A new MIGS in a new space

An investigator for the CyPass Micro-Stent offers advice on training, the learning curve and patient selection.

By Steven R. Sarkisian, Jr., MD

As a glaucoma specialist, I have witnessed the reasons why surgical treatment is often the most effective treatment for glaucoma, a leading cause of blindness worldwide.

Since the mid 2000s, with the introductions of the ExPress mini-shunt and canaloplasty, we have found more efficient and safe ways to lower IOP. More recently, with the advent of trabecular micro-bypass with the iStent (Glaukos), when combined with cataract removal, we have been able to lower IOP even more safely and treat patients earlier, rather than when patients are desperate and already have had advanced damage. Patient compliance is also improved with the reduction in the number of medications.

After the introduction of the iStent, and with several future MIGS (micro-invasive glaucoma surgery) devices in active clinical trials, a joint meeting between the American Glaucoma Society and the FDA took place two years ago at the AGS annual meeting in Washington, DC, which helped define MIGS, how they should be tested in trials, and what their parameters are.

In July, the FDA approved the CyPass (Alcon), for patients with mild to moderate, open-angle glaucoma and cataracts. Here, placement is in the supraciliary part of the eye, and based on results of the COMPASS trial, patients have experienced remarkable results. Data from this trial, presented at AAO 2016, demonstrated a statistically significant drop in IOP with CyPass combined with phacoemulsification, compared with phacoemulsification alone, as well as a significant reduction in medications (See “More on COMPASS, page 56).

Figure 1. UBM of the CyPass in the angle.
Figure 2. The CyPass in the angle after implantation.

Personal observations

Alcon started a controlled release of the CyPass starting with AAO 2016 in Chicago. As an initial clinical trial investigator for the CyPass I can provide information on how to implant the CyPass, the learning curve and patient selection.

A training tale

But first, a story about the CyPass’ learning curve.

Last September, I traveled to the Sinskey Eye Hospital in Addis Ababa, Ethiopia on an ASCRS Foundation-funded trip to teach the Sinskey Eye Hospital doctors how to implant the CyPass. For those of you who are unfamiliar with sub-Saharan African and cataract-related blindness, a BMJ article from 2013 pointed out that between 21% and 67% of blindness in these countries is due to cataracts. (In 2015, says the ASCRS website, the hospital was slated to perform 1,500 cataract surgeries, either via phaco or manually.)

The training time was quick; the Ethiopian surgeons’ learning curve was very short for implanting the CyPass. The main barriers were the same that you would expect with any surgeon performing gonioscopic surgery for the first time. They quickly learned how to hold a surgical gonioprism in their nondominant hand, how to properly inflate the anterior chamber with viscoelastic, and how to correctly implant the MIG itself.

It was really gratifying to see how the excellent phaco surgeons at the Sinskey were able to adopt the necessary techniques.

Surgical suggestions

To maximize visibility of the angle, I recommend not pushing too hard or too gently on the cornea with the gonioprism. If you push too hard, you will get striae in the cornea; push too gingerly, and you will get air in the interface.

Moreover, overfilling the anterior chamber with viscoelastic will distort the angle landmarks, while under-filling with viscoelastic might cause the iris to billow anteriorly and obstruct your view. Finally, make your incision anterior to any blood vessels during cataract surgery, which avoids blood getting into the interface between the gonioprism and the cornea during the procedure.

The Goldilocks factor

Many surgeons might feel intimidated by placing an implant into the superciliary space; however, due to the anatomy of the eye, the stent cannot go through the scleral wall. It stays behind the pars plana and will not make a hole in the retina. Because the implant is designed to solely fit into the superciliary space, if it does slide, it will not move out of the superciliary space.

Which brings me to my next point: It is recommended that you do not implant the CyPass beyond the first of its three retention rings.

Over-implanting the CyPass will cause the iris to obstruct it; under-implanting it will allow contact with the cornea.

As you start out, I think it is important to remove all the viscoelastic from the capsular bag after the lens is placed, and consider placing some Miostat (carbachol intraocular solution, USP) or Miochol (acetylcholine chloride intraocular solution, Bausch + Lomb) into the anterior chamber to bring the pupil down to maximize your view, particularly if you are less experienced with angle surgery.

Once the pupil is brought down, place a cohesive viscoelastic in the anterior chamber, then load the CyPass onto the injector system (place viscoelastic onto the cornea before positioning the microscope and patient). To place the device into the eye, as you go across the eye to do so, turn the implant to the side so that it enters in a planar fashion, returning it upright before implantation.

Once the CyPass is in position, locate the scleral spur and engage the tip of the CyPass posterior to the scleral spur and gently push posteriorly. If in the correct position, the implant will start to disappear into the superciliary space. Take care to avoid the three or nine o’clock position due to the ciliary plexus’ presence. Some localized bleeding after the implantation is expected — this is usually resolved by postop day one.

Finally, remove the viscoelastic from the eye, and check and hydrate the wounds.

Figure 3. An animated view of the CyPass in the supraciliary space.

Picking your patients

When selecting patients, I recommend starting with those who have mild to moderate glaucoma and are controlled on one or two medicines. Once you develop experience with implanting the CyPass, you could certainly treat patients who are not controlled on one or two medicines; however, inform these patients that they may still require medications.

Conclusion

The CyPass is a proven new weapon in our fight against glaucoma. Thus far, the superciliary space has not been explored during the modern era of glaucoma surgery. Historically, cyclodialysis clefts — created on purpose or as a result of trauma — can have disastrous results when the cleft closes abruptly or as a result of severe hypotony. However, with the CyPass, because of its small size, hypotony is extraordinarily rare and the presence of the CyPass prevents closure.

This will be an interesting year as MIGS surgeons explore how to fit the CyPass into current treatment patterns. OM

ARTICLES REFERENCED:

About the Author

Steven R. Sarkisian, Jr., MD, is the director of the glaucoma fellowship at the Dean McGee Eye Institute and serves as a clinical professor of ophthalmology at the University of Oklahoma in Oklahoma City. He has been a primary investigator in most of the seminal clinical trials for glaucoma, including the TVT study, the ABC study, the ExPress vs Trab study, and the FDA clinical trials for the CyPass implant, the iStent inject and iStent Supra implants, and the iDose sustained release travoprost implant.