A newly designed glaucoma drainage implant made of poly(styrene-b-isobutylene-b-styrene): biocompatibility and function in normal rabbit eyes

Clinicopathologic correlations of poly-(styrene-b-isobutylene-b-styrene) glaucoma drainage devices of different internal diameters in rabbits

BACKGROUND AND OBJECTIVE

To assess the biocompatibility and intraocular pressure (IOP) lowering effect of a novel glaucoma drainage implant in rabbits.

MATERIALS AND METHODS

Sixteen New Zealand white rabbits received one of three glaucoma drainage implants fabricated from poly-(styrene-b-isobutylene-b-styrene [SIBS]) with an internal diameter of the lumen of either 70 (6 eyes), 100 (6 eyes), or 150 (4 eyes) μm. Clinical follow-up examinations were performed during 6 months and postmortem eyes were studied with light microscopy.

RESULTS

Smaller internal diameter implants were associated with fewer complications. IOP levels were not statistically different among the groups. No eyes developed serious complications. Mild chronic inflammation was observed around the tube using light microscopy.

CONCLUSION

SIBS glaucoma drainage implants did not produce clinically detectable intraocular inflammation in a rabbit model. The 70- and 100-μm SIBS drainage devices demonstrated fewer postoperative complications. IOP levels were not statistically different from control eyes in all groups.

In vivo biocompatibility assessment of (PTFE-PVDF-PP) terpolymer-based membrane with potential application for glaucoma treatment

The aim of the work was to evaluate the in vivo biological behaviour of polymeric membrane materials for glaucoma implants. The base material was biostable synthetic terpolymer (PTFE-PVDF-PP) with proved biocompability (PN-EN ISO 10993). The samples manufactured in the form a membrane were subjected to chemical and physical treatment to create an open pore system within the polymer matrix. As a porogenic phase biodegradable natrium alginate in a fibrous form was employed. The non-perforating deep sclerectomy technique was performed in a rabbit model. The clinical observations were made after 14 and 30 days. During the study clinical symptoms of a moderate degree were observed, and histopathological changes were typical for foreign body implantation. At the end stage of the study no significant difference in histopathological assessment was found between control and experimental group. Similarities observed in both groups and relatively mild histopathological changes in the tissue surrounding the implant indicate that the observed symptoms come from a deep scleral trauma caused by surgery, and not by the presence of the implant itself.

A review of in vivo animal studies in retinal prosthesis research

BACKGROUND

The development of a functional retinal prosthesis for acquired blindness is a great challenge. Rapid progress in the field over the last 15 years would not have been possible without extensive animal experimentation pertaining to device design and fabrication, biocompatibility, stimulation parameters and functional responses. This paper presents an overview of in vivo animal research related to retinal prosthetics, and aims to summarize the relevant studies.

METHODS

A Pubmed search of the English language literature was performed. The key search terms were: retinal implant, retinal prosthesis, artificial vision, rat, rabbit, cat, dog, sheep, pig, minipig. In addition a manual search was performed based on references quoted in the articles retrieved through Pubmed.

RESULTS

We identified 50 articles relevant to in vivo animal experimentation directly related to the development of a retinal implant. The highest number of publications related to the cat (n = 18).

CONCLUSION

The contribution of animal models to the development of retinal prosthetic devices has been enormous, and has led to human feasibility studies. Grey areas remain regarding long-term tissue-implant interactions, biomaterials, prosthesis design and neural adaptation. Animals will continue to play a key role in this rapidly evolving field.

Modern concepts in antiglaucomatous implant surgery

BACKGROUND

Antiglaucomatous implant surgery is a continously evolving field in glaucoma treatment.

METHODS

A literature search with the terms "glaucoma implant surgery", "aqueous shunts" and "glaucoma drainage devices" was carried out, especially giving prominence to innovative surgical developments in glaucoma implant surgery and to recently established clinical evidence on traditional shunt surgery.

RESULTS

Episcleral glaucoma drainage devices have recently proven their efficacy in large studies. Longterm data about their clinical efficacy and their risk/safety profile are sufficiently available. New antiglaucomatous devices try to target alternative drainage routes, for example trabecular or uveoscleral outflow. Valid longterm data from prospective randomized clinical trials are not available for these devices as yet.

CONCLUSIONS

Although valid data on clinical application of the new glaucoma implants are not available as yet, profound knowledge about their theoretical concept and their practical management is obligatory for all glaucoma clinicians.

Carbodiimide cross-linked hyaluronic acid hydrogels as cell sheet delivery vehicles: characterization and interaction with corneal endothelial cells

It was reported that cell-adhesive gelatin discs have been successfully used as delivery vehicles for intraocular grafting of bioengineered corneal endothelial cell sheets. Development of alternative biomaterials to bovine-based gelatin vehicles can potentially eliminate the risk of bovine spongiform encephalopathy. In the present work, to investigate whether it was appropriate for use as cell sheet delivery vehicles, 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) cross-linked hyaluronic acid (HA) hydrogels were studied by determinations of morphological characteristic, mechanical and thermal property, water content, in vitro degradability and cytocompatibility. Glutaraldehyde (GTA) cross-linked HA samples were used for comparison. It was found that HA discs after cross-linking significantly increased its tensile stress but reduced its tensile strain, water uptake and enzymatic degradability. The results of differential scanning calorimetry demonstrated that cross-linking could lead to the alteration of polymer structure. In addition, the EDC-cross-linked HA discs had a smoother surface structure, a faster degradation rate and a relatively lower cytotoxicity as compared to the GTA cross-linked counterparts. It is concluded that EDC can be successfully applied for HA cross-linking to fabricate structurally stable, mechanically reinforced, readily deformable, transparent and cytocompatible HA hydrogel discs with the potential to be applied as delivery vehicles for corneal endothelial cell therapy.