The primary issue with regard to cataract surgery and glaucoma surgery in the same eye is how to position the cataract operation in the management scheme of the patient’s condition. Is it better to choose one sequence and type of surgery before the other, or to combine the two procedures? Although this has been a matter of unresolved controversy, the choice of surgery has been dramatically influenced in the past two decades by three significant and independent advances. The first is the evolution of ever more refined small-incision phacoemulsification techniques and small-profile intraocular lens (IOL) implants – thus allowing for smaller wounds, less postoperative inflammation, and choices for surgical entry sites. The second advance is the demonstrated advantage of using antimetabolites to enhance filtration surgery. Third is the availability of novel glaucoma procedures – non-penetrating glaucoma surgeries and endocyclophotocoagulation – which have also been combined with small-incision cataract surgery. Together these auspicious developments have resulted in a panoply of surgical solutions far superior to what was available to our patients a generation ago.
Despite the wider spectrum of surgical options, however, the quality of clinical reports, in terms of their epidemiologic and methodological rigor, leave much to be desired. In the absence of firm, evidence-based data, personal clinical experience and preference dominate the decision-making process.
CATARACT SURGERY IN THE GLAUCOMATOUS EYE
Glaucoma and cataract often occur together, especially in the elderly, and each condition can influence management of the other. Progressive lens change can mimic progressive visual field loss, reduce visual acuity, and narrow the drainage angle. Glaucoma medications that cause miosis can aggravate visual impairment from cataract; and the now rarely-used anticholinesterase class of miotics can accelerate the development of cataracts. In addition, prior glaucoma surgery leads to a clinically significant acceleration of cataract morbidity in the years following trabeculectomy. Thus each of these diseases must be considered when treating the other.
The first consideration is which specific type of glaucoma is being treated; different diseases have different surgical outcomes and complications. Next is the decision regarding the sequence of procedures. Unless a minimal and unpredictable long-term IOP-lowering effect of 2–4 mm is deemed sufficient for glaucoma control, cataract extraction alone is usually insufficient to address the pressure-lowering (or medication-reduction) needs of the glaucomatous eye. Some advocate that either a cataract or filtration procedure be done first and separately; others recommend combination surgery in one procedure. Here, too, results differ between phacoemulsification and extracapsular cataract extraction (ECCE) procedures, as well as whether and how antimetabolites are used. However, rigorous evaluation of the literature on techniques and timing for cataract and filtration surgery has failed to demonstrate convincing evidence of an unequivocally superior approach. Nevertheless, suggestive trends (such as use of mitomycin-C, separate incision sites, and phacoemulsification rather than ECCE) were discerned. Similarly, surgical alternatives such as trabeculotomy, and both older and newer forms of non-filtering trabecular surgery have been used to control IOP at the time of cataract surgery, but all such reports lack sufficient statistical rigor.
Other considerations are important in individualizing treatment for a given patient. Such issues include the efficacy of and compliance with the current medical regimen, the financial costs or possible side effects of the medical regimen, the chosen target pressure for the eye, the surgeon’s skill and experience, the status of the optic nerve and visual field, and the visual requirements and quality of life that the patient desires to obtain. Every effort should be made in the preoperative evaluation to distinguish between the cataractous and glaucomatous components of a patient’s visual status. This requires dilation for visual field studies, cataract inspection, and detailed ophthalmoscopy.
TYPES OF GLAUCOMA AND THEIR INFLUENCE ON CATARACT MANAGEMENT
In the absence of peripheral anterior synechiae, eyes with cataract, glaucoma, and progressively narrow angles may respond to approaches other than a combined procedure. Lens size increases with aging and can further narrow an already compromised angle. Laser iridotomy in such patients may facilitate IOP control by relieving any pupillary block component and allowing the angle to widen. Many such patients with primary angle-closure glaucoma (PACG) often show a significant improvement in their IOP control after cataract removal, implying that there is some phacomorphic component to their underlying disease, even in the presence of an iridotomy. Accordingly, if a non-Asian patient with PACG presents with relatively good IOP control on minimal medical therapy and evidence of greater than 50% available trabecular meshwork, it may be sufficient to proceed with cataract extraction and IOL implantation alone, reasonably anticipating a good chance that the glaucoma will remain controlled, if not improved. An alternate approach combining phacoemulsification with goniosynechialysis has also been advocated, avoiding filtration surgery.
Diabetic eyes with primary open-angle glaucoma risk worsening of their ocular health after cataract surgery, with or without lens implantation. In the days of intracapsular cataract extraction, the incidence of neovascular glaucoma was reported to be as high as 9% after intracapsular surgery, a rate nearly identical to that reported for neovascular glaucoma after ECCE surgery in the presence of either an inadvertent or deliberate capsulotomy (11%). These rates are in contrast to the much-reduced risk of a rubeotic glaucoma in the presence of an intact capsule. Often, violation of the capsule is unavoidable at the time of cataract/IOL surgery; later it may be unavoidable because of the need for a capsulotomy to maximize either vision or ophthalmologic visualization of the fundus.
Similar findings were reported in a large retrospective study of large-incision ECEE cases in which an important distinction was made as to whether proliferative diabetic retinopathy was present before cataract surgery. If present, there was a 40% rate of neovascular glaucoma and a greater than 20% rate of vitreous hemorrhage related to the cataract extraction. Every effort should be made to address a preproliferative retina with panretinal photocoagulation before cataract extraction. In the presence of actual iris neovascularization or proliferative retinopathy, reports on the efficacy of intravitreal bevacizumab (Avastin™) for temporarily inducing neovacular regression in the anterior segment (and by implication its potential utility in the preoperative setting) are encouraging.
Although immediate postoperative problems with fibrin formation and hyphema are seen, the overall success rate for both visual improvement and IOP control is still good in the eyes of diabetic patients. There is, however, a higher likelihood of developing pupillary block glaucoma in such eyes. Although peripheral iridectomy is currently not routinely performed by most lens implant surgeons (especially with temporal corneal incisions), it is highly advisable that either surgical iridectomy, or access for a postoperative laser iridotomy, be considered in planning cataract surgery in patients with diabetic retinopathy.
Patients that present with pseudoexfoliation are certainly more prone to develop cataracts and have a much higher association of glaucoma (as well as subtle systemic anomalies ) which must be detected before cataract extraction is undertaken. Many features of the eye with pseudoexfoliation make cataract surgery particularly challenging, including (1) a tendency toward incomplete mydriasis, with a subsequent small pupil that can complicate cataract extraction; (2) a tendency toward multiple surgical challenges – phacodonesis, lens subluxation, zonular laxity or dehiscence, and capsular rupture with lens dislocation and vitreous loss ; (3) a cornea that may be more vulnerable to endothelial damage; (4) a tendency toward hyphema during surgery, and (5) a tendency for unreliable zonular integrity, such that even an in-the-bag lens implant can displace into the vitreous. Undiagnosed lens subluxation from weak zonules is often noted intra-operatively, but when this condition is anticipated, good results are nevertheless possible with careful phacoemulsification, judicious use of viscoelastics, pupillary retractors, capsular tension rings and other advanced cataract techniques.
Eyes with uveitic glaucoma embrace a wide spectrum of diseases and perisurgical responses. Although cataract/IOL surgery can be performed without incident in eyes with Fuchs’ heterochromic uveitis, other reports have observed several specific features of this condition that bear directly on the management of cataractous eyes. In more than 103 patients with this condition, some 25% had open-angle glaucoma. However, many patients developed persistent inflammation and peripheral anterior synechiae, rubeosis of the iris and angle, pupillary block, and recurrent hyphemas. When these patients underwent glaucoma surgery, more than half failed standard filtration operations (in the absence of antimetabolites). Similar problems may arise in eyes with other conditions of chronic uveitis and secondary glaucoma. The underlying inflammatory condition, rather than the glaucoma, is responsible for a host of potential postsurgical complications from combined surgery: filtration failure, accelerated posterior capsular fibrosis, cystoid macular edema (CME), fibrinous iritis, etc. Maximal perioperative control of inflammation is essential.
Occasionally a loose or subluxed lens resulting from traumatic rupture of some of the zonules can be appreciated. In such cases, the lens can shift forward, increasing pupillary block and narrowing the angle. This may be suspected if the chamber is shallow unilaterally, if there is a history of trauma, or if any iridodonesis is evident. In such cases, cycloplegia can deepen the chamber, widen the angle, and allow the surgeon to detect vitreous anterior to the lens if true subluxation exists. Laser iridotomy can be attempted to improve glaucoma control in these eyes, performed away from any area of vitreous prolapse. As with traumatic cataracts, such surgical situations may require complex maneuvers: lensectomy with vitrectomy; capsular tension rings and pupillary retractors; sulcus-IOL support, etc.
If the angle is open and the cornea healthy, anterior chamber IOL implantation is an option. An alternative is scleral fixation of a posterior chamber IOL behind the iris plane after vitrectomy or loss of the capsule. This challenging option should be reserved for surgeons skilled in this procedure. Many complications with this technique have been reported in patients undergoing penetrating keratoplasty, including CME, glaucoma exacerbation, and decentered IOLs. This higher-risk profile merits caution when surgery in the glaucomatous eye is being considered.
SELECTING THE APPROPRIATE SURGICAL APPROACH
For the vast majority of patients with glaucoma and visually significant cataract, there are three choices:
Undergo cataract extraction alone, and pay no surgical attention per se to the glaucomatous condition;
Undergo glaucoma filtering surgery first and allow full healing before undergoing a second operation for cataract removal;
Undergo a single combined cataract and IOL implantation operation at the time of the glaucoma filtering procedure.
Before cataract extraction, it is important to achieve the best possible IOP control, which is defined as a tolerable medical regimen that meets the target pressure, preserving the optic nerve and visual field from progressive worsening. Maximal presurgical therapy also includes the application of selective or argon laser trabeculoplasty, whose beneficial effects are not likely to change after cataract surgery.
Cataract surgery alone cannot be expected to provide clinically meaningful IOP control. Whether using phacoemulsification or ECCE with IOL, the long-term pressure reduction after cataract surgery is in the order of 2–4 mmHg, with the great majority of eyes requiring the same or an increased glaucoma medical regimen after 1 year. In a patient with minimal disc and field change and reasonably well-controlled IOP on a simple medical regimen, these findings may suggest a course of cataract extraction alone. An attractive approach is to proceed with a temporal, clear-corneal phacoemulsification or small-incision ECCE procedure ; these approaches for cataract-only surgery will not adversely impact later filtration surgery if needed, since the superior conjunctiva remains untouched. In summary, pre-cataract IOP control in glaucoma is unlikely to be lost after cataract-IOL surgery alone and may be, at least, temporarily improved.
Another option is that the glaucoma be surgically addressed first and cataract extraction subsequently undertaken. In the presence of marginal cataractous changes or of a complicated glaucoma that has resisted IOP control by medications or prior surgery, establishing successful filtration may well be the first priority. The question is what effect later cataract surgery may have on an established, successful filter.
Most studies report a high likelihood for a subsequent cataract procedure to compromise a pre-existing filter, with a bleb failure rate as high as 30–40% after lens surgery. This phenomenon was reported even with a clear corneal cataract approach designed to avoid disrupting the conjunctiva. This suggests that the inflammation caused by lens extraction is detrimental to long-term bleb survival – although the presence of a bleb is helpful in blunting the post-cataract IOP spike. Whether the survival of a pre-existing bleb can be enhanced by intraoperative needling or perioperative applications of topical mitomycin-C or subconjunctival 5-fluorouracil (5-FU) has not been systematically studied. Reports of the effect of phacoemulsification-IOL procedures, even performed temporally, uniformally conclude that there is some adverse effect on pre-existing glaucoma control: an increase in postoperative IOP, an increased need for glaucoma medications, or alterations in bleb morphology. It is therefore realistic to anticipate loss of some IOP control from a pre-existing filtration surgery, to a greater or lesser extent, if the eye later undergoes cataract surgery by either ECCE or phacoemulsification, with or without antimetabolite supplementation of the original bleb.
The arguments for combining trabeculectomy with cataract extraction are persuasive on many grounds. In the absence of pre-existing retinal disease, there is every expectation that excellent visual acuity will be obtained in the overwhelming majority of patients. Although trabeculectomy in a combined cataract surgery may not be as effective in lowering the IOP when compared with trabeculectomy performed alone, the combined procedure nevertheless provides long-term lower IOPs than when cataract surgery is performed in a glaucomatous eye without filtration.
The decision for a combined surgery is not formulaic, and requires a blend of multiple considerations, both positive and negative. We commonly encounter variations of four basic situations, which often present in combinations unique to each eye. These scenarios are:
Cataractous loss of acuity in an eye with glaucomatous disc or visual field changes, unreliably maintaining IOPs below a designated ‘target range’ despite medical or laser management.
Cataractous loss of acuity in an eye requiring medications, where faulty compliance with, allergic sensitivity to, or unsustainable cost of medical therapy recommend a surgical solution to IOP management.
Cataractous loss of acuity in eye with far advanced visual field loss near fixation or with extensive disc damage, which despite adequate IOP control, nevertheless would be at risk following cataract surgery alone: either at risk for precipitous deterioration by any potential IOP spike, or whose maximal utilization of topical medications precludes additional agents should IOPs rise postoperatively.
Uncontrolled glaucoma in an eye with borderline clinically cataractous changes, anticipating accelerated cataract progression following filtration surgery. Such situations might include either the patient’s preference for a single operation rather than a two-staged surgery, or the patient’s physical fraility (usually elderly with multiple medical problems) meriting a single surgical intervention.
As always with any surgery, benefits and risks need be weighed and disclosed: for example, a combined phaco/filter usually requires a longer interval for visual rehabilitation than cataract alone; a trabeculectomy alone usually provides lower IOPs than a combined procedure – yet subsequent cataract surgery often adversely affects prior filtration control.
A particularly compelling argument for a combined procedure is to protect the glaucomatous eye as much as possible from the likelihood of significant IOP elevations after cataract surgery when performed alone. There is ample evidence for cataract extraction causing significant pressure spikes in glaucoma. One series reported a 2.5 times greater incidence of elevated IOPs in the absence of trabeculectomy than when the combined procedure was performed ; this protective advantage of the concomitant trabeculectomy has also been reported by others. Pressure spikes have been detected in nearly two-thirds of patients with pre-existing glaucoma undergoing cataract surgery, in contrast to 10% of normal eyes.
Nevertheless, the combination of trabeculectomy with cataract extraction does not guarantee the absence of a pressure rise. Krupin and co-workers investigated the IOP course in glaucomatous patients who underwent ECCE with or without a concomitant trabeculectomy. They reported an alarming IOP rise on the first day after surgery among the ECCE-only eyes; an IOP rise of 10 mmHg or more occurred in 69% of patients, with three-quarters of those eyes measuring an absolute IOP over 25 mmHg. Of the patients undergoing ECCE trabeculectomy, 14% showed an IOP rise of 10 mmHg or more. Of these, 21% showed an IOP over 25 mmHg. Such patients may continue to show IOP fluctuations for several months after ECCE surgery, and close surveillance is warranted. Similar IOP spikes have also been reported in up to 40% of eyes using phacoemulsification combined with trabeculectomy and mitomycin-C. It should be understood that a combined procedure can definitely reduce, but not predictably eliminate, the problem of intermittent IOP elevations.
SELECTING THE APPROPRIATE PROCEDURE: HISTORICAL CONSIDERATIONS
There are few more dramatic illustrations of evolutionary changes in glaucoma surgery in the past quarter-century than the literature on combined cataract and glaucoma surgery. This reflects the advent both of antimetabolite therapy in filtration surgery and of small cataract incisions, in which the same 3–4-mm wound is used for phacoemulsification, IOL insertion, and filtration. Because a spectrum of equipment and techniques may be available to the surgeon at different times, it is useful to understand the results of key technical variations in the development of combined procedures.
By the end of the 1980s, the efficacy of the combined ECCE + IOL + trabeculectomy procedure had been established. Visual results were encouraging, IOPs were brought down to the mid- to high-teens in the majority of cases, and fewer glaucoma medications were required. It was also noted that long-term IOP control was often seen in the absence of anatomic blebs.
When ECCE + IOL + trabeculectomy was compared with phacoemulsification + IOL + trabeculectomy , the latter procedure was usually found to be superior. Phacoemulsification + IOL + trabeculectomy reliably resulted in better visual acuity, lower IOPs with fewer medications, fewer postoperative complications (e.g., postoperative IOP spikes), and more robust-appearing blebs. These advantages were usually ascribed to the smaller wound incision of the phacoemulsification site, where the filtration procedure was also performed.
When antimetabolites were used as adjunct to the combined procedures, there again seemed to be an advantage to a smaller wound. Surprisingly, when ECCE + IOL + trabeculectomy + 5-FU injections postoperatively were undertaken, there was no greater reduction of IOP than when 5-FU was not administered. In contrast, when phacoemulsification + IOL + trabeculectomy + 5-FU was performed, lower IOPs were usually (but not always ) seen compared with a combined phacoemulsification + IOL + trabeculectomy procedure without 5-FU. This enhanced effect was also seen when the trabeculectomy was performed superiorly and the cataract incision made through the temporal clear cornea.
The choice of antimetabolite is also important, with mitomycin-C apparently conferring sustained and lower IOP reduction compared with 5-FU. When results of ECCE + IOL + trabeculectomy + mitomycin-C were reported, the IOPs were brought into the low- to mid-teens – better than when 5-FU was used with this procedure. However, the ECCE + IOL + trabeculectomy + mitomycin-C results were not as good as with the phacoemulsification method: only 60% of ECCE-treated patients had visual acuity better than 0.5, and 15% showed significant astigmatism of greater than 2D against the rule.
In summary: unlike the valuable role of 5-FU as an effective antimetabolite when used with trabeculectomy alone, there is abundant evidence that 5-FU’s efficacy is virtually nil when used with trabeculectomy at the time of any kind of cataract surgery. This is significantly different from the utility of mitomycin-C with either trabeculectomy alone or with combined procedures.
Low IOPs and good visual acuity results have been consistently reported with the phacoemulsification + IOL + trabeculectomy + mitomycin-C procedure, although some have doubted the contribution of the mitomycin-C in all cases. Intraocular pressures tend to run in the low teens, medications are virtually eliminated, and blebs tend to be large and functional. In two placebo-controlled, double-masked studies, the combined procedure with mitomycin-C was unequivocally more successful than no antimetabolite at lowering IOPs and reducing postsurgical glaucoma medications.
As with all filtration surgery combined with mitomycin-C, the complications of hypotony and bleb leaks are not uncommon, and higher rates of endophthalmitis may be associated with the thin, cystic avascular blebs that form. Risk factors that favor use of mitomycin-C include African-American patients, higher pre-surgical IOPs (over 21 mmHg), more than two pre-operative antiglaucoma medications, and diabetes.
SURGICAL TECHNIQUES FOR COMBINED PROCEDURES
It thus seems that the most advantageous factors for successful combined cataract and glaucoma surgery are a small wound (as in phacoemulsification) and a potent antimetabolite (mitomycin-C). The technology for the variety of combined glaucoma and cataract techniques is not universally available, however. This section surveys the technical aspects of performing the combined procedure, both with a small incision for phacoemulsification and with a larger ECCE wound.
GENERAL PREOPERATIVE CONSIDERATIONS
It is important to inform the patient that a combined cataract and glaucoma operation may take longer to heal than a simple IOL implant procedure. In the event that the patient is taking a carbonic anhydrase inhibitor and filtration surgery is undertaken, it is common to eventually discontinue the systemic medication postoperatively to enhance filtration; but this may risk possible loss of IOP control in the fellow, unoperated eye. Accordingly, the patient may have to consider that the decision whether to undergo filtration surgery in one eye may soon lead to filtration surgery in the other eye as well.
It is useful to stop any miotic several days before surgery, both to reduce postoperative inflammation and to allow maximal dilation for cataract surgery. Preoperative dilation in the clinic by the surgeon should provide information as to the maximum pupillary dilation that can be expected in the operating room. Other topical glaucoma medications can be used until the day of surgery. α-agonists, such as apraclonidine or brimonidine, when applied immediately preoperatively, may cause conjunctival vasoconstriction and thus enhance hemostasis. In conjunction with the patient’s primary care physician, it may be advisable to preoperatively discontinue systemic medications, such as anticoagulants (aspirin, coumadin, etc.) or α 1 -adrenergic receptor agonists (e.g., tamsulosin, used for benign prostatic hypertrophy, and responsible for floppy-iris syndrome during cataract surgery), although most reports find discontinuing either class of drug irrelevant.
SMALL-INCISION COMBINED SURGERY
Many technical variations are available for small-incision *
* In this discussion, ‘small incision’ refers to phacoemulsification surgery – and not the small-wound ECCE surgery often performed in Nepal and elsewhere. That particular technique, when performed temporally, is fully compatible with a combined, two-site filtration surgery performed superiorly.combined surgery, few of which have been rigorously evaluated in a prospective, controlled fashion. Often the selection is based on the surgeon’s technical skill and experience in performing phacoemulsification surgery and in managing filtration surgery with antimetabolites ( Box 35-1 ). The technique that we use is illustrated in step-by-step detail in Figures 35-l through 35-13 .
Single vs. separate incision sites
Fornix vs. limbal conjunctival flap
Type of scleral incision: phaco tunnel vs. trabeculectomy flap
Mitomycin-C use: When to apply? Concentration? Duration?
Management of small pupil: Stretch? Iris hooks? Pupil expander? Large iridectomy?
Phacoemulsification technique: Divide-and-conquer? Stop-and-chop?
IOL type: Foldable IOL though small wound? Silicone or acrylic?
Anticipating complications (no capsular support): Sulcus suture fixation? Anterior chamber – IOL temporally?
Scleral tunnel or flap closure: Anticipate laser lysis? Pre-place releasable sutures? Adjustable sutures?
Immediate postoperative therapy: Topical glaucoma medications? Intravenous or oral carbonic anhydrase inhibitors?
There is no demonstrated superiority with regard to whether the combined procedure should be performed using one small incision site for the cataract removal, IOL placement, and trabeculectomy or if separate surgical sites should be made. Some have advocated a straightforward trabeculectomy superiorly, usually with an antimetabolite, and performing the cataract surgery separately from a temporal, corneal approach. Others use the single incision for the entire procedure.
Fornix versus limbal conjunctival flap
Prospective assessments of the advantages of performing the combined procedure under a fornix-based or limbus-based conjunctival flap have shown few differences. As the standard approach to cataract surgery when performed alone, the fornix-based flap is a familiar technique; in contrast, the limbus-based flap may obstruct the view of the limbus during surgery, and assistance may be required to shift the conjunctiva back and forth. When antimetabolites are used, the fornix flap requires considerable attention to meticulous water-tight wound closure to minimize postoperative leaks. Conversely, the fornix flap has been associated with blebs that appear non-cystic and less thin than those seen with the limbal flap.
Some surgeons fashion their small-incision phacoemulsification incisions beneath either the triangular or rectangular scleral flap used in routine trabeculectomy surgery. One of our two standard techniques is to fashion a non-frowned, scleral tunnel for the phacoemulsification under a limbal-based conjunctival flap, and later extend the 12 o’clock edge to the limbus, converting the cataract wound into a filtration site (see Figs. 35-1 through 35-13 ). Our other approach uses a fornix-based conjunctival flap: we construct the same scleral tunnel, but without cutting any radial incisions towards the limbus. Through this tunnel a trabeculectomy is made with a small scleral punch, so that the tunnel itself acts as a valve, reducing the occurrence of hypotony as well as directs aqueous outflow posteriorly away from the limbus. The scleral tunnel construction advocated by Khaw at Moorfields, and illustrated in the previous chapter ( Fig. 34-19 ), is compatible without any modification whatsoever for phacoemulsification, which is performed prior to the use of the scleral punch.
Although 5-FU is effective with trabeculectomy alone – either applied on a 5-FU saturated sponge (5 mg/cc) to the surgical site, or injected sub-conjunctivally post-operatively – this anti-metobolite confers virtually none of its bleb-sustaining effects when used during concomitant cataract surgery. In contrast, mitomycin-C has proven potent in combined surgeries. It was originally used in doses of 0.5 mg/ml and applied for 5 minutes either over the trabeculectomy flap or in the scleral bed under the flap. Others have found efficacy at lower doses and shorter durations (e.g., 0.25 mg/ml applied for 2–3 minutes), with the parameters adjusted according to whether the risk of filtration failure is high (e.g., with previous surgery, uveitis). Although most surgeons prefer placement of the mitomycin-C over the surgical incision site before entering the anterior chamber, it can also be safely applied at the conclusion of the surgery before closing the conjunctival flap.
Managing the small pupil
A glaucomatous eye may fail to sufficiently dilate for optimal cataract removal for a variety of reasons: pupillary dysfunction (as in pseudoexfoliation); prior use of miotics; posterior synechiae to the anterior lens capsule following laser iridotomies, etc. Multiple approaches are available for the mechanical enlargement of the pupil. Either a sector iridectomy (excising iris) or radial iridotomy (incising from the pupil to the iris insertion) can be performed, and optionally resutured at the end of surgery to restore a round pupil. Such techniques have optical benefits for the patient and may reduce the incidence of posterior chamber lens capture ( Fig. 35-14 ). Multiple, small, radial sphincterotomies under viscoelastic can be performed with scissors intraoperatively; in combination with mechanical stretching of the sphincter, this can result in a large enough pupillary diameter to proceed with surgery. Exaggerated mechanical stretching alone is often sufficient, using a two-handed technique with small iris hooks or notched instruments, opposed 180° apart and pulling the pupil to 8 mm or so along two to three axes.