Coincident cataract and glaucoma surgery

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CHAPTER 36 Coincident cataract and glaucoma surgery

John P. Berdahl, Tom W. Samuelson

Introduction

The management of coincident cataract and glaucoma presents common and challenging decisions for the ophthalmic surgeon. Emerging data and technological advances continue to shape the approach to coexisting cataract and glaucoma 1–3. Historically this generally involved sequential surgery with initial glaucoma surgery followed by cataract extraction months later when the intraocular pressure (IOP) was controlled and the bleb had matured. The rationale for the sequential approach was based on the poor success rate of combined extracapsular cataract extraction (10 mm scleral incision) and glaucoma filtration surgery. While the advantage of the sequential approach is the high success rate of primary filtration surgery, the disadvantages are that the patient undergoes at least two operations, prolonged poor vision, and the risk of bleb failure after the cataract operation. As techniques improved with clear cornea small incision phacoemulsification and guarded filtration surgery with anti-metabolites, glaucoma surgeons began to reconsider combined rather than sequential surgery4,5. As new procedures such as canaloplasty, ab interno trabeculectomy (Trabectome), endoscopic cyclophotocoagulation, and trabecular meshwork stents evolve, there may be a decreased need to perform traditional filtering procedures including glaucoma drainage devices. Modern techniques of clear cornea small incision cataract surgery alone lower IOP and may be the preferred initial step to manage most cases of coexisting glaucoma and cataract6–8. However, combined surgery remains an important option for select cases with advanced glaucoma or markedly elevated IOP. We describe techniques for the surgical treatment of coexisting cataracts and glaucoma.

Indications

Traditional indications for combined cataract and glaucoma surgery are uncontrolled glaucoma that requires surgery in a patient with visually significant cataract, or the need for cataract extraction in a patient with advanced or poorly controlled glaucoma. The mere coexistence of glaucoma and cataract is not in itself an indication for combined cataract and glaucoma surgery 9. Mild to moderate glaucoma that is controlled well on medication is usually best managed by cataract extraction alone. In these instances, it is best to perform the cataract extraction with a conjunctival sparing approach such as a clear corneal incision. If the glaucoma later becomes uncontrolled, a glaucoma procedure can be performed readily. Small incision cataract extraction techniques have made the ‘cataract extraction first, glaucoma surgery later if necessary’ approach more feasible. (Table 36.1)7.

Table 36.1 Options for surgical management of coincident cataract and glaucoma *

Trabeculectomy first; cataract extraction later	Combined cataract extraction–trabeculectomy/tube shunt^†	Cataract extraction first; glaucoma surgery later if needed^‡
Consider if employing large incision 10–11 mm extracapsular cataract extraction		Mild to moderate glaucoma, well-controlled intraocular pressure with additional medical options available
	Far advanced glaucoma	Untreated or medically controlled ocular hypertension with additional medical options available
	Patients on MTMT or patients intolerant to medications Patients poorly compliant with medications Low target intraocular pressure

MTMT = maximally tolerated medical therapy.

* Assumes visually significant cataract.

^† Small incision approach.

^‡ Conjunctival sparing technique – preferably clear cornea.

The goals of combined cataract and glaucoma surgery vary from patient to patient depending on both the severity of the cataract and that of the glaucoma. For example, a patient with advanced, but non-progressive glaucoma whose IOP is well controlled with minimal medication may require only careful observation or additional short-term medications following cataract extraction. In such patients, it is possible to avoid the problems associated with glaucoma surgery and still get the patient through the surgery without further visual loss. Conversely, a patient with progressive glaucoma and poorly controlled IOP often requires more aggressive pressure lowering and a long-term solution to achieve optimal IOP. Although rare in developed countries, extremely dense, brunescent cataracts that cannot be removed with standard clear cornea phacoemulsification techniques may require extracapsular cataract extraction. In these cases surgeons should place extracapsular incisions strategically to allow for future glaucoma procedures. Management of individual patients differs according to the specific goals of treatment and likely outlook for each eye.

Anesthesia

Combined cataract and glaucoma procedures can be performed with retrobulbar, peribulbar/subTenon’s, or topical anesthesia. Topical anesthesia with subconjunctival supplementation is adequate for the majority of cases. While local subconjunctival injection of anesthetic is adequate for most cases, if additional anesthesia or akinesia is needed a small incision can be made in the conjunctiva and large bore blunt tip cannula can be passed along the sclera posteriorly into the muscle cone to perform an intraoperative ‘subTenon’s’ block. Prior to administering anesthesia, intravenous sedation may be employed. A combination of agents with ultra-short-acting sedative and amnesiac properties such as methohexital 20–30 mg (Brevitol, Jones Medical), midazolam HCl 1 mg (Versed, Roche Laboratories), or alfentanil 250 µg (Alfenta, Janssen Pharmaceutica Inc.) may be given intravenously to reduce anxiety and pain. This combination of medications provides several minutes of deep sedation during which the block can be given without pain or patient awareness. The block consists of 2% xylocaine (Lidocaine, Astra) without epinephrine. Hyaluronidase (Wydase, Wyeth-Ayerst) is generally not necessary but can be used. In most cases, bupivacaine HCL (Marcaine, Sanofi Winthrop) 0.75 is not needed, but it may be used if the anticipated surgical time is to be longer than 1 hour. Within minutes after administration of the block, the patient is aware and able to cooperate with the surgeon. During the procedure only light sedation or none at all will be required. It is important to control the patient’s systemic blood pressure during the surgery for many reasons, but primarily to reduce the risk of suprachoroidal hemorrhage. After the peribulbar or retrobulbar block, it may be helpful to apply pressure to the globe for several minutes, using digital compression over a closed eyelid or a mechanical device such as a Honan balloon, or a mercury bag. However, external compression strategies, while common with larger incision extracapsular techniques, are less commonly utilized in the small incision phacoemulsification era and are generally unnecessary.

The theory behind the use of external compression is that the pressure prevents bleeding into the retrobulbar space, facilitates diffusion of the anesthetic solution into the orbital tissues, and softens the eye, making the surgery safer 9. As the risk of applying external compression to eyes with badly damaged optic nerves is not clear, it is advisable to limit the magnitude and duration of ocular compression to 20–30 mmHg and 5 to 10 minutes in such patients.

For patients with markedly elevated IOP, preoperative intravenous mannitol will minimize the abrupt change in intraocular pressure following the incision. The need for mannitol to suppress IOP is infrequent, however, and depends on the clinical circumstance and the general health of the patient, especially from a cardiopulmonary perspective. Osmotic agents like mannitol are preferred over aqueous suppressants because they dehydrate the vitreous, thereby reducing vitreous volume and softening the eye. Conversely, aqueous suppressants retard aqueous production during the early perioperative period. At least theoretically, reduced aqueous outflow through the new filter could exacerbate hypotony and later bleb fibrosis.

Preoperative considerations

Preoperative clinical assessment is vital. Gonioscopy should be performed. The conjunctiva should be examined carefully. Topical steroids should be administered if the conjunctiva is inflamed 10. The surgeon should carefully examine the eye for the presence of exfoliative material, which can be associated with a more aggressive postoperative inflammatory response, weakened zonular fibers, and poor pharmacologic dilation11,12. It is important to note the pupillary response to pharmacologic dilatation. If dilatation is poor and pupil manipulation is anticipated, the patient should be informed, as such manipulation may result in anisocoria or pupillary distortion. This precaution is particularly important for younger patients with light irides in whom the cosmetic effect of anisocoria or irregular pupil will be more apparent. Depending on the surgical procedure, patients should be educated preoperatively about the specific features of the postoperative period with combined cataract and glaucoma surgery, which may require frequent doctor visits and prolonged visual recovery, beyond that expected for standard cataract surgery in non-glaucomatous eyes.

Surgical technique

Small incision cataract extraction techniques have vastly improved treatment of cataracts in patients with glaucoma. Standard cataract surgery is described in great detail in Chapter 8. Rarely, other techniques, such as extracapsular or intracapsular extraction may be necessary. Surgeons should either be competent in these other techniques or refer specific cases9. When possible, a clear cornea incision is preferable to preserve the conjunctiva and the trabecular meshwork for any future glaucoma procedures. Current techniques for combined glaucoma surgery using small incision phacoemulsification will be described here.

Cataract surgery alone as a glaucoma procedure

Studies following cataract extraction in the 1970s and 1980s demonstrated minimal reduction of IOP 13–15. However, advances in surgical technique and intraocular lens technology means that these results probably don’t apply today. As extracapsular surgery became the standard, studies began to demonstrate an average lowering of IOP by 2–4 mmHg16–18. Studies that stratify patients based on preoperative IOP clearly demonstrated that patients with higher preoperative IOP enjoy the greatest reduction of IOP after cataract surgery and that IOP can be controlled in 20% of patients with cataract surgery alone1,19–21. Long-term studies have shown a drop in IOP of about 3 mmHg with 75–85% of patients maintaining an IOP reduction up to 10 years7,8,22–25.

The method of cataract extraction may influence the reduction in IOP. Phacoemulsification (particularly clear cornea phacoemulsification) seems to lower IOP more than manual extracapsular cataract extraction 16,17,26,27. PXF patients may have an even greater long-term decrease in IOP than POAG patients, even though IOP often rises in the immediate postoperative period28–30. Factors that have been identified to be important in the perioperative control of IOP include pressurization of the eye at the time of surgery, immediate postoperative medications, and viscoelastic type31–34. The surgeon should remove all viscoelastic carefully and ensure that the eye is not over-pressurized at the time of surgery. Despite limitations, cataract surgery seems to be emerging as a safe way to lower IOP in patients with mild to moderate glaucoma while avoiding the morbidity of traditional glaucoma surgery.

Results of combined cataract extraction and trabeculectomy

Overall, combined phacotrabeculectomy and trabeculectomy alone have similar outcomes. A couple of studies have compared phacotrabeculectomy with trabeculectomy alone. In one retrospective study 85 eyes that underwent trabeculectomy were compared with 105 eyes that had had phacotrabeculectomy. The mean postoperative IOP was similar in both groups at all time points up to 2 years. However, the mean IOP decrease from baseline was higher in the trabeculectomy alone group 35. Another study showed a similar success rate of 70% in patients having either combined phacotrabeculectomy or trabeculectomy alone36. In a retrospective study of 60 eyes that underwent phacotrabeculectomy, 95% achieved an IOP of 21 mmHg or less with or without medication, 50% of eyes had an IOP less than 15 mmHg, and 57% of eyes had a 30% reduction in IOP. Best corrected vision of 20/40 or better was maintained in 87% of eyes37.

A prospective study of phacotabeculectomy looked at 304 consecutive eyes over 1 year showing a mean IOP of 15.5 mmHg with nine eyes requiring a reoperation 38. Two studies comparing one-site and two-site phacotrabeculectomy showed similarly safety and IOP control over a 3-year follow-up period in patients with POAG and pseudoexfoliative glaucoma (PXFG) with a mean postoperative IOP of 15 mmHg in all groups39,40.

Single-site combined filter and cataract extraction

When performing combined cataract extraction and filtering surgery, a one-site or two-site incision may be used. In a one-site approach the entire procedure can be performed through the conjunctival and scleral incisions used in standard trabeculectomy mimicking a guarded filtration procedure as described in Chapter 35 41–43. Either a limbus-based or fornix c based conjunctival flap can be used and the merits of each technique are discussed in Chapter 21 9.

Anti-metabolites are typically used in combined cataract and filtration surgery since the goal of the procedure is a long-term functioning bleb. Mitomycin C (MMC) is applied to the proposed filtration site following dissection of the conjunctival flap (Fig. 36.1A) (see Chapter 25) with saturated pledget tips. The conjunctival incision should be protected from MMC exposure (Fig. 36.1B,C; Fig. 36.2). A complete discussion regarding the use of anti-metabolites in filtration surgery can be found elsewhere, but the role of MMC in combined cataract and glaucoma surgery is less clear5,44–49. Many surgeons believe the potential benefits of MMC in conjunction with meticulous surgical techniques outweigh the risks; others disagree. 5-fluorouracil can also be used safely for phacotrabeculectomy50.

Fig. 36.1 (A) The anti-metabolite is applied to the proposed filtration site between uncut sclera and the conjunctival flap. (B) The posterior edge of the conjunctival incision is protected from exposure to the anti-metabolite. (C) After application of the anti-metabolite, the entire surgical site is irrigated with copious balanced salt and the diluent is removed with a suction catheter.

From Samuelson TW. Management of coincident cataract and glaucoma. Curr Opin Ophthalmol 1993;4:90–6. Copyright Rapid Science Publishers.

Fig. 36.2 A 3.5 mm scleral flap is dissected. The dissection is carried anteriorly well into clear cornea.

From Samuelson TW. Management of coincident glaucoma and cataract. Curr Opin Ophthalmol 1995;6:14–21. Copyright Rapid Science Publishers.

The scleral flap is identical to that used in standard guarded filtration procedure. Alternatively, some surgeons modify the scleral flap in combined glaucoma surgery to mimic the scleral tunnel approach of standard cataract surgery. The size and shape of the scleral flap are quite varied among surgeons yielding equally effective results (Fig. 36.3). A paracentesis tract is then performed using a no. 75 blade to facilitate two-handed phacoemulsification.

Fig. 36.3 If a 5.5 mm polymethyl methacrylate intraocular lens is used, the scleral flap is larger, measuring 5 mm at the limbus.

From Samuelson TW. Management of coincident glaucoma and cataract. Curr Opin Ophthalmol 1995;6:14–21. Copyright Rapid Science Publishers.

The anterior chamber is then entered with a keratome beneath the scleral flap, and viscoelastic material is placed in the anterior chamber. A continuous-tear capsulotomy of approximately 5 mm in diameter is made. It is best to avoid a large capsulotomy, which could allow dislocation of the intraocular lens secondary to postoperative IOP fluctuations. Hydrodissection is performed with balanced salt solution on an irrigating cannula. After hydrodissection, the lens nucleus is emulsified using phacoemulsification as the individual surgeon prefers. The remaining cortical material is removed by meticulous aspiration and irrigation. Viscoelastic is placed into the anterior chamber and capsular bag and a foldable lens implant is then placed within the bag. The pupil is constricted by instilling a cholinergic agent such as acetylcholine (Miochol, Ciba-Vision) or carbachol (Miostat, Alcon) into the anterior chamber. Using an intraocular cholinergic helps stabilize the intraocular lens behind the pupil, decreases the likelihood of an immediate postoperative IOP spike, and facilitates completion of a peripheral iridectomy if the-surgeon prefers to perform one. Finally, the residual viscoelastic material is evacuated from the eye through the aspiration irrigation cannula.

Next, the surgeon must excise the trabecular block. An incision has already been made with the keratome into the anterior chamber beneath the scleral flap. A Kelly Descemet’s punch completes the trabecular block excision (Fig. 36.4A). In general, the two most important factors ensuring patency of the filtration fistula are adequate bulk aqueous flow and retardation of the healing process. The trabecular block excision must be performed far enough anteriorly to avoid incising the vascularized structures of the angle, such as the scleral spur or even the ciliary processes.

Fig. 36.4 (A) After placement of the foldable intraocular lens, a trabecular block excision is performed utilizing a Kelly Descemet’s punch. A peripheral iridectomy is then performed. (B) The sclerostomy is then carefully inspected to be certain that there is no bleeding or internal obstruction to filtration.

From Samuelson TW. Management of coincident glaucoma and cataract. Curr Opin Ophthalmol 1996;7:53–8. Copyright Rapid Science Publishers.

After completion of the sclerostomy, a peripheral iridectomy can be performed although, for most eyes undergoing combined surgery, an iridectomy may be omitted. After the trabecular block excision and iridectomy, the sclerostomy site should be examined carefully to ensure that it is entirely free of debris such as blood, cortex, iris, vitreous, or Descemet’s membrane (Fig. 36.4B). The scleral flap is then closed with interrupted sutures as in a standard trabeculectomy (Fig. 36.5). Filtration is assessed in three ways: First, the anterior chamber should maintain normal depth. A deep chamber alone is inadequate to gauge filtration: many eyes maintain a formed chamber intraoperatively despite profound hypotony. Therefore, the eye should be palpated digitally during re-formation. The eye should become firm, but not hard and then should soften slightly over the first several seconds after irrigation is discontinued. Finally, a surgical spear (sponge) should be placed in all regions around the scleral flap to observe for ‘passive flow’, that is spontaneous aqueous flow without external pressure on the globe. If anti-metabolites have been employed, it is desirable to have very little, if any, passive flow. However, it should be possible to produce flow readily by applying gentle pressure adjacent to the filtration site. This is the ‘active filtration test’. An important observation in filtration surgery is that it is much easier to increase filtration postoperatively than it is to slow it down. Therefore, filtration surgery should be performed by creating a leaky fistula and controlling the filtration in a reversible fashion. This is accomplished with releasable sutures or argon laser suture lysis. The ‘active flow test’ is intended to simulate the effect of eyelid activity on the filtration site. If there is considerable filtration on passive testing, then there is a substantial risk for overfiltration and hypotony. If the filtration proves to be inadequate postoperatively, suture lysis can be performed to augment flow (Fig. 36.6)51,52. Closure of limbus-based or fornix-based flaps is described in Chapter 35.

Fig. 36.5 The scleral flap is closed with interrupted 10-0 nylon sutures. It is anticipated that 30–40% of patients will require argon laser suture lysis in the first 2 or 3 postoperative weeks to augment filtration.

From Samuelson TW. Management of coincident glaucoma and cataract. Curr Opin Ophthalmol 1996;7:53–8. Copyright Rapid Science Publishers.

Fig. 36.6 A diffuse filtration bleb is present on postoperative day 1. With a limbal-based conjunctival flap, wound leaks are rare.

From Samuelson TW. Management of coincident glaucoma and cataract. Curr Opin Ophthalmol 1996;7:53–8. Copyright Rapid Science Publishers.

Two-site combined filter and cataract extraction

Two-site surgery (a separate clear cornea cataract incision and a scleral incision for the filter) has become the preferred approach for combined procedures with the increasing popularity of clear cornea cataract surgery. Such an approach typically provides better exposure for the phacoemulsification portion of the procedure as the surgeon can more easily manage in the setting of a prominent brow, blepharospasm, or deeply set eye. Since the clear corneal cataract incision does not interfere with the filter, either limbus-based or fornix-based surgery can performed per the surgeon’s preference as described in Chapter 35. The clear cornea incision should be made at or near the 0 or 180° meridian to ensure that the filter site is avoided. Since it is easier to complete the scleral flap on a firm eye, one technique is to perform as much of the filter portion of the surgery as possible before creating an intraocular wound. This includes creation of a peritomy, dissection of conjunctiva and Tenon’s over the filter site, cautery of the sclera bed, creation of a partial thickness sclera flap, and application of MMC. It is best to apply the MMC prior to creation of an intraocular incision to prevent intraocular toxicity53. After the steps above are completed a standard clear cornea cataract surgery can be performed. However, perhaps a more popular and practical approach is to complete the entire clear corneal cataract surgery prior to initiating the trabeculectomy portions of the procedure. This latter strategy has some distinct advantages.

Ergonomically, there is less need to change position of the operating microscope between the different stages of the procedure. Further, if there are unexpected events during cataract surgery, the surgeon could elect to delay or forego the trabeculectomy. The surgeon should ensure that the capsulectomy is not larger than 5 mm to prevent IOL dislocation secondary to postoperative IOP fluctuations. Viscoelastic is not removed immediately and a temporary 10-0 nylon suture is used to seal the clear corneal wound to maintain a firm eye for the rest of the procedure. Following completion of the cataract surgery, the trabeculectomy portion of the procedure may ensue or resume. Following the peritomy, scleral flap, and anti-metabolite application, a standard sclerectomy is performed. As an alternative to a standard sclerectomy, an ExPress mini shunt can be placed through a 25 g needle tract 54. The scleral flap is secured with 10-0 nylon sutures. The clear cornea suture is loosened and the viscoelastic is aspirated from the eye. Then the cornea suture is retied to ensure an adequate seal. At this point the aqueous flow can be tested as described above and if flow is adequate the conjunctiva is reapproximated. A cholinergic agent such as acetylcholine (Miochol, Ciba-Vision) or carbachol (Miostat, Alcon) is injected intraocularly to protect the IOL and cornea in the event of postoperative hypotony.

Combined cataract extraction and glaucoma drainage devices

Glaucoma drainage devices (GDD) such as the Ahmed, Baerveldt, or Molteno have become increasingly popular in recent years. Data from the tube versus trabeculectomy controlled clinical trial have shown that GDDs have acceptable short-term safety and efficacy profile 55. The principles of combined cataract and GDD surgery are similar to combined cataract and trabeculectomy. A two-site approach is preferred utilizing a temporal clear corneal incision for the cataract surgery. Prior to intraocular penetration, as much of the tube surgery should be performed as possible including the peritomy, cautery, posterior dissection of Tenon’s layer, identification of the extraocular muscles, and fixing the plate to the sclera. The basic approach to combined cataract extraction with GDD placement will be described below. Differences between the individual tube shunts and detailed surgical techniques are described in great detail in Chapter 39.

A superotemporal peritomy is created using a non-toothed forceps and Westcott scissors. It is important to create a large enough peritomy to ensure accurate identification of the extraocular muscle insertion sites as well as adequate exposure for placement of the tube shunt. Next Stevens scissors are used to bluntly dissect in the superotemporal quadrant to create space for the tube shunt. Conjunctival and Tenon’s tissue must be mobilized adequately to cover the entire shunt plate, tube, and insertion site without undue tension. If any part of the tube is exposed, the procedure has a high risk for failure. Depending on the type of implant, the GDD is prepared and the extraocular muscles are identified. Gentle cautery is performed as necessary to achieve hemostasis. Mitomycin C is not typically used in conjunction with GDDs. The plate of the shunt is placed approximately 10 mm posterior to the limbus and affixed with 9-0 prolene or other long-lasting suture. Standard clear cornea cataract surgery is performed and the viscoelastic is temporarily left in the eye. A 10-0 nylon suture is placed though the clear corneal incision to help maintain a firm globe while the tube shunt is completed. Next the tube shunt is cut to size with a bevel-up configuration so that approximately a 2 mm length of the tube is present in the anterior chamber. A 23 g needle is inserted 1–2 mm posterior to the limbus with an angulation that ensures it is parallel to the iris. A tube introducer or tiers are used to place the tube through the needle tract and into the anterior chamber. The surgeon should ensure that the tube is parallel to the iris. If the tube is angulated anteriorly corneal decompensation could occur; if the tube is angulated posteriorly it could be blocked by iris tissue. A small scleral, corneal, or pericardial patch graft is cut to size and secured to the sclera over the tube shunt using 7-0 Vicryl suture. The conjunctiva is reapproximated using non-toothed forceps and 7-0 Vicryl suture. The clear corneal suture is loosened and viscoelastic is removed from the anterior chamber with aspiration and the clear corneal suture is retied. A cholinergic agent can be instilled into the anterior chamber to constrict the pupil.

Combined cataract extraction and other glaucoma procedures

Cataract surgery can be performed simultaneously with other glaucoma procedures including canaloplasty (iScience)56, ab-internal trabecular meshwork excision (Trabectome, Neomedix)38, trabecular meshwork stents (iStent, Glaukos), and endoscopic cyclophotocoagulation (EndoOptiks)57. The specifics of these procedures are discussed in Chapters 43 and 45, but a brief description is below.

During combined cataract extraction and canaloplasty, a standard canaloplasty is performed first. The entire canaloplasty procedure can be completed prior to starting the cataract extraction, however, many surgeons will perform the cataract portion of the procedure following the un-roofing of Schlemm’s canal but prior to dissection of the trabeculo-Descemet’s window. The basic steps for canaloplasty include a superior peritomy, creation of a partial thickness scleral flap (of similar thickness to a standard trabeculectomy flap), followed by a deep scleral flap, created in the bed of the partial thickness flap. The deep flap is one tissue plane above the choroid and, when dissected anteriorly, Schlemm’s canal is identified and deroofed. A microcatheter is advanced 360° around the canal of Schlemm. A 9-0 or 10-0 prolene suture is then tied the catheter and the catheter withdrawn. As the catheter is withdrawn, high viscosity viscoelastic material is injected into the canal every 2 clock hours, effectively ‘viscodilating’ the canal for its entire circumference. The circumferential prolene suture is then placed under appropriate tension and tied. The deep scleral flap is then dissected more anteriorly, thus creating the trabeculo-desmetic window. The scleral flap and conjunctiva are sutured closed. Standard clear cornea cataract surgery can then be performed with the surgeon’s typical technique. Canaloplasty is a technically challenging procedure, but has the advantage of creating a 360° continuity of Schlemm’s canal and it is not dependent on conjunctival healing or an external filtration bleb.

When performing combined cataract extraction and ab-internal trabecular meshwork excision (Trabectome), viscoelastic is used to form the anterior chamber, and a gonioprism is used to visualize the angle. The trabecular meshwork excision can be performed through a clear cornea incision. The surgeon’s typical cataract surgery subsequently can be performed through the same clear cornea incision.

A standard cataract surgery is performed initially during combined cataract extraction and trabecular meshwork stent placement (Glaukos iStent)58. A cholinergic agent is used to constrict the pupil. With viscoelastic in the eye, a gonioprism is used to visualize the angle and one or more stents can be placed into the trabecular meshwork through the same clear cornea incisions used for the cataract surgery.

During combined cataract extraction and endoscopic cyclophotocoagulation a standard cataract extraction is performed initially. With viscoelastic in the eye, a fiberoptic device is used to visualize the ciliary body and cyclophotocoagulation can be performed through the same clear cornea incisions used for the cataract surgery.

Although the procedures mentioned above are new with relatively little long-term data, each provides a less invasive approach than traditional glaucoma surgery. None of these procedures relies on conjunctival healing and its inherent variability. The final IOP achieved by the procedures above are limited by episcleral venous pressure and this may prevent very low IOP from being attained, a potential disadvantage in cases of advanced glaucoma. However, the IOP floor provided by episcleral venous pressure should also help prevent postoperative hypotony. Further studies will help characterize the appropriate role each new technology will play in the management of patients with coincident cataract and glaucoma.

Postoperative care

Diligent postoperative care after any glaucoma surgery is vital to the success of the operation, as postoperative care determines the outcome of surgery in many cases. Patients should be educated regarding their role in the important postoperative period. In most cases preoperative glaucoma medications should be discontinued. If the patient was taking oral carbonic anhydrase inhibitors preoperatively, then the fellow eye should be monitored carefully for increased IOP. Aggressive topical steroid use, for example every 2 hours while awake, is recommended during the first postoperative week. Topical antibiotics are instilled for at least 1 week after the procedure.

Postoperative care for combined filter and cataract extraction

Postoperative care for combined filter and cataract extraction is delicate and requires diligent follow-up. Topical steroid administration may be continued for 3–4 months postoperatively following filtering procedures. Tapering of the steroid dose is based on the amount of inflammation in and around the bleb, not intraocular inflammation, which generally subsides long before the bleb becomes quiet. Inflammatory intraocular lens deposits, more common with earlier IOL biomaterials, have been shown to peak at approximately 3 months after cataract extraction in high risk eyes 59,60. Therefore, the topical steroids are continued for at least 3 months unless the eye and the bleb are unusually quiet. Topical steroids may be tapered more rapidly in hypotonous eyes. Cycloplegia and mydriatic agents are used in the event of hypotony, shallow anterior chamber, and prominent inflammation or fibrin formation. However, these agents are not necessary on a routine basis.

The early postoperative period is critical: during this time procedures often fail and complications are most common. If the IOP is higher than the mid-teens during the first postoperative week after filtering procedures, focal pressure is applied adjacent to the filtration site with a cotton-tip applicator (CTM, Carlo Traverso Maneuver) to augment filtration 61. This maneuver separates the flap edges, releasing aqueous from the anterior chamber through the filtration site. In most cases, the CTM pressure will instantaneously inflate the bleb, lowering the IOP. This technique is favored over releasing aqueous through the clear corneal paracentesis tract, because it encourages outflow through the sclerostomy site and can dislodge fibrin or other debris that may be limiting outflow. Not uncommonly, a single CTM procedure will bring the pressure into the favorable range. Finally, if the IOP is not lowered with CTM, gonioscopy should be performed. If the internal sclerostomy is patent, it may be assumed that the resistance to outflow is related to a tight scleral flap or conjunctival fibrosis. Argon laser suture lysis should then be considered. If suture lysis is planned on a given postoperative visit, CTM should not be performed because it is easier to lyse the suture when the eye is firm and the suture is under tension. The surgeon should resist the temptation to perform Argon laser suture lysis too early. It is not uncommon for retained viscoelastic material or perioperative inflammation to cause elevation of IOP during the early postoperative period. The IOP often falls as the viscoelastic material clears the eye. If anti-metabolites have not been used, the schedule for releasing sutures is accelerated (Table 36.2). The schedule of postoperative visits is individualized according to each patient’s progress. Typically, however, patients are seen at least two to four times during the first two postoperative weeks. During each visit the surgeon should record the visual acuity, IOP, bleb appearance, and chamber depth. The bleb appearance should reflect the IOP. For example, if the IOP is very low, one would expect to see an exuberant bleb. Any discrepancy between bleb appearance and IOP warrants search for a bleb leak. The entire bleb and wound should be painted with fluorescein and examined for Seidel positivity, using a fluorescein-impregnated ‘strip’ to paint the surface of the conjunctiva and then inspecting meticulously as the slit lamp into the blue filter in front of the brightest illuminating beam.

Table 36.2 Postoperative titration of intraocular pressure, timing of suture release, and suture lysis*

The importance of performing ‘controlled’ filtration surgery to avoid hypotony cannot be overemphasized. The risk to hypotonous eyes is substantial. Flat chambers, choroid effusions, suprachoroidal hemorrhage, and hypotonous maculopathy are risks associated with over-filtration. The risk of hypotonous maculopathy is greatest in young myopic patients 62. Over-filtration in the early postoperative period may be exacerbated by decreased aqueous production by a ciliary body that is recovering from years of chronic aqueous suppression, as well as from perioperative inflammation. Postoperative outflow should be titrated based on the individual response to surgery. With controlled glaucoma filtration surgery the scleral flap is closed more tightly, but in a ‘reversible’ fashion. This approach limits filtration in the early postoperative period, decreasing the likelihood of hypotony. Once adequate aqueous production is established, manifest by a deep chamber and stable or rising intraocular pressure, the surgeon may augment filtration by performing suture lysis or release. The ability to titrate filtration and avoid early perioperative hypotony has greatly enhanced the safety of filtration surgery. Patients have faster visual rehabilitation when the IOP is in the physiological range. For example an IOP of 18 mmHg on postoperative day 1 is much more desirable than a pressure of 2 mmHg. With CTM and judicious suture lysis the target IOP can be achieved. Moreover, it is common for the IOP to fall spontaneously over the first postoperative week as residual viscoelastic material clears the eye.

Finally, part of the routine postoperative regimen should include discussion to educate patients of the potential hazards of blebs such as late leaks or late bleb infections. It is generally helpful to provide the patient with an educational brochure describing the benefits of early and aggressive treatment for bleb-related conjunctivitis and blebitis.

Postoperative management of combined GDD and cataract extraction

Postoperative management of combined GDD and cataract extraction depends on the type of GDD used. The subtle differences between the GDDs and the postoperative care of each is described in Chapter 40. Generally, GDDs require less postoperative management and have fewer complications than filtering procedures55. During the immediate postoperative period steroid eye drops are used every 2 hours for the first week and then tapered for 3–4 months until they can be discontinued. Antibiotics are stopped at 1 week. One unique characteristic of GDDs is the so called ‘hypertensive phase’, which is a result of a breakdown in the blood–tissue barrier round the plate. This is typically addressed with ocular massage and/or temporary use of topical aqueous suppressants63,64. Hypotony can be seen in the early postoperative period and is addressed in a manner similar to filters. Problems with ocular motility are seen more commonly after tube shunts. Fortunately, persistent diplopia is less than 5% and can be corrected usually with strabismus surgery or glasses with prism.

Postoperative management of other glaucoma procedures and cataract extraction

The optimal postoperative management of canaloplasty, endoscopic cyclophotocoagulation, ab-interno trabecular meshwork excision, and trabecular bypass shunts is still being determined and is beyond the scope of this chapter (see Chapter 41). Generally, one of the main advantages to these procedures collectively is the relatively quick recovery and a less intensive postoperative medication and follow-up regimen. Steroids should probably be used more frequently than with cataract surgery alone in the initial postoperative period. However, a quick tapering can usually be employed and the patient can be completely off steroids 4–6 weeks after surgery. Immediately after surgery all glaucoma medications should be stopped and added back as needed. Prostaglandins are typically added back first, although this may increase the chances of postoperative cystoid macular edema. Aqueous suppressants also can be used.

Pupil management

Perhaps the single most challenging aspect of combined cataract and glaucoma surgery is cataract extraction in the presence of poor pharmacologic pupillary dilatation. Chronic miotic therapy frequently reduces the pupillary response to mydriatic agents. Additionally, conditions such as PXF, floppy iris syndrome secondary to urinary outflow treatment with agents such as the alpha blocking agent tamsulosin 65, or chronic inflammation may further limit dilatation of the pupil. A variety of techniques to enhance pupillary dilatation have been described. Traditional incisional iris surgery such as sector iridectomy or multiple small sphincterotomies has been replaced with less invasive methods. While incisional iris surgery adequately enhances visualization of the lens during phacoemulsification, the cut edges of the iris may be drawn into the phacoemulsification port during lens removal. This may result in significant iris trauma and postoperative inflammation. Most surgeons prefer non-incisional techniques to enlarge the pupil such as sphincter stretching, iris retraction hooks, or a Malyugin ring66. In eyes with poor dilatation, exposure can be improved with a simultaneous push–pull technique of sphincter stretching by means of two instruments such as Kuglen hooks or Graether ‘collar buttons’ (Fig. 36.7A). The sphincter is stretched first in the vertical direction, then in the horizontal meridian. The sphincter is stretched to the point of minute tears in the pupillary margin, which are typically seen as small, very focal hemorrhages in the iris sphincter. Additional viscoelastic material is then instilled into the anterior chamber to mechanically expand the pupil. This technique provides an additional 2 or 3 mm of pupillary dilatation. When stretching techniques are inadequate, flexible iris retraction hooks (Greishaber and Company, Langhorne, PA) or a Malyugin ring can be used. (Fig. 36.7B and Fig. 36.8A,B). The pupil stretch technique is simple, fast, effective, and avoids incisional iris surgery, while resulting in a round pupil postoperatively67–69. However, it is not as reliable as the use of hooks or a Malyugin ring. Moreover, stretching techniques are not recommended for floppy iris syndrome. In such cases, rings and hooks provide better stenting of the iris and are less likely to result in intraoperative miosis.

Fig. 36.7 (A) The pupil is stretched by a simultaneous push-pull technique with a Kuglen hook and a Graether collar button. The pupillary sphincter is stretched in the vertical and horizontal meridian. (B) When pupillary stretch provides inadequate visualization, flexible iris retraction hooks (Greishaber and Company, Langhorne, PA) may be utilized.

From Samuelson TW, Lindquist TD. Combined small-incision phacoemulsification, intraocular lens implantation, and trabeculectomy. Ophthalmic Surgery. Update 2, Section E, page I-E-15, with permission.