Two new Micro-Invasive Glaucoma Surgery (MIGS) implants gained FDA approval in 2016: the Alcon CyPass Micro-Stent® and the Allergan XEN® Gel Implant. Of these, only the CyPass Micro-Stent® offers a bleb-free method of reducing intraocular pressure (IOP).
The CyPass Glaucoma Micro-Stent® is the first FDA approved implant that lowers IOP by shunting fluid from the anterior chamber into the supraciliary space (between the iris root and the sclera (wall of the eye). This allows fluid to leave the eye without the formation of a bleb. Additionally, as it does not require an intact collector channel system, it has the potential to work in patients who would not be candidates for the other bleb-free Micro-Invasive Glaucoma Surgeries: Ab-Interno Canaloplasty (ABiC) and iStent.
Note: Cypass Micro-Stent starts at 4:38 mark.
Unlike Ab-Interno Canaloplasty (which can be performed with or without cataract surgery), both the iStent and the CyPass Micro-Stent® are FDA approved as a treatment of glaucoma only when combined with cataract surgery. This limited approval complicates things a bit as it’s now well accepted that cataract surgery alone can reduce IOP. Thus, the only way to tell how well the CyPass Micro-Stent® works is to compare the results of glaucoma patients who had cataract surgery alone to those who had cataract surgery plus placement of the CyPass Micro-Stent®.
Such a study was performed and the results were presented at the American Glaucoma Society (AGS) 2017 Annual Meeting in Coronado, CA by Dr. Quang Nguyen. This was a good sized, prospective, randomized study of 505 patients with mild to moderate glaucoma and visually symptomatic cataracts.
Patients were followed for two years after surgery at which time the average IOP (without medications) of those who had cataract surgery alone dropped by just over 5mmHg. The average IOP of those who had both cataract surgery and CyPass Micro-Stent® was 7mmHg.
At first blush, a 2mmHg difference may not seem like much. And, had these been patients with severe or “end-stage” glaucoma such results might have been worthy of little more than a yawn. However, these patients only had mild to moderate glaucoma. The earlier the stage of glaucoma, the less aggressive the IOP lowering must be in order to achieve adequate protection.
It should also be noted that the safety profile of the CyPass Micro-Stent® was excellent. As with other Micro-Invasive Glaucoma Surgeries, there was a small risk of hyphema (blood in the front of the eye), inflammation, IOP elevation, as well as hypotony (IOP that was too low). Final vision was similar in both cataract surgery only and cataract surgery plus CyPass Micro-Stent® groups.
Although the absolute IOP lowering benefit of the CyPass Micro-Stent® may be pretty far from a “mic drop”, this newly available Micro-Invasive Glaucoma Surgery adds an important treatment option for those with both mild to moderate glaucoma and vision-limiting cataract. Because it shunts fluid into a space not used by any other currently FDA approved glaucoma treatment it could also potentially be added to other treatments.
In theory, it may someday be possible to perform multiple low-risk glaucoma surgeries (each only reducing the IOP by 2-3mmHg) in order to add up to an IOP lowering benefit in the same range as one might expect from a glaucoma drainage device but with far less risk. Of course, as with all new treatments, insurance coverage will ultimately determine whether what is possible is also financially practical.
- Vold S, Ahmed II, Craven ER, et. al. CyPass Study Group. Two-Year COMPASS Trial Results: Supraciliary Microstenting with Phacoemulsification in Patients with Open-Angle Glaucoma and Cataracts. Ophthalmology 2016 Oct;123(10):2103-12.
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About the Author: David Richardson, MD
Medical Director, San Marino Eye
David Richardson, M.D. is widely recognized as one of the top cataract and glaucoma surgeons in the US and is among an elite group of glaucoma surgeons in the country performing the highly specialized canaloplasty procedure. Morever, Dr. Richardson is one of only a few surgeons in the greater Los Angeles area that performs Micropulse® "Cyclophotocoagulation" (MP3) glaucoma laser surgery. Dr. Richardson graduated Magna Cum Laude from University of Southern California and earned his Medical Degree from Harvard Medical School. He completed his ophthalmology residency at the LAC+USC Medical Center/ Doheny Institute. Dr. David Richardson is also an Adjunct Assistant Professor of Clinical Ophthalmology at Keck School of Medicine of USC. Twice weekly, he treats veterans at the VA Greater Los Angeles Veterans Healthcare System.
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