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Using multiple trabecular micro-bypass stents in cataract patients to treat open-angle glaucoma
ARTICLE
Using multiple trabecular micro-bypass stents in cataract patients to treat open-angle glaucoma Graham W. Belovay, MD, Abdulla Naqi, MD, Brian J. Chan, MD, Mahmoud Rateb, MD, Iqbal Ike K. Ahmed, MD
PURPOSE: To evaluate the efficacy of multiple trabecular micro-bypass stents combined with cataract surgery in patients with open-angle glaucoma (OAG) and cataract. SETTING: Private practice, Mississauga, Ontario, Canada. DESIGN: Comparative case series. METHODS: Eyes with OAG had implantation of 2 or 3 micro-bypass stents with concurrent cataract surgery and follow-up through 1 year. Efficacy measures were intraocular pressure (IOP) and topical ocular hypotensive medication use. Safety assessment included complications and corrected distance visual acuity (CDVA). RESULTS: The study comprised 53 eyes (47 patients); 28 had implantation of 2 stents and 25 had implantation of 3 stents. The overall mean 1-year postoperative IOP was 14.3 mm Hg, which was significantly lower than preoperative IOP overall and in each group (P<.001). The target IOP was achieved in a significantly higher proportion of eyes at 1 year versus preoperatively (77% versus 43%; P<.001). Overall, 83% of eyes had a decrease in topical ocular hypotensive medication at 1 year from preoperatively, with a 74% decrease in the mean number of medications (from 2.7 to 0.7) at 1 year (P<.001). The 3-stent group was on significantly fewer medications than the 2-stent group at 1 year (0.4 versus 1.0; PZ.04). CONCLUSIONS: Using multiple micro-bypass stents with concurrent cataract surgery led to a mean postoperative IOP of less than 15 mm Hg and allowed patients to achieve target pressure control with significantly fewer medications through 1 year. Financial Disclosure: Dr. Ahmed is a consultant to Glaukos Corp. No other author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2012; 38:1911–1917 Q 2012 ASCRS and ESCRS
Open-angle glaucoma (OAG) can be managed in several ways depending on the target intraocular pressure (IOP), medication use, severity of glaucoma, quality of life, surgeon experience, and the surgical techniques available. In general, newly diagnosed glaucoma is managed with medical therapy, possibly in combination with laser trabeculoplasty. It is typically not until the later stages of the disease when the patient is on maximum medical therapy that ab externo filtering procedures are considered. In the case of glaucoma and visually clinically significant cataract, combined cataract and glaucoma procedures have been shown to not only lower IOP but to also reduce the number of glaucoma medications.1–3 Unfortunately, traditional ab externo glaucoma surgical procedures (eg, trabeculectomy, tubes, deep sclerectomy) are associated with significant risks and Q 2012 ASCRS and ESCRS Published by Elsevier Inc.
complications, including infection, corneal decompensation, choroidal hemorrhage, hypotony, diplopia, and vision loss.1–7 Thus, despite their effective control of IOP, they should not be considered benign operations. In the case of mild to moderate glaucoma and clinically significant cataract, less invasive surgical alternatives, such as microinvasive surgeries, can be performed in conjunction with cataract surgery. The use of less invasive treatments to reduce IOP and glaucoma medications is a desirable approach to treating glaucoma, especially if this approach does not limit other options in the future. The iStent implant (Glaukos Corp.) is a trabecular bypass device. It is the first of a class of new ab interno devices that enables minimally invasive glaucoma surgery. Several studies have shown the effectiveness and safety of implanting this stent in eyes with mild to 0886-3350/$ - see front matter http://dx.doi.org/10.1016/j.jcrs.2012.07.017
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moderate glaucoma to achieve this goal. Fea8 and Samuelson et al.9 compared phacoemulsification with and without stent implantation and found that the combined surgery was more effective at controlling IOP than cataract surgery alone; the safety profiles of both groups were similar. Spiegel et al.10,11,A studied stent implantation with concurrent cataract surgery in glaucoma patients and found effective IOP control through 24 months (16.9 mm Hg versus 21.9 mm Hg preoperatively). Also, medication use was reduced (0.4 versus 1.4 preoperatively). None of these studies reports major surgical complications. Earlier work12 suggests that more advanced OAG patients may require postoperative target pressures of 15 mm Hg or less to prevent further glaucomatous progression. Studies of the trabecular bypass stent by Zhou and Smedley13 and Bahler14 addressed this lower threshold. They established a theoretical in vitro perfusion model that predicted that multiple trabecular stents may increase facility of outflow and reduce IOP versus a single implant. Bahler et al.14 found that subsequent placement of a second stent reduced the mean IOP by an additional 3.6 mm Hg in 7 of 9 enucleated cadaver eyes. The current study evaluated the effects of multiple trabecular micro-bypass stents in combination with cataract surgery on IOP and glaucoma medication use in patients with OAG and concurrent cataract.
PATIENTS AND METHODS This was an open-label nonrandomized prospective singlecenter series of eyes with OAG that had implantation of 2 or 3 trabecular micro-bypass stents with concurrent cataract surgery. Key inclusion criteria were visually significant cataract, IOP that was not well controlled on medication or was well controlled but with a substantial (R3) medication burden, and follow-up through 12 months postoperatively. Ethics approval was obtained from IRB Services, Ltd., Aurora, Ontario, Canada, and all patients provided informed consent. Submitted: November 29, 2011. Final revision submitted: July 3, 2012. Accepted: July 6, 2012. From the University of Toronto (Belovay, Naqi, Rateb, Ahmed), Toronto, Ontario and McMaster University (Chan), Hamilton, Ontario, Canada; University of Utah (Ahmed), Salt Lake City, Utah, USA. Presented in part at the American Glaucoma Society Meeting, San Diego, California, USA, March 2010, and at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Boston, Massachusetts, USA April 2010. Corresponding author: Iqbal Ike K. Ahmed, MD, Credit Valley EyeCare, 3200 Erin Mills Parkway, Unit 1, Mississauga, Ontario, L5L 1W8, Canada. E-mail: [email protected].
Preoperatively, demographic information (age, sex, and race), ocular history (including type of glaucoma), glaucoma medications, and results from a recent visual field were recorded. The preoperative ocular examination included Snellen corrected distance visual acuity (CDVA), IOP (Goldmann applanation tonometry [GAT]), cup-to-disc ratio, anterior chamber angle (Shaeffer grade), and lens opacity grade (Lens Opacity Classification III15). Target IOP and the stage of glaucoma were determined using the Canadian Ophthalmological Society evidence-based clinical practice guidelines for the management of glaucoma in the adult eye.16 Patients with a remote history of angle-closure glaucoma requiring laser peripheral iridotomy and open angles at the time of surgery were classified as mixed mechanism. Ocular hypotensive medications were not discontinued before surgery. Using the technique described by Spiegel et al.,10 the same surgeon (I.I.K.A.) implanted 2 or 3 iStents in the eye after phacoemulsification. The stents were inserted in the nasal region of the trabecular meshwork separated by 1 to 2 clock hours. Eyes requiring greater IOP control (ie, to achieve the target IOP) as determined by the operating surgeon received 3 stents instead of 2 stents. Intraoperatively, the type of intraocular lens, the number of stents implanted, and the complications were recorded. Postoperatively, patients were seen at 1 day, 1 week, and 1, 3, 6, and 12 months. Snellen visual acuity, IOP (with GAT), glaucoma medications, stent placement using gonioscopy, and complications were assessed at these visits by the examining physician. The examiners were not masked to the number of stents. The number of ocular hypotensive medications was reduced gradually based on the postoperative IOP target in each case. Statistical analyses were performed using SPSS software (version 15, International Business Machines Corp.) in an intent-to-treat analysis. A paired t test was used to determine the significance of the change in IOP and glaucoma medications from baseline to 12 months. A 2-sample t test was used to compare the IOP and glaucoma medications between each time point and each stent group. A Mann-Whitney test was performed to compare outcomes between the 2-stent group and the 3-stent group. Demographic data were compared between groups using a 2-sample t test or Fisher exact test. Significance was set at 5%.
RESULTS The study enrolled 53 eyes of 47 patients. Table 1A shows the patients’ demographics and Table 1B, the preoperative characteristics. All eyes had cataract requiring surgery. Glaucoma diagnoses at time of surgery included primary OAG, pseudoexfoliative, and mixed mechanism. Previous glaucoma surgeries included laser peripheral iridotomy, argon laser trabeculoplasty (ALT), and selective laser trabeculoplasty (SLT). Eight eyes had 2 procedures (laser peripheral iridotomy and ALT, n Z 1; laser peripheral iridotomy and SLT, n Z 4; ALT and SLT, n Z 3). Those with laser peripheral iridotomies, with the exception of the mixedmechanism patients, had the procedures performed by their referring physicians for reasons unknown. No eye had a history of trabeculectomy or shunt implantation. Approximately half the eyes had a preoperative CDVA
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Table 1A. Demographics. Parameter Mean age (y) G SD Sex, n (%) Male Female Race, n (%) White Black South Asian Far East Asian
Overall (N Z 47)*
2-Stent Group (n Z 26)
3-Stent Group (n Z 23)
P Value
77.2 G 7.4
78.8 G 7.0
75.0 G 7.3
.07† .54z
14 (30) 33 (70)
7 (27) 19 (73)
9 (39) 14 (61)
29 (62) 7 (15) 7 (15) 4 (8)
18 (69) 4 (15) 2 (8) 2 (8)
11 (48) 4 (17) 5 (22) 3 (13)
.43x
*Two patients received 2 stents in 1 eye and 3 stents in the other eye † Two-sample t test z Fisher exact test x Fisher exact test with Monte Carlo simulation
of 20/50 to 20/100, with the remainder having a CDVA of 20/40 or better or 20/200 or worse. Eight eyes had mild glaucoma, 23 had moderate glaucoma, and 22 had advanced glaucoma. Of the 53 eyes, 28 had implantation of 2 stents and 25 had implantation of 3 stents. Forty-one patients (87%) had 2 or 3 stents implanted in 1 eye only. Two patients received 3 stents bilaterally, 2 received 2 stents bilaterally, and 2 received 2 stents in 1 eye and 3 stents in the other eye. The mean preoperative medicated IOP was similar between the 2-stent group and the 3-stent group. Overall preoperatively, fewer than half the eyes were at the target IOP levels. The mean number of preoperative medications was similar between the 2-stent group and the 3-stent group. More eyes in the 3-stent group than in the 2-stent group were taking 4 or more medications. Overall Intraocular Pressure and Medications Overall, the decrease in the mean IOP from preoperatively (18.0 G 4.0 mm Hg) to 1 year postoperatively (14.3 G 2.9 mm Hg) was statistically significant (P!.001) (Figure 1). Thirty-seven eyes (70%) achieved an IOP of 15 mm Hg or less at 1 year, and 41 eyes (77%) achieved the target IOP. The mean overall number of topical ocular hypotensive medications decreased significantly from 2.7 G 1.0 preoperatively to 0.7 G 1.1 medications at 1 year (P!.001) (Figure 1). The mean reduction at 1 year was 2.0 G 1.4 medications, representing a 74% reduction. Forty-four patients (83%) reduced the number of medications at 1 year, and 31 (59%) discontinued use of all medications in the study eye. The remaining eyes ended up on 1 medication (13 [24%]) or 2 or 3 medications (3 [6%] and 5 [9%], respectively); 1 eye was using 4 medications at 1 year.
Intraocular Pressure and Medications by Stent Group The 1-year IOP was significantly lower than the preoperative IOP in the 2-stent group (mean 13.8 mm Hg postoperatively) and the 3-stent group (mean 14.8 mm Hg postoperatively) (both P!.001) (Figure 2). There was no significant difference in IOP reduction between the 2 groups (PZ.78). Twentyone eyes (75%) in the 2-stent group achieved a 1-year postoperative IOP of 15 mm Hg or less. The IOP reduction was greater in the 3-stent group, with a mean reduction of 3.9 mm Hg versus 3.5 mm Hg in the 2-stent group (PZ.76). Target IOP was achieved by 20 eyes (71%) in the 2-stent group and 21 eyes (84%) in the 3-stent group. The mean number of topical ocular hypotensive medications significantly decreased to 1.0 medication and 0.4 medication, respectively, at 1 year (P!.001) (Figure 3), representing a 64% reduction in medications in the 2-stent group and 85% reduction in the 3-stent group. The 3-stent group was on significantly fewer medications at 1 year than the 2-stent group (PZ.04). At 1 year, medication use had been stopped in 13 eyes (46%) in the 2-stent group and 18 eyes (72%) in the 3-stent group. Complications The most common complication was blockage of the opening of the stent lumen, which occurred in 8 eyes in the early postoperative period. Stent blockage was successfully treated with a neodymium:YAG laser or argon laser in 6 eyes and then repeated in 1 of these eyes. Laser treatment was not performed in 2 eyes because of good IOP control with a second patent stent in 1 eye and because the blockage was partial in 1 eye. One eye presented with small hyphema 1 day postoperatively that resolved by 4 weeks postoperatively. One of the stents in 1 eye was not seated well in the
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Table 1B. Preoperative characteristics. Parameter Glaucoma, n (%) Primary open angle Pseudoexfoliative Mixed mechanism Other ocular conditions, n (%) ARMD High myopia Suprasellar lesion (treated with radiation) Branch vein occlusion Diabetic retinopathy ARMD scar Optic nerve head drusen Previous glaucoma procedures, n (%) LPI ALT SLT O1 previous procedure Eye, n (%) Right Left CDVA, n (%) 20/40 or better 20/50–20/100 20/200 or worse Mean C:D ratio G SD Mean Shaffer grade G SD Visual field Mean Deviation (dB) G SD Mean pattern SD (dB) G SD Intraocular pressure Mean (mm Hg) G SD !15 mm Hg, n (%) 15–18 mm Hg, n (%) O18 mm Hg, n (%) Target intraocular pressure Mean (mm Hg) G SD At or lower than target, n (%) Medications Mean (n) G SD 1 medication 2 medications 3 medications O3 medications
Overall (N Z 53)
2-Stent Group (n Z 28)
3-Stent Group (n Z 25)
P Value
37 (70) 14 (26) 2 (4)
21 (75) 7 (25) 0
16 (64) 7 (28) 2 (8)
.55* 1.00*
(4) (4) (4) (2) (2) (2) (0)
4 (14) 1 (4) 1 (4) 1 (4) 0 0 1 (4)
0 1 (5) 1 (5) 0 1 (4) 1 (4) 0
11 (21) 9 (17) 17 (32) 8 (15)
4 (14) 6 (21) 7 (25) 3 (11)
7 (28) 3 (12) 10 (40) 5 (20)
24 (45) 29 (55)
11 (39) 17 (61)
13 (52) 12 (48)
14 (26) 26 (49) 13 (25) 0.74 G 0.16 2.9 G 0.7
6 (21) 15 (54) 7 (25) 0.76 G 0.16 2.9 G 0.8
8 (32) 11 (44) 6 (23) 0.71 G 0.17 2.8 G 0.6
.23† .93†
11.5 G 7.6 6.9 G 3.8
12.6 G 7.1 7.9 G 3.4
10.2 G 8.1 5.9 G 4.1
.24† .06†
18.0 G 4.0 11 (21) 22 (42) 20 (38)
17.3 G 4.0 6 (21) 13 (46) 9 (32)
18.6 G 4.0 5 (20) 9 (36) 11 (44)
.24†
16.2 G 2.1 23 (43)
15.7 G 1.9 14 (50)
16.7 G 2.3 9 (36)
.08†
2.7 G 1.0 7 (13) 15 (28) 19 (36) 12 (23)
2.8 G 0.8 2 (7) 8 (29) 13 (46) 5 (18)
2.6 G 1.2 5 (20) 7 (28) 6 (24) 7 (28)
.70†
2 2 2 1 1 1 1
.31* .47* .38* .45* .42*
.76†
ALT Z argon laser trabeculoplasty; AMD Z age-related macular degeneration; C:D Z cup-to-disc ratio; CDVA Z corrected distance visual acuity; IOP Z intraocular pressure; LPI Z laser peripheral iridotomy; SLT Z selective laser trabeculoplasty *Fisher exact test † Two-sample t test
canal after surgery but was otherwise stable; thus, no intervention was performed. A steroid response resulting in elevated IOP was identified at 5 weeks in 1 eye and at 1 month in another eye. Both cases resolved once the steroids were discontinued. One patient died from an unrelated systemic illness.
Corrected Distance Visual Acuity Table 2 shows the CDVA at 1 year. One patient did not have vision recorded at the final visit. Of the remaining 52 eyes, 47 (89%) had improved CDVA or maintained the preoperative CDVA. Of the 5 eyes with CDVA worsening at 1 year, 4 improved at
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Figure 1. Overall mean IOP (mm Hg) and number of glaucoma medications from baseline through 12 months. Bars represent the standard deviation (IOP Z intraocular pressure).
Figure 2. Mean IOP (mm Hg) at each visit through 12 months stratified by number of stents. Bars represent the standard deviation (IOP Z intraocular pressure).
subsequent visits. The remaining 1 patient was lost to follow-up.
requiring fewer medications. However, no attempt to reduce the number of medications preoperatively was made, potentially overestimating this effect. Compared with studies of implantation of a single stent,8–11 use of multiple stents in this study resulted in a greater propensity to achieve a postoperative IOP of 15 mm Hg or less and a greater absolute reduction in medications. This finding is consistent with the ex vivo work of Zhou and Smedley13 and Bahler et al.14 The use of multiple stents may exploit a greater range of circumferential flow and allow access to a greater array of collector channels to establish physiologic flow of aqueous humor into the episcleral venous system. Eyes in the 2-stent group had a significant reduction in IOP and medications (P!.001 in all cases). Target IOP was achieved in most cases (71%). Despite a high mean preoperative medication burden in these moderate to advanced OAG patients, the majority (79%) had a reduced preoperative medication burden at 1 year. The IOP and number of medications also significantly decreased from preoperatively in the 3-stent group (P!.001); the target IOP was achieved by 84% compared with 43% preoperatively. There was a significant reduction in medications, with 88% of eyes
DISCUSSION Samuelson et al.9 established that a single trabecular bypass stent significantly reduced IOP and medication burden at 1 year in patients having combined cataract– glaucoma implant procedures compared with patients having cataract surgery only. Studies by Fea8 and Spiegel et al.11 provide corroborating evidence of the treatment effect of a single stent. In this open-label nonrandomized prospective series, implantation of 2 or 3 trabecular bypass stents in eyes having combined cataract surgery resulted in significantly lower mean IOP at 1 year than preoperatively (P!.001), with 77% of eyes achieving the postoperative target pressure. This is despite no preoperative medication washout period. The number of glaucoma medications was also significantly decreased from 2.7 medications preoperatively to 0.7 medications at 1 year (P!.001), with 83% of eyes
Table 2. Corrected distance visual acuity at 1 year. Number (%) CDVA 20/40 or better 20/50–20/100 20/200 or worse Figure 3. The mean number of glaucoma medications used in each eye from baseline through month 12 stratified by number of stents. Bars represent the standard deviation (*PZ.009; 4PZ.04).
Overall*
2-Stent Group*
3-Stent Group
37 (64) 11 (21) 4 (8)
18 (64) 6 (21) 3 (11)
19 (76) 5 (20) 1 (4)
CDVA Z corrected distance visual acuity *Missing 1
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requiring fewer medications and 72% of eyes on no medications at 1 year. These data show high rates of IOP reduction and medication reduction with 2-stent or 3-stent implantation and the potential to achieve target IOP levels after multiple stent implantation. The significantly lower postoperative medication burden in the 3-stent than in the 2-stent group suggests that stent titration is feasible. This allows the operating surgeon to determine the appropriate number of stents required to achieve the desired postoperative target IOP. Furthermore, if necessary, it may allow the option of implanting additional micro-bypass devices in subsequent procedures to optimize the benefit-to-risk ratio while preserving future management options. No major surgical problems or postoperative complications were reported during the study. The most common complication of a blocked stent by the iris was in most cases resolved by performing a laser iridotomy that was well tolerated by the patient. In some instances, no intervention was required because the pressure was under control. The postoperative hyphema resolved within the first month without sequelae. Because of the nature of the insertion, minimal reflux of blood is an anticipated normal physiologic response immediately after stent implantation. Despite a poor preoperative CDVA in approximately one fourth of these eyes with advanced glaucoma, the CDVA improved or was maintained in most eyes and most patients achieved a postoperative CDVA of 20/40 or better. These postoperative findings are similar to those reported by others.8–11,17 Further studies are needed to refine the relationship observed between the number of stents implanted with concurrent cataract surgery and IOP control. Determining the criteria for the number of stents to implant will also require further investigation. Although the outcomes in the 2-stent group and 3-stent group were similar, we attempted to select more severe patients for implantation of 3 stents. However, our baseline analysis showed no significant difference between the 2 groups in any measure. Thus, a masked randomized trial is needed to better evaluate the relative efficacy of 2 versus 3 stents. Furthermore, this series did not use a control group having cataract surgery without stent implantation, although previous studies8,9 established the benefit of stent implantation and cataract surgery versus cataract surgery only. The 6 cases of bilateral implantation could add additional bias; however, the cases were spread evenly between the groups, minimizing the overall impact. Despite its limitations, this study contributes to the body of evidence showing the efficacy and safety of trabecular micro-bypass stent implantation and suggests that the implantation of multiple stents may be an alternative to more
invasive surgeries, such as trabeculectomy and tube shunt placement, although this would have to be evaluated in a future prospective study. The data reported by Samuelson et al.9 suggest that a single stent implanted in combination with cataract surgery achieves postoperative target pressures that are clinically meaningful for mild to moderate OAG patients with comorbid cataracts. For more moderate to advanced OAG patients with comorbid cataracts, this study found that 2 or 3 stents implanted in combined cataract procedures achieved mean IOPs that were clinically meaningful for these patients. Therefore, single and multiple implants in combined cataract procedures may be preferable to the problems of compliance (long-term morbidity and nonadherence) associated with chronic use of multiple medications to control OAG. This may also improve patient convenience and quality of life. The clinical utility and demonstrated efficacy and safety of single and multiple stent implantation enables surgeons to select the implant therapy that is most appropriate to achieve desired patient target pressures. This approach appears to offer a high benefit-to-risk ratio for a given OAG disease stage severity and desired postoperative target IOP. WHAT WAS KNOWN Implantation of 1 trabecular micro-bypass stent combined with cataract surgery is safe and can more effectively reduce IOP and topical ocular hypotensive medication use compared with cataract surgery alone. WHAT THIS PAPER ADDS The implantation of 2 or 3 trabecular micro-bypass stents combined with cataract surgery was performed safely with a reduction in IOP and topical ocular hypotensive medications. Implantation of multiple trabecular micro-bypass stents has the potential to further reduce IOP and topical ocular hypotensive medications versus implantation of 1 trabecular micro-bypass stent.
REFERENCES 1. Funnell CL, Clowes M, Anand N. Combined cataract and glaucoma surgery with mitomycin C: phacoemulsificationtrabeculectomy compared to phacoemulsification-deep sclerectomy. Br J Ophthalmol 2005; 89:694–698. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1772685/pdf/ bjo08900694.pdf. Accessed July 17, 2012 2. Tsai H-Y, Liu CJ, Cheng C-Y. Combined trabeculectomy and cataract extraction versus trabeculectomy alone in primary angle-closure glaucoma. Br J Ophthalmol 2009; 93:943–948
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3. Friedman DS, Jampel HD, Lubomski LH, Quigley H, Congdon N, Levkovitch-Verbin H, Robinson KA, Bass EB. Surgical strategies for coexisting glaucoma and cataract; an evidence-based update. Ophthalmology 2002; 109:1902–1913 4. Hoffmann E, Schwenn O, Karallus M, Krummenauer F, Grehn F, Pfeiffer N. Long-term results of cataract surgery combined with trabeculotomy. Graefes Arch Clin Exp Ophthalmol 2002; 240:2–6 5. Hau S, Barton K. Corneal complications of glaucoma surgery. Curr Opin Ophthalmol 2009; 20:131–136. Available at: http:// journals.lww.com/co-ophthalmology/fulltext/2009/03000/corneal_ complications_of_glaucoma_surgery.13.aspx. Accessed July 17, 2012 6. Minckler DS, Francis BA, Hodapp EA, Jampel HD, Lin SC, Samples JR, Smith SD, Singh K. Aqueous shunts in glaucoma; a report by the American Academy of Ophthalmology (Ophthalmic Technology Assessment). Ophthalmology 2008; 115:1089–1098. Available at: http://www.amo-romania.com/ Document_Files/Ophthalmology%202008%20Jun.115(6)% 20p1089-98_AqueousShuntsinGlaucoma_vdcgv5.pdf. Accessed July 17, 2012 7. Jampel HD, Musch DC, Gillespie BW, Lichter PR, Wright MM, Guire KE; and the Collaborative Initial Glaucoma Treatment Study Group. Perioperative complications of trabeculectomy in the Collaborative Initial Glaucoma Treatment Study (CIGTS). Am J Ophthalmol 2005; 140:16–22. Available at: http://new-glaucoma-treatments.com/wp-content/imagesfiles/ Perioperative%20Complications%20of%20Trab%20CIGTS. pdf. Accessed July 17, 2012 8. Fea AM. Phacoemulsification versus phacoemulsification with micro-bypass stent implantation in primary open-angle glaucoma: randomized double-masked clinical trial. J Cataract Refract Surg 2010; 36:407–412 9. Samuelson TW, Katz LJ, Wells JM, Duh Y-J, Giamporcaro JE; for the US iStent Study Group. Randomized evaluation of the trabecular micro-bypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology 2011; 118:459–467 J, Garcıa-Sa nchez J, Lamielle H. 10. Spiegel D, Garcıa-Feijoo Coexistent primary open-angle glaucoma and cataract: preliminary analysis of treatment by cataract surgery and the iStent trabecular micro-bypass stent. Adv Ther 2008; 25:453–464 €h H, Garcıa€rmer J, Ho 11. Spiegel D, Wetzel W, Neuhann T, Stu nchez J. CoexisFeijoo J, Martınez-de-la-Casa JM, Garcıa-Sa tent primary open-angle glaucoma and cataract: Interim analysis of a trabecular micro-bypass stent and concurrent cataract surgery. Eur J Ophthalmol 2009; 19:393–399
12. The AGIS Investigators. The Advanced Glaucoma Intervention Study (AGIS): 7. The relationship between control of intraocular pressure and visual field deterioration. Am J Ophthalmol 2000; 130:429–440 13. Zhou J, Smedley GT. A trabecular bypass flow hypothesis. J Glaucoma 2005; 14:74–83 14. Bahler CK, Smedley GT, Zhou J, Johnson DH. Trabecular bypass stents decrease intraocular pressure in cultured human anterior segments. Am J Ophthalmol 2004; 138:988–994 15. Chylack LT Jr, Wolfe JK, Singer DM, Leske MC, Bullimore MA, Bailey IL, Friend J, McCarthy D, Wu S-Y; for the Longitudinal Study of Cataract Study Group. The Lens Opacities Classification System III. Arch Ophthalmol 1993; 111:831–836. Available at: http://archopht.jamanetwork. com/data/Journals/OPHTH/18057/archopht_111_6_035.pdf. Accessed July 17, 2012 16. Canadian Ophthalmological Society evidence-based clinical practice guidelines for cataract surgery in the adult eye. Can J Ophthalmol October 2008; 43(suppl 1):S7–S57. Available at: http://www.eyesite.ca/CJO/43S1/i08-133.pdf. Accessed July 17, 2012 ndez-Barrientos Y, Garcia -Feijoo J, Martınez-de-la17. Ferna ndez-Pe rez C, Garcia Sa nchez J. Casa JM, Pablo LE, Ferna Fluorophotometric study of the effect of the Glaukos trabecular microbypass stent on aqueous humor dynamics. Invest Ophthalmol Vis Sci 2010; 51:3327–3332. Available at: http://www.iovs. org/content/51/7/3327.full.pdf. Accessed July 17, 2012
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First author: Graham W. Belovay, MD University of Toronto, Toronto, Ontario, Canada
Using multiple trabecular micro-bypass stents in cataract patients to treat open-angle glaucoma Graham W. Belovay, MD, Abdulla Naqi, MD, Brian J. Chan, MD, Mahmoud Rateb, MD, Iqbal Ike K. Ahmed, MD
PURPOSE: To evaluate the efficacy of multiple trabecular micro-bypass stents combined with cataract surgery in patients with open-angle glaucoma (OAG) and cataract. SETTING: Private practice, Mississauga, Ontario, Canada. DESIGN: Comparative case series. METHODS: Eyes with OAG had implantation of 2 or 3 micro-bypass stents with concurrent cataract surgery and follow-up through 1 year. Efficacy measures were intraocular pressure (IOP) and topical ocular hypotensive medication use. Safety assessment included complications and corrected distance visual acuity (CDVA). RESULTS: The study comprised 53 eyes (47 patients); 28 had implantation of 2 stents and 25 had implantation of 3 stents. The overall mean 1-year postoperative IOP was 14.3 mm Hg, which was significantly lower than preoperative IOP overall and in each group (P<.001). The target IOP was achieved in a significantly higher proportion of eyes at 1 year versus preoperatively (77% versus 43%; P<.001). Overall, 83% of eyes had a decrease in topical ocular hypotensive medication at 1 year from preoperatively, with a 74% decrease in the mean number of medications (from 2.7 to 0.7) at 1 year (P<.001). The 3-stent group was on significantly fewer medications than the 2-stent group at 1 year (0.4 versus 1.0; PZ.04). CONCLUSIONS: Using multiple micro-bypass stents with concurrent cataract surgery led to a mean postoperative IOP of less than 15 mm Hg and allowed patients to achieve target pressure control with significantly fewer medications through 1 year. Financial Disclosure: Dr. Ahmed is a consultant to Glaukos Corp. No other author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2012; 38:1911–1917 Q 2012 ASCRS and ESCRS
Open-angle glaucoma (OAG) can be managed in several ways depending on the target intraocular pressure (IOP), medication use, severity of glaucoma, quality of life, surgeon experience, and the surgical techniques available. In general, newly diagnosed glaucoma is managed with medical therapy, possibly in combination with laser trabeculoplasty. It is typically not until the later stages of the disease when the patient is on maximum medical therapy that ab externo filtering procedures are considered. In the case of glaucoma and visually clinically significant cataract, combined cataract and glaucoma procedures have been shown to not only lower IOP but to also reduce the number of glaucoma medications.1–3 Unfortunately, traditional ab externo glaucoma surgical procedures (eg, trabeculectomy, tubes, deep sclerectomy) are associated with significant risks and Q 2012 ASCRS and ESCRS Published by Elsevier Inc.
complications, including infection, corneal decompensation, choroidal hemorrhage, hypotony, diplopia, and vision loss.1–7 Thus, despite their effective control of IOP, they should not be considered benign operations. In the case of mild to moderate glaucoma and clinically significant cataract, less invasive surgical alternatives, such as microinvasive surgeries, can be performed in conjunction with cataract surgery. The use of less invasive treatments to reduce IOP and glaucoma medications is a desirable approach to treating glaucoma, especially if this approach does not limit other options in the future. The iStent implant (Glaukos Corp.) is a trabecular bypass device. It is the first of a class of new ab interno devices that enables minimally invasive glaucoma surgery. Several studies have shown the effectiveness and safety of implanting this stent in eyes with mild to 0886-3350/$ - see front matter http://dx.doi.org/10.1016/j.jcrs.2012.07.017
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moderate glaucoma to achieve this goal. Fea8 and Samuelson et al.9 compared phacoemulsification with and without stent implantation and found that the combined surgery was more effective at controlling IOP than cataract surgery alone; the safety profiles of both groups were similar. Spiegel et al.10,11,A studied stent implantation with concurrent cataract surgery in glaucoma patients and found effective IOP control through 24 months (16.9 mm Hg versus 21.9 mm Hg preoperatively). Also, medication use was reduced (0.4 versus 1.4 preoperatively). None of these studies reports major surgical complications. Earlier work12 suggests that more advanced OAG patients may require postoperative target pressures of 15 mm Hg or less to prevent further glaucomatous progression. Studies of the trabecular bypass stent by Zhou and Smedley13 and Bahler14 addressed this lower threshold. They established a theoretical in vitro perfusion model that predicted that multiple trabecular stents may increase facility of outflow and reduce IOP versus a single implant. Bahler et al.14 found that subsequent placement of a second stent reduced the mean IOP by an additional 3.6 mm Hg in 7 of 9 enucleated cadaver eyes. The current study evaluated the effects of multiple trabecular micro-bypass stents in combination with cataract surgery on IOP and glaucoma medication use in patients with OAG and concurrent cataract.
PATIENTS AND METHODS This was an open-label nonrandomized prospective singlecenter series of eyes with OAG that had implantation of 2 or 3 trabecular micro-bypass stents with concurrent cataract surgery. Key inclusion criteria were visually significant cataract, IOP that was not well controlled on medication or was well controlled but with a substantial (R3) medication burden, and follow-up through 12 months postoperatively. Ethics approval was obtained from IRB Services, Ltd., Aurora, Ontario, Canada, and all patients provided informed consent. Submitted: November 29, 2011. Final revision submitted: July 3, 2012. Accepted: July 6, 2012. From the University of Toronto (Belovay, Naqi, Rateb, Ahmed), Toronto, Ontario and McMaster University (Chan), Hamilton, Ontario, Canada; University of Utah (Ahmed), Salt Lake City, Utah, USA. Presented in part at the American Glaucoma Society Meeting, San Diego, California, USA, March 2010, and at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Boston, Massachusetts, USA April 2010. Corresponding author: Iqbal Ike K. Ahmed, MD, Credit Valley EyeCare, 3200 Erin Mills Parkway, Unit 1, Mississauga, Ontario, L5L 1W8, Canada. E-mail: [email protected].
Preoperatively, demographic information (age, sex, and race), ocular history (including type of glaucoma), glaucoma medications, and results from a recent visual field were recorded. The preoperative ocular examination included Snellen corrected distance visual acuity (CDVA), IOP (Goldmann applanation tonometry [GAT]), cup-to-disc ratio, anterior chamber angle (Shaeffer grade), and lens opacity grade (Lens Opacity Classification III15). Target IOP and the stage of glaucoma were determined using the Canadian Ophthalmological Society evidence-based clinical practice guidelines for the management of glaucoma in the adult eye.16 Patients with a remote history of angle-closure glaucoma requiring laser peripheral iridotomy and open angles at the time of surgery were classified as mixed mechanism. Ocular hypotensive medications were not discontinued before surgery. Using the technique described by Spiegel et al.,10 the same surgeon (I.I.K.A.) implanted 2 or 3 iStents in the eye after phacoemulsification. The stents were inserted in the nasal region of the trabecular meshwork separated by 1 to 2 clock hours. Eyes requiring greater IOP control (ie, to achieve the target IOP) as determined by the operating surgeon received 3 stents instead of 2 stents. Intraoperatively, the type of intraocular lens, the number of stents implanted, and the complications were recorded. Postoperatively, patients were seen at 1 day, 1 week, and 1, 3, 6, and 12 months. Snellen visual acuity, IOP (with GAT), glaucoma medications, stent placement using gonioscopy, and complications were assessed at these visits by the examining physician. The examiners were not masked to the number of stents. The number of ocular hypotensive medications was reduced gradually based on the postoperative IOP target in each case. Statistical analyses were performed using SPSS software (version 15, International Business Machines Corp.) in an intent-to-treat analysis. A paired t test was used to determine the significance of the change in IOP and glaucoma medications from baseline to 12 months. A 2-sample t test was used to compare the IOP and glaucoma medications between each time point and each stent group. A Mann-Whitney test was performed to compare outcomes between the 2-stent group and the 3-stent group. Demographic data were compared between groups using a 2-sample t test or Fisher exact test. Significance was set at 5%.
RESULTS The study enrolled 53 eyes of 47 patients. Table 1A shows the patients’ demographics and Table 1B, the preoperative characteristics. All eyes had cataract requiring surgery. Glaucoma diagnoses at time of surgery included primary OAG, pseudoexfoliative, and mixed mechanism. Previous glaucoma surgeries included laser peripheral iridotomy, argon laser trabeculoplasty (ALT), and selective laser trabeculoplasty (SLT). Eight eyes had 2 procedures (laser peripheral iridotomy and ALT, n Z 1; laser peripheral iridotomy and SLT, n Z 4; ALT and SLT, n Z 3). Those with laser peripheral iridotomies, with the exception of the mixedmechanism patients, had the procedures performed by their referring physicians for reasons unknown. No eye had a history of trabeculectomy or shunt implantation. Approximately half the eyes had a preoperative CDVA
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Table 1A. Demographics. Parameter Mean age (y) G SD Sex, n (%) Male Female Race, n (%) White Black South Asian Far East Asian
Overall (N Z 47)*
2-Stent Group (n Z 26)
3-Stent Group (n Z 23)
P Value
77.2 G 7.4
78.8 G 7.0
75.0 G 7.3
.07† .54z
14 (30) 33 (70)
7 (27) 19 (73)
9 (39) 14 (61)
29 (62) 7 (15) 7 (15) 4 (8)
18 (69) 4 (15) 2 (8) 2 (8)
11 (48) 4 (17) 5 (22) 3 (13)
.43x
*Two patients received 2 stents in 1 eye and 3 stents in the other eye † Two-sample t test z Fisher exact test x Fisher exact test with Monte Carlo simulation
of 20/50 to 20/100, with the remainder having a CDVA of 20/40 or better or 20/200 or worse. Eight eyes had mild glaucoma, 23 had moderate glaucoma, and 22 had advanced glaucoma. Of the 53 eyes, 28 had implantation of 2 stents and 25 had implantation of 3 stents. Forty-one patients (87%) had 2 or 3 stents implanted in 1 eye only. Two patients received 3 stents bilaterally, 2 received 2 stents bilaterally, and 2 received 2 stents in 1 eye and 3 stents in the other eye. The mean preoperative medicated IOP was similar between the 2-stent group and the 3-stent group. Overall preoperatively, fewer than half the eyes were at the target IOP levels. The mean number of preoperative medications was similar between the 2-stent group and the 3-stent group. More eyes in the 3-stent group than in the 2-stent group were taking 4 or more medications. Overall Intraocular Pressure and Medications Overall, the decrease in the mean IOP from preoperatively (18.0 G 4.0 mm Hg) to 1 year postoperatively (14.3 G 2.9 mm Hg) was statistically significant (P!.001) (Figure 1). Thirty-seven eyes (70%) achieved an IOP of 15 mm Hg or less at 1 year, and 41 eyes (77%) achieved the target IOP. The mean overall number of topical ocular hypotensive medications decreased significantly from 2.7 G 1.0 preoperatively to 0.7 G 1.1 medications at 1 year (P!.001) (Figure 1). The mean reduction at 1 year was 2.0 G 1.4 medications, representing a 74% reduction. Forty-four patients (83%) reduced the number of medications at 1 year, and 31 (59%) discontinued use of all medications in the study eye. The remaining eyes ended up on 1 medication (13 [24%]) or 2 or 3 medications (3 [6%] and 5 [9%], respectively); 1 eye was using 4 medications at 1 year.
Intraocular Pressure and Medications by Stent Group The 1-year IOP was significantly lower than the preoperative IOP in the 2-stent group (mean 13.8 mm Hg postoperatively) and the 3-stent group (mean 14.8 mm Hg postoperatively) (both P!.001) (Figure 2). There was no significant difference in IOP reduction between the 2 groups (PZ.78). Twentyone eyes (75%) in the 2-stent group achieved a 1-year postoperative IOP of 15 mm Hg or less. The IOP reduction was greater in the 3-stent group, with a mean reduction of 3.9 mm Hg versus 3.5 mm Hg in the 2-stent group (PZ.76). Target IOP was achieved by 20 eyes (71%) in the 2-stent group and 21 eyes (84%) in the 3-stent group. The mean number of topical ocular hypotensive medications significantly decreased to 1.0 medication and 0.4 medication, respectively, at 1 year (P!.001) (Figure 3), representing a 64% reduction in medications in the 2-stent group and 85% reduction in the 3-stent group. The 3-stent group was on significantly fewer medications at 1 year than the 2-stent group (PZ.04). At 1 year, medication use had been stopped in 13 eyes (46%) in the 2-stent group and 18 eyes (72%) in the 3-stent group. Complications The most common complication was blockage of the opening of the stent lumen, which occurred in 8 eyes in the early postoperative period. Stent blockage was successfully treated with a neodymium:YAG laser or argon laser in 6 eyes and then repeated in 1 of these eyes. Laser treatment was not performed in 2 eyes because of good IOP control with a second patent stent in 1 eye and because the blockage was partial in 1 eye. One eye presented with small hyphema 1 day postoperatively that resolved by 4 weeks postoperatively. One of the stents in 1 eye was not seated well in the
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Table 1B. Preoperative characteristics. Parameter Glaucoma, n (%) Primary open angle Pseudoexfoliative Mixed mechanism Other ocular conditions, n (%) ARMD High myopia Suprasellar lesion (treated with radiation) Branch vein occlusion Diabetic retinopathy ARMD scar Optic nerve head drusen Previous glaucoma procedures, n (%) LPI ALT SLT O1 previous procedure Eye, n (%) Right Left CDVA, n (%) 20/40 or better 20/50–20/100 20/200 or worse Mean C:D ratio G SD Mean Shaffer grade G SD Visual field Mean Deviation (dB) G SD Mean pattern SD (dB) G SD Intraocular pressure Mean (mm Hg) G SD !15 mm Hg, n (%) 15–18 mm Hg, n (%) O18 mm Hg, n (%) Target intraocular pressure Mean (mm Hg) G SD At or lower than target, n (%) Medications Mean (n) G SD 1 medication 2 medications 3 medications O3 medications
Overall (N Z 53)
2-Stent Group (n Z 28)
3-Stent Group (n Z 25)
P Value
37 (70) 14 (26) 2 (4)
21 (75) 7 (25) 0
16 (64) 7 (28) 2 (8)
.55* 1.00*
(4) (4) (4) (2) (2) (2) (0)
4 (14) 1 (4) 1 (4) 1 (4) 0 0 1 (4)
0 1 (5) 1 (5) 0 1 (4) 1 (4) 0
11 (21) 9 (17) 17 (32) 8 (15)
4 (14) 6 (21) 7 (25) 3 (11)
7 (28) 3 (12) 10 (40) 5 (20)
24 (45) 29 (55)
11 (39) 17 (61)
13 (52) 12 (48)
14 (26) 26 (49) 13 (25) 0.74 G 0.16 2.9 G 0.7
6 (21) 15 (54) 7 (25) 0.76 G 0.16 2.9 G 0.8
8 (32) 11 (44) 6 (23) 0.71 G 0.17 2.8 G 0.6
.23† .93†
11.5 G 7.6 6.9 G 3.8
12.6 G 7.1 7.9 G 3.4
10.2 G 8.1 5.9 G 4.1
.24† .06†
18.0 G 4.0 11 (21) 22 (42) 20 (38)
17.3 G 4.0 6 (21) 13 (46) 9 (32)
18.6 G 4.0 5 (20) 9 (36) 11 (44)
.24†
16.2 G 2.1 23 (43)
15.7 G 1.9 14 (50)
16.7 G 2.3 9 (36)
.08†
2.7 G 1.0 7 (13) 15 (28) 19 (36) 12 (23)
2.8 G 0.8 2 (7) 8 (29) 13 (46) 5 (18)
2.6 G 1.2 5 (20) 7 (28) 6 (24) 7 (28)
.70†
2 2 2 1 1 1 1
.31* .47* .38* .45* .42*
.76†
ALT Z argon laser trabeculoplasty; AMD Z age-related macular degeneration; C:D Z cup-to-disc ratio; CDVA Z corrected distance visual acuity; IOP Z intraocular pressure; LPI Z laser peripheral iridotomy; SLT Z selective laser trabeculoplasty *Fisher exact test † Two-sample t test
canal after surgery but was otherwise stable; thus, no intervention was performed. A steroid response resulting in elevated IOP was identified at 5 weeks in 1 eye and at 1 month in another eye. Both cases resolved once the steroids were discontinued. One patient died from an unrelated systemic illness.
Corrected Distance Visual Acuity Table 2 shows the CDVA at 1 year. One patient did not have vision recorded at the final visit. Of the remaining 52 eyes, 47 (89%) had improved CDVA or maintained the preoperative CDVA. Of the 5 eyes with CDVA worsening at 1 year, 4 improved at
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Figure 1. Overall mean IOP (mm Hg) and number of glaucoma medications from baseline through 12 months. Bars represent the standard deviation (IOP Z intraocular pressure).
Figure 2. Mean IOP (mm Hg) at each visit through 12 months stratified by number of stents. Bars represent the standard deviation (IOP Z intraocular pressure).
subsequent visits. The remaining 1 patient was lost to follow-up.
requiring fewer medications. However, no attempt to reduce the number of medications preoperatively was made, potentially overestimating this effect. Compared with studies of implantation of a single stent,8–11 use of multiple stents in this study resulted in a greater propensity to achieve a postoperative IOP of 15 mm Hg or less and a greater absolute reduction in medications. This finding is consistent with the ex vivo work of Zhou and Smedley13 and Bahler et al.14 The use of multiple stents may exploit a greater range of circumferential flow and allow access to a greater array of collector channels to establish physiologic flow of aqueous humor into the episcleral venous system. Eyes in the 2-stent group had a significant reduction in IOP and medications (P!.001 in all cases). Target IOP was achieved in most cases (71%). Despite a high mean preoperative medication burden in these moderate to advanced OAG patients, the majority (79%) had a reduced preoperative medication burden at 1 year. The IOP and number of medications also significantly decreased from preoperatively in the 3-stent group (P!.001); the target IOP was achieved by 84% compared with 43% preoperatively. There was a significant reduction in medications, with 88% of eyes
DISCUSSION Samuelson et al.9 established that a single trabecular bypass stent significantly reduced IOP and medication burden at 1 year in patients having combined cataract– glaucoma implant procedures compared with patients having cataract surgery only. Studies by Fea8 and Spiegel et al.11 provide corroborating evidence of the treatment effect of a single stent. In this open-label nonrandomized prospective series, implantation of 2 or 3 trabecular bypass stents in eyes having combined cataract surgery resulted in significantly lower mean IOP at 1 year than preoperatively (P!.001), with 77% of eyes achieving the postoperative target pressure. This is despite no preoperative medication washout period. The number of glaucoma medications was also significantly decreased from 2.7 medications preoperatively to 0.7 medications at 1 year (P!.001), with 83% of eyes
Table 2. Corrected distance visual acuity at 1 year. Number (%) CDVA 20/40 or better 20/50–20/100 20/200 or worse Figure 3. The mean number of glaucoma medications used in each eye from baseline through month 12 stratified by number of stents. Bars represent the standard deviation (*PZ.009; 4PZ.04).
Overall*
2-Stent Group*
3-Stent Group
37 (64) 11 (21) 4 (8)
18 (64) 6 (21) 3 (11)
19 (76) 5 (20) 1 (4)
CDVA Z corrected distance visual acuity *Missing 1
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requiring fewer medications and 72% of eyes on no medications at 1 year. These data show high rates of IOP reduction and medication reduction with 2-stent or 3-stent implantation and the potential to achieve target IOP levels after multiple stent implantation. The significantly lower postoperative medication burden in the 3-stent than in the 2-stent group suggests that stent titration is feasible. This allows the operating surgeon to determine the appropriate number of stents required to achieve the desired postoperative target IOP. Furthermore, if necessary, it may allow the option of implanting additional micro-bypass devices in subsequent procedures to optimize the benefit-to-risk ratio while preserving future management options. No major surgical problems or postoperative complications were reported during the study. The most common complication of a blocked stent by the iris was in most cases resolved by performing a laser iridotomy that was well tolerated by the patient. In some instances, no intervention was required because the pressure was under control. The postoperative hyphema resolved within the first month without sequelae. Because of the nature of the insertion, minimal reflux of blood is an anticipated normal physiologic response immediately after stent implantation. Despite a poor preoperative CDVA in approximately one fourth of these eyes with advanced glaucoma, the CDVA improved or was maintained in most eyes and most patients achieved a postoperative CDVA of 20/40 or better. These postoperative findings are similar to those reported by others.8–11,17 Further studies are needed to refine the relationship observed between the number of stents implanted with concurrent cataract surgery and IOP control. Determining the criteria for the number of stents to implant will also require further investigation. Although the outcomes in the 2-stent group and 3-stent group were similar, we attempted to select more severe patients for implantation of 3 stents. However, our baseline analysis showed no significant difference between the 2 groups in any measure. Thus, a masked randomized trial is needed to better evaluate the relative efficacy of 2 versus 3 stents. Furthermore, this series did not use a control group having cataract surgery without stent implantation, although previous studies8,9 established the benefit of stent implantation and cataract surgery versus cataract surgery only. The 6 cases of bilateral implantation could add additional bias; however, the cases were spread evenly between the groups, minimizing the overall impact. Despite its limitations, this study contributes to the body of evidence showing the efficacy and safety of trabecular micro-bypass stent implantation and suggests that the implantation of multiple stents may be an alternative to more
invasive surgeries, such as trabeculectomy and tube shunt placement, although this would have to be evaluated in a future prospective study. The data reported by Samuelson et al.9 suggest that a single stent implanted in combination with cataract surgery achieves postoperative target pressures that are clinically meaningful for mild to moderate OAG patients with comorbid cataracts. For more moderate to advanced OAG patients with comorbid cataracts, this study found that 2 or 3 stents implanted in combined cataract procedures achieved mean IOPs that were clinically meaningful for these patients. Therefore, single and multiple implants in combined cataract procedures may be preferable to the problems of compliance (long-term morbidity and nonadherence) associated with chronic use of multiple medications to control OAG. This may also improve patient convenience and quality of life. The clinical utility and demonstrated efficacy and safety of single and multiple stent implantation enables surgeons to select the implant therapy that is most appropriate to achieve desired patient target pressures. This approach appears to offer a high benefit-to-risk ratio for a given OAG disease stage severity and desired postoperative target IOP. WHAT WAS KNOWN Implantation of 1 trabecular micro-bypass stent combined with cataract surgery is safe and can more effectively reduce IOP and topical ocular hypotensive medication use compared with cataract surgery alone. WHAT THIS PAPER ADDS The implantation of 2 or 3 trabecular micro-bypass stents combined with cataract surgery was performed safely with a reduction in IOP and topical ocular hypotensive medications. Implantation of multiple trabecular micro-bypass stents has the potential to further reduce IOP and topical ocular hypotensive medications versus implantation of 1 trabecular micro-bypass stent.
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3. Friedman DS, Jampel HD, Lubomski LH, Quigley H, Congdon N, Levkovitch-Verbin H, Robinson KA, Bass EB. Surgical strategies for coexisting glaucoma and cataract; an evidence-based update. Ophthalmology 2002; 109:1902–1913 4. Hoffmann E, Schwenn O, Karallus M, Krummenauer F, Grehn F, Pfeiffer N. Long-term results of cataract surgery combined with trabeculotomy. Graefes Arch Clin Exp Ophthalmol 2002; 240:2–6 5. Hau S, Barton K. Corneal complications of glaucoma surgery. Curr Opin Ophthalmol 2009; 20:131–136. Available at: http:// journals.lww.com/co-ophthalmology/fulltext/2009/03000/corneal_ complications_of_glaucoma_surgery.13.aspx. Accessed July 17, 2012 6. Minckler DS, Francis BA, Hodapp EA, Jampel HD, Lin SC, Samples JR, Smith SD, Singh K. Aqueous shunts in glaucoma; a report by the American Academy of Ophthalmology (Ophthalmic Technology Assessment). Ophthalmology 2008; 115:1089–1098. Available at: http://www.amo-romania.com/ Document_Files/Ophthalmology%202008%20Jun.115(6)% 20p1089-98_AqueousShuntsinGlaucoma_vdcgv5.pdf. Accessed July 17, 2012 7. Jampel HD, Musch DC, Gillespie BW, Lichter PR, Wright MM, Guire KE; and the Collaborative Initial Glaucoma Treatment Study Group. Perioperative complications of trabeculectomy in the Collaborative Initial Glaucoma Treatment Study (CIGTS). Am J Ophthalmol 2005; 140:16–22. Available at: http://new-glaucoma-treatments.com/wp-content/imagesfiles/ Perioperative%20Complications%20of%20Trab%20CIGTS. pdf. Accessed July 17, 2012 8. Fea AM. Phacoemulsification versus phacoemulsification with micro-bypass stent implantation in primary open-angle glaucoma: randomized double-masked clinical trial. J Cataract Refract Surg 2010; 36:407–412 9. Samuelson TW, Katz LJ, Wells JM, Duh Y-J, Giamporcaro JE; for the US iStent Study Group. Randomized evaluation of the trabecular micro-bypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology 2011; 118:459–467 J, Garcıa-Sa nchez J, Lamielle H. 10. Spiegel D, Garcıa-Feijoo Coexistent primary open-angle glaucoma and cataract: preliminary analysis of treatment by cataract surgery and the iStent trabecular micro-bypass stent. Adv Ther 2008; 25:453–464 €h H, Garcıa€rmer J, Ho 11. Spiegel D, Wetzel W, Neuhann T, Stu nchez J. CoexisFeijoo J, Martınez-de-la-Casa JM, Garcıa-Sa tent primary open-angle glaucoma and cataract: Interim analysis of a trabecular micro-bypass stent and concurrent cataract surgery. Eur J Ophthalmol 2009; 19:393–399
12. The AGIS Investigators. The Advanced Glaucoma Intervention Study (AGIS): 7. The relationship between control of intraocular pressure and visual field deterioration. Am J Ophthalmol 2000; 130:429–440 13. Zhou J, Smedley GT. A trabecular bypass flow hypothesis. J Glaucoma 2005; 14:74–83 14. Bahler CK, Smedley GT, Zhou J, Johnson DH. Trabecular bypass stents decrease intraocular pressure in cultured human anterior segments. Am J Ophthalmol 2004; 138:988–994 15. Chylack LT Jr, Wolfe JK, Singer DM, Leske MC, Bullimore MA, Bailey IL, Friend J, McCarthy D, Wu S-Y; for the Longitudinal Study of Cataract Study Group. The Lens Opacities Classification System III. Arch Ophthalmol 1993; 111:831–836. Available at: http://archopht.jamanetwork. com/data/Journals/OPHTH/18057/archopht_111_6_035.pdf. Accessed July 17, 2012 16. Canadian Ophthalmological Society evidence-based clinical practice guidelines for cataract surgery in the adult eye. Can J Ophthalmol October 2008; 43(suppl 1):S7–S57. Available at: http://www.eyesite.ca/CJO/43S1/i08-133.pdf. Accessed July 17, 2012 ndez-Barrientos Y, Garcia -Feijoo J, Martınez-de-la17. Ferna ndez-Pe rez C, Garcia Sa nchez J. Casa JM, Pablo LE, Ferna Fluorophotometric study of the effect of the Glaukos trabecular microbypass stent on aqueous humor dynamics. Invest Ophthalmol Vis Sci 2010; 51:3327–3332. Available at: http://www.iovs. org/content/51/7/3327.full.pdf. Accessed July 17, 2012
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First author: Graham W. Belovay, MD University of Toronto, Toronto, Ontario, Canada