Surgeons present varied uses of iStent

John Berdahl, MD, and Carlos Buznego, MD, discuss different ways to use the device in glaucoma patients.

Issue: November 25, 2015

Welcome to another edition of CEDARS/ASPENS Debates. CEDARS/ASPENS is a joint society of cornea, cataract and refractive surgery specialists, here to discuss some of the latest hot topics in ophthalmology.

There has been much written recently about the use of the iStent (Glaukos), a newer surgical device for the treatment of glaucoma. Rather than our usual format of the two authors debating the merits of this device, John Berdahl, MD, and Carlos Buznego, MD, will each give their perspective on attributes of the iStent. Each opinion addresses somewhat controversial uses of the iStent, with the authors stating their case for use in these situations. We hope you enjoy the discussion.

Kenneth A. Beckman, MD, FACS
OSN CEDARS/ASPENS Debates Editor

iStent and pseudophakia

The iStent has filled an incredible void in the clinical management of glaucoma. Because the iStent is the first glaucoma device ever to be approved through the premarket approval process, it has some of the most robust data supporting its efficacy ever produced by a glaucoma device. The label for the iStent shows that its indication for use is in the treatment of mild to moderate open-angle glaucoma in combination with cataract surgery. The reason why the label states “in combination with cataract surgery” is because the trial was performed in conjunction with cataract surgery. The obvious question becomes, is it effective in the absence of cataract surgery?

We, as physicians, perform off-label treatments all the time. For example, no antibiotic has been approved for the prevention of endophthalmitis after cataract surgery; however, the standard of care is to give every patient antibiotic prophylaxis for the prevention of endophthalmitis. Off-label use is not synonymous with “cowboy care” or unjustified treatment. When used judiciously, off-label use is simply applying the technologies and treatments that we know or believe to be best for our patients in a particular situation. Oftentimes evidence-based medicine is not applicable to an individual’s situation, or available data exist to support a treatment modality but not enough to get FDA labeling.

With all that in mind, it makes sense that using the iStent in pseudophakic individuals should lower IOP by bypassing the trabecular meshwork system. Studies by Poley and colleagues have shown that cataract surgery lowers IOP by itself. In fact, the Glaukos FDA trial is the best data in existence demonstrating cataract surgery alone lowers IOP. However, cataract surgery plus an iStent lowers IOP more. Samuelson and colleagues studied the iStent in pseudophakic individuals and found that pseudophakic iStents lower IOP. We also have used the iStent in pseudophakic patients and presented this data at the American Society of Cataract and Refractive Surgery meeting in 2014. We found that IOP was lowered on average 4.1 mm Hg by iStent alone in pseudophakic individuals, and there was a decrease in the medication burden by roughly 40%.

The job of a physician is to combine the available evidence, individual experience and logical approaches to provide the best treatment possible for patients in their moment of vulnerability. The beauty of being a physician is we can always ask ourselves, “What would I do if it were my eye?” If I were pseudophakic and had progressive glaucoma or could not tolerate medications and needed further intervention, I would definitely choose an iStent before a trabeculectomy or a tube shunt because of the morbidity shown in the Tube Versus Trabeculectomy Study and the safety and efficacy shown by the iStent both in combination with cataract surgery and in pseudophakic individuals.

References:
Ferguson TJ, et al. Evaluation of trabecular micro-bypass stent in pseudophakia. Paper presented at: ASCRS-ASOA symposium and congress; April 2014; Boston. https://ascrs.confex.com/ascrs/14am/webprogram/Paper4104.html.
Gedde SJ, et al. Am J Ophthalmol. 2012;doi:10.1016/j.ajo.2011.10.026.
Poley BJ, et al. J Cataract Refract Surg. 2008;doi:10.1016/j.jcrs.2007.12.045.
Samuelson TW, et al. Ophthalmology. 2011;doi:10.1016/j.ophtha.2010.07.007.
Samuelson TW. Phakic or pseudophakic OAG subjects implanted with 2 trabecular bypass stents: 18-month findings. Paper presented at: ASCRS-ASOA symposium and congress; April 2014; Boston. https://ascrs.confex.com/ascrs/14am/webprogram/Paper5159.html.

For more information:
John Berdahl, MD, can be reached at Vance Thompson Vision, 3101 W. 57th St., Sioux Falls, SD 57108; email: johnberdahl@gmail.com.

Disclosure: Berdahl reports he is a consultant for Glaukos.

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Combining presbyopic IOL surgery with iStent

The iStent has been available to U.S. surgeons for more than 3 years, and it is gaining popularity among anterior segment surgeons as an innovative and effective way to manage patients with visually significant cataract and coexistent open-angle glaucoma. When this procedure is combined with presbyopic IOL implantation, we can help patients become not just glasses-free, but also drop-free — a true win-win for both patients and doctors.

Although glaucoma can be a relative contraindication to implantation of multifocal IOLs, careful selection of candidates can allow surgeons to offer improved visual function to these patients. Obvious contraindications include uncontrolled IOP, central or paracentral scotomas, and prior penetrating glaucoma surgery, while family history of glaucomatous blindness and use of more than three medications are relative contraindications for presbyopic IOL implantation.

In 2013, we published our results comparing multifocal IOL implantation in glaucoma patients with a control group of patients with glaucoma. Visual acuity results in the two groups revealed no statistically significant difference in uncorrected or best corrected visual acuity.

In order to achieve the best results with presbyopic IOL surgery, we must strive for rapid healing and avoidance of ocular inflammation. Surgeons must utilize a procedure that is as atraumatic as possible. Clearly a minimally invasive glaucoma surgery would be the natural procedure to pair with presbyopic IOL implantation. The iStent is the ideal approach because it utilizes no additional incisions or manipulations other that the straightforward implantation of the iStent into the trabecular meshwork to facilitate aqueous drainage into Schlemm’s canal. Eyes that undergo cataract surgery and iStent implantation are quiet and indistinguishable in the postop clinic from eyes that undergo cataract surgery alone.

Obviously, presbyopic IOL patients’ expectations are high, and we must take great measures to avoid complications. The FDA clinical trial results confirm that the iStent has a superb safety profile. Complication rates comparing cataract surgery alone with cataract surgery plus iStent were identical.

Surgeons are continually striving to improve surgical approaches in an effort to meet ever-increasing patient expectations. Patients with coexistent cataract and glaucoma who desire to reduce dependence on glasses can be effectively managed by combining cataract surgery/presbyopic IOL with MIGS utilizing the implantation of the iStent.

References:
Kotha A, et al. Visual outcomes of glaucoma patients receiving presbyopia-correcting IOLs. Poster presented at: ASCRS; March 2013; San Francisco. http://ascrs2011.abstractsnet.com/acover.wcs?entryid=000083.
Samuelson TW, et al. Ophthalmology. 2011;doi:10.1016/j.ophtha.2010.07.007.

For more information:
Carlos Buznego, MD, can be reached at Center for Excellence in Eye Care, Baptist Medical Arts Building, 8940 North Kendall Drive, Suite 400-E, Miami, FL 33176; email: cbuznego19@gmail.com.

Disclosure: Buznego reports he is a consultant, lecturer and shareholder for Glaukos.