EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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72 EW RESIDENTS November 2012 EyeWorld journal club Review of "Using multiple trabecular patients to treat open-angle glaucoma" by Ambika Hoguet, M.D., Timothy Sullivan, M.D., Kevin Rosenberg, M.D., Peter Chang, M.D., and Paul A. Sidoti, M.D., program director, New York Eye and Ear Infirmary, New York Paul A. Sidoti, M.D. This month, I invited the New York Eye and Ear Infirmary residents to review this paper on micro-bypass stents, which is very timely in light of the recent FDA approval of the iStent. —David F. Chang, M.D., EyeWorld chief medical editor T he iStent implant (Glaukos Corp., Laguna Hills, Calif.) is an ab interno trabecular bypass device that was recently FDA approved for use in patients with open-angle glaucoma who are undergoing cataract surgery. The iStent is among a small but growing number of min- imally invasive surgical treatments for glaucoma that are associated with significantly reduced rates of serious complications (such as infec- tion, suprachoroidal hemorrhage, choroidal effusion, and ocular hypotony) relative to traditional external drainage procedures such as trabeculectomy and aqueous shunt implantation. There is growing liter- ature supporting the relative effec- tiveness of the iStent in increasing the outflow facility of aqueous humor from the eye. Several authors have reported the effectiveness of single stent implantation in lower- ing IOP for patients with mild to moderate glaucoma.1-4 In "Using multiple trabecular micro-bypass stents in cataract patients to treat open-angle glau- coma," published in the November Using multiple trabecular micro- bypass stents in cataract patients to treat open-angle glaucoma Graham W. Belovay, M.D., Abdulla Naqi, M.D., Brian J. Chan, B.H.Sc., Mahmoud Rateb, M.D., Iqbal (Ike) K. Ahmed, M.D. J Cataract Refract Surg (Nov) 2012; 38: 1911-1917 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 post-operative IOP was 14.3 mm Hg, which was significantly lower than pre-operative IOP overall and in each group (P<.001). The target IOP was achieved in a significantly higher proportion of eyes at 1 year versus pre- operatively (77% versus 43%; P<.001). Overall, 83% of eyes had a decrease in topical ocular hypotensive medication at 1 year from pre-operatively, 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; P=.04). Conclusions: Using multiple micro-bypass stents with concurrent cataract surgery led to a mean post-operative 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. issue of the Journal of Cataract & Refractive Surgery, Belovay, et. al. discuss the effects of using multiple trabecular micro-bypass stents at the time of cataract surgery to lower IOP and reduce medication burden in patients with coexisting glaucoma and cataract. The purpose of this study was to evaluate the safety and effectiveness of multiple stent im- plantations and to determine whether additional stents provided any incremental benefit with respect to IOP reduction and the need for glaucoma medications. As glaucoma remains a leading cause of blindness worldwide, we applaud the authors for attempting to further elucidate the clinical effectiveness of this new surgical alternative for lowering IOP and potentially limiting or prevent- ing disease progression in patients with open-angle glaucoma. The current study was designed as an observational, open-label, non- randomized, prospective, single-cen- ter study. A sample size of 53 eyes of 47 patients was included. As the term observational indicates, there was no control group or random as- signment to treatment groups. Addi- tionally, both the study patients and investigators were aware of the treat- ment (i.e., the number of stents) being administered. The inclusion criteria for this study were visually significant cataract "requiring surgery" and IOP that was poorly controlled on medications or that required >3 medications for adequate control. The severity of glaucoma for each patient (mild, moderate, or advanced) was deter- mined using the clinical practice guidelines of the Canadian Ophthal- mological Society. Each patient enrolled in the study underwent implantation of two or three iStents after phacoemulsification and IOL implantation. Post-op, the IOP and visual acuity were measured at 1 day, 1 week, and 1, 3, 6, and 12 months. There was no statistically signifi- cant difference in any of the pre-op characteristics evaluated for patients in the two-stent versus the three- stent group. Overall, the results of the study pointed toward a favorable result in patients undergoing cataract extraction and multiple iStent placements. The authors reported a significant decrease in mean post-op IOP at 1 year, com- pared with the pre-op level for all patients (p<0.001), with 70% of eyes achieving an IOP of 15 mm Hg or less and 77% reaching their target IOP. This effect held up when evaluating the two- and three-stent groups separately. Although there was a slightly greater mean reduc- tion in IOP following surgery for eyes in the three-stent (mean reduc- tion 3.9 mm Hg) versus the two- stent (mean reduction 3.5 mm Hg) group, this difference did not reach statistical significance (p=0.76). The mean number of glaucoma medica- tions required to control IOP at 1 year post-op was reduced by 74% relative to the pre-op number for all patients (p<0.001). Adjunctive glau- coma medications were decreased from a pre-op average of 2.7 to an average of 0.7 one year following surgery with 83% of patients using fewer medications. Patients with three stents required significantly fewer medications at 1 year (85% mean reduction relative to pre-op number) compared with those receiving two stents (64% mean reduction relative to pre-op number) (p=0.04). During the 1-year follow-up pe- riod of the study, few complications were reported. The most common was blockage of the stent lumen, which was treated successfully using a YAG or argon laser in six of the eight eyes in which this occurred. From the authors' description, it appears that the proximal opening of the stent in the anterior chamber became obstructed in these patients. It is unclear how frequently distal obstruction of a stent (not visible on examination or amenable to laser treatment) may have occurred. Other complications included one eye with hyphema and two eyes with a presumed steroid-induced IOP elevation. As the authors point out, this is a relatively safe proce- dure for most patients. The visual acuity outcome for patients in this study is somewhat concerning. The authors report that 15 (29%) of the patients had a corrected distance vi- sual acuity (CDVA) at 1 year follow- ing surgery of 20/50 or worse. Five of these eyes demonstrated worsen- ing CDVA relative to their pre-op level. Unfortunately, no explanation for either the reduction of CDVA or failure of CDVA to improve at 1 year