An Interventional Glaucoma Solution for Long-Term Success

The PRESERFLO™ MicroShunt subconjunctival glaucoma drainage device, made from a uniquely biocompatible, degradation-resistant material called SIBS, is designed to reduce IOP in patients with primary open-angle glaucoma (1).

Since its first commercialization in 2018, over 65,000 PRESERFLO MicroShunts have been implanted globally, generating an extensive amount of real-world evidence showing that the device an effective and predictable option in a busy interventional glaucoma market that sees many devices come and go.

Attesting to the PRESERFLO MicroShunt’s success and longevity, Keith Barton, Consultant Ophthalmologist, at Moorfields Eye Hospital, and Professor of Ophthalmology at UCL, London, talks to us about his long experience with the device, and how he uses it to secure the best outcome for his patients.

How long have you been using the PRESERFLO MicroShunt, and how many surgeries have you done with it?
 

I put in the first PRESERFLO MicroShunt in the UK in May 2016. Since then, according to our International Glaucoma Surgery Registry data (IGRS. org), I have implanted just over 300.

Keith Barton

How has the PRESERFLO MicroShunt changed the way you work from a surgical perspective?
 

While I still think trabeculectomy is the most effective procedure for people with advanced glaucoma, in virgin eyes that have no failure risk factors, that number is diminishing. At one end of the spectrum, tube surgery is making more of an impact, whereas the PRESERFLO MicroShunt is impacting the other end of the spectrum. It is my go-to procedure for patients who don’t have vision-threatening field defects, for example, paracentral defects or very advanced glaucoma. In other words, patients that have had no previous surgery and whose conjunctiva is in reasonable shape.

For patients who haven’t endured years and years of eye drops, PRESERFLO is great. And the results of the INN005 study assessing the efficacy and safety of MicroShunt or trabeculectomy in patients with primary open-angle glaucoma (POAG), for example, showed that early postoperative adverse events were significantly less common overall in the MicroShunt group (2), interventions were significantly less common overall at two years postop (3), and incidences of bleb leak were proportionally lower with MicroShunt compared with trabeculectomy (p=0.113) (3). My only caveat to that is you have to be careful when using PRESERFLO in high-scarring ethnicities where the efficacy will be less.

Can you touch on why you don’t implant PRESERFLO MicroShunt at the 12 o’ clock position?
 

This goes back to trabeculectomy. Traditionally, surgeons used to position trabeculectomies in the 10 o’clock and 2 o’clock positions – you could almost tell whether the surgeon was righthanded or left-handed, according to the position of the trabeculectomy. Over the years, my colleagues and I have repeatedly emphasized the importance of performing trabulectomies at 12 o’clock in order to maximize bleb coverage by the eyelids and hence minimize the risk of uncomfortable exposed blebs which are at a higher risk of infection. With the PRESERFLO MicroShunt, however, the bleb is much further from the limbus and consequently the risk of a limbal dysfunctional bleb is much lower if the bleb is slightly temporal or nasal. In addition, due to the position of the vascular supply, the 12 o’clock position bleeds much more and also risks the PRESERFLO draining straight onto superior rectus. My preference is therefore slightly temporal because the temporal quadrant has more space and, if you do get a limbal dysfunctional bleb, temporal tends to be less dysesthetic than nasal. Overall the PRESERFLO blebs are nice – they’re really good blebs.

Can you talk about how you use stenting in the PRESERFLO procedure?
 

I’m happy to implant a PRESERFLO MicroShunt in the very elderly, high myopes, or anyone who would otherwise be at a high risk of hypotony, by inserting a ripcord inside the implant to reduce flow. I usually adjust the ripcord so there’s not too much and not too little drainage. I do not block it completely; the intention is to have a physiological IOP level on day 1. So basically, I do not stent PRESERFLOs to occlude them but simply to reduce the flow a little bit, so that the risk of hypotony is low and that hopefully the pressure in the early post-op period is fine. This takes a few minutes extra and works very well.

The mitomycin dosage is likely to be important as I did not experience any significant hypotony when using lower doses of mitomycin C. The mito itself does not cause hypotony, but if you have excessive drainage after surgery and you’ve used high doses of Mitomycin C, the hypotony is likely to be worse and for longer. Stenting takes that out of the equation for patients at higher risk e.g., in their mid-80s or older and very high myopes. There has been a randomized clinical trial of PRESERFLO, the FDA study, but lower doses of mitomycin C were used in that study than the levels we routinely use in practice. In general, with PFM you need to use higher mitomycin doses than with trabeculectomy, so now use 0.5 mg/ml for three minutes on sponges for almost everybody except the very elderly, in whom I’ll use 0.4mg/ml, but I also stent them, which removes the concern about hypotony.

What would you say about the impact and longevity of PRESERFLO MicroShunt compared to other MIGS and MIGS-like devices from the last 5-10 years?
 

Unlike canal-based MIGS, for example, PRESERFLO MicroShunt actually lowers the pressure quite significantly. There is an IRIS registry publication in Ophthalmology Glaucoma this year that reports that in a large cohort of patients, after standalone canal-based MIGS, more than 30% of patients required further glaucoma surgery in three years (4). I fear that there is a huge amount of selfdeception developing in the glaucoma community as to the benefits of canalbased surgery, borne out of the attraction of innovative procedures that have a better safety profile and are easier. Canal-based MIGS are very innovative and certainly very cool and have a good safety profile, but they are not nailing glaucoma properly for those that are uncontrolled. This is where PRESERFLO comes in. In a post hoc analysis of the FDA randomised clinical trial, PRESERFLO reduced the pressure by 40 percent at one year (2). Additionally, in my experience this procedure requires a lot less followup and a lot less intervention than a trabeculectomy, so I’m very optimistic.

Overall, the key to success is case selection. If you use PRESERFLO MicroShunt with patients where there’s a realistic chance of success, it has a high chance of working very well!

The 2023 EGS guide on surgical innovation in glaucoma (5) discussed the efficacy of PRESERFLO versus another commercially available MIBS device, Xen 45, with the panel expressing a clear opinion that PRESERFLO was more efficacious. What is your experience around this subject?
 

Overall, I prefer PRESERFLO because of the more posterior drainage bleb that is more diffuse and, in my experience, less likely to cause dysesthesia and other blebrelated problems. The caveat to that is that the difference is probably more related to surgical technique than the device itself. While the Xen is shorter, which is a disadvantage compared with the 8.5 mm PRESERFLO, I think that the difference between the two devices would be reduced where the Xen is implanted ab externo with MMC sponge application like a PRESERFLO.

Mitomycin C (MMC) is not approved for the specific use shown in this presentation. Long term effects of MMC with the use of this device have not been evaluated. Necessary precautions and interventions on the use of MMC are highly recommended.

The PRESERFLO^® MicroShunt glaucoma drainage system is intended for reduction of intraocular pressure in eyes of patients with primary open-angle glaucoma where IOP remains uncontrollable while on maximum tolerated medical therapy and/or where glaucoma progression warrants surgery. Please read the PRESERFLO^® MicroShunt Instructions for Use carefully and complete the relevant training before using the device.

Adverse events should be reported. Reporting forms and information can be found at www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. Adverse events should also be reported to Santen UK Limited (email: medinfo@santen.co.uk or telephone: 0345 075 4863).

This sponsored feature was commissioned by Santen.

^{PMS-UKIE-240034 Date of preparation:
October 2024}

Preserflo Instructions for Use - UK | Santen