New options for combined cataract and glaucoma surgery

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1 REVIEW C URRENT OPINION New options for combined cataract and glaucoma surgery Donald L. Budenz a and Steven J. Gedde b Purpose of review To review the current literature regarding the effectiveness and risks of new surgeries that can be combined with phacoemulsification in the management of cataract and glaucoma. Recent findings Surgical options for concurrently managing cataract and glaucoma have expanded in recent years. Endoscopic cyclophotocoagulation, trabecular micro-bypass stent, ab interno trabeculectomy, and canaloplasty may be performed in conjunction with cataract extraction to provide additional intraocular pressure (IOP) reduction. Studies evaluating these new glaucoma procedures combined with phacoemulsification generally include retrospective case series without a comparison group. Because cataract surgery alone is associated with IOP reduction, the relative contribution of the glaucoma procedure in lowering IOP cannot be determined in these studies. Randomized clinical trials are needed to better evaluate the efficacy and safety of newer glaucoma procedures in combination with cataract surgery. Summary The newer glaucoma procedures appear less effective than trabeculectomy, but they are associated with a lower risk of surgical complications. Keywords cataract surgery, glaucoma surgery, phacoemulsification INTRODUCTION Cataract and glaucoma frequently coexist in our elderly patient population. It has been estimated that 20% of cataract procedures are performed annually in the USA in individuals with comorbid glaucoma and ocular hypertension. Phacoemulsification combined with trabeculectomy has historically been the preferred surgical approach for concurrently managing cataract and glaucoma. However, a growing concern about intraoperative and postoperative complications associated with trabeculectomy has prompted many surgeons to explore alternative procedures. Several new glaucoma procedures have been introduced into clinical practice which may be performed in conjunction with cataract surgery [1 && ]. Recent studies have evaluated the safety and efficacy of endoscopic cyclophotocoagulation (ECP), trabecular micro-bypass stent (istent), ab interno trabeculectomy (Trabectome), and canaloplasty combined with phacoemulsification. Most of these studies consist of retrospective case series that lack a control group. Retrospective [2] and prospective [3 && ] studies have shown that cataract surgery alone may result in a modest (2 3 mmhg) reduction in intraocular pressure (IOP). Therefore, determination of the relative contribution of a glaucoma procedure in lowering the IOP requires prospective comparison with a control group consisting of cataract surgery alone. Unfortunately, randomized clinical trials that assess the new glaucoma procedures are generally lacking. The purpose of this article is to provide an evidence-based review of the new options for combined cataract and glaucoma surgery. a Department of Ophthalmology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina and b Bascom Palmer Eye Institute, Miller School of Medicine, University of Miami, Miami, Florida, USA Correspondence to Donald L. Budenz, MD, MPH, 5151 Bioinformatics, CB7040, Chapel Hill, NC 27517, USA. Tel: ; fax: ; dbudenz@med.unc.edu Curr Opin Ophthalmol 2014, 25: DOI: /ICU ß 2014 Wolters Kluwer Health Lippincott Williams & Wilkins

2 Glaucoma KEY POINTS Glaucoma and elevated IOP are common in patients undergoing cataract surgery. Endoscopic cyclophotocoagulation (ECP), trabecular micro-bypass stent (istent), ab interno trabeculectomy (Trabectome), and canaloplasty are newer glaucoma procedures that may be performed in conjunction with phacoemulsification. Because phacoemulsification can produce intraocular pressure (IOP) reduction, studies evaluating the efficacy of combined cataract and glaucoma procedures should include a comparison group of phacoemulsification alone. The newer glaucoma procedures appear less effective in lowering IOP than trabeculectomy, but they are associated with fewer surgical complications. ENDOSCOPIC CYCLOPHOTOCOAGULATION ECP is a newer method of cyclophotocoagulation involving laser treatment of the ciliary processes under direct visualization. ECP has been used in the management of refractory glaucomas and pediatric patients, but it is most commonly performed in combination with phacoemulsification in eyes with medically controlled or uncontrolled glaucoma. Despite the availability of ECP since the mid-1990s, its benefit in reducing the IOP when combined with phacoemulsification has not been clearly demonstrated. Most studies reporting the outcomes of phacoemulsification ECP are retrospective case series that lack a control group [4 &,5 &,6 8]. A randomized clinical trial comparing phacoemulsification alone with phacoemulsification ECP would help to clarify the efficacy of phacoemulsification ECP (Table 1). A prospective randomized trial compared phacoemulsification ECP to phacoemulsification trabeculectomy (48% of cases received adjunctive mitomycin C) in a relatively small number of patients (29 in each treatment group) [10]. A higher success rate (IOP <19 mmhg without glaucoma medications) was observed after phacoemulsification trabeculectomy (42%) compared with phacoemulsification ECP (30%) with a mean follow-up of 2 years. A retrospective study compared phacoemulsification ECP in 626 eyes to phacoemulsification alone in 81 eyes [9]. The methodology for this investigation was not described, including the criteria used for unequal matching (approximately 8 : 1). Mean IOP decreased by 17.6% in the phacoemulsification ECP group with an associated 57.5% decrease in the mean number of glaucoma medications, and mean IOP increased by 4.2% in the phacoemulsification group without a change in the mean number of glaucoma medications with an average follow-up of 3.2 years. Most surgeons suggest that ECP results in a mildto-moderate decrease in IOP and medical therapy. IOP reduction ranging from 17.6 to 57% has been reported following phacoemulsification ECP. These highly variable results may relate to differences in study populations, length of follow-up, and treatment protocol (i.e., degrees of laser application, ECP through the bag or under the intraocular lens, Table 1. Studies of combined phacoemulsification and endoscopic cyclophotocoagulation (%) Clement et al. [4 & ] PE ECP NR 23.9% Decrease 45.8% Decrease Lindfield et al. [5 & ] PE ECP (29%) 33.0% Decrease 5.1% Increase Lima et al. [6] PE ECP (Mean) NR 46.7% Decrease 74.3% Decrease Kahook et al. [7] PE ECP (1 site) (53%) 32.2% Decrease 21.9% Decrease PE ECP (2 sites) (48%) 46.9% Decrease 79.7% Decrease Berke [9] PE ECP (Mean) NR 17.6% Decrease 57.5% Decrease PE % Increase 0% Gayton et al. [10] PE ECP (Mean) 12 (21%) 28.8% Decrease 34.4% Decrease PE trab (Mean) 31.9% Decrease 29.2% Decrease Uram [8] PE ECP (Mean) 0 (<1 year) 23.9% Decrease 45.8% Decrease ECP, endoscopic cyclophotocoagulation; IOP, intraocular pressure; meds, glaucoma medications; NR, not reported; PE, phacoemulsification; trab, trabeculectomy Volume 25 2 March 2014

3 Combined cataract and glaucoma surgery Budenz and Gedde ECP with or without scleral indentation, and cessation or continuation of medical therapy). The long-term results of phacoemulsification ECP are not well known, and concern exists that the IOP-lowering effect of ECP may diminish over time [11]. A histopathologic study demonstrated that ECP causes localized shrinkage of ciliary processes and reduction in blood flow with partial reperfusion by 1 month [12]. It has been speculated that the partial return of blood flow may lead to an increase in aqueous production with a corresponding rise in IOP. The need to retreat an eye with ECP after an initial effect may be explained by this phenomenon. Surgical complications The safety profile of ECP in the existing medical literature is varied and likely relates to the glaucoma subtype treated [13 && ]. Surgical complications observed in a large series of 368 eyes treated with phacoemulsification ECP included IOP spike (14.4%), postoperative fibrin exudates in anterior chamber (7.06%), cystoid macular edema (4.34%), transient hypotony (2.17%), and iris bombé (1.08%) [6]. Lower rates of surgical complications have been reported with micro-invasive glaucoma surgery (MIGS) [1 && ]. Additionally, the pressure-lowering effect of cyclodestruction cannot be reversed in patients with hypotony-related sequelae. Limited data exist in the peer-reviewed literature describing the efficacy and safety of phacoemulsification ECP. A randomized clinical trial comparing phacoemulsification ECP to phacoemulsification alone is needed to better evaluate this technique, and current information about the benefit of phacoemulsification ECP is mostly uncontrolled. istent The trabecular meshwork micro-bypass stent (istent, Glaukos, Corp., Laguna Hills, California, USA) is a titanium implant that is inserted into Schlemm s canal through the trabecular meshwork internally. The implant is designed to shunt fluid from the anterior chamber into Schlemm s canal, bypassing the trabecular meshwork. The device is placed after completion of cataract surgery, so that the anterior chamber is maximally deep and so that it does not get dislodged during the phacoemulsification procedure. There have been several studies of cataract surgery combined with istent, some of which have a comparison group of patients undergoing cataract surgery alone. In the longest and largest prospective randomized clinical trial of the istent conducted by Samuelson and colleagues [14,15 && ], istent combined with phacoemulsification produced IOP lowering similar to phacoemulsification alone at 1 year [14]. However, IOP was controlled on 1 2 fewer medications than before surgery [14]. At 2 years, the differential effect of phacoemulsification istent compared with phacoemulsification alone is more pronounced, as the IOP-lowering effect of cataract surgery diminishes [15 && ]. Although the istent only lowered pressure by 8% in this study, the effect on number of medications used was profound, with an over 80% reduction in medications out to 24 months (Table 2). Studies by Spiegel [18] and Fea [16] have shown an approximately 20% reduction in IOP after a Table 2. Studies of combined phacoemulsification and istent (%) Craven et al. (2012) [15 && ] PE 1 istent (16.2%) 8.1% Decrease 81.3% Decrease PE (17.9%) 0.6% Decrease 66.7% Decrease Samuelson et al. (2011) [14] PE 1 istent (14.5%) 8.0% Decrease 86.7% Decrease PE (10.6%) 5.0% Decrease 73.3% Decrease Fea (2010) [16] PE 1 istent % Decrease 80.0% Decrease PE 24 3 (12.5%) 9.2% Decrease 31.6% Decrease Fernández-Barrientos et al. (2010) [17] PE 2 istents % Decrease 100% Decrease PE % Decrease 41.7% Decrease Spiegel et al. (2009) [18] PE 1 istent (12.5%) 20.3% Decrease 75.0% Decrease IOP, intraocular pressure; meds, glaucoma medications; PE, phacoemulsification ß 2014 Wolters Kluwer Health Lippincott Williams & Wilkins 143

4 Glaucoma single istent combined with cataract surgery. Patients were also able to reduce the number of medications by %. The study by Fea [16] also included a comparison group of patients who underwent phacoemulsification alone, and this group had a reduction in IOP of 9.2% compared with the phacoemulsification istent group that had a reduction in IOP of 17.3%. However, the average number of medications was reduced by 80% in the combined group vs. only 30% in the cataract surgery alone group. The study by Spiegel did not have a comparison group. Recent studies suggest that implantation of multiple istents provides better IOP lowering than a single istent [17,19 & ]. It remains to be seen whether the manufacturer will be able to provide more than one device per package or whether insurers or patients will pay for additional devices to be implanted. New designs of this device and similar trabecular bypass devices are in trials now that may obviate the need to place more than one istent. In the meantime, placement of a single istent device with cataract surgery has little IOP advantage over cataract surgery alone. Surgical complications istent is a relatively safe procedure. The majority of complications is related to malposition of the implant and stent obstruction [14,15 &&,16 18]. istent performed with cataract surgery is a safe procedure, but it offers little additional IOP-lowering effect compared with cataract surgery alone. Its main advantage appears to be in the reduction in hypotensive medication use. The pivotal randomized prospective trial comparing phacoemulsification istent to phacoemulsification alone provides the best information on the efficacy of the procedure and serves as a model for future trials of devices such as this. Second and third generation designs may provide additional IOP-lowering effects. TRABECTOME Ab interno trabeculotomy, also known as Trabectome (NeoMedix, Tustin, California, USA), is a new procedure in which sections of the trabecular meshwork are ablated using electrocautery delivered by a probe introduced through the anterior chamber. The amount of trabecular meshwork that is ablated varies depending on the exposure and visualization, but typically is 3 4 clock hours. When combined with cataract surgery, the Trabectome is typically delivered prior to phacoemulsification as excellent visualization is needed to perform the procedure and corneal clarity may be reduced after phacoemulsification, making visualization difficult. Several studies have demonstrated that phacoemulsification Trabectome lowers IOP by about 4 7 mmhg [20 22,23 & ]. One of these studies [21] included a comparison group of patients who underwent phacoemulsification alone. Unfortunately, patients were not randomized and differed by 6 mmhg in IOP at baseline. In this study, the phacoemulsification Trabectome group had a mean preoperative IOP of 22.2 mmhg, whereas the preoperative IOP in the phacoemulsification alone group averaged 16.2 mmhg. The IOP-lowering effect of phacoemulsification alone is known to be highly correlated with the preoperative IOP [3 &&,14,15 &&,24 && ]. Specifically, patients with high preoperative IOPs may have a large IOP-lowering effect from phacoemulsification, whereas those with a low IOP may have little to no effect. So the comparison of combined phacoemulsification Trabectome to phacoemulsification alone does not seem valid in this study. In addition, the change in medical therapy in the phacoemulsification alone group was not reported. The investigators performed a subanalysis in which they matched 10 patients from each group on baseline IOP and compared the results. The phacoemulsification Trabectome patients averaged 25% lower IOP, and the phacoemulsification alone group had a 5% rise in IOP at 12 months. A randomized clinical trial would allow a better comparison of phacoemulsification Trabectome and phacoemulsification alone (Table 3). Complications Transient hyphema and postoperative elevation of IOP are the main complications of Trabectome combined with phacoemulsification, as with Trabectome alone. The mechanism, extent, and duration of the IOP elevation following Trabectome are unknown and unpredictable, adding some uncertainty to the postoperative management of these patients. There is inconclusive evidence that Trabectome added to phacoemulsification has better IOP-lowering effect compared with phacoemulsification Volume 25 2 March 2014

5 Combined cataract and glaucoma surgery Budenz and Gedde Table 3. Studies of combined phacoemulsification and Trabectome (%) Francis (2010) [21] PE Trabectome (41%) 31.1% Decrease 41.7% Decrease PE (71.7%) 11.7% Decrease NR Mosaed et al. (2010) [22] PE Trabectome (8%) 22.8% Decrease 33.5% Decrease Francis and Winarko (2011) [20] PE Trabectome (5%) 30.3% Decrease 43.3% Decrease Ahuja et al. (2013) [23 & ] PE Trabectome (67%) 22.2% Decrease 31.9% Decrease IOP, intraocular pressure; meds, glaucoma medications; PE, phacoemulsification; NR, not reported. alone. Prospective randomized clinical trials are needed to demonstrate this. However, the procedure seems to lower IOP better than IOP-matched controls and the complications are minimal. CANALOPLASTY Canaloplasty is an ab externo procedure during which Schlemm s canal is cannulated with a fiber optic probe (iscience International, Menlo Park, California, USA), and a suture is then introduced 3608 and tightened until the trabecular meshwork is put on adequate stretch to improve aqueous humor outflow. Ideally, high-resolution ultrasound is used to confirm that the tissues of interest are properly stretched. The procedure is technically more difficult than those previously described and has the additional disadvantage of causing conjunctival scarring, which makes subsequent glaucoma surgery less successful and technically more difficult. An additional disadvantage is the expense of the equipment that is needed to perform the operation. Combined phacoemulsification canaloplasty was shown to lower IOP by approximately 40% in three studies [25 27]. The remarkably similar results of these studies may be because of pooling of data from the same patients in all three reports. None of the studies used a comparison group of phacoemulsification alone. A more recent small independent study by Matlach et al. [28 & ], also without a comparison group of phacoemulsification alone patients, found an average 55% drop in IOP after 12 months. In the only study to date comparing phacoemulsification canaloplasty to phacoemulsification alone, Arthur et al. [29 && ] have reported a more profound IOP-lowering effect of the combined procedure throughout 24 months, although half to two-thirds of patients were. The study was retrospective, so there was no randomization and the starting IOPs were relatively low in each group (16.2 in the phacoemulsification group and 18.2 in the phacoemulsification canaloplasty group). In addition, the phacoemulsification canaloplasty group started with mean baseline IOPs that were 2 mmhg higher than in the phacoemulsification group. Although there was no statistically significant difference in IOP at baseline or 24 months, patients in the combined group were on fewer medications and were less likely to fail by the standard criteria as outlined in the Tube vs. Trabeculectomy Study [30] (Table 4). Table 4. Studies of combined phacoemulsification and canaloplasty (%) Matlach et al. (2013) [28 & ] PE canaloplasty (21%) 55.5% Decrease 64.3% Decrease Arthur et al. (2013) [29 && ] PE canaloplasty (66%) 29.1% Decrease 76.9% Decrease PE (54%) 13.0% Decrease 7.1% Increase Lewis et al. (2011) [26] PE canaloplasty (10%) 42.1% Decrease 80% Decrease Bull et al. (2011) [27] PE canaloplasty (19%) 43.2% Decrease 66.7% Decrease Shingleton et al. (2008) [25] PE canaloplasty (53.7%) 43.9% Decrease 86.7% Decrease IOP, intraocular pressure; meds, glaucoma medications; PE, phacoemulsification; trab, trabeculectomy ß 2014 Wolters Kluwer Health Lippincott Williams & Wilkins 145

6 Glaucoma Complications Transient hyphema, inadvertent filtering bleb, Descemet s detachment, and suture erosion through the trabecular meshwork may be seen after phacoemulsification canaloplasty. In addition, suture placement within the canal may not be possible in approximately 15 25% of patients [25,26]. Phacoemulsification canaloplasty appears to be more effective at lowering IOP than phacoemulsification alone and may be an effective and well tolerated alternative to phacoemulsification trabeculectomy. Negative aspects of this procedure include its technical difficulty and the creation of conjunctival scarring which could limit the success of subsequent trabeculectomy. Although rare so far, there is also concern over possible long-term erosion of the suture used in canaloplasty into the anterior chamber because of constant tension on the trabecular meshwork. CONCLUSION The surgical options for concurrently managing cataract and glaucoma have expanded in recent years. Canaloplasty, Trabectome, istent, and ECP may be performed in conjunction with phacoemulsification to provide additional IOP reduction and reduce the burden of glaucoma medical therapy. These new procedures appear to be less effective than trabeculectomy. However, they offer a more favorable safety profile with a lower risk of surgical complications. The role of newer glaucoma procedures in glaucoma management remains the subject of debate; however, they are most appropriately combined with phacoemulsification in patients with mild glaucomatous damage in whom low levels of IOP are not needed. Phacoemulsification ECP has the advantage of ease of performance and lack of conjunctival scarring associated with the procedure. However, the modest IOP-lowering effect, variable and unpredictable response, and inability to reverse its effect make phacoemulsification ECP a less desirable alternative than traditional or other new glaucoma procedures. istent and Trabectome, when combined with phacoemulsification, seem to provide little IOP lowering compared with phacoemulsification alone. Their main advantage appears to be in the ability to reduce the medication burden of patients. Each procedure has different kinds of complications that must be taken into account when recommending one or the other procedure, but istent and Trabectome, when combined with phacoemulsification, have the least serious complications. Acknowledgements None. Conflicts of interest There are no conflicts of interest. REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the annual period of review, have been highlighted as: & of special interest && of outstanding interest 1. Saheb H, Ahmed II. Micro-invasive glaucoma surgery: current perspectives && and future directions. Curr Opin Ophthalmol 2012; 23: A comprehensive review of the surgical techniques, efficacy, and complications of new microincisional glaucoma procedures. 2. Poley BJ, Lindstrom RL, Samuelson TW. Long-term effects of phacoemulsification with intraocular lens implantation in normotensive and ocular hypertensive eyes. J Cataract Refract Surg 2008; 34: Mansberger SL, Gordon MO, Jampel H, et al. Reduction in intraocular && pressure after cataract extraction: The Ocular Hypertension Study. Ophthalmology 2012; 119: A prospective study on the IOP-lowering effect of cataract surgery in patients with ocular hypertension. 4. Clement CI, Kampougeris G, Ahmed F, et al. Combining phacoemulsification & with endoscopic cyclophotocoagulation to manage cataract and glaucoma. Clin Exp Ophthalmol 2013; 41: A retrospective case series of patients who had undergone cataract surgery and endolaser cyclophotocoagulation. 5. Lindfield D, Ritchie RW, Griffiths MFP. Phaco-ECP : Combined endoscopic & cyclophotocoagulation and cataract surgery to augment medical control of glaucoma. BMJ Open 2012; 2:1 6; e A retrospective case series of patients who had undergone cataract surgery and endolaser cyclophotocoagulation. 6. Lima FE, Carvalho DM, Avila MP. Phacoemulsification and endoscopic cyclophotocoagulation as primary surgical procedure in coexisting cataract and glaucoma. Arq Bras Oftalmol 2010; 73: Kahook MY, Lathrop KL, Noecker RJ. One-site versus two-site endoscopic cyclophotocoagulation. J Glaucoma 2007; 16: Uram M. Combined phacoemulsification, endoscopic ciliary process photocoagulation, and intraocular lens implantation in glaucoma management. Ophthalmic Surg 1995; 26: Berke SJ. Endolaser cyclophotocoagulation in glaucoma management. Tech Ophthalmol 2006; 4: Gayton JL, Van Der Karr M, Sanders V. Combined cataract and glaucoma surgery: trabeculectomy versus endoscopic laser cycloablation. J Cataract Refract Surg 1999; 25: Yip LW, Yong SO, Earnest A, et al. Endoscopic cyclophotocoagulation for the treatment of glaucoma: An Asian experience. Clin Exp Ophthalmol 2009; 37: Lin SC, Chen MJ, Lin MS, et al. Vascular effects on ciliary tissue from endoscopic versus trans-scleral cyclophotocoagulation. Br J Ophthalmol 2006; 90: && Ishida K. Update on results and complications of cyclophotocoagulation. Curr Opin Ophthalmol 2013; 24: A comprehensive review of the indications, surgical technique, efficacy, and complications of cyclophotocoagulation procedures for glaucoma. 14. Samuelson TW, Katz LJ, Wells JM, et al. Randomized evaluation of the trabecular micro-bypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology 2011; 118: && Craven ER, Katz LJ, Wells JM, Giamporcaro JE, istent Study Group. Cataract surgery with trabecular micro-bypass stent implantation in patients with mildto-moderate open-angle glaucoma and cataract: two-year follow-up. J Cataract Refract Surg 2012; 38: A 2-year follow-up of a prospective, randomized clinical trial reporting the efficacy and complications of istent combined with cataract surgery compared to cataract surgery alone. 16. Fea AM. Phacoemulsification versus phacoemulsification with micro-bypass stent implantation in primary open-angle glaucoma: randomized doublemasked clinical trial. J Cataract Refract Surg 2010; 36: Fernández-Barrientos Y, García-Feijoó J, Martínez-de-la-Casa JM, et al. Fluorophotometric study of the effect of the Glaukos trabecular microbypass stent on aqueous humor dynamics. Invest Ophthalmol Vis Sci 2010; 51: Spiegel D, Wetzel W, Neuhann T, et al. Coexistent primary open-angle glaucoma and cataract: Interim analysis of a trabecular micro-bypass stent and concurrent cataract surgery. Eur J Ophthalmol 2009; 3: Volume 25 2 March 2014

7 Combined cataract and glaucoma surgery Budenz and Gedde 19. Belovay GW, Naqi A, Chan BJ, et al. Using multiple trabecular micro-bypass & stents in cataract patients to treat open-angle glaucoma. J Cataract Refract Surg 2012; 38: A retrospective comparison between the use of two vs. three istents combined with cataract surgery. 20. Francis BA, Winarko J. Combined Trabectome and cataract surgery versus combined trabeculectomy and cataract surgery in open-angle glaucoma. Clin Surg Ophthalmol 2011; 29: Francis BA. Trabectome combined with phacoemulsification versus phacoemulsification alone: a prospective, nonrandomized controlled surgical trial. Clin Surg Ophthalmol 2010; 28: Mosaed S, Rhee DJ, Filippopoulos T, et al. Trabectome outcomes in adult open-angle glaucoma patients: one year follow-up. Clin Surg Ophthalmol 2010; 28: Ahuja Y, Pyi SMK, Malihi M, et al. Clinical results of ab interno trabeculotomy & using the Trabectome for open-angle glaucoma: The Mayo Clinic series in Rochester, Minnesota. Am J Ophthalmol 2013; 156: A retrospective case series of patients who underwent Trabectome or combined phaco-trabectome at a single institution. 24. Yang HS, Lee J, Choi S. Ocular biometric parameters associated with && intraocular pressure reduction after cataract surgery in normal eyes. Am J Ophthalmol 2013; 156: A large prospective study of 999 patients showing that level of preoperative IOP is highly correlated with the IOP reduction after phacoemulsification alone. 25. Shingleton B, Tetz M, Korber N. Circumferential viscodilation and tensioning of Schlemm canal (canaloplasty) with temporal clear corneal phacoemulsification cataract surgery for open angle glaucoma and visually significant cataract: one-year results. J Cataract Refract Surg 2008; 34: Lewis RA, von Wolff K, Tetz M, et al. Canaloplasty: three-year results of circumferential viscodilation and tensioning of Schlemm canal using a microcatheter to treat open-angle glaucoma. J Cataract Refract Surg 2011; 37: Bull H, von Wolff K, Körber N, Tetz M. Three-year canaloplasty outcomes for the treatment of open-angle glaucoma: European study results. Graefes Arch Clin Exp Ophthalmol 2011; 249: Matlach J, Freiberg FJ, Leippi S, et al. Comparison of phacotrabeculectomy & versus phacocanaloplasty in the treatment of patients with concomitant cataract and glaucoma. BMC Ophthalmol 2013; 13:1 12. This retrospective chart review compared the results of phacoemulsification canaloplasty with phacoemulsification trabeculectomy. 29. Arthur SN, Cantor LB, WuDunn D, et al., safety, and survival rates of && IOP-lowering effect of phacoemulsification alone or combined with canaloplasty in glaucoma patients. J Glaucoma [Epub ahead of print] A retrospective chart review comparing PE-canaloplasty with PE alone using historical controls. 30. Gedde SJ, Schiffman JC, Feuer WJ, et al., Tube Versus Trabeculectomy Study Group. The Tube versus Trabeculectomy Study: Design and baseline characteristics of study patients. Am J Ophthalmol 2005; 140: ß 2014 Wolters Kluwer Health Lippincott Williams & Wilkins 147