A Novel Glaucoma Implant: A Comparative SIBS vs. PDMS Study in Normal Rabbit Eyes

Abstract

 

Purpose:

 

To compare the clinical findings, flow patency and histopathological results of the Miami–InnFocus Drainage Implant (the MiDi) made of poly(styrene–b–isobutylene–b–styrene) ("SIBS") versus silicone rubber (PDMS) controls implanted in normal rabbits eyes.

 

Methods:

 

The MiDi is a 11 mm long tubular implant (outer diameter = 0.25 mm, lumen = 0.07 mm) made of SIBS (poly(styrene–b–isobutylene–b–styrene), InnFocus LLC, Miami, FL). In 16 New Zealand white healthy rabbit eyes, the proximal end of the MiDi was inserted into the anterior chamber (AC) in the superotemporal quadrant, 2 mm posterior to the limbus, while the distal end was placed in the subconjunctival space. A control group of 9 healthy rabbit eyes was implanted with similar tubes made from PDMS, using the same surgical technique. Intraocular pressure (IOP) measurements and slit lamp follow–up were recorded immediately after surgery and at 1, 3, 7, 14, 21, 30, 60 and 90 days post–surgery. For long term biocompatibility determination, 4 rabbits are currently past 8 months. Flow patency (using 0.01% fluorescein injections into the AC), light microscopy and immunostaining against collagen IV, macrophages and α–smooth muscle actin (SMA) were performed at 3 and 6 months.

 

Results:

 

Three and 6 months results for the SIBS and PDMS devices are tabulated below (See Table). This newly designed glaucoma shunt made of SIBS is clinically biocompatible in the rabbit model and maintained 100% patency at 6 months after insertion. Histologically, minimal capsule fibrosis and minimal collagen deposits were observed around the SIBS implant. The most remarkable difference was the absence of myofibroblast in the surrounding tissue in the SIBS group when compared to tubes made of silicone (PDMS).  

 

Conclusions:

 

The study demonstrates the biocompatibility of the MiDi implant made of SIBS in the rabbit model.

 

Keywords: wound healing • aqueous • intraocular pressure