The development of a micro‐shunt made from poly(styrene‐block‐isobutylene‐block‐styrene) to treat glaucoma

Abstract

Glaucoma is the second leading cause of blindness with ∼70 million people worldwide who are blind from this disease. The currently practiced trabeculectomy surgery, the gold standard treatment used to stop the progression of vision loss, is rather draconian, traumatic to the patient and requires much surgical skill to perform. This article summarizes the more than 10‐year development path of a novel device called the InnFocus MicroShunt®, which is a minimally invasive glaucoma drainage micro‐tube used to shunt aqueous humor from the anterior chamber of the eye to a flap formed under the conjunctiva and Tenon's Capsule. The safety and clinical performance of this device approaches that of trabeculectomy. The impetus to develop this device stemmed from the invention of a new biomaterial called poly(styrene‐block‐isobutylene‐block‐styrene), or “SIBS.” SIBS is ultra‐stable with virtually no foreign body reaction in the body, which manifests in the eye as clinically insignificant inflammation and capsule formation. The quest for an easier, safer, and more effective method of treating glaucoma led to the marriage of SIBS with this glaucoma drainage micro‐tube. This article summarizes the development of SIBS and the subsequent three iterations of design and four clinical trials that drove the one‐year qualified success rate of the device from 43% to 100%. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 211–221, 2017.

Translating Minimally Invasive Glaucoma Surgery Devices

“…The InnFocus/PreserFlo MicroShunt (InnFocus, Miami, FL) is also a tube that drains aqueous humor into the subconjunctival space but differs from the XEN gel stent as it is inserted ab externo and is composed of Poly (Styrene‐block‐IsoButylene‐block‐Styrene (SIBS)), a thermoplastic elastomer whose physical properties overlap both silicone rubbers and polyurethanes . The InnFocus MicroShunt also has “fins” designed to prevent leakage around the tube . The current InnFocus MicroShunt design is a long circular tube (8.5 mm length, 350 μm outer diameter, and 70 μm ID).…”

“…The current InnFocus MicroShunt design is a long circular tube (8.5 mm length, 350 μm outer diameter, and 70 μm ID). A device attached to a 7 mm diameter SIBS plate of 350 μm thickness was also developed but resulted in a constrained drainage field and cystic bleb development with a qualified success of 58% in a clinical study of 12 patients . Subsequent developments of the InnFocus MicroShunt focus around the tube design alone with the use of intraoperative mitomycin C application as per the Moorfields Safer Surgery System …”

“…The InnFocus made of SIBS has been shown to cause minimal inflammation or scar formation with 100% patency at 6 months in animal studies . Subsequent studies have demonstrated the device biocompatibility in accordance with International Organization for Standardization standards . However, preliminary studies of the device without the use of mitomycin C resulted in a small drainage field, cystic bleb formation, and a low qualified success rate (58%), therefore demonstrating that the biocompatibility of the material alone was not sufficient to prevent device failure …”

Calcification resistance of polyisobutylene and polyisobutylene‐based materials

“…High molecular weight rubbery polyisobutylene (PIB) is arguably the most biocompatible and biostable (bioinert) synthetic elastomer available . The PIB chain consists of densely packed chemically inert ─CH 2 C(CH 3 ) 2 ─ repeat units that are impervious to enzymes, resist the attack of the immune system, and prevent the diffusion of even the smallest of molecules (including H 2 ).…”

Role of nuclear factor (erythroid-derived 2)-like 2 in the age-resistant properties of the glaucoma trabecular meshwork

“…As a result, glaucoma is now classified within a group of chronic neurodegenerative conditions that collectively, are the leading cause of irreversible blindness worldwide (1)(2)(3)(4)(5)(6). As indicated by glaucoma epidemiological surveys, primary open-angle and angle-closure glaucoma occur in the majority of patients with glaucoma (7)(8)(9).…”