PreserFlo Microshunt occlusion

Bonatti et al have presented the successful resolution of early fibrin occlusion of PreserFlo MicroShunt with Nd:YAG laser treatment. It is regarded as the first reported case of such a nature.

The PreserFlo microshunt device is indicated in patients with moderate or advanced open-angle glaucoma who require further intraocular pressure (IOP) reduction to prevent disease progression. 

The 70-mm lumen implant redirects aqueous fluid from the anterior chamber to the subtenon space. The microshunt works immediately after its implantation, significantly reducing the IOP, typically in the single digits on the initial post-operative period.

Obstruction of the implant lumen can reduce the aqueous flow through the shunt and prevent this pressure reduction.

The authors performed a PreserFlo MicroShunt implant with phacoemulsification and acrylic intraocular lens implantation on the left eye of a 64-year-old male patient with primary open-angle glaucoma (POAG).

On the first postoperative day, he presented with an uncomfortable left eye with best corrected visual acuity (BCVA) of 6/15, mild corneal edema, and a centered intraocular lens. No filtering bleb was observed and IOP in that eye was 39 mmHg. The intracameral portion of the PreserFlo MicroShunt was in a good position in the anterior chamber, but fibrin strands were observed in the AC going toward the internal ostium of the shunt.

Apparently, the fibrin deposition was limiting drainage through the shunt. The authors used neodymium-doped yttrium aluminum garnet (Nd:YAG) laser to clear the obstructing material. 

The material was lysed under direct visualization using 10 single shots with a power of 1.1 mJ. 

Upon breaking the material, the authors immediately observed a fibrin strand being aspirated into the shunt lumen, indicating patency of the implant. However, 10 minutes after the procedure, the filtering bleb remained flat, and the IOP was 38 mmHg, without any evidence of fibrin in the anterior chamber.

It was suspected that the previously noted fibrin strand was trapped inside the shunt lumen and the patient underwent another laser procedure. 

With the aid of a Ritchie lens, the authors lasered the midsection of the shunt's lumen under the conjunctiva. Two single shots were given with a power of 1.0 mJ until gas bubbles were observed inside the lumen. After 15 minutes, the patient was symptomatically comfortable, an elevated filtering bleb was observed, and the IOP was 12 mmHg. 

At the 1-week postoperative visit, there was no evidence of fibrin in the AC, BCVA was 6/6 and IOP was 4 mmHg. 

At his last visit, 12 months after surgery, his IOP was 15 mmHg with brimonidine-timolol combination twice daily.

REFERENCE:

Bonatti R, Hodgson K, Nicolela M. Successful resolution of early fibrin occlusion of PreserFlo MicroShunt with Nd:YAG laser treatment. Can J Ophthalmol. 2025 Jun;60(3):e482-e485. doi: 10.1016/j.jcjo.2025.01.003. Epub 2025 Feb 6. PMID: 39870357.