A Histological Comparative Study Between SIBS and PDMS Encircling Band and Buckle for the Treatment of Retinal Detachment

Abstract

Purpose: : To histologically assess the ocular biocompatibility and inflammatory response of poly(styrene–b–isobutylene–b–styrene) (SIBS) implants as compared to trimethyl terminated polydimethylsiloxane (PDMS, silicone rubber) implants for the treatment of retinal detachment in a rabbit model (Moshfeghi A, Archives 2004).

Methods: : Identical scleral encircling bands (0.60×2.5×125mm), sleeves (1.6×2.5×5mm), and buckles (2.5mm groove, 5mm long) were implanted in 8 NZW rabbits. 4 received an FDA approved medical grade PDMS implants (Labtician Inc, Canada) and 4 a SIBS implant (9 mol% styrene, InnFocus LLC, USA). SIBS is a thermoplastic elastomeric triblock copolymer, FDA approved for use in a cardiovascular drug eluting stent (TAXUS^TM, Boston Scientific Corp, MA) that demonstrated exceptional biocompatibility, and structural integrity in patients. Histological sequence: 1 rabbit of each treatment group at 1.5, 3, 6, and 12 months. Tissue samples were processed for paraffin embedding and slides were stained with Hematoxylin and Eosin, Periodic Acid–Schiff, and Masson Trichrome. Capsule thickness was measured at 4 places around the implant.

Results: : There were no clinical signs of infection, inflammation or extrusion in the 8 rabbits. Histopathologically, in the first 5 euthanized thus far (SIBS at 1.5, 3, and 6 months, PDMS at 3 and 6 months) a thin capsule was seen against the lining of the 5 episcleral implants surface. For SIBS, capsule thickness varied from 3.7 to 9.4µm, for PDMS from 7.0 to 9.5µm. Inflammatory cells (giant cells and histiocytes) and fibrous tissue were only noted in the outlying areas surrounding the four 5.0 Dacron sutures utilized to fixate the implants. All other areas had very little reaction. In one SIBS eye, one of the sutures had failed and the implant had migrated at the limbus. No inflammatory cells were noted and the capsule thickness was 9µm. There were no statistically significant histological differences between SIBS and PDMS implants.

Conclusions: : SIBS encircling and buckle implants are well tolerated in the rabbit model.

Keywords: retinal detachment • retina • sclera