PRESERFLO MICROSHUNT DEVICE

 

The PRESERFLO MicroShunt is an ab externo glaucoma drainage device made of an extremely flexible SIBS [poly (Styrene-block-IsoButylene-block-Styrene)] polymer with a tube of 350 μm outer diameter and a lumen of 70 μm. 

It has triangular fins that prevent migration of the tube into the AC. The device is designed to be implanted under the subconjunctival/Tenon space.

SIBS (Poly(styrene-block-isobutylene-block-styrene)) is a uniquely biocompatible, degradation-resistant material proven to minimize inflammation, scarring, and encapsulation.

Contraindications to implantation of the PRESERFLO Microshunt may include cases of shallow anterior chamber, inability of the patient to adhere to postoperative visits and/or medications, and/or intolerance or allergy to Mitomycin-C (MMC).

SURGICAL TECHNIQUE:

A 3 to 4 clock-hour fornix-based conjunctival peritomy is created – typically in the superonasal or superotemporal quadrants. Mitomycin-C soaked sponges are then applied to the scleral bed.

Mitomycin-C concentration and duration of applications are left to the surgeon’s discretion based on judgment of risk for postoperative fibrosis.

After removal of the sponges, the scleral bed is rinsed with balanced salt solution.

The sclera is then marked 3 mm posterior the limbus.

A scleral tunnel is initiated at this point along the curvature of the globe, followed by change trajectory at the level of the trabecular meshwork before entering the anterior chamber parallel to the iris plane.

The device is then inserted through this tract using non-toothed forceps, with care to maintain the proximal tip in a bevel-up position.

The device is advanced until the fins are just tucked within the distal end of the scleral tunnel.

In this position, 2 to 3 mm of the proximal end of the device should extend into the mid-anterior chamber and parallel to iris plane.

When properly positioned and unobstructed, aqueous flow should be visible at the distal end of the device. If no flow is visible and an obvious proximal obstruction is not visualized, the distal end may be “primed” using an anterior chamber cannula and balanced salt solution. A corneal paracentesis may be created at surgeon discretion for additional control of the anterior chamber or to test device patency via injection of balanced salt solution.

Once the device has been placed and flow has been verified, conjunctiva and Tenon capsule are repositioned over the device, taking care to avoid distal obstruction of implant.

The distal end of the implant should lie flush with the sclera and a second instrument may be used to direct it in this manner.

The conjunctiva and Tenon capsule are then closed using the surgeon’s preferred technique.

A fluorescein strip is used to confirm adequate wound closure and the eye is protected according to the surgeon’s usual protocol.

RESULTS:

Studies have largely shown positive outcomes with the PRESERFLO Microshunt device. The success rates with this device are comparable to trabeculectomy success rates. However, higher doses of MMC are associated with better results.