses of ocular hypertension and glaucoma suspect when IOP is significantly elevated despite the use of multiple medications. (This may also be a situation in which cataract surgery combined with nonpenetrating deep sclerectomy/viscocanalostomy or other still unproven newer options such as endocyclophotocoagulation (ECP), Schlemm's canal surgery, etc., can be considered.) Combined surgery is usually advisable when glaucoma is uncontrolled with maximum medical therapy, glaucoma control requires more than two medications (or fewer if unused medications are contraindicated), and damage is advanced with visual field loss threatening or involving fixation even if the IOP is controlled.
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Surgical options in patients with cataract and glaucoma
Before any surgical procedure is performed, advantages and disadvantages must be considered, taking into account the severity of the disease, condition of the fellow eye, availability and affordability of medications, compliance with medication schedules, and compliance with follow-up visits. Patient compliance with long-term follow-up is important to provide continued monitoring of the IOP, discs, visual fields and bleb appearance. As with most surgical procedures, the precise indications for combined surgery vary among surgeons depending on the level of comfort, experience, and skill. The surgeon and patient must balance the benefits and risks of performing combined cataract and glaucoma surgery with those of performing either procedure alone.
Cataract surgery alone (phacoemulsification)
Cataract surgery alone can be performed efficiently with rapid, if not immediate, visual recovery in most cases. Postoperative elevation of IOP is a risk in all eyes. Its occurrence must be considered when choosing a surgical procedure in eyes with ocular hypertension, pigment dispersion syndrome, pseudoexfoliation, primary open-angle glaucoma, postoperative pressure spike in the fellow eye, and a family history of glaucoma. One study measured IOP after phacoemulsification performed with clear corneal and sclerocorneal incisions in eyes without glaucoma. Peak elevations were higher for sclerocorneal than clear corneal incisions, measuring 43 and 37mmHg 6 h postoperatively for each group, respectively, and 30mmHg for both groups 24 h postoperatively. At 15 months, peak IOP measured 19mmHg in both groups. Eyes with glaucoma would be expected to be at greater risk of IOP elevation.[6,][12–14]
Although no formal surveys have polled surgeons regarding approaches to coexisting cataract and glaucoma, as a general rule of thumb, cataract surgery alone will be considered if the glaucoma is adequately controlled with two or fewer medications (with no contraindications or allergy to the remaining available medications) and visual field loss does not involve fixation (Table 22-1). The surgeon must anticipate the possibility of an acute and/or chronic postoperative elevation of IOP that could require an increase in medical therapy. Perioperative beta-blocker and carbonic anhydrase inhibitor therapy should be considered to reduce this risk. Postoperative IOP elevation may be more likely in the presence of coexisting uveitis, when iris manipulation or posterior synechialysis is required, if peripheral anterior synechiae are present, when cortex or viscoelastic agents are incompletely removed, and so on. In addition, there may be a relative contraindication to the use of prostaglandin analogues and miotics postoperatively because of the potential increased risk of inflammation and cystoid macular edema. If visual field loss involves or threatens fixation, delay in lowering a postoperative IOP spike could result in progression of glaucoma damage with increased visual disability. These risks warrant consideration of combined surgery. The authors favor a conservative approach and, when in doubt, consider combined surgery.
Table 22-1 -- Indications for single or combined surgery
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Phacoemulsification |
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Indications |
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Presence of a cataract that impairs visual function or prevents adequate view of the optic nerve, with:
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Trabeculectomy |
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Indications |
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Cataract does not decrease visual function or impair view of optic nerve, and cataract progression that would require surgery is not anticipated (surgeon's judgment), with:
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Combined surgery |
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Indications |
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Cataract decreases visual function or prevents view of optic nerve or is likely to do so if trabeculectomy alone were performed (surgeon's judgment), and:
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Cataract surgery employing techniques other than small-incision clear corneal phacoemulsification (such as extracapsular cataract extraction, which usually requires a larger incision and may be associated with more extensive inflammation) may have a greater risk of postoperative IOP elevation and glaucoma damage. Larger incisions and the use of superior incisions, especially ones that involve conjunctiva and sclera, can make future trabeculectomy surgery technically more difficult. This is another reason that temporal “near clear” or clear corneal incisions are preferred, particularly in glaucoma patients.
Trabeculectomy surgery
Trabeculectomy surgery alone may be considered when the IOP is uncontrolled despite maximum medical therapy and the cataract does not decrease visual function. Even with uneventful trabeculectomy surgery, however, a cataract can progress. If cataract surgery is necessary in the near future, even a clear corneal approach may result in scarring of the filtering bleb with elevation of IOP, requiring additional medical therapy or glaucoma surgery.[15,][16] The surgeon's judgment must be used in determining the best procedure for these patients (see Table 22-1).
In cases of marked IOP elevation (e.g., with corneal edema, neovascular glaucoma, traumatic glaucoma) with coexisting cataract, a staged approach with either trabeculectomy with mitomycin C (MMC) or tube implant surgery may be the safest and best choice, deferring consideration of the cataract to a future time when conditions are more controlled. On the other hand, if lens-induced glaucoma is suspected, combined surgery may be the best approach.
Combined cataract and trabeculectomy surgery
Combined surgery attempts to manage both cataract and glaucoma using one surgical procedure. The choice of this procedure should be determined on an individual basis for each patient (see Table 22-1). Although combined surgery has been considered controversial in the past, it is now accepted as an indicated procedure in selected eyes with coexisting cataract and glaucoma. (For this discussion, combined surgery is defined as phacoemulsification with posterior chamber IOL implantation and trabeculectomy.)[7]
Glaucomatous eyes have compromised trabecular meshwork and reduced aqueous outflow. There is a greater risk of postoperative IOP elevation that may further increase when posterior synechialysis or pupil manipulation is required. Although visual recovery after combined surgery may be delayed compared with cataract surgery alone, it is more rapid than when the glaucoma and cataract are managed separately in a two-stage approach. Combined surgery facilitates the management of postoperative IOP elevations versus cataract surgery alone.[17] However, early postoperative elevations of IOP can occur when combined surgery is performed.[8,][18] Use of releasable sutures with combined surgery permits secure wound closure, minimizing risk of a flat or shallow anterior chamber, and permits suture removal to increase aqueous flow and lower IOP postoperatively when the eye is stable.[9] (Laser suture lysis of simple interrupted sutures can be used in place of releasable sutures.)[19]
Although most filtering blebs function successfully, those that fail are more likely to do so within 6 months, with the rest failing years later.[20] Although the use of antimetabolites decreases the incidence of bleb failure, it is important to preserve conjunctiva for possible future filtering surgery. Conjunctival dissection in combined surgery should be restricted to a single superior quadrant (the superotemporal quadrant provides the greatest exposure), leaving the remaining superior quadrant for future glaucoma surgery if needed.
Combined surgery with MMC has been reported to reduce IOP from 13.4% to 34% with 1.2 to 1.4 fewer glaucoma medications. These results were statistically better than both combined surgery with 5-fluorouracil (5-FU) and with no antimetabolite use, which were the same.[9,][11] Lack of efficacy of MMC in an additional study may have been due to surgical technique or the risk factors in the patient population studied.[21] It has been suggested that more intensive follow-up and postoperative manipulations were required in the non-MMC group to achieve results statistically similar to the MMC group.
Combined phacoemulsification, IOL implantation, and trabeculectomy surgery with MMC is most applicable in eyes that have uncontrolled glaucoma with maximum medical therapy and a cataract that impairs vision. Eyes requiring more than two glaucoma medications, eyes controlled on fewer than two medications with others contraindicated or ineffective, and eyes with visual field damage that is advanced or involves fixation may also be good candidates for combined surgery with MMC to minimize the possibility of potentially damaging postoperative IOP elevation. Combined surgery will permit better management of postoperative IOP elevation and provide a high probability of improved short-term and long-term IOP control with fewer medications. In these eyes, it is safer to perform one combined procedure than two separate procedures. Although trabeculectomy with MMC performed alone may have the potential for greater reduction of IOP and glaucoma medications than combined surgery with MMC, the success of combined surgery with MMC more than justifies its use in appropriate patients. In addition, the techniques presently employed in combined surgery do not increase risk more than performing the procedures separately and may even reduce the risk with only one trip to the operating room.
If the glaucoma is controlled with fewer than two medications, with the ability to add others, and visual field loss is mild in an eye with a visually disabling cataract, combined surgery with MMC may not be required. Phacoemulsification with IOL alone may be performed to avoid some of the potential complications of combined surgery, such as bleb dysesthesia, bleb infection, endophthalmitis, etc. Although unlikely, significant IOP elevation can occur. One study showed that one of 17 eyes with stable open-angle glaucoma requiring one or two medications for control had an IOP elevation to 30mmHg 1 day following clear corneal phacoemulsification surgery.[22] If postoperative elevation of IOP does occur, significant glaucoma progression is unlikely.
Eyes with a functioning filtering bleb and controlled IOP also require special decision making when planning cataract removal. Present techniques of clear corneal phacoemulsification have a decreased risk of early postoperative elevations of IOP. In 69 eyes undergoing small-incision clear corneal phacoemulsification with a functioning filtering bleb, two eyes required subsequent additional glaucoma surgery. Sixteen eyes required more glaucoma medications postoperatively than preoperatively. If preoperative IOP was less than 15mmHg, the chance of needing more medications was 27.6%, and if greater than 15mmHg, the chance of needing more was 41.7%. Thus, the surgeon must be aware that, even in this situation, dangerous elevations of IOP could occur with cataract surgery alone and that there is a risk that increased glaucoma therapy will be required.[15,][16] If a previously filtered eye has a questionably functioning filtering bleb with a significant cataract and IOP is uncontrolled or controlled with multiple medications in the presence of advanced glaucoma damage, combined surgery may be a good option. Internal or external revision of the existing trabeculectomy combined with phacoemulsification could also be considered.
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Antimetabolites
Daily postoperative subconjunctival 5-FU injections enhanced filtration success when trabeculectomy was performed alone.[23–25] Although in an early report 5-FU mildly improved filtration success in combined surgery, other studies found no benefit.[26–29]
Chen's pioneering work with MMC,[30] a stronger antimetabolite than 5-FU that could be applied topically at the time of filtering surgery, offered the potential of improved filtration success with combined surgery. The initial report of combined surgery with MMC showed improved IOP control with fewer glaucoma medications at 1-year follow-up. Subsequent investigations have supported these results.[9,][30–32]
Although MMC improves the success of filtration in combined surgery, it also may increase the risk of complications such as hypotony maculopathy, bleb leaks, bleb infection, and endophthalmitis. As a result, the concentration of MMC and duration of application have decreased since its initial use. Although MMC appears to have a fairly flat dose–response curve, reduced exposure seems to decrease the incidence of complications.[26,][27,][33,][34]
Many variables are associated with MMC use. Surgeons using similar concentrations and exposure times of MMC may get different results, and surgeons using different concentrations and exposure times may get similar results. The choice of sponge material may be one of these variables. Different cellulose spears, instrument wipes, and corneal caps may each absorb different amounts of MMC and, when placed in contact with tissue, result in different antimetabolite effect. Surgeons may choose materials that will not tear or fragment during application, cut variable-sized pieces of the material to be placed in contact with the tissue, place pressure on the material containing MMC through the overlying conjunctiva to squeeze MMC into the tissues, or use a cellulose spear to absorb any MMC containing liquid that seeps out from beneath the conjunctival flap and threatens to contact the edges of the conjunctival incision. In addition, many surgeons wipe the subconjunctival space lateral and posterior (the space posterior to the conjunctival incision in limbus-based flaps) to the bleb area for about 15–20 s with the hope that a more diffuse, lower-profile filtering bleb will form. This may result in a less localized and cystic bleb with less potential to develop a late leak through a thinned wall.
Each surgeon should develop his or her own technique, starting with conservative MMC exposure times to minimize the risk of complications. The surgeon should consider the risk/benefit ratio of MMC use and err on the side of less rather than more antimetabolite exposure to avoid complications, realizing that additional glaucoma surgery could be required. When the surgeon is comfortable with the technique and the results, the exposure times can be modified and individualized depending on the severity of glaucoma, risk factors for failure, ability to perform additional glaucoma surgery in the future, and so on. (See Application of Mitomycin for specific parameters of one technique of MMC use.)
Application of mitomycin before or after entering the anterior chamber
When MMC was first used in combined surgery, many surgeons applied the antifibrotic agent near the end of the procedure, after watertight closure of the scleral flap. The area was irrigated with balanced salt solution (BSS), and the conjunctiva was closed. No clinically evident adverse effects were noted. Concern subsequently developed over the possibility of toxicity to corneal endothelial cells and the ciliary body epithelium. Experiments in rabbits showed that MMC penetrated the sclera and resulted in detectible aqueous levels. A reversible decrease in aqueous production followed application of MMC to the scleral surface in monkey eyes. However, the dose of MMC used in these studies was larger than that used clinically in humans.[35–38]
MMC can be applied before entering the anterior chamber or after removing the cataract and securely closing the wound to prevent MMC entry into the eye. Cohen[26] provided evidence that topical application of MMC at the end of the procedure after secure closure of the scleral incision does not cause loss of corneal endothelial cells. This method permits the surgeon to abort the use of MMC if a defect occurred in the conjunctiva or in the scleral wound that would contraindicate its use and, therefore, might be safer for the surgeon who is less experienced with combined surgery. When the surgeon is comfortable with the surgical technique, if desired, MMC can be applied before entering the anterior chamber. (See Application of Mitomycin.) Because of the variability of response to MMC seen in the conjunctiva of individual eyes, some surgeons have recently advocated a subconjunctival injection of a standard dose of MMC that is usually performed at the beginning of the operation.
Subconjunctival or sub-tenon's injection of antimetabolite postoperatively
Based on the work by Gressel, Parrish, and Folberg,[23] which initially showed that daily postoperative subconjunctival injections of 5-FU improve success of trabeculectomy surgery, many surgeons will augment intraoperative antimetabolite therapy with postoperative 5-FU if bleb failure is threatened (increased bleb vascularization, decreased filtration, etc.). Kapetansky has very recently shown a beneficial effect with the use of (usually a single) postoperative subconjunctival injection of the vascular endothelial growth factor (VEGF) inhibitor, bevacizumab, in trabeculectomy eyes at high risk of failure in the first 1–2 months postoperatively (personal communication).
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Results following combined surgery
Several prospective and retrospective studies, using varying techniques of MMC application in varying concentrations, found significantly lower IOP with fewer glaucoma medications. Mean IOP decreased 5mmHg in the MMC group versus 3mmHg in the placebo group. The mean number of medications required for IOP control decreased 0.5 to 2.7 in the MMC groups versus 0.7 to 0.9 in the placebo groups. Fifty percent to 100% of eyes in the MMC groups versus 10% to 67% in the placebo groups were controlled without medications.[9–11,][39]
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Complications following combined surgery
Complications and their frequency were listed in several prospective and retrospective studies and included vitreous loss (2–7%), wound leak (1–30%), iris incarceration in sclerostomy (2%), shallow anterior chamber (7–14%), serous choroidal detachment (14–27%), hypotony (6–18%), and fibrin formation in the anterior chamber (7–19%). With improved surgical techniques and modified methods and durations of MMC application, complications have been significantly reduced. (The management of complications is discussed under Postoperative Management and Complications.)
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Combined surgery method
Preoperative preparations
Medications
As with operative technique, the preoperative regimen varies by surgeon. Topical corticosteroid eyedrops are used every 2 h starting the day before surgery. Topical antibiotic eyedrops are used every 2 h starting the evening before surgery. A combination antibiotic-steroid ointment is applied to the eyelashes at bedtime the evening before surgery. A nonsteroidal anti-inflammatory eyedrop is applied twice the morning of surgery. Cyclopentolate 1%, phenylephrine 2.5%, and homatropine 2% eyedrops are applied every 5–10 min for four applications before surgery. One drop of betaxolol (Betoptic) is applied 30 min before surgery. One drop of 5% povidone-iodine (Betadine) solution is administered immediately before the facial prep.[40]
Topical antiglaucoma therapy has been shown to have an adverse effect on the conjunctival inflammatory cellular profile and on filtering surgery success. The use of steroid drops has been shown to have a beneficial effect on both of these parameters. This is why corticosteroid eyedrops are started preoperatively.[41] Consideration should be given to discontinuing IOP-lowering agents that compromise the blood–aqueous barrier, increase the risk of iritis, and make pupillary dilation difficult (such as miotics) several days to a week before surgery. This should not be done if other glaucoma medications cannot be substituted to blunt possible IOP elevation in eyes with advanced glaucoma.
Anesthesia
Although topical anesthesia is used by many surgeons for combined surgery, the authors usually use either a short- or long-acting retrobulbar block. The short-acting block is performed with 3–4mL of 2% lidocaine (xylocaine) with 150 units of hyaluronidase. The long-acting retrobulbar block is performed with 3–4mL of 4% lidocaine (xylocaine) and 0.75% bupivacaine (marcaine) in a 1:1 mixture, with 150 units of hyaluronidase combined with a Van Lint block using the same anesthetic mixture and requiring a patch postoperatively. Preoperative discussion with the patient of anesthetic options may be helpful. A postoperative eye patch is not used with short-acting blocks.
The long-acting block may be helpful in more difficult cases when pupil stretch or posterior synechialysis is required and phacoemulsification and cortex removal will be done through a small pupil and capsulorrhexis.
Operative technique
Conjunctival Flap
One author (JC) prefers a limbus-based flap, while another (AK) prefers a fornix-based flap. Although a limbus-based flap requires more manipulation and is technically more cumbersome than a fornix-based flap, it provides greater certainty of watertight closure and avoidance of postoperative incision leak. In contrast, the fornix-based flap provides easier and better surgical exposure but has a greater risk of postoperative wound leak. Although there is evidence that limbus- and fornix-based flaps result in the same long-term IOP results, an incision leak is counterproductive to bleb formation.[18,][42] When antimetabolites are used with the surgery, leaks may heal more slowly and be more difficult to repair with a fornix-based flap.[9,][23] However, the authors will usually perform a fornix-based flap if significant subconjunctival scar tissue exists from previous surgery. The morphology of the blebs that form with limbus-based vs. fornix-based flaps is different. Although both techniques can create broad and diffuse blebs, the bleb may be more elevated, increasing the risk of dysesthesia, with limbus-based flaps. The modified fornix-based technique of creating the conjunctival incision approximately 1.5mm posterior to the conjunctival insertion at the limbus can create a bleb that is fairly flat anteriorly. This may decrease the risk of dysesthesia and increase the possibility of being able to resume contact lens wear after the incision has healed.
Limbus-based conjunctival flap
Dissection is performed in the superotemporal quadrant to minimize anatomic restrictions from the brow and the superior orbital rim. The initial incision should be made 8–9mm posterior to the limbus and penetrate the conjunctiva and Tenon's capsule to expose the sclera, using sharp scissors and toothed forceps. Blunt scissors and nontoothed forceps (e.g., Pierse forceps, instrument #2-136, Duckworth & Kent, St. Louis, Mo.) extend the incision parallel to the limbus and laterally in both directions to permit adequate exposure. The incision width usually approximates 12mm (Figure 22-1). The incision should remain about 8–9mm from the limbus along the entire length to minimize the limitation of filtration from the incision scar and to avoid the thinner and more delicate conjunctiva that is sometimes present closer to the limbus. Tenon's tissue is bluntly pushed anteriorly with a dry cellulose sponge or curved edge of a blade to expose the limbus. (Sometimes the insertion of Tenon's tissue must be cut to provide adequate exposure. If at all possible, Tenon's capsule insertion should be left intact to provide extra integrity to the bleb.) Blunt dissection is also performed beneath the edge of the conjunctival incision posteriorly with scissors.
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Figure 22-1 A, Initial incision for limbus-based conjunctival flap is made with sharp scissors and toothed forceps, 8–9mm posterior to the limbus, exposing sclera. B, Limbus-based flap should be about 12mm wide to provide adequate exposure. |
Fornix-based conjunctival flap
Either directly superiorly or in the superotemporal quadrant, non-toothed tissue forceps and sharp scissors are used to create a limbal conjunctival incision approximately 7mm wide. The authors prefer making the conjunctival incision approximately 1.5mm posterior to the conjunctival insertion in contrast to the standard fornix-based technique of incising the conjunctiva at its insertion to the cornea. Blunt scissors are used to extensively bluntly dissect posteriorly to provide adequate exposure for the scleral incision and a larger potential space for filtration (Figure 22-2).
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Figure 22-2 A, Limbal conjunctival incision is made to create a standard fornix-based conjunctival flap. B, Alternate technique for fornix-based conjunctival flap, with the conjunctival incision performed 1.5mm from the conjunctival insertion. |
Scleral Incision and Paracentesis
A three-stage tunnel incision is made with the initial vertical incision approximately 2mm posterior to the limbus. The first-stage vertical incision is performed at about one-half scleral depth and the necessary width for insertion of the desired IOL (the authors use a 0.37mm preset diamond blade) (Figure 22-3A). The second stage of the incision is made horizontally, parallel to Descemet's membrane (the authors use a crescent steel blade), and extends approximately 1–2mm anterior to the limbus. MMC is now used. (See Application of Mitomycin later in text.) If the initial scleral incision inadvertently is made full thickness (as in eyes with thin sclera), the flap can still be dissected anteriorly using only half the scleral thickness. However, it is important to tightly suture the deeper full-thickness area of the incision separately from the rest of the superficial flap prior to MMC application to prevent the development of postoperative hypotony from ciliary body toxicity or a second pathway for aqueous outflow. A keratome blade (appropriate for the size of the phacoemulsification tip) makes the vertical third stage of the incision and enters the anterior chamber (see Figure 22-3B). A narrow, sharp-pointed blade is then used to make a small peripheral paracentesis opening in the cornea, at a position 3 clock hours to the left of the scleral incision (right-handed surgeon) for insertion of a manipulating instrument. A viscoelastic agent is then injected to fill and maintain the anterior chamber.
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Figure 22-3 A, First-stage vertical incision is performed at about one-half scleral depth and the necessary width for insertion of the desired intraocular lens. B, Three-stage scleral incision is made into the anterior chamber. |
Alternatively, some surgeons prefer creating the same type of scleral flap they usually create for a straight trabeculectomy – whether triangular, trapezoidal, rectangular or square. This can help to create consistency in management and results between straight trabeculectomies and combined phaco-trabeculectomies.
Application of Mitomycin
Two small pieces of a cellulose spear (the authors use i-Spear ophthalmic sponge, Alcon, Fort Worth, Tex.), each the approximate size of the scleral flap, are soaked in MMC (0.4 mg/mL). These two pieces are then placed on the scleral surface, overlying and extending beyond the scleral tunnel on both sides (Figure 22-4A). This will spread the MMC effect beyond the area overlying the scleral tunnel and hopefully extend the area of filtration laterally in both directions. The conjunctiva is brought down over the sponges (see Figure 22-4B). The edges of the conjunctival incision should not touch the sponges or any liquid containing MMC. A cellulose sponge should be used to absorb any excess liquid that flows out from under the conjunctival flap. After 1 min of tissue exposure, one of the sponges is removed, and the remaining sponge is positioned centrally on the scleral flap. After an additional minute, the second sponge is removed, and the conjunctival and corneal surfaces, the tissues beneath the edges of the conjunctiva laterally, and the scleral tunnel are irrigated with 15mL of BSS. An intact piece of cellulose sponge, about 2×3mm in size, is securely grasped by toothed forceps and wiped beneath the previously dissected posterior subconjunctival space (limbus-based flap) for 15–30 s (see Figure 22-4C). This area is also irrigated with 15 ml of BSS. (When a fornix-based flap is used, a similar maneuver can be performed deeper than the area previously exposed.)
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Figure 22-4 A, Two pieces of cellulose sponge are placed on the scleral surface, overlying and extending beyond the scleral tunnel on both sides. B, Conjunctiva is brought down over the sponges. C, An intact piece of cellulose sponge, about 2×3mm in size, is securely grasped by toothed forceps and wiped beneath the previously dissected posterior subconjunctival space. |
A total of 1 3/4 min of MMC exposure time beneath the limbus-based conjunctival flap is used for most eyes. The duration of exposure may be decreased by 15–30 s if the need for IOP reduction is less because of less severe glaucoma, a reduced tendency for healing related to older age, systemic use of corticosteroids or other immunocompromising drugs, and so on. The duration may be increased by 15–30 s if there are risk factors for failure, such as thicker tissue, younger age, previous surgery, African-American race, or history of inflammation. Evidence has shown that the dose–response curve of MMC is fairly flat but that longer exposure times may have an increased incidence of complications.[33]
With fornix-based flaps, two round methylcellulose corneal shields are cut in half. The corneal shield material has excellent integrity, eliminating any concerns over pieces of the sponge material falling apart or being left behind. It also keeps a fairly low profile even after being soaked, allowing a greater surface area of contact with the sclera and Tenon's capsule. The first two pieces are wiped around and then placed in the superonasal and superotemporal subconjunctival space. The third piece is placed over the superior rectus insertion, and the fourth piece is wiped around anteriorly, both nasally and temporally, and then placed anteriorly near the area where the posterior edge of the scleral flap will be created. This creates a wedge-shaped area of MMC exposure with the greatest exposure applied posteriorly. While the sponges are in place, the anterior edge of the conjunctival flap is pressed down onto the sclera at the incision site with a cyclodialysis spatula to prevent any external leakage of MMC. The incision surface is then briefly irrigated with BSS to remove any MMC that may have oozed out while the sponges were being inserted. Exposure time varies from a total of 1.5 to 2.5 min for combined surgery, depending on the multiple factors listed in the previous paragraph.
Management of the Small Pupil and Posterior Synechia
Long-term use of glaucoma (especially miotic) eyedrops may limit the effectiveness of pupillary dilation in preparation for phacoemulsification. If the patient is using miotic eyedrops and the IOP and stage of glaucoma permit, discontinuation of the miotics and, if possible, substitution of other glaucoma drops may enhance the mydriasis. The minimum acceptable and comfortable pupil size may vary depending on the specific type and severity of the cataract. A “soft” cataract may not require surgical enlargement of the pupil even if dilation is poor. A brunescent cataract, however, may require surgical enlargement of the pupil even if it dilates moderately. Although manipulation of the pupil may result in decreased sphincter function, patients rarely complain of any problems and are far better off avoiding more serious events such as a capsule defect or vitreous loss. Each surgeon must determine what pupil size is adequate.
The dilated preoperative examination helps predict whether pupil manipulation will be necessary. Stripping a pupillary membrane or lysis of posterior synechia may significantly enhance pupil size. “Viscodilation” with a cohesive viscoelastic may be all that is required to enlarge the pupil to a comfortable size for capsulorrhexis. If further enlargement is required, the authors have found pupil stretch to be successful virtually 100% of the time. Although iris hooks, pupil ring expanders, and minisphincterotomies will enhance pupil size, they are rarely required because of the success of pupil stretch, improved techniques of phacoemulsification, and newer viscoelastics. (See Chapter 21, Phacoemulsification in the Presence of a Small Pupil.)
If pupil enlargement is required, the authors employ a bimanual stretch maneuver. Two instruments designed for iris manipulation are used (Osher Y-hook, E0577, Storz, Claremont, Calif.; Kuglen Iris Hook and IOL Manipulator, 6-400 and 6-402, Duckworth & Kent, St. Louis, Mo.). One instrument is placed in the anterior chamber through the paracentesis opening while the other enters through the phacoemulsification incision, and the pupil is stretched by simultaneously pushing and pulling the pupillary edge of the iris in opposite directions in the same meridian (6 clock hours apart) (Figure 22-5A).[43–45] For additional enlargement, a second stretch maneuver can be performed in a meridian about 90° from the first (see Figure 22-5B), or the two stretch instruments can be placed less than 6 clock hours apart before stretching. A slow and gradual stretch will minimize the risk of an atonic pupil. Self-limited bleeding may occur from the tears in the pupillary margin of the iris. Elevation of the IOP by filling the anterior chamber with BSS or viscoelastic can help tamponade the bleeding.
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Figure 22-5 A, Pupil is stretched by simultaneously pushing and pulling the pupillary edge of the iris in opposite directions in the same meridian (6 clock hours apart). B, Additional enlargement can be achieved by performing a second stretch maneuver 90° away from the first. |
In the rare cases when bimanual stretch inadequately dilates the pupil, iris retraction hooks can be helpful. Pupil stretching usually does not have any long-term effect on postoperative vision, IOP or inflammation.[72,][73]
Capsulorrhexis
Continuous circular capsulorrhexis is performed using a 22-gauge needle with a right-angle bend made about 1mm from the tip. An alternate method using capsule forceps is preferred by many surgeons. The size of the capsulorrhexis is often limited by suboptimal pupillary dilation and may require enlargement later in the procedure when the chamber has been deepened by a viscoelastic agent. (See earlier section, Management of the Small Pupil and Posterior Synechia.) Too small a capsulorrhexis may compromise phacoemulsification and cortical aspiration, increase the risk of a radial extension of the capsulorrhexis, and result in intraoperative and postoperative complications. (Also seeChapter 14, Capsulorrhexis.)
Hydrodissection, Hydrodelineation, and Viscodissection
The nuclear and cortical lens layers are hydrodissected from the lens capsule by gently injecting BSS just beneath the edge of the capsulorrhexis with a blunt 27-gauge cannula, using moderate infusion pressure. The pupil is observed for passage of a fluid wave across the red reflex. When dense cataracts preclude observation of the fluid wave, slight anterior movement of the nucleus confirms hydrodissection. Injection of fluid into the cataractous lens can achieve hydrodelineation by separating the nuclear, epinuclear, and cortical layers. (A 27-gauge J-shaped cannula can direct the hydrodissection to the cortex beneath the scleral incision and achieve better mobilization of the more difficult-to-remove cortex in this area.) Successful hydrodissection is crucial in poorly dilated pupils. It is helpful to test for adequate hydrodissection by rotating the nucleus (with viscoelastic in the anterior chamber) using one or two manipulating instruments. The injection of a viscoelastic may also be used to dissect cortex or nucleus away from the lens capsule when normal irrigation–aspiration techniques may be dangerous (e.g., with a small pupil or capsulorrhexis, capsule defect). (Also see Chapter 15, Hydrodissection and Hydrodelineation.)
Phacoemulsification and Cortical Aspiration
Phacoemulsification is performed using the preferred technique of the surgeon. The authors usually create a central groove greater than two-thirds of the depth of the lens and use a second instrument to help crack the nucleus into two halves. Each half is then rotated and chopped into smaller pieces, which permit easier and safer phacoemulsification in the posterior chamber.
Aspiration of the cortex is performed in the usual manner. This can be more challenging in the presence of a small pupil and capsulorrhexis. An iris manipulating hook should be used to push the iris peripherally and expose the peripheral capsular bag, when it is inadequately seen, to ensure removal of hidden cortex. Use of a separate aspiration cannula (Surgical Design Corporation, Long Island City, NY; Oasis Medical Inc., Glendora, Calif.) that is small enough to be passed through the paracentesis opening or the use of a 90° angled irrigation–aspiration tip can be extremely helpful in removing cortex from the capsular bag opposite the paracentesis and beneath the area of the scleral incision (Figure 22-6A). A J-shaped cannula on a syringe containing BSS can also be used to remove the subincisional cortex after having inflated the bag and anterior chamber with viscoelastic (see Figure 22-6B). (Also see Chapter 16, Principles of Nuclear Phacoemulsification, and Chapter 17, Phaco Chop.)
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Figure 22-6 A, Separate aspiration canula, small enough to be passed through the paracentesis opening, can be extremely helpful in removing cortex from beneath the area of the scleral incision. B, J-shaped cannula on a syringe containing balanced salt solution can also be used to remove the subincisional cortex after inflating the capsular bag with viscoelastic. |
Intraocular Lens Implantation
The tunnel incision is enlarged to the required size for IOL implantation. Use of IOL injectors may require little or no enlargement, depending on the specific IOL, cartridge and injector used. (Also see Part VI, Intraocular Lenses.)
Trabeculectomy or Sclerectomy
The left side of the scleral tunnel is cut anteriorly to permit elevation of the corner and exposure of the tunnel floor (Figure 22-7A). This creates an “L” shaped flap. A pair of nontoothed forceps is used to elevate the roof of the scleral tunnel to perform the trabeculectomy or sclerectomy.
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Figure 22-7 A, Left side of the scleral tunnel is cut anteriorly to permit elevation of the corner and exposure of the tunnel floor. B, Sharp blade is used to make an incision in the scleral floor of the tunnel, parallel to the limbus, about 0.5–1mm anterior to the posterior edge of the tunnel. C, Kelly punch is used to create a sclerectomy on the left side of the tunnel. |
A sharp blade is used to make an incision in the scleral floor of the tunnel, parallel to the limbus, about 0.5–1mm anterior to the posterior edge of the tunnel (see Figure 22-7B). A Kelly punch (instrument #E-2798, Storz, Claremont, Calif.) is used to create a 1×2mm opening into the anterior chamber on the left side of the tunnel (Figures 22-7C and 22-8A). Trabecular meshwork or peripheral cornea anterior to the trabeculum is removed. (Alternatively, the punch can be passed into the phacoemulsification incision and punch posteriorly; see Figure 22-8B.) If preferred, a freehand dissection is performed by making the same incision in the tunnel floor. Radial incisions are made anteriorly with a fine scissors (e.g., Vannas, instrument #E3389, Storz, Claremont, Calif.) on both sides of this incision. While the deep scleral tissue is grasped with toothed forceps, the scissors are used to cut the anterior edge, excising the tissue and creating a 1–2mm filtration opening (Figure 22-9). An assistant can elevate the roof of the tunnel with nontoothed forceps or a cellulose sponge, or the surgeon can use the edge of the Vannas scissors to elevate the scleral flap during this dissection.
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Figure 22-8 A, Kelly punch creates a sclerectomy (side view of Figure 22-7C). B, Alternatively, the punch can be passed into the phacoemulsification incision and punch posteriorly. |
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Figure 22-9 Sclerectomy can be created freehand with scissors and forceps. |
It is important to avoid extending the sclerectomy to the posterior edge of the tunnel floor to prevent simulation of a “full-thickness filtering procedure” with free access of aqueous flow through the incision to the scleral surface. Leaving a portion (0.5–1mm) of the scleral floor intact forces the aqueous humor to percolate from the trabeculectomy or sclerectomy opening, across a short portion of the scleral floor, and through the incision to the scleral surface, resulting in slight resistance to flow. If the trabeculectomy or sclerectomy opening is inadvertently created over the ciliary body and uvea, the dissection should be extended anteriorly over the iris. If required, a fine-needle-tip cautery can be used at low power to control bleeding.
Peripheral Iridectomy
Although some surgeons have suggested that an iridectomy is not necessary, it is safest to perform one.[74] Without an iridectomy, a shallow anterior chamber or application of digital pressure could result in occlusion of the trabeculectomy or sclerectomy opening from iris prolapse.
The iridectomy is performed by carefully grasping the peripheral iris as posteriorly as possible through the trabeculectomy or sclerectomy opening with a fine-toothed forceps. The peripheral iris is elevated with a slight side-to-side pulling motion, and Vannas scissors create the iridectomy opening (Figure 22-10A). The size of the iridectomy should approximate the size of the trabeculectomy or sclerectomy opening. Prolapsed iris tissue should be irrigated or gently massaged into the anterior chamber by bluntly rubbing in a peripheral to central motion on the corneal surface over the iridectomy with the elbow of the 19-gauge irrigation cannula. Aqueous humor will pass through the sclerectomy opening and the scleral incision into the subconjunctival space (Figure 22-10B). A fine-needle-tip cautery can be used at low power to control bleeding from the iridectomy edge. Great caution must be taken while cauterizing in this area. If the cautery disrupts the zonules in the area, vitreous can prolapse through the iridectomy and sclerostomy even in a phakic eye. Vitreous prolapse from any cause must be meticulously managed to prevent the vitreous from occluding the internal sclerostomy and causing failure of the trabeculectomy.
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Figure 22-10 A, Peripheral iris is elevated with a slight side-to-side pulling motion, and Vannas scissors are used to create the iridectomy opening. B, Aqueous passes through the sclerectomy opening and the scleral incision into the subconjunctival space. |
Scleral Flap Closure with Releasable Sutures
The scleral flap is closed with releasable sutures.[46] These will secure the wound and provide nearly watertight closure, preventing early postoperative hypotony, flat anterior chamber, and associated complications. Three or four releasable sutures are usually used, placing one at the corner and two along the scleral incision. A fourth suture can be placed in the side scleral incision. When the anterior chamber has stabilized and bleb healing has produced some resistance to aqueous flow, the sutures can be released to increase aqueous flow and help reach the target IOP. The number of sutures placed varies significantly among surgeons. However, the greater the number of sutures placed, the greater control one can have in reaching the goal IOP by reducing the effect of each suture as it is released or lysed.
The releasable sutures are placed in three steps. Using a narrow cutting needle on a 9-0 nylon suture (#7760, Ethicon, Sommerville, NJ) the first bite is placed through partial-thickness cornea, about 2mm central and parallel to the limbus (Figures 22-11A and B). The second bite is placed radial to the limbus (approximately 90° to the first bite), passing through partial-thickness cornea beneath the conjunctival insertion at the limbus and exiting on the scleral side of the limbus (see Figures 22-11C and D). (In the early postoperative period, epithelial cells grow over the suture lying on the corneal surface between the first and second bites.) The third bite is placed across the scleral flap incision (see Figures 22-11E and F). After placing the first suture, the second and third sutures are also placed (see Figure 22-11G). Before tying the releasable sutures, the viscoelastic is aspirated from behind and in front of the IOL.
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Figure 22-11 A and B, First bite is passed through partial-thickness cornea, about 2mm central and parallel to the limbus. C and D, Second bite is placed radial to the limbus (approximately 90° to the first bite), passing through partial-thickness cornea beneath the conjunctival insertion at the limbus and exiting on the scleral side of the limbus. E and F, Third bite is placed across the scleral flap incision. G, After placing the first suture, the second and third sutures are also placed. H, Releasable sutures are tied by grasping the suture exiting the sclera from the third bite and passing three throws around a tying forceps. I, Tying forceps then used to grasp the suture on the scleral flap surface between the second bite and the third bite. J, Three throws are brought down over the grasped suture, creating a loop knot that secures the scleral incision. K, Suture is trimmed long enough so that it lies flat on the scleral surface. L, Suture lying on corneal surface is trimmed where it entered the cornea for the first bite. |
The releasable sutures are tied by grasping the suture exiting the sclera from the third bite and passing three throws around a tying forceps (see Figure 22-11H). The tying forceps then are used to grasp the suture on the scleral flap surface between the second bite and the third bite (see Figure 22-11I), and the three throws are brought down over the grasped suture, creating a loop knot that secures the scleral incision (see Figure 22-11J). The suture is trimmed long enough so that it lies flat on the scleral surface (see Figure 22-11K). The suture lying on the corneal surface is trimmed where it entered the cornea for the first bite (see Figure 22-11L). Forceps are used to pull gently on the suture, and scissors are used to push gently on the cornea so that when the suture is cut at the corneal surface, it retracts into the corneal tissue.
After placement of the releasable sutures, acetylcholine (Miochol-E) is injected through the paracentesis tract to deepen the anterior chamber and to constrict the pupil. Scleral flap closure should be secure enough to prevent aqueous leak from pressure elsewhere on the globe, but to permit slight aqueous leak when blunt pressure is applied to the posterior lip. An elevated IOP on the first postoperative day is preferable to hypotony, particularly if MMC has been used. It is easier to manage the former. (Management of IOP and release of sutures are discussed later in this chapter.)[46–48]
The technique of laser suture lysis of standard simple interrupted sutures is described later in this chapter. Three other releasable suture techniques have been described by Hoskins and Migliazzo,[49] Savage et al.,[50] McAllister and Wilson,[51] Shin,[52] and Johnstone[53] and can be researched if desired.
Conjunctival Flap Closure
The limbus-based conjunctival flap is closed with a 9-0 absorbable monofilament suture on a tapered vascular (noncutting) needle. Using a running suture technique, the deeper Tenon's layer is closed with locking stitches, and the superficial conjunctival layer is closed with a nonlocking stitch. Widely spaced stitches are used in the deeper Tenon's layer, and stitches 0.5–1mm from the incision edge and separated by 1–2mm are used in the conjunctival layer (Figure 22-12A).
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Figure 22-12 A, Using a running suture technique, the deeper Tenon's layer is closed with locking stitches, and the superficial conjunctival layer is closed with a nonlocking stitch. B, Mattress and a lateral running (noncutting needle on 9-0 or 10-0 Vicryl) suture closes the conjunctiva laterally. C, Overlapping running suture, using 9-0 nylon (Ethicon 2890) can also be used to close the conjunctiva at the limbus. D, Running horizontal mattress suture conjunctiva to conjunctiva closure with 9-0 monofilament Vicryl on a tapered vascular needle (Ethicon V402G) for alternate fornix-based technique (from Figure 22-2B). |
On the other hand, if the standard fornix-based flap incision was created by disinserting the conjunctiva at the limbus, it can be closed by securing one side of the conjunctival flap to the peripheral cornea with a mattress suture. The other side of the conjunctival flap incision is then pulled, stretching the conjunctival edge against the peripheral cornea, and another mattress suture is placed. The limbal edge of conjunctiva is inspected, and additional mattress sutures are placed as necessary for secure closure. The surgeon must be sure that the exposed “elbow” of the releasable suture, between the first and second bites (the place where the suture is grasped when removed postoperatively), is not covered by the conjunctival flap. A running (noncutting needle on 9-0 or 10-0 absorbable) suture closes the conjunctiva laterally (see Figure 22-12B). It is helpful to start this closure with a bite of episclera at the limbus. An overlapping running suture, using 9-0 nylon (Ethicon 2890) can also be used to close the conjunctiva at the limbus (see Figure 22-12C).
An alternative closure of a standard fornix-based conjunctival flap has been reported by Wise,[54] using a 9-0 nylon suture on a VAS-100 needle (Ethicon 2890, Ethicon, Inc., Somerville, NJ). The VAS-100 needle is a very useful needle in glaucoma surgery. It is finer than a standard spatulated needle, thus creating a smaller hole (particularly useful in thin conjunctiva), yet it is stronger than a standard tapered vascular needle and can be passed through cornea and sclera without bending easily. The VAS-100 needle is also available on a monofilament 9-0 Vicryl suture by special order.
The alternative technique fornix based conjunctival flap (with the conjunctival incision 1.5mm posterior to the limbus) is closed with a running horizontal mattress technique using a monofilament 9-0 Vicryl on a tapered vascular needle (Ethicon V402G, Sommerville, NJ) suturing conjunctiva to conjunctiva. The narrow anterior lip of conjunctiva is often quite thin near the limbus and requires gentle care. The suture is pulled down toward through the cornea after each pass out through the anterior edge of the incision, to cinch the incision edges together (Figure 22-12D).
Phacoemulsification and Trabeculectomy at Separate Sites
Combined surgery with separate-site temporal clear corneal phacoemulsification and superonasal trabeculectomy has been advocated by some surgeons. This approach requires the surgeon to change positions and move the microscope when switching from one surgical site to the other. For younger surgeons who have trained in the era of temporal corneal phacoemulsification, they may feel more comfortable using this same approach instead of a scleral tunnel technique used with one-site surgery. If a two-site approach is used, it is important to make sure that the incision is completely corneal to avoid any disruption of the temporal conjunctiva that could create a leak in the bleb. Although one study suggested slight benefit in IOP control, another study did not confirm this finding.[55,][56] The authors generally use this approach when superotemporal scarring requires superonasal filtration, when the presence of extremely thin conjunctiva increases the risk of a defect from the added manipulation, or in very deep set eyes.
Intraoperative medications
At the completion of the procedure aqueous betamethasone (Celestone) is injected subconjunctivally. An antibiotic preparation may also be injected subconjunctivally at the surgeon's discretion. In addition, one drop of 5% povidone-iodine solution (Betadine) is placed in the fornix at the conclusion of the procedure. If the anesthetic block requires postoperative patching, antibiotic-steroid ointment is also applied.
Basic postoperative management
Frequency of Examinations
The early postoperative period is critical to the success of combined surgery. This is when elevated IOP is most likely to occur and when it can most effectively be managed. Examinations should be performed 1 day after surgery and at least weekly during the first postoperative month.
Postoperative Medications
Topical prednisolone acetate 1% corticosteroid eyedrops are used every 2 h while awake for the first few weeks following surgery, and are then gradually tapered and discontinued around the end of the third postoperative month. There has been some very recent debate about the potential benefits/risks of long-term, low-dose maintenance anti-inflammatory therapy to reduce the risk of wound remodeling and late fibrosis causing bleb failure. However, there have not been any randomized, peer-reviewed studies that have critically evaluated these claims. Topical antibiotic eyedrops (the authors use a quinolone eyedrop) are used four times a day during the first 7–10 days and then discontinued. If releasable suture removal is anticipated, the antibiotic drops are continued. Topical nonsteroidal antiinflammatory eyedrops are used three times a day for about 3 weeks. Postoperative subconjunctival injections of 5-FU may be administered for augmentation of intraoperative antifibrosis effect.
Postoperative management and complications
Postoperative Elevated Intraocular Pressure
Determining the cause of elevated intraocular pressure
Elevation of IOP often occurs in the early postoperative period. It is important to proceed through a stepwise logical evaluation of potential causes along the path of aqueous filtration from the anterior chamber to the subconjunctival space. Careful examination of the anterior chamber may reveal the presence of noncirculating cells, indicating retained viscoelastic material that interferes with flow at the trabeculectomy or sclerectomy opening. Gonioscopy should be performed to rule out obstruction of the internal sclerostomy opening by vitreous, iris, fibrin, or a blood clot or incompletely removed Descemet's membrane, sclera, or cornea. Because of the risk of prolapsed vitreous occluding the internal sclerostomy, it is very important that a capsular tear and vitreous prolapse is managed with an adequate anterior vitrectomy. Examination of the filtering bleb may reveal a shallow or flat bleb from tight wound closure and inadequate filtration, an encysted filtering bleb, a subconjunctival hemorrhage, or blood clot blocking filtration through the scleral flap. Hemorrhage in the filtering bleb may occur intraoperatively from bleeding associated with tissue dissection; from anesthetic, antibiotic, or steroid injection; or postoperatively from suture release or laser lysis. Rarely, postoperative subconjunctival hemorrhage can occur from relaxation of a vessel in spasm or from clot lysis before a vessel has healed.
Late postoperative elevation of IOP is almost always due to episcleral scarring in the filtering bleb. This may occur gradually over time or may be precipitated by episodes of inflammation from uveitis, subsequent eye surgery, and so on. However, gonioscopy should still also be performed in these cases to rule out internal obstruction.
Treatment of Early Postoperative Elevation of Intraocular Pressure
Blockage of internal filtration opening
If the internal sclerectomy is blocked by a blood clot or fibrin, injection of tissue plasminogen activator into the anterior chamber may correct the obstruction.[57] If the iris, vitreous, Descemet's membrane, or lens capsule is preventing aqueous outflow, Nd:YAG or argon laser treatment may open the obstruction, but surgical intervention and wound revision will probably be required. Some cases of iris incarceration can be successfully managed with the use of a miotic such as pilocarpine. However, even if successful, the risk of recurrence is high and should be managed by some maneuver to prevent recurrence. Long-term miotic use in these cases is not ideal. Argon laser iridoplasty can be used to shrink and stretch the iris around the iridectomy to reduce its laxity and prevent recurrent incarceration.
Tight wound closure and technique of removal of releasable sutures
If the elevated IOP is due to inadequate filtration from tight scleral flap closure, removing releasable sutures can loosen the scleral flap and increase filtration. (Similar principles also apply to laser lysis of conventional sutures.) Before considering suture release or lysis, digital or instrument pressure is critical to determine the current resistance to outflow. If the IOP drops and a significant bleb rises with light pressure, then suture release will carry a high risk of inducing hypotony. On the other hand, if the IOP does not drop and a bleb can not be raised even with firm pressure, then the risk of inducing hypotony is usually low. In general, the authors try to avoid resuming anti-glaucoma drops, if possible, because of their potential of increasing conjunctival inflammation. At the same time, this must also be weighed with the IOP level and the severity of glaucoma damage. If the current IOP is at a level deemed to be dangerously high even for a few weeks, then consideration must be given to temporarily restarting at least some IOP lowering medical therapy. The surgeon, however, must use a reasoned and rational approach (Table 22-2). If the sutures are released before adequate healing has occurred, hypotony and overfiltration can result. If suture release is delayed too long and too much healing has occurred, increased filtration and lowered IOP will not be achieved. Virtually all combined procedures are now performed with adjunctive antimetabolite therapy. In most patients, this will slow wound healing and delay suture release compared with when antimetabolite therapy is not used.
Table 22-2 -- Removal of releasable sutures*
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A. Surgery performed with antimetabolites |
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B. Surgery performed without antimetabolites |
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* |
These principles also apply to laser suture lysis. |
The vascularity of the filtering bleb serves as a helpful indication of the extent of underlying wound healing. Highly vascularized filtering blebs indicate a high probability of more rapidhealing and should prompt consideration of earlier suture removal. Avascular or relatively avascular filtering blebs suggest slower healing and should prompt consideration of delayed suture removal. (It is advisable to consider discussing with the patient the pros and cons of suture removal or laser suture lysis so that they are aware of the possible complications.) Rather than using a “cookbook” approach to the steroid drop regimen, the regimen is based on the vascularity and appearance of the bleb. If significant conjunctival injection develops and persists, the authors will not hesitate to increase the steroid drops to hourly for as long as necessary. In the end, once the eye has completely healed, the ideal bleb is minimally ischemic. Significant residual vascularity of the bleb even beyond 3 months postoperatively still indicates a greater risk of long-term bleb failure.
During the first postoperative week, every effort should be made to avoid suture removal because of the increased risk of overfiltration, hypotony, chamber flattening, and associated complications. An IOP in the 20s for a short period will usually not cause progression of glaucoma damage. If a limbus-based conjunctival flap was used, digital, cotton swab, or instrument pressure can be applied while observing the bleb for enlargement.[53,][58] If a fornix-based conjunctival flap was used, digital pressure or instrument pressure could cause a bleb leak and may need to be avoided during this period, depending on the closure technique used. However, with the technique of closing the fornix-based conjunctival flap with a running horizontal mattress suture, wound leaks are quite rare, even with the application of pressure on the first postoperative day. Topical and, if needed, oral therapy (including acetazolamide and hyperosmotic) can be administered, and, if necessary, paracentesis can be performed at the slit lamp examination (preceded by a drop of topical anesthetic, topical antibiotic, and 5% povidone-iodine solution [Betadine]). However, it is important to keep in mind that complete turnover of aqueous volume occurs in approximately 100 min, limiting the duration of effect of a therapeutic paracentesis. This also applies to digital pressure and massage. The IOP should be monitored for 30–60 min and then rechecked the following day to ensure stability.
During the second postoperative week, healing has progressed and removal of releasable sutures is safer. It is preferable to first apply gentle and then stronger digital pressure to stimulate filtration. Sometimes this maneuver will dislodge a fibrin clot or disrupt initial wound healing and result in lasting IOP control. IOP should be rechecked in 20–30 min to determine if the effect is lasting. If the IOP has returned to an undesirable level, and depending on the stage of glaucoma damage and the risk factors for failure (previous surgery, race, type of glaucoma, etc.), suture release can be performed. The surgeon should realize that complications of suture release can still occur.
During the third postoperative week, suture removal is usually safe. If suture removal is performed, the principles of adjunctive digital pressure, reevaluation of IOP in 30 min and avoidance of multiple suture removal in 1 day, should be followed. As healing progresses, the effect of suture release decreases, depending on the duration and concentration of MMC, surgical technique, individual patient variables, etc.
The technique of suture release involves elevation of the upper eyelid (an assistant may be helpful but is not required) and use of a fine forceps to grasp the suture where it changes direction at the elbow between the first (intracorneal) and the second (sublimbal) bites of the releasable suture. If necessary, the superficial layers of the corneal epithelium (which have grown over this portion of suture that was on the epithelial surface at the time of surgery) are penetrated to grasp the suture. The intracorneal segment of suture is teased out of the tissue and then pulled with constant gentle traction to release the loop knot and remove the suture (Figure 22-13A and B). In the rare cases where whilst trying to remove a releasable suture it breaks, the scleral portion of the suture can still by lysed with an argon laser as described below. The bleb is observed for enlargement during suture removal, and the IOP is measured. If the IOP is unchanged, gentle digital pressure can be applied to initiate or promote filtration. If IOP decreased, it may be checked again in about 20 min to determine if the effect is lasting. Follow-up can be planned for the next day or in 1 week, depending on the surgeon's preference. As a general rule, only one suture should be released on any day, and the sutures are removed from left to right, with the corner suture removed last.
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Figure 22-13 A, Intracorneal segment of suture is teased out of the tissue. B, Suture is pulled to release the loop knot and remove the suture. C, If suture removal is not needed, the sutures can be trimmed by teasing the intracorneal portion out of the tissue, pulling slightly with forceps and depressing the cornea with scissors so that the cut end will retract into the tissue. |
If the surgeon decides that suture removal will not be necessary, the sutures can remain (the 9-0 nylon will dissolve over the next 2–3 years) or can be trimmed by teasing the intracorneal portion (the first of the three bites) out of the tissue, pulling it slightly with forceps while depressing the cornea with scissors so that the cut end will retract into the tissue (see Figure 22-13C).
Laser suture lysis
Argon laser suture lysis can be very useful in the postoperative management of trabeculectomy surgery. The timing of suture lysis is similar to the removal of releasable sutures. If available, the Hoskins or the Ritch lens (Ocular Instruments, Bellevue, Wash.) can compress the overlying conjunctiva (and its blood vessels) and aid in visualization of the scleral flap sutures. If these lenses are not available, the corner of a four-mirror Posner goniolens (Ocular Instruments, Bellevue, Wash.) can serve the same purpose. If visualization is difficult because of thick or boggy overlying tissue or engorged blood vessels, topical phenylephrine may be helpful.
In eyes with residual subconjunctival blood overlying the scleral flap sutures, use of the argon or green wavelength risks absorption of the laser energy by the blood and the overlying conjunctiva. This could result in a full-thickness conjunctival defect that may not heal. Laser suture lysis with a krypton or red wavelength laser permits selective treatment of the suture and minimizes risk to the conjunctiva. The diode infrared wavelength can also be used for laser suture lysis, but is less effective.
Laser suture lysis settings are 50 μ spot size, 70–100 ms burn duration, and 260–400 mW of power (Table 22-3). Ideally, one should attempt to cut the suture at both ends to ensure that the long episcleral piece of suture lays flat and does not perforate the conjunctiva.
Table 22-3 -- Laser suture lysis settings
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Spot size: 50 μm |
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Burn duration: 70 to 100 ms |
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Power: 260 to 400 (average 300) mW |
Management of Subconjunctival Hemorrhage
Subconjunctival hemorrhage in the filtering bleb may increase the risk of bleb failure. More aggressive use of topical corticosteroid eyedrops is usually adequate to preserve the filtering bleb. Earlier suture release, subconjunctival injection of corticosteroids adjacent to the filtering bleb, and subconjunctival 5-FU injections may be considered.
Encysted Filtering Bleb
An encysted filtering bleb is characterized by a localized highly elevated bleb associated with a high IOP. It is usually evident within the first postoperative month and may develop as early as several weeks following surgery. Conservative management with addition of IOP-lowering agents is usually successful in controlling IOP. Needling the filtering bleb at the slit lamp examination (preceded by topical anesthetic, broad-spectrum topical antibiotic, and 5% povidone-iodine solution [Betadine]) or in the operating room may restore diffuse filtration and lower IOP. However, the success of needling revisions tends to be lower in eyes with true encapsulated blebs. The conjunctiva is slightly elevated by a subconjunctival injection of sterile BSS or anesthetic such as 1% lidocaine (xylocaine) with epinephrine for vasoconstriction, administered about 1 cm from the bleb. A cotton-tipped applicator is used to push the BSS toward the bleb. A needle knife is passed into the subconjunctival space through the same entry point used for the BSS injection. The knife is passed beneath the elevated conjunctiva to the bleb where the wall is punctured and cut. If the nature of the bleb permits, the knife can also be passed across the bleb to cut the opposite wall. This procedure can be augmented with daily subconjunctival injections of 5-FU or a pre-needling injection of mitomycin C to prevent healing. Hypotony can result from this procedure. A recent case report showed a beneficial effect of adjunctive bevacizumab on the outcome of a needling revision of an encapsulated bleb that had previously failed an earlier needling with adjunctive mitomycin C.[71]
Treatment of Late Postoperative Intraocular Pressure Elevation
Scarring of the filtering bleb, the most common cause of late IOP elevation, may be managed by needling the bleb and scleral flap. This technique is best performed when the scleral flap edges can be seen through the conjunctiva by slit-lamp examination. (IOP reduction first may be attempted by the addition of eyedrops to avoid the risks of subconjunctival hemorrhage and hypotony.) Although some surgeons prefer to perform this at the slit lamp, others may prefer the operating room.
Late scleral flap needling (and injection of antimetabolite)
The eye is prepared by several applications of a topical anesthetic eyedrop and a drop of 5% povidone-iodine solution (Betadine). A subconjunctival injection of BSS separates scar tissue and creates a plane for safer passage of the needle. A 27-gauge or 30-gauge needle or needle knife is inserted into the subconjunctival space at least 1 cm from the scleral flap and is passed beneath the conjunctiva to the scarred filtering bleb or the scleral flap incision. A back-and-forth motion is used to disrupt the scar tissue, elevate the scleral flap, and, if necessary, penetrate the sclerostomy. Restoration of aqueous flow is indicated by elevation of the filtering bleb. After removal of the needle, the entry point is observed for aqueous leakage. If necessary, careful light cautery can be applied to shrink the conjunctiva surrounding the leak to achieve closure. The leaking area is first dehydrated with a sterile cotton tip applicator. A low-temp disposable cautery unit is then brought very close to the conjunctiva, without actually touching the conjunctiva, and a brief light treatment of cautery applied. Direct contact with the conjunctiva can sometimes have the opposite effect and enlarge the defect. Suture closure is rarely necessary.
Antimetabolite can be injected before needling. A mixture of bupivacaine 0.75% with epinephrine (marcaine) or lidocaine 1% with epinephrine (xylocaine), and MMC 0.4 mg/mL is prepared for injection by aspirating 0.01mL of the MMC into a 30-gauge needle on a 1mL syringe, followed by 0.02mL of bupivacaine (or lidocaine). This small volume only partially fills the hub of the needle. The needle is inserted into the subconjunctival space 1 cm from the bleb, and the mixture is injected near the site of revision, elevating the tissue. A sterile cotton swab is used to spread the mixture in the subconjunctival space. After 15 or 20 min, a second needle (or “Angled Stiletto” knife, Becton-Dickinson), passed through the same entry point as the first, is used to revise the bleb, scleral flap, and, if necessary, the sclerostomy.[59] Great care must be taken to avoid any risk of the antimetabolite entering the central portion of the bleb cavity and potentially entering the anterior chamber which could lead to corneal decompensation.
A similar technique has been reported, employing a needle revision of the filtering bleb with postoperative injections of 5-FU.[60]
Other Causes of Intraocular Pressure Elevation
Rare causes of postoperative elevation of IOP may include aqueous misdirection (malignant glaucoma, ciliary block glaucoma), suprachoroidal hemorrhage, choroidal effusion, and so on. Management of these entities is complex. Publications and texts should be consulted to develop appropriate strategies of treatment.
Postoperative hypotony mechanisms
Hypotony may result from excessive outflow or inadequate production of aqueous. In the early postoperative period, excessive outflow from a wound leak or bleb leak is more common than overfiltration with a large bleb, aqueous flow through a cyclodialysis cleft or aqueous underproduction from iridocyclitis, choroidal detachment, or, rarely, from a previous cyclodestructive procedure. (Hyposecretion of aqueous from iridocyclitis may be clinically diagnosed by noting stagnant or slowly moving cells in the anterior chamber after residual viscoelastic has been ruled out.)
An aqueous leak can usually be identified by applying fluorescein solution and patiently observing the bleb surface under blue light for an interruption in the fluorescein pattern. Painting the area of interest with a fluorescein strip will sometimes reveal aqueous leaks that may be difficult to identify with liquid fluorescein. Sometimes hypotonous eyes will only demonstrate a leak with application of gentle digital pressure to the globe.
The need for intervention becomes more urgent if secondary complications from hypotony are present, such as flat anterior chamber, significant choroidal effusions, macular choroidal folds sometimes associated with disc edema or congestion (hypotony maculopathy), and, of course, choroidal hemorrhage.
Overfiltration with leak: early
A wound leak or conjunctival button hole is counter-productive to the development of a bleb and should be closed as soon as possible. However, some incision leaks may close spontaneously, particularly at the limbus. The management options for a wound leak depend on the leak location and appearance, and include: bandage contact lens for tamponade; application of cyanoacrylate or tissue glue to seal the leak and use of a large bandage contact lens to prevent discomfort;[61,][62] reducing the frequency of the corticosteroid drops to facilitate healing; suture repair (either at the slit lamp or in the operating room depending on the surgeon and patient's comfort level); and even conjunctival graft in extreme and rare circumstances. Compression sutures are sometimes successful in localizing a conjunctival defect and closing the aqueous leak, and can be a very helpful tool.[63]
A low IOP, with or without wound leak, is sometimes associated with a shallow or flat anterior chamber as well as choroidal effusions. Iridocorneal apposition can persist for some time without risk of corneal endothelial injury or permanent injury. However, IOL-corneal contact has a much greater risk of endothelial injury, and is an absolute indication for anterior chamber reformation with a viscoelastic agent.[64,][75] This can be done in the office in most circumstances. A dilated fundus exam should be performed to document the presence and extent of choroidal effusions. Topical cycloplegic drops such as cyclopentolate, scopolamine, homatropine and atropine can also help to deepen the anterior chamber.
Overfiltration with leak: late (greater than 3 months postoperative)
Conservative attempts to close late bleb leaks may have limited success and depend on the degree of conjunctival ischemia in the leaking area. A large bandage contact lens may tamponade the leak and permit healing. Late leaks, which are usually associated with devitalized conjunctival tissue, most often require extensive bleb revision with creation of a new bleb surface. Late bleb leaks are also of great concern because of the increased risk of bleb failure, bleb infection and endophthalmitis. If there is no evidence of blepharitis or other factors that might predispose to endophthalmitis, there has been no previous occurrence of blebitis, and the IOP is normal (in the teens), the leak may be observed after educating the patient about signs and symptoms of infection and giving instructions to contact the doctor immediately if they occur. The patient may be given a prescription for a broad-spectrum antibiotic to use if signs and symptoms of infection arise until the doctor can be seen. Some surgeons have advised against the chronic prophylactic use of antibiotics in chronic bleb leaks because of the possibility of selecting for antibiotic resistant bacteria.
Overfiltration without leak: extensive bleb
Overfiltration may occur in the first few days following surgery as a result of inadequate scleral flap closure. (Most surgeons will ensure tight scleral flap closure, realizing that postoperative elevations of IOP can be treated with medications, paracentesis, or suture release rather than risk hypotony, which is more difficult to manage.) If overfiltration results in complications, such as choroidal detachment, shallow or flat anterior chamber, or hypotony maculopathy, management may include decreasing frequency of topical corticosteroids, deepening of the anterior chamber by cycloplegics, pressure patch (with “torpedo” on the eyelid in the area of the filtering bleb) or injection of viscoelastic, resuturing of the scleral flap, and so on. The method and nature of management should be determined by the associated risks and the potential benefits of the treatment.
If hypotony is present beyond the normal period of resolution, and if reversible causes, such as choroidal detachment, and more permanent causes, such as cyclodialysis cleft, have been excluded, several management possibilities may be considered. Injection of autologous blood into the bleb, external local application of trichloroacetic acid, and treatment with cryotherapy have been effective in decreasing filtration.[65] Placement of a barrier suture across the filtering bleb can also limit the area of filtration and decrease bleb size.[63] Rarely, return to the operating room to place additional scleral flap sutures may be required.
In the absence of a bleb leak, hypotony may be observed without definitive treatment, as long as there are no complications. Many eyes will tolerate an IOP below 6mmHg indefinitely. Others may develop a choroidal detachment with an IOP as high as 10–12mmHg.
Overfiltration without leak: cyclodialysis cleft
Management of a cyclodialysis cleft may initially be attempted by use of topical cycloplegic eyedrops but may require laser treatment, cryotherapy, or transscleral suturing.[66,][67]
Decreased ciliary body production of aqueous: cyclitis
This can be one of the most challenging problems associated with hypotony. Aggressive anti-inflammatory therapy may be helpful. This is a phenomenon that the authors have observed most commonly in patients of African ancestry. Hourly corticosteroid drops may need to be used for many weeks, sometimes also augmented with the use of oral prednisone. Reopening the conjunctival flap and resuturing the scleral flap to reduce or stop filtration may be necessary in rare circumstances.
Large uncomfortable bleb
Uncommonly, even though filtration provides excellent IOP control, the bleb size will cause discomfort or interfere with tear lubrication, and result in dellen formation or punctate corneal staining. This can be one of the most frustrating challenges for both the patient and the physician. Topical lubricants (drops during the day and ointment at bedtime) and topical nonsteroidal anti-inflammatory eyedrops may be helpful. Specialized techniques of laser treatment, use of trichloroacetic acid, and surface cryotherapy may improve comfort, though there is some risk of creating a bleb leak. Compression sutures have also been helpful. If all else has failed, bleb revision surgery can be considered with the risk that filtration will be compromised.[20,][68–70]
Blebitis and endophthalmitis
Significant risk factors for blebitis and endophthalmitis include the presence of chronic blepharitis, poor hygiene, a thin-walled bleb, an avascular bleb, and a bleb leak. Patients should be alerted to the signs and symptoms of bleb infection, which are redness, discharge, pain, photophobia, and reduced vision, and they should be advised to contact their ophthalmologist immediately if they occur. If infection is limited to the bleb, a culture of the lids, conjunctiva, and bleb may be helpful in determining the etiologic agent. Intensive topical broad-spectrum antibiotic therapy may be curative. Evidence of more severe infection with hypopyon or vitreous involvement warrants more aggressive therapy that may include vitreous tap or vitrectomy and intraocular injection of antibiotics.[70]
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Conclusion
Combined phacoemulsification and trabeculectomy is an excellent surgical technique for the management of coexisting glaucoma and cataract. The patient can benefit from decreased disability and morbidity by having one rather than two procedures performed. However, the surgeon must understand the appropriate indications and the special techniques required for intraoperative and postoperative care of these patients. This approach represents an exciting challenge for the surgeon with great potential for preserving visual function, increasing visual acuity, and improving quality of life.
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