Cataract Extraction in Patients with Glaucoma
RONALD L. FELLMAN and GEORGE L. SPAETH
Table Of Contents
CLINICAL ASPECTS OF OPTIC NERVE HEAD DAMAGE
VISUAL FIELD LOSS AND ITS RELATION TO CATARACT–GLAUCOMA SURGERY
ANTERIOR-SEGMENT TISSUE ALTERATIONS SECONDARY TO GLAUCOMATOUS DISEASE REQUIRE ADDITIONAL PLANNING
INTRAOCULAR PRESSURE CHANGES ASSOCIATED WITH LENS EXTRACTION
CASE 1: ANTICIPATED LENS EXTRACTION WITH MILD TO MODERATE DISC DAMAGE AND IOP WITHIN TARGET PRESSURE RANGE
CASE 2: ANTICIPATED LENS EXTRACTION WITH MILD TO MODERATE DISC DAMAGE AND IOP WITHIN 4 MM HG OF TARGET PRESSURE RANGE
CASE 3: ANTICIPATED LENS EXTRACTION WITH MILD TO MODERATE DISC DAMAGE AND IOP FAR OUTSIDE OF TARGET PRESSURE RANGE
CASE 4: ANTICIPATED LENS EXTRACTION WITH ADVANCED DISC DAMAGE AND IOP WITHIN OR OUTSIDE TARGET PRESSURE RANGE
CASE 5: ANTICIPATED LENS EXTRACTION POST SUCCESSFUL TRABECULECTOMY
CASE 6: ANTICIPATED LENS EXTRACTION POST FAILED TRABECULECTOMY WITH ADVANCED DISC DAMAGE AND IOP OUTSIDE TARGET PRESSURE RANGE
EXTRACAPSULAR CATARACT EXTRACTION VIA NUCLEAR EXPRESSION COMBINED WITH GLAUCOMA FILTRATION SURGERY
|This chapter provides a framework for meaningful decision-making
regarding patient care in the setting of both cataract and glaucoma. The
multitude of technological, procedural, and pharmacologic advances
now available to ophthalmologists enables them to provide superior outcomes
for their patients afflicted with cataract and glaucoma. The knowledge
necessary to accomplish this is straightforward for some cases
and exceedingly complex in others. The underlying theme throughout this
chapter is that the management approach in the patient who has both
glaucoma and cataract must be in many ways totally different from that
of a person with cataract uncomplicated by glaucoma. The failure to
appreciate this difference may lead to unnecessary morbidity and visual
The trend in conversion from extracapsular cataract extraction (ECCE) to small incision cataract surgery continues to improve visual outcomes. The benefits from small incision cataract surgery for the stable glaucoma patient are extraordinary. The capacity to immediately improve vision with small incision cataract surgery alone, avoid the complications of trabeculectomy, potentially lower intraocular pressure (IOP) over the long-term and spare valuable conjunctiva for future glaucoma surgery is a surgical triumph for these patients. Consequently, a stable glaucoma patient on one or two medications with mild disc damage and symptomatic cataract may no longer require a combined or staged procedure. When filtration surgery is required, the capability to modulate wound healing and alter aqueous flow after trabeculectomy decreases complications and increases efficacy. From a pharmacologic viewpoint, the potent prostaglandin analogues enhance outflow thereby decreasing the need for more complex filtration surgery.
Patients with advanced disc damage, uncontrolled glaucoma at any stage, or complex cataracts present a much more challenging situation. They are far from elementary and present the ophthalmic surgeon and patient with many demanding problems. The knowledge and wisdom necessary to achieve a favorable outcome in these difficult cases requires a fusion of higher level preoperative, intraoperative, and postoperative decision-making skills. This situation is seen most commonly in patients requiring combined procedures who have advanced optic nerve damage complicated by any of the following: systemic diseases, especially diabetes mellitus; secondary glaucomas; anterior segment anomalies; miosis with posterior synechiae; pseudoexfoliation; keratopathy and complex cataracts. Society's perception of cataract surgery as a quick-fix operation with a rapid return of splendid vision is often not true for these patients who invariably perceive they are undergoing “routine” cataract surgery.1 Optic nerve damage or other concomitant eye diseases may limit visual recovery after flawless phacotrabeculectomy leaving a disappointed patient. Moreover, filtration surgery slows improvement in visual acuity.2,3 Informed consent with special emphasis on postoperative complications is especially important in glaucoma patients undergoing high-risk filtration surgery. Surgeons and their staff must spend additional time counseling patients who require filtration surgery due to the myriad of potential complications inherent to this procedure, which are far greater than routine lens extraction.
In years past, patients with both cataract and glaucoma frequently provided overwhelming surgical challenges for the ophthalmologist. The ability to carry out phacoemulsification through a 3.2-mm corneal incision along with inserting a foldable IOL is a vast improvement over 11-mm incisions that were common a decade ago (Fig. 1). The anatomical and inflammatory changes to the eye are less with small incision techniques, improving the likelihood of success with concomitant glaucoma surgery. Pharmacologic inhibition of fibrosis along with postoperative wound revision increases the long-term success rate of filtration surgery when combined with lens extraction. (Fig. 2). The learning curve may be steep at times, but the blending of cataract and glaucoma surgical skills slowly falls into place as the surgeon constantly learns and upgrades his or her technique.
Small incision cataract surgery combined with continuous curvilinear capsulorrhexis (CCC), improved management of miotic pupils, divide-and-conquer nucleofractis phacoemulsification, clear corneal incision, capsular tension rings,4 phaco-chop, improved viscoelastics, piggy-back IOL systems, and foldable intraocular lenses (IOL) greatly improve cataract surgical outcomes. The use of dyes to stain the anterior capsule in patients with an absent red reflex as in a white cataract improves visualization for anterior capsulorrhexis. These techniques, in combination with antimetabolite-assisted guarded filtration surgery (GFS) and postoperative scleral flap suture lysis or releasable sutures, improve results for glaucoma patients with surgical cataracts. The ability to combine these two procedures through one small incision and simultaneously modulate wound healing provides excellent visual results.
Small-incision cataract surgery, however, is not appropriate for every glaucoma patient. The surgeon must be facile and maintain skill in all branches of cataract surgery, including intracapsular cataract extraction (ICCE), manual nuclear expression with extracapsular cataract extraction (ECCE), and phacoemulsification of soft or hard nuclei. A fusion of these skills is necessary because a subluxated rock hard nucleus may require ICCE, the nucleus may be too dense for emulsification requiring manual expression, the cornea may be cloudy preventing phacoemulsification, or the surgeon may find it necessary to convert to ECCE techniques during small-incision surgery.
Nonpenetrating glaucoma surgery is an alternative to trabeculectomy in the management of the patient with combined cataract and glaucoma. These procedures decrease the complications related to trabeculectomy, but fail to reduce IOP as effectively long-term. Nonpenetrating techniques are still in development and there place in the management of the patient with combined cataract and glaucoma continues to evolve.
This chapter provides a framework to help the surgeon caring for a patient with both cataract and glaucoma decide when to perform a cataract extraction alone, a glaucoma procedure alone, or a combined cataract-glaucoma procedure. The case studies found later in this chapter emphasize the order and timing of surgery for patients with both cataract and glaucoma. Furthermore, techniques that are especially appropriate when performing cataract extraction in patients with glaucoma will be presented in detail. The theme running through these decisions is based on the following section on guiding principles and on the concept that any additional surgical step carries with it the increased risk of complication.
|Glaucoma is a disease in which ocular tissues become damaged by IOP that
is higher than the tissues can tolerate. Glaucoma is not a single condition; the
word encompasses a variety of entities of different pathogenesis
and different intensity. Common to all the glaucomas is the end
organ damage of an optic neuropathy with characteristic structural changes
to the optic disc with associated visual dysfunction.|
Knowledge of the basic principles related to the effects and side effects of cataract extraction in patients with glaucoma is essential if the surgeon is to choose a course that is most appropriate for each individual case. Some of these principles are known by all, and many are established but not well appreciated. Some of the principles that follow are neither well known nor well established but are based on our personal experience or the experiences of those whose clinical judgment appears to us to be sound. Principles not given a supporting reference usually fall into this category. An evidence-based approach to the literature is emphasized where appropriate and recently thoroughly reviewed.5,6
|CLINICAL ASPECTS OF OPTIC NERVE HEAD DAMAGE|
|Short-term, moderate elevation of IOP is not likely to affect a
healthy optic nerve.|
Optic nerves vary in their ability to resist the damaging effects of IOP.7–15 Normal optic nerves of healthy adults are not usually damaged by IOPs below the diastolic ophthalmic artery pressure (around 30 to 35 mm Hg) unless the pressure persists for a minimum of 2 to 3 months. The exception is patients with sickle-cell disease.16–18 In addition, healthy optic nerves in adults can withstand short-term (perhaps up to 2 weeks) elevations of IOP below the systolic level of ophthalmic artery blood pressure (average, 70 mm Hg) without sustaining apparent damage (with the exception of sickle-cell abnormalities). IOPs greater than systolic retinal artery blood pressure damage all optic nerves permanently when such an elevation persists for more than a few minutes.
Glaucomatous optic nerves are more likely to be damaged by elevated IOP.
There are a variety of factors associated with IOP induced visual field loss; most notable is ocular perfusion pressure.19 Optic discs already compromised by glaucomatous disease or other optic neuropathies are at greater risk for further damage and can be permanently damaged by increases in IOP of relatively small magnitude and short duration. Precise data are lacking, but pressure elevations as small as a 50% increase (i.e., 20 to 30 mm Hg) for 1 month can be expected to cause a permanent worsening of optic nerve function in patients with serious disc disease prior to the pressure elevation.
Optic discs that are badly damaged by glaucoma (“sick discs”) can be further damaged permanently by pressure elevations as short as: 1 day or less when the pressure elevation is in the range of 50 mm Hg or more; 1 day when IOP is 30 to 50 mm Hg; or several days when the IOP spike is in the range of the diastolic ophthalmic artery blood pressure.
The visually damaging pressure level of IOP can be estimated.
The pressure at which a patient develops a hemorrhage of the optic disc or at which progressive disc damage or visual field loss occurs before cataract extraction gives a rough estimate of the level of IOP the optic nerve is able to tolerate. This pressure provides a baseline to use for predicting future damage. For example, a patient whose IOPs are fairly consistent at about 15 mm Hg and who develops an optic disc hemorrhage with pressures in that range is very likely to be at risk for progressive optic disc deterioration with IOPs above 15 mm Hg. In contrast, a patient who develops a disc hemorrhage when IOPs are averaging around 25 mm Hg probably has an optic disc that is more resistant to the damaging effects of IOP. This patient may do well with a long-term IOP of 15 to 20 mm Hg. These factors help the comprehensive ophthalmologist decide how high and how long a postoperative IOP spike is tolerable.
Pseudopits of the optic nerve are a sign of a pressure-sensitive optic nerve.
|VISUAL FIELD LOSS AND ITS RELATION TO CATARACT–GLAUCOMA SURGERY|
|Visual field defects of a diffuse type are generally characteristic of
patients whose optic nerves are relatively resistant to the damaging effects
of IOP.22–24 Dense paracentral defects, however, are characteristic of patients whose
optic discs are more sensitive to the damaging effects of IOP.25,26|
FACTORS AFFECTING THE LIKELIHOOD OF VISUAL FIELD DAMAGE
Patients with visual field loss that extends into fixation are more likely to have their visual acuity damaged by postoperative pressure elevations than are patients whose field defects spare the area of fixation. Appropriate preoperative planning, such as combined or staged surgery to eliminate damaging postoperative pressure elevations is essential for this group of patients. In addition, patients with preoperative visual field defects that split into fixation may experience a sudden decrease in acuity associated with an otherwise uncomplicated intraocular surgery. This phenomenon of wipeout occurs in 1% to 5% of cases.27,28 “Wipeout” also appears to be related to severe postoperative hypotony and is more common in patients whose postoperative IOPs are less than 5 mm Hg. Hypotony maculopathy is a well-recognized cause of visual loss following filtration surgery. Every conceivable effort should be made to avoid long-term maculopathy and keratopathy due to excessive filtration. In spite of a surgeon's best effort, this complication will always be an issue with filtration surgery.
THE EFFECT OF CATARACT ON AUTOMATED PERIMETRY
Nonglaucomatous patients with progressive nuclear sclerosis develop a generalized depression in their field. This is detected during automated perimetry on the Humphrey Field Analyzer (HFA) and is expressed with software analysis on the glaucoma hemifield test as a generalized depression. This generalized depression is also reported as an abnormal global index expressed as decreased mean deviation. Glaucoma patients develop both generalized or localized visual field defects. Nuclear sclerosis causes a worsening of both pre-existing generalized and localized glaucomatous field defects. A cataract by itself does not produce a dense scotoma.29 Worsening of a scotoma without an increase in generalized depression of the rest of the field is not due to a nuclear cataract. The best method of determining whether field progression is due to cataract or glaucoma is to dilate the pupil and compare the optic disc to an earlier less-cataractous state. A thorough understanding of normal and abnormal visual field indices related to automated perimetry is essential in order to reliably interpret automated visual fields.30
Following uncomplicated cataract extraction in glaucoma patients, there is an overall improvement in mean deviation,31,32 and foveal threshold33 however, dense paracentral scotomas may appear deeper as noted by a worsening of the corrected pattern standard deviation, (CPSD).34 This worsening of CPSD appears to be less with phacotrabeculectomy augmented with Mitomycin C.35 From a perimetric psychophysical viewpoint,36 the statistical worsening of the CPSD is likely due to raising the height of the island of vision while the floor of the scotoma remains the same.
|ANTERIOR-SEGMENT TISSUE ALTERATIONS SECONDARY TO GLAUCOMATOUS DISEASE REQUIRE ADDITIONAL PLANNING|
|The anatomic and physiologic alterations of glaucomatous eyes are protean.|
Recognition of these alterations facilitates treatment of the disease process. A severe attack of angle-closure glaucoma causes corneal endothelial damage, cataract, trabecular damage, posterior synechiae, and iris necrosis. These tissue alterations will alter the surgeon's approach to cataract surgery. Corneal decompensation after otherwise uncomplicated cataract extraction is common in patients having sustained a severe attack of acute angle-closure glaucoma.37 Surgeons contemplating cataract extraction in these eyes naturally desire to avoid as much corneal trauma as possible. Glaucoma patients with concomitant corneal disease such as iridocorneal endothelial syndrome (ICE) should be informed of likely corneal decompensation associated with glaucoma or cataract surgery.
The atonic pupil that follows a severe angle-closure attack is fixed and dilated. This pupil alteration may cause the surgeon to choose an IOL with a larger optic to prevent glare and monocular diplopia associated with the larger pupil. Patients should be instructed that visual aberrations associated with abnormal pupils from glaucomatous disease might alter visual performance post cataract surgery. Eyes with short axial lengths typically have a very shallow anterior chamber. This makes it even more difficult for the surgeon to work, especially when introducing any instrument into the eye. In addition, eyes with unusual axial lengths require more sophisticated IOL calculation formulas; otherwise, undesirable postoperative hyperopia occurs.
The iris of glaucoma patients is usually abnormal.
Widespread glaucomatous iris abnormalities include abnormal blood vessel permeability, flaccid iris tone, rigid or atrophic muscles, and friability. The iris of patients with the exfoliation syndrome is extremely tender and easily torn. Pigment dispersion, breakdown of the blood–aqueous barrier, and hyphema at the time of surgery and postoperatively are common in these eyes. The lens capsule and zonules tend to be more fragile in patients with glaucoma than in those without glaucoma.38,39 The problem is most severe in those with the most advanced glaucoma who have been treated most intensively. Surgery is extremely complicated in the exfoliation syndrome because of zonular dehiscence, loose zonules, sticky cortex, and altered blood–aqueous barrier. The lenses of patients with long-standing glaucoma and advanced cataracts are often partially “loose” even though they do not appear frankly dislocated. Long-term parasympathomimetic drug therapy produces leaky iris vessels with breakdown of the blood–aqueous barrier, posterior synechiae, peripheral anterior synechiae, and rigid miotic pupils. Inability to sufficiently dilate the pupil is a leading cause of vitreous loss at the time of cataract surgery. The final outcome of cataract extraction is worsened by preoperative long-term use of para sympathomimetic drugs because the pupil does not dilate well, the iris is more likely to bleed when traumatized, breakdown of the blood–aqueous barrier is excessive,40 and there is an increased likelihood of vitreoretinal interface problems.
The conjunctiva of patients with glaucoma is often abnormal.
The tissues of patients with glaucoma who have been treated medically for glaucoma are not as healthy as the tissues of patients who do not have glaucoma.41 The conjunctiva undergoes several tissue alterations due to topical antiglaucoma therapy. These tissue alterations may lead to higher intraoperative complications and long-term filtration failure.
|INTRAOCULAR PRESSURE CHANGES ASSOCIATED WITH LENS EXTRACTION|
|IOP rises during the first 24 hours following cataract extraction.|
Cataract extraction with complete wound closure is associated in all cases with a postoperative rise in IOP. The greater the inflammation and the more seriously damaged the outflow channels, the greater the intensity and rise of IOP after cataract extraction. Viscoelastic substance,42 severity of pre-existing glaucomatous trabecular damage, suture deformation with trabecular collapse, cortical and pigmentary debris, blood components, breakdown of the blood–aqueous barrier, and altered prostaglandin metabolism all factor into the decrease in outflow facility. The severity, height, and duration of IOP rise are worse if the surgery is complicated by loss of vitreous. The highest IOP after either ICCE or ECCE appears to occur around 6 hours after surgery.43–45 As many as 15% of nonglaucomatous patients undergoing uncomplicated ECCE with posterior chamber intraocular lens (PCIOL) develop pressure spikes greater than 40 mm Hg within 24 hours of surgery without prophylactic pressure-lowering drugs.46 On the first postoperative day, as many as 55% of patients post-ECCE with a PCIOL develop IOPs in excess of 25 mm Hg.47 This occurs even when viscoelastic material is removed at the time of surgery but without the advantage of pressure-reducing drugs used at the conclusion of surgery.
Even in normal eyes, mean IOP rises approximately 30% on the first day after uncomplicated phacoemulsification with 6% of patients experiencing IOPs greater than 30 mm Hg.48 IOP elevations during the first postoperative day are common following uncomplicated phacoemulsification with either scleral or clear corneal incisions.49 After phacoemulsification and foldable IOL implantation, the immediate postoperative IOP increase is higher in eyes undergoing sclerocorneal incisions compared with clear corneal incisions.50
Pressure elevation in glaucomatous eyes after cataract extraction is much worse and of longer duration than in nonglaucomatous eyes.
Postoperative pressure spikes may lead to blindness and visual field loss in glaucomatous eyes.51 These pressure elevations are a particular problem in patients unable to tolerate carbonic anhydrase inhibitors (CAIs) or topical beta-adrenergic blocking agents. Several measures can be taken to control and monitor immediate postoperative IOP rises in all eyes undergoing cataract extraction:
Postoperatively, patients with badly damaged optic nerves may lose considerable visual acuity or visual field during the above pressure-lowering efforts. Patients with mild to moderate glaucoma damage generally tolerate the above-mentioned procedures without significant visual loss. Patients with badly damaged optic nerves require additional planning in order to prevent loss of vision. This may require treatment by combining cataract and glaucoma surgery, or staging the procedures with filtration surgery followed later by cataract extraction. Patients with advanced nerve damage require more frequent postoperative visits starting as early as 4 to 6 hours after surgery in order to detect the first potentially damaging postoperative IOP spike. If the surgeon is not comfortable with a combined procedure and the IOP is dangerously elevated, a filtration procedure alone may be preferable to stabilize the glaucoma, followed later by lens extraction.
Argon laser trabeculoplasty (ALT) tends to be less effective in aphakic or pseudophakic patients than in phakic patients.
Use laser trabeculoplasty before cataract extraction to gain better control of glaucoma in preparation for cataract surgery. If indicated, ALT is more effective when performed before lens extraction; in addition, postoperative pressure spikes are dampened in these eyes67–68 Following effective ALT, decrease glaucoma medications in anticipation of cataract extraction, allowing room to resume drugs after surgery if IOP is problematic. ALT is effective in approximately two thirds of patients with open angles post-failed filtration surgery.69 Selective laser trabeculoplasty (SLT) appears similar to ALT in reducing IOP before lens extraction while maintaining IOP control in the postoperative period.
Cataract extraction alone, after the initial pressure spike, often leads to long-term lowering of IOP, most notably after clear corneal phacoemulsification.
This lowering of IOP occurs with both ICCE and ECCE surgery. The magnitude of the pressure lowering appears to be increased in patients having PCIOL implantation at the time of the cataract extraction.70–73 The reduction in IOP associated with phacoemulsification is greater than ECCE. Stable, medically controlled glaucoma patients who undergo uncomplicated clear corneal phacoemulsification show a significant reduction in the number of postoperative glaucoma medications at one year, particularly in patients with pseudoexfoliation syndrome.74,75 Even nonglaucomatous patients with normal IOP before uncomplicated clear corneal phacoemulsification experience reduced postoperative IOP.76 A similar IOP lowering effect is seen at 5 years with phacoemulsification through a scleral approach.77 The mechanism of IOP lowering after phacoemulsification is unclear. However, patients with a reduced preoperative facility of outflow show a significant improvement in outflow facility following phacoemulsification at one year.78 Long-term IOP control after phacoemulsification with a foldable IOL is slightly better with a clear corneal approach compared to sclerocorneal.79
IOP CHANGES ASSOCIATED WITH COMBINED CATARACT AND GLAUCOMA SURGERY
Immediate IOP control after combined cataract-glaucoma surgery is better than cataract extraction alone.
Immediate IOP control after combined procedures is especially beneficial in patients with advanced disc damage who are already on maximal medical therapy. Phacotrabeculectomy with eventual bleb failure has a similar long-term pressure-lowering efficacy of phacoemulsification alone. However, the combined procedure that eventually fails is not a complete failure if the optic nerve damage from the immediate spike in IOP is prevented.80 Combining cataract extraction with any of a variety of methods that allows for increased outflow effectively minimizes the pressure spike that occurs after cataract surgery (Table 1). Phacotrabeculectomy protects against early postoperative elevations in IOP compared with phacoemulsification alone. This difference in IOP is detectable at 4 hours after surgery with 5% of phacotrabeculectomy eyes experiencing IOP greater than 30 mm Hg compared with 23% with phacoemulsification alone.81 If the IOP is elevated a few days after surgery, release of scleral flap sutures enhances filtration, and the timing of this is critical to long-term bleb survival.82
Long-term IOP control after combined cataract-glaucoma surgery is better than cataract extraction alone.
Combining a cataract extraction with a filtration procedure without using an antimetabolite, results in a long-term lowering of IOP slightly greater than that caused by cataract extraction alone.83–87 Long-term IOP control after phacotrabeculectomy is better than with ECCE-trabeculectomy, with fewer medications needed in the phacotrabeculectomy group.88
5-Fluorouracil (5-FU) does not improve the IOP-lowering effect of combined cataract and glaucoma surgery.
Adjunctive use of 5-FU at the time of cataract extraction has, in the dosage and methods so far used, not appreciably improved the long-term pressure lowering associated with ECCE combined with a guarded filtration procedure.89–91 There also appears to be limited pressure-lowering benefit from postoperative 5-FU injections for combined same-site phacotrabeculectomy.92–94 There is limited data on the efficacy of intraoperative 5-FU for combined phacotrabeculectomy.
Mitomycin-C (MMC) does improve the IOP-lowering effect of combined cataract and glaucoma surgery.
Antimetabolite usage is worth the long-term risks of blebitis and hypotony in patients who are likely to go blind without its application. However, patients without advanced disc damage who can tolerate one or two postoperative glaucoma medications may not need an antimetabolite and certainly should not be exposed to high concentrations of MMC.
Combined same-site phacotrabeculectomy with MMC lowers IOP more effectively with fewer postoperative medications and larger filtration blebs than without MMC.95–97 MMC also improves the success rate in blacks, eyes of patients on two or more glaucoma medications, eyes with IOP 20 mm Hg or higher, and prior failed trabeculectomy.98,99 Antimetabolite use in combined procedures is associated with a lower postoperative IOP with reduced need for long-term glaucoma medications.100 MMC appears to have a beneficial effect on long-term filtration surgery and on combined surgery without the corneal toxicity of 5-FU.101 However, long-term bleb morphology with MMC is different from that with 5-FU. Excessive concentrations or durations of MMC cause progressive conjunctival necrosis with bleb leaks, hypotony, and possible endophthalmitis. Antimetabolite usage has decreased with trabeculectomy surgery and is reserved for high-risk patients likely to scar down without its usage.
COMBINED CATARACT AND GLAUCOMA SURGERY
Phacotrabeculectomy is more effective than ECCE-trabeculectomy with or without postoperative 5-FU injections.102–105 The smaller incision associated with phacoemulsification likely leads to less intraocular inflammation and wound healing, allowing better bleb formation. Phacotrabeculectomy with intraoperative or postoperative 5-FU significantly lowers IOP but not as successfully as 5-FU trabeculectomy alone.106 This is probably related to the prolonged anterior chamber flare following phacoemulsification compared with trabeculectomy with peripheral iridectomy.107 Combined same-site phacoemulsification, posterior chamber IOL, and trabeculectomy without antimetabolite significantly lowers IOP.108–111 Results of same-site phacotrabeculectomy appear similar with either a 3.5-mm incision with a foldable IOL or a 5.2-mm incision with a rigid single piece PMMA lens.112,113
Phacotrabeculectomy with intraoperative 5-FU is as efficacious as a 5-FU trabeculectomy followed by phacoemulsification.114 Visual acuity and complications of combined phacotrabeculectomy are comparable to a two-staged approach with the obvious benefit of earlier visual rehabilitation.115 Foldable silicone lenses are associated with an increase in postoperative inflammation compared to PMMA lenses.116
SINGLE-SITE VERSUS TWO-SITE COMBINED CATARACT AND GLAUCOMA SURGERY
Combined ECCE-trabeculectomy techniques now yield to smaller incision combined phacotrabeculectomy. The methods for combining phacotrabeculectomy vary, depending on physician training, preference and patient anatomy. For example, physicians with two-site experience will have an easier access to the surgical site in a patient with enophthalmos and a prominent brow who requires a combined procedure. A temporal approach for the lens extraction is much easier in this particular case. IOP control following one-site versus two-site phacotrabeculectomy with MMC is similar but with a trend for less postoperative glaucoma medications,117 improved IOP control,118 less induced astigmatism,119 and better bleb formation in the two-site group.120
CATARACT EXTRACTION CAUSES PARTIAL OR COMPLETE FAILURE OF EXISTING FILTERING BLEBS
Cataract extraction by any technique performed in a patient with a pre-existing filter will have an effect on the previous filtering bleb.121–124 Bleb failure is more likely with ECCE compared with small-incision phacoemulsification.125 However, even patients undergoing topical anesthesia with clear corneal phacoemulsification and foldable IOL may experience bleb failure. One of three patients with a functioning filter and preoperative mean IOP of 12 mm Hg without antiglaucoma medications experiences bleb failure after lens extraction (Table 2). These patients require long-term drug therapy or bleb needling to control IOP. 126 Additional incisional glaucoma surgery may eventually be required in up to 10% of patients.127 Intraoperative iris manipulation may cause significant breakdown of the blood–aqueous barrier, resulting in inflammation that causes bleb failure. Even after uncomplicated clear corneal phacoemulsification, IOP may increase an average of 2 to 3 mm Hg due to bleb fibrosis.128 Approximately 20% of filtered patients require a long-term increase in glaucoma medications following uncomplicated clear corneal phacoemulsification with a foldable copolymer acrylic IOL129 (Fig. 3). In situations in which the bleb is not working at all, the eye will have a postoperative pressure spike that mimics that in the patient not having had a prior filtering procedure. In situations in which the bleb is marginal, the pressure spikes tend to be lower, and the final postoperative IOP tends to be around 50% higher than it was preoperatively. These patients require combined procedures in order to reestablish long-term filtration. In situations in which the bleb is very thin, polycystic, and associated with an IOP around 5 to 8 mm Hg on no antiglaucoma therapy; uncomplicated cataract extraction will have a minimal effect on the level of IOP. Patients with functioning glaucoma drainage implants usually have minimal long-term changes in IOP after uncomplicated cataract extraction.130
1. Uveitic glaucoma
6. Large cataract incision
11. Iridocapsular adhesions secondary to can-opener capsulotomy
Tissue plasminogen activator (TPA), a protease with fibrinolytic-thrombolytic activity, may be helpful in dissolving either fibrin or blood clots that are obstructing bleb flow. TPA may be injected into the anterior chamber to dissolve fibrin clots that impede flow into the trabeculectomy site.131 The application of TPA may salvage a failing bleb after cataract surgery but sometimes leads to hypotony or hyphema.
Gonioscopy is essential in determining the etiology of bleb failure post cataract extraction. If a gossamer fibrin membrane forms over the internal trabeculectomy stoma post lens extraction, use the YAG laser to disrupt the membrane and re-establish flow. Needle the bleb when filtration becomes delimited by fibrosis. There are a variety of bleb needling techniques that are all designed to increase external filtration into and around the bleb.132, 133
Bleb failure after cataract extraction is actually beneficial in the setting of preoperative hypotony maculopathy.134,135 The surgeon may elect to use postoperative corticosteroids sparingly in order to encourage inflammation and wound healing. However, elderly patients with long-standing pale avascular blebs and reduced aqueous production are less likely to experience long-term IOP elevation.
PHACOTRABECULOTOMY FOR UNCONTROLLED GLAUCOMA AND SYMPTOMATIC CATARACT
Patients who are at high risk for complications related to trabeculectomy are candidates for trabeculotomy. The magnitude of IOP reduction with trabeculotomy is significantly less than with trabeculectomy. Patients with a history of bleb related endophthalmitis, profound hypotony from trabeculectomy, symptomatic filtering blebs or cicatricial ocular surface disease are candidates for trabeculotomy. Trabeculotomy with careful scleral and conjunctival wound closure in adults is not associated with postoperative hypotony. Postoperative hyphema is common but generally clears within a week and a pressure spike on postoperative day 1 is common. The technique varies depending on surgeon preference.136 The results with either a one- or two-site technique are similar.137 Postoperative IOP control with phacotrabeculotomy is superior to phacoemulsification alone138 and appears to be most effective in patients older than age 70.139
PHACOVISCOCANALOSTOMY AND PHACO/DEEP SCLERECTOMY FOR UNCONTROLLED GLAUCOMA AND SYMPTOMATIC CATARACT
Nonpenetrating procedures as they exist today generally decrease postoperative complications but do not reduce IOP as successfully as trabeculectomy.140 The success rate also appears to be highly dependent on race, length of topical antiglaucoma therapy, and prior ocular surgery.141,142 Deep sclerectomy combined with phacoemulsification results in an IOP reduction similar to phacotrabeculectomy at one year with comparable visual outcome.143 Phacoviscocanalostomy lowers IOP by approximately 33%144 through either a one- or two-site approach145 (Fig. 4). Nonpenetrating procedures are in evolution, and their place in long-term glaucoma care is still unclear.
CATARACT EXTRACTION ALONE REDUCES IOP IN MOST EYES WITH ANGLE-CLOSURE GLAUCOMA
Uncomplicated cataract extraction substantially reduces IOP, along with the number of postoperative glaucoma medications in eyes with angle-closure glaucoma.146,147 When preoperative gonioscopy reveals PAS, along with adjacent areas of appositional closure, lens extraction alone in select cases may be a reasonable alternative to filtration surgery.148,149 Phacomorphic angle-closure disease due to enlargement of the lens with progressive angle crowding is eliminated following lens extraction. The width and depth of the anterior chamber angle in eyes with angle-closure glaucoma increases significantly after cataract extraction with IOL implantation and becomes similar to open-angle glaucoma and normal eyes.150,151 (Fig. 5). Combining phacoemulsification, IOL implantation, and limited goniosynechialysis is effective in the treatment of cataract and chronic angle-closure glaucoma.152 Phacoemulsification with implantation of a foldable IOL is more effective in reducing IOP and improving visual acuity than surgical peripheral iridectomy in eyes with acute angle-closure glaucoma.153
SUCCESSFUL TRABECULECTOMY SIGNIFICANTLY DECREASES AXIAL LENGTH CAUSING INACCURATE IOL CALCULATIONS
Surgeons contemplating “routine” cataract extraction in patients with pre-existing successful trabeculectomy surgery must convey their concerns regarding postoperative refractive surprises. Axial length decreases an average of 0.4 mm after trabeculectomy, with some eyes decreasing as much as 2.8 mm.154 After lens extraction the axial length increases toward the eyes' original shape, thereby inducing myopia. There is a significant association between decrease in axial length and use of antimetabolites.155 Because the incidence of cataract after filtering surgery is increased,156 surgeons benefit from obtaining preoperative biometry for future comparisons.
ANTERIOR CHAMBER LENSES ARE LESS PREFERABLE THAN POSTERIOR CHAMBER LENSES IN PATIENTS WITH GLAUCOMA
First-generation anterior chamber lenses contacted uveal tissue and caused inflammation, glaucoma, and hyphema. Superior haptic design and AC stability are worthy improvements in these lenses. Owing to the greater inflammatory response and potential for suprachoroidal hemorrhage associated with suturing in a posterior chamber lens, it is not known whether a sutured-in posterior chamber lens or a new-generation anterior chamber lens is preferable in cases in which a bag fixated posterior chamber IOL cannot be used. Placement of the PCIOL in the bag is preferable to sulcus placement because the lens tends to be more posterior and thereby causes less inflammation. Posterior chamber lenses designed for bag fixation should not be placed in the sulcus owing to the increased likelihood of iris chaffing, pigment release, inflammation, and worsening of glaucoma.
EYES WITH GLAUCOMA ARE PREDISPOSED TO SUPRACHOROIDAL HEMORRHAGE, BOTH INTRAOPERATIVELY AND POSTOPERATIVELY
Suprachoroidal hemorrhage is a devastating, painful complication of ocular surgery. It may occur intraoperatively157 or postoperatively. The major predisposing factor is always hypotony. This occurs most frequently in glaucoma patients with aphakic vitrectomized eyes undergoing filtration surgery.158–165 Suprachoroidal hemorrhage is also more likely to occur in myopic, hypertensive patients with long-standing glaucoma with high IOPs at the time of cataract extraction. Visual loss may be severe or mild depending on immediate extrusion of uvea and retina, length of time for wound closure, and subsequent retinal detachment. Should a suprachoroidal effusion or hemorrhage occur during small-incision cataract surgery, the self-sealing anatomy of the wound and the controlled irrigation pressure system allow for a rapid watertight wound closure, preventing expulsion of intraocular contents.
Identification of patients at high risk for suprachoroidal hemorrhage may considerably alter the surgeon's thought processes. The following factors are considered:
Postoperative suprachoroidal hemorrhage is most likely to occur during the first 2 weeks after trabeculectomy, especially following premature suture lysis. Commonly, a choroidal effusion develops as a result of hypotony. As the choroidal effusion increases in size, stretching of the long ciliary artery in the suprachoroidal space occurs. This vessel may break at a critical point, precipitating this sight-threatening event.166 Surgeons should never be timid in returning to the operating room to drain a choroidal effusion, especially in high-risk monocular patients.
THE EFFECT OF GLAUCOMA SURGERY ON VISUAL ACUITY VARIES DEPENDING ON THE PREOPERATIVE STATUS OF THE PATIENT AND THE TECHNIQUE OF GLAUCOMA SURGERY
Patients with small pupils and axial cataracts frequently have significant improvement in visual acuity after glaucoma surgery, especially when accompanied by sector iridectomy. On the other hand, a persistent shallow anterior chamber after glaucoma surgery is associated with development or worsening of pre-existing cataract, especially if accompanied by excessive inflammation. If the anterior chamber is totally flat (lens-corneal touch), development of cataract is rapid and severe. In addition, a flat chamber leads to peripheral anterior synechiae, iridocorneal adhesions, blockage of the trabeculectomy stoma, and corneal decompensation.
A shallow anterior chamber after cataract-glaucoma surgery requires explanation and documentation. Grade the chamber depth at each visit to facilitate determination of change.167 A shallow chamber should be a warning sign of excessive outflow, decreased aqueous inflow, abnormal diversion of aqueous humor168 or pupillary block.169 The management of a shallow chamber is highly dependent on its cause. The most common cause of postoperative shallow chamber is excessive outflow through the trabeculectomy flap or a conjunctival wound leak. Fornix-based conjunctival incisions are more likely to leak than limbus-based incisions, especially with concomitant antimetabolite therapy. Flat anterior chamber after glaucoma filtration surgery is more likely in patients with preoperative hyperopia, shallow anterior chambers, and loose lenses. These same patients are more prone to develop aqueous misdirection syndrome.
The principles just enumerated are not agreed upon by all surgeons. However, most of them appear to be relatively well established. By taking them into account when planning how to proceed in a particular case, the surgeon will find that the most appropriate methodology for that particular case will usually become apparent. It is critical to recall that glaucoma is a protean disease and that the most appropriate procedure is determined by the specific characteristics of the patient in question.
|Clinical examples often help clarify the thought processes outlined earlier in the guiding principles. The concept of target pressure implies a range necessary to prevent further glaucomatous damage. This is based on the height of the preoperative IOP, state of the optic nerve, and general health of the patient. These values are not written in stone but serve as a guideline when faced with a patient who has progressive disease in spite of maximal tolerated medical therapy. In general, patients with progressive glaucomatous damage with preoperative IOPs in the high teens to low 20s require postoperative IOPs in the mid teens (14–17 mm Hg). Patients with progressive glaucomatous damage with preoperative IOPs in the high teens require IOPs in the low to mid teens (12–15 mm Hg) and patients worsening with IOPs in the low teens may require single digit IOPs to prevent further glaucomatous damage.170 Complications are obviously more likely to occur when the surgeon must try to reduce IOP into single digits. The risk to the patient may be immediate and apparent as when IOP plummets after suture lysis and vision dramatically decreases. The benefits to the patient at this time seem obscure, but the well-educated patient understands that without trying to lower IOP into a safer range,171 visual loss will progress in a relentless fashion.|
|CASE 1: ANTICIPATED LENS EXTRACTION WITH MILD TO MODERATE DISC DAMAGE AND IOP WITHIN TARGET PRESSURE RANGE|
|A patient with long-standing, moderately well-controlled primary open-angle or chronic angle-closure glaucoma tolerating one or two antiglaucoma medications develops nuclear sclerotic cataracts. Visual field loss and optic nerve damage are minimal to moderate; the neuroretinal rim is intact for 360 degrees, and there are no sulfa allergies. Temporal clear corneal cataract surgery with foldable IOL implantation is optimal for this case. The conjunctiva and superior sclera are spared for future glaucoma surgery. Administration of an oral carbonic anhydrase inhibitor blunts the IOP spike associated with lens extraction. Long-term IOP control may improve with fewer glaucoma medications. Considering that the intraoperative and postoperative complications of cataract surgery alone are less than those with a combined procedure, this stable patient is better served with cataract surgery alone. Surgeons who are not comfortable with clear corneal cataract surgery can use either a temporal or superior temporal scleral tunnel approach, avoiding the superior nasal area for future filtration. The patient should understand beforehand that trabeculectomy might be necessary at any time if excessive IOP threatens the health of the optic nerve.|
|CASE 2: ANTICIPATED LENS EXTRACTION WITH MILD TO MODERATE DISC DAMAGE AND IOP WITHIN 4 MM HG OF TARGET PRESSURE RANGE|
|The patient's clinical history is the same as the case given earlier, but IOP is elevated approximately 4 mm Hg above target range. The simplest approach is to accomplish laser trabeculoplasty before cataract surgery. If the patient responds to laser trabeculoplasty, preoperative antiglaucoma medications may be decreased, further preparing the eye for cataract surgery. Temporal clear corneal cataract surgery with foldable IOL implantation along with perioperative administration of oral CAIs is again optimal for this case. If the patient has already failed ALT, SLT may reduce IOP before lens extraction.|
|CASE 3: ANTICIPATED LENS EXTRACTION WITH MILD TO MODERATE DISC DAMAGE AND IOP FAR OUTSIDE OF TARGET PRESSURE RANGE|
|Open-angle glaucoma patients with symptomatic cataract, mild to moderate disc damage and significantly uncontrolled IOP require phacotrabeculectomy. The spike in IOP associated with lens extraction may damage eyes with uncontrolled preoperative IOP. A combined procedure will protect the optic nerve and associated ocular structures from severe IOP elevation. Some surgeons believe that a filtering procedure should be performed first, before the lens extraction. However, proponents of this approach are rapidly decreasing due to the effectiveness of phacotrabeculectomy.|
|CASE 4: ANTICIPATED LENS EXTRACTION WITH ADVANCED DISC DAMAGE AND IOP WITHIN OR OUTSIDE TARGET PRESSURE RANGE|
|As stated earlier in this chapter, badly damaged optic nerves cannot tolerate pressure spikes. The majority of patients with advanced disc damage and cataract require a combined procedure in order to suppress the anticipated marked rise in IOP that may permanently snuff out vision. The additional risk of filtration surgery is justified in these difficult cases. If the cataract is not mature or the risk of lens extraction very high, stage visual rehabilitation with filtration surgery followed months later by cataract extraction.|
|CASE 5: ANTICIPATED LENS EXTRACTION POST SUCCESSFUL TRABECULECTOMY|
|A patient with long-standing primary open-angle glaucoma
with a successful glaucoma filtration procedure and IOP of 10 mm Hg on
no antiglaucoma medications develops a significant, moderately dense
nuclear sclerotic cataract. This patient is best served by small incision
cataract extraction with foldable IOL implantation. Less desirable
options include ECCE with IOL implant via clear cornea, temporal limbus, or
inferior approach. Astigmatism, wound instability, prolonged visual
recovery, visual fluctuation, exposed sutures, and bleb failure are
the major drawbacks to large-incision lens extraction. Even
after the surgeon has mastered large-incision clear corneal cataract
extraction, long-term wound shift and astigmatism are a chronic
problem (Fig. 6). Inferior cataract extraction is difficult for those not experienced
with it. With the advent of small-incision phacoemulsification
surgery, the surgeon is now able to use a limbus approach adjacent
to the bleb or a clear corneal temporal approach. Postoperative inflammation
is less with the smaller incision, and filtering blebs are more
likely to survive. Patients with IOP greater than 10 mm Hg after a
filtering procedure are more likely to experience permanent IOP elevation
after phacoemulsification. Patients should understand that IOP elevation
post cataract extraction is always an issue, even with a functioning
|CASE 6: ANTICIPATED LENS EXTRACTION POST FAILED TRABECULECTOMY WITH ADVANCED DISC DAMAGE AND IOP OUTSIDE TARGET PRESSURE RANGE|
|The inflammation associated with lens extraction at any site usually causes
complete failure of a marginal functioning bleb. In addition, pressure
reduction by medical means is usually minimal in these recalcitrant
cases, and combined surgery is indicated. In the past, these cases
were approached with large-incision ECCE, clear corneal cataract
incision, and bleb revision. Drawbacks included those mentioned earlier
for large incision clear corneal cataract extraction, and bleb revision
is often associated with conjunctival buttonholes, wound leaks, subconjunctival
hematoma, destruction of friable sclera, and associated
hypotony. With the advent of modern-day cataract surgery, a
phacotrabeculectomy is often possible adjacent to the failed filter (Fig. 7). The ability to combine cataract extraction with implant and filtration
surgery all through the same small incision has greatly improved
outcomes for patients with marginal preoperative filters. There are
several other viable options in this case. If the surgeon elects to remove
the cataract through a temporal clear corneal incision, the bleb
may be revised or a new adjacent filter fashioned. As mentioned earlier, revising
a failed filter is technically challenging. If the surgeon
believes it is not feasible to revise the filter or fashion a new one, a
glaucoma drainage implant is a reasonable option combined with temporal
|The preoperative assessment of a glaucoma patient under consideration for
cataract extraction includes those evaluations used for routine cataract
surgery in addition to those for glaucoma surgery. For patients
on pilocarpine or other miotic medications, determine the state of visual
function with a dilated pupil. Patients who cannot function satisfactorily
with a small pupil, such as those with axial cataracts, may perform
in an entirely satisfactory manner when the pupil is larger. This
is important information to know, because it may be possible to defer
cataract extraction in these patients and carry out filtration surgery
alone. Miotics are no longer necessary after trabeculectomy, and visual
function may be satisfactory for years. At the time of surgery, the
surgeon positions the filter slightly nasally for future superior
temporal phacoemulsification. Surgeons who are comfortable with clear
corneal phacoemulsification can position the filter closer to 12 o'clock
and remove the cataract through a temporal approach in the future. Before
surgery, inform the patient that their cataract might worsen
after filtration surgery, especially if the anterior chamber shallows
or if inflammation is severe.173|
An assessment of the patient's longevity and a determination of the rate at which glaucoma is progressing helps the physician and the informed patient determine the best procedure to improve vision and stabilize the glaucoma. Patient expectations are typically high before surgery, but glaucomatous damage may dampen these emotions. The surgeon should explain, if possible with the aid of the patient's visual field before surgery, that vision will improve in some areas but will not likely return in regions of the field that have dense scotomas.
The immediate visual needs of the patient, condition of the optic nerve, number and tolerance of antiglaucoma medications, prior surgery, and severity of cataract are important factors in deciding on cataract extraction alone, glaucoma surgery alone, staged surgery, or combined surgery. Patients with life-threatening systemic conditions may only need lens extraction because the risks of filtration surgery may be unjustified granted their tenuous health status. These patients may be candidates for less aggressive pressure lowering procedures at the time of lens extraction such as trabeculotomy or nonpenetrating glaucoma surgery.
During preoperative slit-lamp biomicroscopy, the surgeon evaluates the condition of the conjunctiva and decides on a fornix-based or a limbus-based conjunctival approach.174–177 There are definite advantages and disadvantages of each approach (Table 3). With proper wound construction, there appears to be very little difference in long-term IOP control between the two incisional groups. However, the long-term bleb appearance varies considerably between the two incisional groups,178 with a limbus-based conjunctival flap more likely to develop a cystic bleb especially if an antimetabolite is used179 (Fig. 8).
Careful attention to detail includes degree of pupillary dilation and nuclear sclerosis, along with examination for guttata, phacodonesis, posterior synechiae, and the exfoliation syndrome. The detection of PAS by routine gonioscopy often guides the surgeon to the appropriate limbal site for wound entry. The degree of nuclear sclerosis and level of surgical skill will help the surgeon decide on manual expression of the nucleus or phacoemulsification. If a filtering bleb is present and functioning well, a temporal clear corneal lens extraction with foldable IOL is preferable. If the bleb is marginal and not likely to survive cataract extraction, a combined procedure is warranted. For example, if the marginal existing bleb is located off center, then a combined phacotrabeculectomy may be accomplished in the adjacent quadrant (Fig. 7).
Evaluation of the posterior pole may be very difficult because of extreme miosis and lens opacification. In addition, a preoperative potential acuity meter (PAM) test may be misleading and inaccurate because of scotomas close to fixation. To achieve maximal pupillary dilation and preserve the blood–aqueous barrier, discontinue miotic drugs several days before surgery. Medical clearance before surgery, along with discontinuation of anticoagulants for an appropriate period, is especially important when incising conjunctival and scleral tissues.
PERIOPERATIVE MANAGEMENT OF THE ANTICOAGULATED PATIENT
Perioperative management has become an important issue in light of the increasingly widespread use of anticoagulants that are prescribed, consumed over the counter, or used as alternative medicinals. The ophthalmologist must weigh the potential risk of a life-threatening event due to increased thrombosis related to discontinuing anticoagulants against the potential for visual loss due to intraoperative or postoperative bleeding. Consultation from the patient's primary care physician (PCP) and other appropriate health care professionals to aid in the determination of the risks associated with discontinuing anticoagulants is wise and essential. Patients who are taking anticoagulants require special preoperative planning concerning cataract and glaucoma surgery (Fig. 9):
The topical anesthesia approach is much more difficult in patients requiring combined cataract and glaucoma surgery. Manipulation of the conjunctiva and scleral cautery are more painful without a peribulbar anesthetic. The skill necessary to do these procedures under topical anesthesia is considerable. Patients requiring phacotrabeculectomy who must be anticoagulated at all times require coverage with short acting low-molecular-weight heparin in the perioperative period coordinated by the patients PCP.
|As exemplified earlier in this chapter, cataract extraction in patients with glaucoma is a highly individual matter, requiring almost totally different approaches in different patients. What follows is a description of techniques that are appropriate for some individuals, specifically patients with significant cupping and visual field loss, elevated IOPs despite maximal medical therapy, and vision that has been reduced to a level interfering with the patient's quality of life because of lens opacification.|
|EXTRACAPSULAR CATARACT EXTRACTION VIA NUCLEAR EXPRESSION COMBINED WITH GLAUCOMA FILTRATION SURGERY|
|All patients are not candidates for phacoemulsification; thus, ophthalmic
surgeons must be prepared to carry out ECCE with trabeculectomy. Perform
a peritomy that extends over the superior 180 degrees of the limbus
and develop a loose fornix-based flap that can later be pulled
over the limbus without traction. Apply the antimetabolite before
scleral incisions. A MMC-soaked sponge cut to cover the proposed
trabeculectomy flap is used. Dosages remain controversial, but 0.2 mg/mL
of MMC for 2 to 4 minutes seems to be safe for most patients undergoing
combined procedures. Care should be taken to avoid spread of the
chemical onto the edges of the conjunctiva where wound healing is critical. The
size of the pledget should cover a generous area, approximately 8 by 5 mm
with the hope of encouraging a diffuse nonlocalized pale
bleb that is not avascular.|
Cauterize all bleeders with wet-field cautery in an area approximately 4 mm × 4 mm at the 12-o'clock position. Remove the corneal epithelium adjacent to the exposed limbus for a width of around 0.5 to 1 mm with a 69 Beaver blade. Scraping the epithelium from the limbus ensures better wound healing at the limbus with less likelihood of an incisional leak. Create a temporal paracentesis site for future injection of balanced salt solution.
Develop a 3 to 3.5 mm wide scleral flap starting approximately 3 mm from the limbus at the 12-o'clock position. One should fashion the scleral flap approximately one half to two thirds thickness and the shape of the flap is of little significance. Extend the wound at two thirds depth on the scleral side of the limbus on both sides of the trabeculectomy flap to a chord length of approximately 10 mm. Place sutures 4 mm apart and free the loops; the two ends are located so as to allow easy identification in case of immediate need.
METHODS OF PUPIL ENLARGEMENT
Enter the anterior chamber through the clear corneal extension of the scleral bed with a super-sharp blade and inject viscoelastic material to facilitate chamber maintenance. If needed, instill epinephrine into the chamber under the iris before viscoelastic injection. The surgeon evaluates the pupil at this time and decides on the method of pupil enlargement if indicated. Enlargement of the pupil is most often necessary in patients on long-term miotic therapy or a history of uveitis. Posterior synechiae are broken with push-pull instruments and viscoelastic is reinserted. If the pupil can be enlarged to 7 mm with this technique, then one may safely continue surgery.
However, often the pupil is still small, and it is not safe to perform a capsulotomy without good visualization. At this juncture, it is helpful to enlarge the pupil by creating a peripheral iridectomy with radial iridotomy extension to the sphincter. Grasp the iris with 0.12 forceps and excise tissue with the DeWecker scissors through the slit like wound in the scleral bed and then reinsert viscoelastic on both sides of the iris to position the iris in midchamber. The radial iridotomy is made by inserting capsulotomy scissors into the wound on both sides of the iris through the iridectomy and cutting all the way to the sphincter. This opens the pupil superiorly, but multiple small inferior sphincterotomies may still be necessary for adequate visualization of the anterior capsule. This technique is particularly suited for nucleus expression because the superior iris is no longer an impediment to extracting the superior pole of the nucleus.
Iris clips are not as helpful for manual expression of the nucleus as they are for phacoemulsification because the superior iris still remains an impediment for manipulating the superior pole of the nucleus.
Once the pupil is adequately enlarged, the surgeon may safely proceed to capsulotomy. A can-opener capsulotomy with two superior relaxing slits is made with a bent 27-gauge cystotome. The slits are beneficial for safe delivery of large dense nuclei. Invariably, there are extensions of the anterior capsulotomy, but the relaxing incisions, combined with good nuclear delivery, allow for posterior capsule integrity. It is possible to deliver the nucleus through a continuous curvilinear capsulorhexis opening, but this is not a consistent maneuver with a dense large nucleus. However, some surgeons prefer to prolapse the nucleus into the anterior chamber and divide the nucleus with phacosection techniques.
Proper expression of the nucleus is the most difficult part of the operation. Separate the nucleus from the epinucleus by hydrodissection with a blunt 27-gauge cannula. Complete hydrodissection in all four quadrants until a fluid wave is seen separating the nucleus from the epinucleus and cortex. Often, the inferior pole of the nucleus will lift up slightly, indicating a thorough hydrodissection plane. One should then rock the nucleus slightly and thoroughly rotate it with a bent cystotome. With the nucleus totally free from epinucleus attachments, tilt the nucleus so the superior pole is positioned above the anterior capsule. If the superior pole is difficult to elevate at this time, it can be rectified at the next surgical step.
Extend the preplaced cataract incision on both sides of the trabeculectomy site by inserting scissors into the scleral bed incision site, with care taken to avoid the iris. Viscoelastic may be necessary to push the iris posteriorly; otherwise, a large iridodialysis may inadvertently be created.
If the superior pole of the nucleus is not well positioned for easy delivery, inject a small volume of viscoelastic gently around the side of the nucleus, and the pole will elevate into the anterior chamber. Raise the irrigation bottle and have the assistant elevate the cornea, using a toothed forceps. Place a lens loop against the superior incision while holding back the tissues to provide a support for the superior zonules. In most cases, the nucleus will deliver itself without any additional work, especially if one uses an irrigating lens loop. If the nucleus does not move, use a Kelman-McPherson forceps or similar instrument to gently skewer the superior pole and rotate the nucleus out of the eye. No counter pressure is applied at the inferior portion of the globe at any stage of nuclear delivery.
Tie the preplaced sutures and add 10-0 nylon sutures as necessary to close the cataract wound. Insufflate the globe to facilitate proper suture tension in order to avoid excessive astigmatism. The corneal block should not be removed at this juncture in order to avoid excessive flow through this area during irrigation and aspiration of cortex. Typically, two additional temporary sutures close the trabeculectomy flap allowing irrigation and aspiration. Once cortical cleanup is complete, remove the temporary sutures and insert a posterior chamber IOL into the capsular bag.
METHOD OF RESTORING A ROUND PUPIL
After the scleral block has been removed, inspect the anterior chamber to make sure it contains sufficient viscoelastic material for safe iris manipulation. Often, the iris is turned on itself and requires correct positioning before suturing. Place a Kelman or similar forceps through the 12-o'clock incision, and grasp the edge of the iris at the pupillary margin. After the iris is carefully withdrawn through the open incision, pass a 10-0 prolene suture on a small needle through the margin of the pupil (not farther up in the iridectomy). There is a tendency not to place the suture all the way at the edge of the pupillary margin. With the Kelman forceps, grasp the iris on the other side of the iridectomy at the pupillary margin, retracting the iris into the incision. Place the needle through the iris at the pupillary margin and tie the suture. After several throws, trim the suture immediately adjacent to the knot. Reposit the iris by gentle manipulation and irrigation with intracameral acetylcholine. Close the trabeculectomy flap with an adequate number of sutures to prevent excessive outflow, but at the same time, allowing enough flow to prevent postoperative pressure spikes. Remove all viscoelastic from the anterior chamber and evaluate flow through the flap with Week cell sponges. If no flow is present, sutures are adjusted or removed. If excessive flow is present, sutures are added to the flap. Once the flow is adjusted, bring Tenon's capsule forward and suture to bare sclera on either side of the trabeculectomy site. Hood the conjunctival flap tightly over the limbal incision and suture on either side of the limbus in a watertight fashion. An alternate method is a running mattress suture closure explained in the next section. Reinsufflate the anterior chamber with balanced salt solution and check the bleb for leaks. Use a tapered needle to close limbal leaks.
Limbus vs fornix based conjunctival flap
In most patients, the surgeon is able to remove the nucleus through a small incision technique and be comfortable with both one- and two- site approaches. The technique for trabeculectomy varies slightly depending on training, exposure, conjunctival scarring and risk factors for filtration failure.180 Preoperatively, the pupil is maximally dilated and fluoroquinolone antibiotic drops instilled. A Honan balloon to soften the globe is not used in patients with fragile optic nerves. Insert a Barraquer wire lid speculum after adequate peribulbar anesthesia, akinesia, prep, and drape. If at all possible, make the decision to create a limbus-based or fornix-based conjunctival flap preoperatively, preferably during visualization of limbus anatomy during biomicroscopy. If scarring is present, a fornix-based flap is preferred. Because of the increase in sutureless clear corneal cataract extractions, surgeons are less familiar with conjunctival incisions and their adequate closure. More often, a limbus-based conjunctival flap is prepared, because ophthalmologists are familiar with its placement and closure associated with trabeculectomy. Surgeons familiar with both limbus and fornix techniques enjoy the versatility to tailor the incision to the needs of the patient (Figs. 10 and 11). Inspect the sclera, apply light cautery and antimetabolite as indicated (Fig. 12).
Preparation of the Scleral Tunnel
Creation of the scleral tunnel is a crucial step in successful wound construction. If the resultant scleral flap is too thin and a tear occurs during closure, excessive filtration with all the risks of hypotony will occur. When the scleral flap is too thick due to a deep plane, premature entry into the anterior chamber with subsequent intraoperative iris prolapse and bleeding occurs. During surgery, this results in a shallow anterior chamber with excessive iris and corneal trauma. Typically, a 50% to 75% depth flap seems to be safest for development of the flap and scleral tunnel. Additionally, if the scleral tunnel incision is extended too far into clear cornea, corneal striae inhibit adequate visualization during phacoemulsification.
After achieving approximately 75% scleral depth, extend the scratch incision for 3 mm and use a crescent blade to tunnel 1 mm into clear cornea (Fig. 13). During development of the tunnel, keep the underside of the crescent blade flat against the curvature of the eye to establish the proper plane. Direct a 3-mm keratome to the end of the scleral pocket and with a dimpling-down maneuver enter the anterior chamber. This completes a triplanar incision, a critical prerequisite for small-incision wound stability.
Inadequate visualization of the anterior capsule due to miosis may lead to a series of surgical mishaps. Inadequate dilation of the pupil is a common problem for all cataract surgeons and occurs most frequently in glaucoma patients. In these patients, the pupils are not only small but also bound down to the lens with pigment and fibrous tissue adherent to the anterior capsule. As these adhesions are lysed, pigment and blood may be liberated into the anterior chamber, further interfering with the surgeon's view.
If the pupil is less than 4 mm after preoperative and intraoperative pharmacologic means, the surgeon must be prepared to use ancillary surgical methods of pupil enlargement (Fig. 14). The methods of pupil enlargement associated with phacoemulsification are different than those required for ECCE. Both are thoroughly covered in this chapter because miosis is still a common problem encountered when performing cataract surgery in glaucoma patients. The most popular methods of pupil enlargement associated with phacoemulsification are two-handed pupil stretching techniques,181 pupil expanders,182 and iris hooks,183,184 (Table 4) Microsphincterotomies created by mechanical iris stretching are preferable to incisional sphincterotomies185 made with scissors. If the sphincter is completely transected by scissors or if stretching is too vigorous, the pupil will remain flaccid postoperatively and an atonic pupil develops.186 If a can-opener capsulorhexis is used, pupil capture is more common as the IOL migrates and the cut end of the capsule adheres to the iris. Iridocapsular adhesions serve as a bridge for the migration of macrophages onto the surface of the IOL preventing optimal vision. Properly performed sphincterotomies along with a complete capsulorrhexis allow excellent postoperative pupil function as long as postoperative inflammation is minimal and adhesions do not occur.
Once the continuous curvilinear pupil is enlarged to a minimum of 6 mm, perform a capsulorrhexis, followed by hydrodissection (Fig. 15). The size of the capsulorrhexis varies depending on the type and size of the IOL. The use of dyes to stain the anterior capsule significantly helps visualize the poorly seen anterior capsule facilitating completion of the capsulorrhexis.187,188 Hydrodissection allows separation of the cortex from the capsule allowing rotation of the nucleus. These maneuvers are essential for easy nucleus rotation and are especially critical for patients with weak or fragile zonules. Make a paracentesis site in the temporal cornea.
At this point, incise only one side of the scleral tunnel to create a partial scleral flap. This allows phacoemulsification without creating striae in the cornea that inhibit visualization but prevents excessive outflow. With a 30-degree tip phacoemulsification handpiece, emulsify and crack the nucleus with a two-handed divide-and-conquer technique. Each quadrant is fragmented with the emulsifier and removed on pulse mode, leaving the epinucleus, which is removed with aspiration and low-power ultrasound (Fig. 16). If the cataract is very dense, use a chopping technique or a Kelman tip. Surgeons comfortable with nuclear cracking techniques have an advantage working with very dense nuclei. Employ the irrigation and aspiration handpiece to remove residual cortex, and clean the posterior capsule with low vacuum. A U-shaped cannula is often very helpful for removing residual subincisional cortex. After irrigation, aspiration, and capsule vacuum, inject viscoelastic into the anterior chamber and expand the capsular bag.
Construct the scleral flap, enlarge the wound and insert the IOL (Fig. 17). Instill miochol into the anterior chamber to achieve miosis. Remove the trabecular block and accomplish the peripheral iridectomy (Fig. 18). Some surgeons feel iridectomy may not be necessary;189 however, patients with increased inflammation due to intraoperative complications, uveitis, diabetes, neovascularization, or at increased risk for pupil block require iridectomy.
There is a difference in wound architecture required for insertion of a rigid IOL and closure of a limbus-based conjunctival flap (Fig. 19).
Close the scleral flap and titrate flow (Fig. 20). There are a variety of techniques to gauge flow through the flap. The punch technique is simple especially when used in conjunction with a scleral tunnel. Extend the punch to the end of the tunnel and excise tissue. This functions similar to a valve effect and only one or two sutures are needed to close the flap. Some surgeons prefer an adjustable releasable suture for this step. It is slightly more difficult to titrate flow with this technique.190 If both sides of the scleral flap are opened and a block removed, the valve-like effect is lost and more sutures are necessary to close the flap. This requires more effort and increased surgical time but increases the ability to titrate flow postoperatively.
Adequate closure of a fornix-based conjunctival flap ensures there is no postoperative wound leak. There are a variety of techniques that have been described. Clearly, electrocoaptation is not desirable for a watertight closure and is avoided. The usual method of pulling a fornix-based flap onto the cornea under tension and held in place by two lateral sutures is simple but is more likely to leak with antimetabolite usage. An MMC compatible suture technique for fornix-based conjunctival flaps is well described and used by the author. 191,192 This technique is time consuming and requires a considerable learning curve but is well worth it (Fig. 21). Close the wound in a watertight fashion; inject subconjunctival antibiotic and corticosteroid. Patch and shield the eye in the usual fashion.
The status of the optic nerve is the major guiding factor in determining the level of postoperative IOP control. If the optic nerve is fragile and the surgeon is unsure of immediate postoperative filtration, use aqueous suppressants such as CAIs to protect the nerve until the first postoperative day when the IOP is monitored. Some patients are evaluated the same day of surgery. It is more desirable to start with an IOP in the teens or higher compared with subnormal IOP because some patients experience aqueous shutdown. With antimetabolites, it is preferable to control IOP medically for a few days before scleral flap suture lysis to avoid hypotony. The timing of suture lysis is critical and factors associated with this should be thoroughly reviewed before lysis. However, if the IOP is elevated, apply focal pressure193 to the filtration site or start medical therapy. Immediate suture lysis is dangerous194 because the wound hasn't adequately healed, subconjunctival resistance has not developed, wound leaks are more common, choroidal effusions may develop, and the blood–aqueous barrier breaks down; all of these factors may lead to a suprachoroidal hemorrhage.
Administer topical corticosteroids in the immediate postoperative to inhibit fibrosis and slowly taper over several weeks.195 The tendency is to discontinue these drugs too early. If it appears that the bleb is failing, 5-FU may be given postoperatively in the usual dosage, but one must watch carefully for corneal toxicity.
The perfect stereotypical operation for combined cataract–glaucoma surgery does not exist because each case demands a slightly different surgical approach. The above-mentioned principles help guide the surgeon to the most rational surgical approach for his or her patient. A recurrent theme is to perform the simplest and safest procedure with the least risk in your hands that will restore and maintain visual acuity and field.
18. Goldberg MF, Tso MOM: Sickled erythrocytes, hyphema, and secondary glaucoma: VII. The passage of sickled erythrocytes out of the anterior chamber of the human and monkey eye: Light and electron microscopic studies. Ophthalmic Surg 10:89, 1979
24. Kurimoto Y, Kobayashi H, Sakaue H et al: Correlation between the optic disc shape and the visual field in glaucoma patients: Objective and quantitative analysis using Heidelberg retinal tomograph and Humphrey field analyzer. Invest Ophthalmol Vis Sci 35(4): 1345, 1994
40. Chen HSL, Steinmann WC, Spaeth GL: The effect of chronic miotic therapy on the results of posterior chamber intraocular lens implantation and trabeculectomy in patients with glaucoma. Ophthalmic Surg 20(11):784, 1989
46. West J, Burke J, Cunliffe I et al: Prevention of acute postoperative pressure rises in glaucoma patients undergoing cataract extraction with posterior chamber lens implant. Br J Ophthalmol 76:534, 1992
48. Pohjalainen T, Vesti E, Uusitalo RJ, Laatikainen L: Intyraocular pressure after phacoemulsification and intraocular lens implantation in nonglaucomatous eyes with and without exfoliation. J Cataract Refract Surg, Mar 27(3):426-31, 2001
59. Rainer G, Menapace R, Findl O et al: Intraindividual comparison of the effects of a fixed dorzolamide-timolol combination and latanoprost on intraocular pressure after small incision cataract surgery. J Cataract Refract Surg 27:706, 2001
62. Kasetti SR, Shrivatsa PD, Subramaniam W et al: Preventing intraocular pressure increase after phacoemulsification and the role of perioperative apraclonidine. J Cataract Refract Surg 28:2177, 2002
71. Steuhl KP, Marahrens P, Frohn C et al: Intraocular pressure and anterior chamber depth before and after extracap-sular cataract extraction with posterior chamber lens implantation. Ophthalmic Surg 23:233, 1992
72. Dimitrov PN, Mukesh BN, Taylor HR, McCarty CA:Intraocular pressure before and after cataract surgery in participants of the Melbourne Visual Impairment Project. Clin Experiemtn Ophthalmol 29:128, 2001
73. Hansen MH, Gyldenkerne GJ, Otland NW et al: Intraocular pressure seven years after extracapsular cataract extraction and sulcus implantation of a posterior chamber intraocular lens. J Cataract Refract Surg 21:676, 1995
74. Shingleton, BJ, Gamell LS, O'Donoghue MW et al: Long-term changes in intraocular pressure after clear corneal phacoemulsification: Normal patients versus glaucoma suspect and glaucoma patients. J Cataract Refract Surg 25:887,1999
85. Steuhl KP, Marahrens P, Frohn C et al: Intraocular pressure and anterior chamber depth before and after extracapsular cataract extraction with posterior chamber lens implantation. Ophthalmic Surg 23:233, 1992
88. Kosmin AS, Wishart PK, Ridges PJ: Long-term intraocular pressure control after cataract extraction with trabeculectomy:phacoemulsification versus extracapsular technique. J Cataract Refract Surg 24:249, 1998
98. Shin DH, Ren J, Juzych MS et al: Primary glaucoma triple procedure in patients with primary open angle glaucoma: The effect of Mitomycin C in patients with and without prognostic factors for filtration failure. Am J Ophthalmol 125:346, 1998
103. Tezel G, Kolker AE, Kass MA, Wax MB: Comparative results of combined procedures for glaucoma and cataract: I. Extracapsular cataract extraction versus phacoemulsification and foldable versus rigid intraocular lenses. Ophthalmic Surg Lasers 28:539, 1997
104. Chia WLA, Goldberg I: Comparison of extracapsular and phacoemulsification cataract extraction techniques when combined with intraocular lens placement and trabeculectomy:short term results. Aust N Z J Ophthalmol 26:19, 1998
105. Shingleton BJ, Jacobson LM, Kuperwaser MC: Comparison of combined cataract and glaucoma surgery using planned extracapsular and phacoemulsification techniques. Ophthalmology Surg lasers 26:414, 1995
119. Rossetti L, Bucci L, Miglior S et al: Temporal corneal phacoemulsification combined with separate incision superior trabeculectomy vs standard phacotrabeculectomy. A comparative study. Acta Ophthalmol Scand Suppl 224:39, 1997
128. Wygnanski-Jaffe T, Barak A, Melamed S, Glovinsky Y: Intraocular pressure increments after cataract extraction in glaucomatous eyes with functioning filtering blerbs. Ophthalmic Surg Lasers 28:657, 1997
129. Crichton ACS, Kirker AW: Intraocular pressure and medication control after clear corneal phacoemulsification and Acrysof posterior chamber intraocular lens implantation in patients with filtering blebs. J Glaucoma 10:38, 2001
137. Tanihara H, Honjo M, Inatani M et al: Trabeculotomy combined with phacoemulsification and implantation of an intraocular lens for the treatment of primary open angle glaucoma and coexisting cataract. Ophthalmic Surg Lasers 28:810, 1997
143. Gianoli F, Schyder CC, Bovey E, Mermoud A: combined surgery for cataract and glaucoma:phacoemulsification and deep sclerectomy compared with phacoemulsification and trabeculectomy. J Cataract Refract Surg 25:340, 1999
152. Lai JS, Tham CC, Lam DS: The efficacy and safety of combined phacoemulsification, intraocular lens implantation, and limited goniosynechialysis, followed by diode laser peripheral iridoplasty, in the treatment of cataract and chronic angle closure glaucoma. J Glaucoma 10:309, 2001
170. Lynn JR, Swanson WH, Fellman RL, Starita RJ.: Does glaucomatous visual filed loss continue despite surgically subnormal IOP? Perimetry Update 1992.93, p 129. Proceedings of the Xth International Perimetric Society Meeting, Kugler Publications, Amsterdam / New York
171. The advanced glaucoma intervention study (AGIS): 7. The relationship between control of intraocular pressure and visual field deterioration. The AGIS Investigators, Am J Ophthalmol, 130:429, 2000
174. Kozobolis VP, Siganos CS, Christodoulakis EV et al: Two-site phacotrabeculectomy with intraoperative mitomycin-C:Fornix-versus limbus-based conjunctival opening in fellow eyes. J Cataract Refract Surg 28:1758, 2002
179. el Sayyad F, el-Rashood A, Helal M et al: Fornix-based versus limbal-based conjunctival flaps in initial trabeculectomy with postoperative 5-fluorouracil: four-year follow up findings. J Glaucoma 8:124, 1999