David F. Chang, MD

The IOP-lowering effect of phacoemulsification alone is not as consistent and as predictable as ophthalmologists would like.1 As a busy cataract surgeon, I therefore anticipate that the iStent Trabecular Micro-Bypass Stent (Glaukos Corporation) will become a commonly used adjunctive device for many of my patients who have mild to moderate glaucoma. All cataract surgeons see a significant number of patients who would be candidates for this combined procedure. Because the trabecular microbypass stent spares conjunctival tissue and avoids the risks of bleb-related complications and hypotony, it represents an adjunctive procedure with a therapeutic upside and virtually no downside. I do believe that longterm studies comparing IOP reduction with combined phacoemulsification and the iStent versus phacoemulsification alone are needed, however, and I look forward to the results.

I participated in a Glaukos-sponsored trial in Armenia, where I had the opportunity to implant dozens of the devices in phakic eyes. The learning curve was fast, the procedure was quick, and the device should be even easier to implant in the pseudophakic angle. The preliminary data showed a convincing reduction in IOP in this setting where there was no phacoemulsification to confound or enhance any IOP lowering effect.2

I will certainly recommend the implantation of the iStent to lower IOP in patients undergoing cataract surgery who have mild to moderate glaucoma that is under borderline control. The prospect of reducing the number of required glaucoma medications will also appeal to patients currently enjoying good IOP control. When the alternative is trabeculectomy, most patients are grudgingly able and willing to put up with the cost, inconvenience, and side effects of topical medication. We physicians, however, worry about pharmaceutical compliance: we never really know how many doses each of our patients misses on average. Moreover, we all became spoiled when latanoprost was first approved to replace pilocarpine as second-line therapy and, eventually, timolol as a first-line drug. Unfortunately, a growing awareness of prostaglandin-associated periorbitopathy is making us realize that every drug category still has significant potential side effects.

For many patients, cataract surgery has become an opportunity to have their first refractive procedure. It now presents the opportunity to have a simultaneous glaucoma surgical procedure.

David F. Chang, MD, is a clinical professor at the University of California, San Francisco, and he is in private practice in Los Altos, California. He has received travel reimbursement from Glaukos Corporation for participation in the company's international trial. Dr. Chang may be reached at (650) 948-9123; dceye@earthlink.net.

  1. Chang TC, Budenz DL, Liu A, et al. Long-term effect of phacoemulsification on intraocular pressure using phakic fellow eye as control. J Cataract Refract Surg. 2012;38:866-870.
  2. Chang DF; Micro-Invasive Glaucoma Surgery (MIGS) Study Group. Intraocular pressure reduction following micro-invasive glaucoma surgery to implant two trabecular micro-bypass stents in OAG. Paper presented at: ASCRS/ASOA Symposium and Congress; April 20-24, 2012; Chicago, IL.

Richard A. Lewis, MD

The launch of the iStent Trabecular Micro- Bypass Stent (Glaukos Corporation) has received more fanfare and notoriety than any other procedure for treating glaucoma since the introduction of laser trabeculoplasty in the 1980s. Considered the classic procedure for microinvasive glaucoma surgery, the iStent is safe and effective, and it is placed through a small ab interno incision. Glaucoma surgery has had few, if any, procedures that fit this description and successfully pass the rigor of a randomized FDA-sponsored clinical trial.

The launch of the first devices for microinvasive glaucoma surgery mandates that clinicians re-evaluate their surgical approach to glaucoma. Until now, glaucoma surgery was truly interventional, requiring patients to understand the risks and surgeons to be skilled at addressing these problems. The true talent of the glaucomatologist is managing postoperative problems, but this is not as relevant for the iStent. Rather, the challenge depends on the surgeon's skill at identifying angle anatomy in order to place the device correctly in the canal and, ideally, near a collector channel. There is little in the way of postoperative care that affects the outcome.

Very few problems were noted postoperatively in the iStent's FDA clinical trials. With concerns about complications minimized, the criteria for considering a procedure combining the placement of the device with cataract extraction will change. IOP lowering without significant surgical risk implies that patients with marginal pressure control will be good candidates for the combined procedure, as will be those who use topical IOP-lowering drugs daily without reliably achieving their target IOPs. This situation is very different than for trabeculectomy, which is typically recommended to address progressive visual field loss despite maximal medical and laser therapy. In other words, I predict that the list of indications for glaucoma surgery will increase. Moreover, the “bar” for combining procedures to include the iStent will be lowered. Perhaps clinicians will consider the device to reduce their patients' dependence on medication or simply to eliminate their notorious problem with adherence.

Not all glaucoma patients require IOPs in the low teens. Some, perhaps many, maintain good visual function with an IOP consistently in the mid- to high teens. I look forward to a time when I can place one (or more) iStent as my fellow clinicians and I learn to modulate IOP and prevent diurnal fluctuation. Will this device eliminate such variation in pressure? Will a more controlled IOP in the mid- to high teens without diurnal fluctuation decrease visual field loss? This is the start of a new era in glaucoma surgery when these important questions may be answered.

Richard A. Lewis, MD, is in private practice in Sacramento, California. He has served as an investigator for Glaukos Corporation and is a consultant to Alcon Laboratories, Inc.; AqueSys, Inc.; Ivantis Inc.; and iScience Interventional. Dr. Lewis may be reached at (916) 649- 1515; rlewiseyemd.yahoo.com.

Richard L. Lindstrom, MD

The approval of the iStent Trabecular Micro- Bypass Stent (Glaukos Corporation) is important to my practice. I have been impressed by the ability of cataract surgery alone to reduce IOP and the burden of medication on patients with glaucoma. In studies at Minnesota Eye Consultants, however, my colleagues and I found that the typical patient with mild to moderate glaucoma required at least one medication—usually a prostaglandin analogue or a b-blocker and, in some cases, both—to maintain a target pressure of approximately 18 mm Hg 1 year after cataract surgery.1,2 I would like to see my patients' pressures closer to 15 mm Hg, and my patients would like to reduce the number of medications they require to a minimum. Studies of the iStent inside and outside the United States confirmed that its implantation concurrent with cataract surgery lowers the IOP 2 to 3 mm Hg more than cataract surgery alone and reduces the burden of medication.3,4

I will offer the iStent to all patients who require cataract surgery and depend on IOP-lowering medication. The benefit is meaningful, and in the US FDA clinical trials, the added risk was essentially zero. Assuming third-party reimbursement, I expect the majority of my patients to find the risk-benefit-cost ratio to be attractive. I will certainly encourage those with glaucomatous damage and a dependence on medical therapy to strongly consider this option, and I expect initially to implant the device in about 10% of my cataract surgery patients. For individuals with severe, poorly controlled glaucoma, I intend to continue to enlist the support of one of my glaucoma subspecialty-trained partners, because many of these patients need target pressures closer to 12 mm Hg and will likely require a trabeculectomy or tube shunt surgery. When a patient presents with ocular hypertension but no nerve damage or need for IOP-lowering medication, for now, I will continue to perform cataract surgery alone.

As I gain more experience with the iStent, the outcomes of my own patients will guide my future position on the device's indications, but I anticipate that they will become broader rather than narrower. For now, glaucoma patients with only mild to moderate nerve damage requiring medical therapy for IOP control who request surgery for a visually significant cataract will be my target patients for the device.

Richard L. Lindstrom, MD, is the founder of and an attending surgeon at Minnesota Eye Consultants, PA, in Bloomington, Minnesota. He is a consultant to Abbott Medical Optics Inc., Alcon Laboratories, Inc., AqueSys, Glaukos Corporation, and Transcend Medical. Dr. Lindstrom may be reached at (612) 813-3600; rllindstrom@mneye.com.

  1. 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;34:735-742.
  2. Poley BJ, Lindstrom RL, Samuelson TW, Schulze R JR. Intraocular pressure reduction after phacoemulsification with intraocular lens implantation in glaucomatous and nonglaucomatous eyes: evaluation of a causal relationship between the natural lens and open-angle glaucoma. J Cataract Refract Surg. 2009;35(11):1946-1955.
  3. Samuelson TW, Katz LJ, Wells JM, et al; US iStent Study Group. Randomized evaluation of the trabecular microbypass stent with phacoemulsification in patients with glaucoma and cataract. Ophthalmology. 2011;118(3):459-467.
  4. 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(3):407-412.

Barbara A. Smit, MD, PhD

Mrs. Jones is visibly upset when I enter the room for her visit. Once again, she tells me, she has run out of eye drops and has not taken any since last Thursday. She asked her pharmacist for a refill, but she was told that she would not be eligible for another 10 days and that her insurance would not cover an early refill. Because of her arthritis, she finds it difficult to administer her drops; she inadvertently squeezes too hard and gets a stream of medication instead of a single drop. Her husband tries to help, but his vision is too poor. She is very worried, because her mother lost her sight to glaucoma and the patient knows she should be using her drops consistently. Sure enough, when I check her IOP, it is above the target range.

Regrettably, situations like the one I described frequently occur in my practice. Glaucoma patients find it difficult to comply with prescribed medical therapy for myriad reasons: cost, an inability to administer eye drops effectively, an intolerance of side effects, poor understanding, and lack of interest. I am referring to those patients whose poor adherence is apparent to me. Multiple articles have shown that compliance with prescribed therapy is even worse than most clinicians think.

I am pleased to have an alternative treatment available for those of my glaucoma patients who also require cataract surgery. I intend to offer the iStent Trabecular Micro-Bypass Stent (Glaukos Corporation) to patients with mild to moderate glaucoma who need cataract surgery and who I feel are good candidates based on the appearance of the angle of their eye. I see the device as a safe treatment for patients who I know have difficulty using their eye drops and those who would simply prefer to be less dependent on medical therapy.

Barbara Smit, MD, PhD, is a glaucoma consultant at the Spokane Eye Clinic and a clinical instructor at the University of Washington School of Medicine in Spokane, Washington. She is an investigator in a trial by Glaukos Corporation. Dr. Smit may be reached at (509) 456-0107; bsmit@spokaneeye.com.