Moving to next pathway
With the recent approval of another device (CyPass Micro-Stent, Alcon Laboratories), the suprachoroidal space may be the next step for patients who need additional control following an iStent. While natural drainage is known to occur through the uveoscleral pathway and attempts have been made at cyclodialysis for over 100 years, overall it is a space that is not well understood and comes with a higher risk-to-benefit ratio for the glaucoma patient.
Initial data for a CyPass inserted at the time of cataract surgery in patients with IOP >21 mm Hg show a mean IOP at baseline of 25.5 mm Hg reduced to a mean of 15.8 at 24 months of follow-up.6
Medications also reduced from a mean of 2.2 at baseline to a mean of 1.0 at 24 months. Transient hypotony occurred in 15.4% of subjects and micro-stent obstruction, typically due to iris overgrowth, occurred in 8.8% of subjects.
One concern with utilizing the suprachoroidal space is the chance of scarring. We do not yet have long-term data to show if this pathway retains patency over the long-term but the rate of secondary procedures (18.5%7, 11%6) required to manage glaucoma noted in published studies needs to be taken into consideration. Early hypotony is likely the biggest initial concern.
By definition, this device is making a cyclodialysis and holding it open so that it cannot heal spontaneously. An implantation with too many lateral movements may allow extra flow resulting in transient hypotony.
Although early hypotony is not usually severe, patients can expererience blurred vision and are less happy.
Surgeons also have to worry about the sequela of low pressure and sequela that can negatively affect visual outcomes including choroidal effusions and hyphemas.
The device is also placed closer to the iris, making it more susceptible to trauma. Simply put, the risk of working in the suprachoroidal space is a step up from that of working in the trabecular meshwork space.
The CyPass may also be an option for initial therapy in a person who is not a candidate for an iStent. Patients that had a lot of argon laser trabeculoplasty and have little spots throughout the trabecular meshwork, or perhaps have visible scarring from other causes, often cannot restore sufficient flow in this area.
Having another lower-risk option is helpful, and this remains true for other therapies (Xen Gel Stent, Allergan; the InnFocus Micro-Shunt, Transcend Medical).