INTRAOCULAR APPLICATION OF FIBRIN GLUE AS AN ADJUNCT TO PARS PLANA VITRECTOMY FOR RHEGMATOGENOUS RETINAL DETACHMENT

Tissue glue for management of large iris cyst

Purpose

To present a novel technique utilizing fibrin glue-assisted adhesion as adjuvant to fine needle aspiration for management of post-surgical peripheral iris stromal cyst.

Observations

A 61 year-old male presented with a 4.20 × 7.56 × 8.22 mm well-circumscribed, fluid-filled peripheral cystic lesion involving the central visual axis with local posterior displacement of the intraocular lens. Surgical drainage was performed with the adjuvant use of fibrin glue to enhance the annealing of cyst walls. The patient tolerated the procedure without significant complications. At final post-operative visit, vision improved to 20/30 and there was no recurrence of the cyst.

Conclusions and importance

To our knowledge, this is the first report describing the use of fibrin glue to successfully treat a post-surgical peripheral iris stromal cyst. Fibrin glue may serve as an effective alternative to ethanol and sclerosing agents in the management of iris cysts.

Advances in biomaterials as a retinal patch for the repair of rhegmatogenous retinal detachment

Rhegmatogenous retinal detachment (RRD) is the most common retinological emergency that can cause blindness without surgical treatment. RRD occurs when liquefied vitreous accumulates between the neurosensory retina and the retinal pigment epithelium via retinal breaks, which are caused by the separation of the vitreous from the retina with aging. Currently, the main treatment option is pars plana vitrectomy, which involves surgical removal of the vitreous and laser photocoagulation around retinal breaks to generate firm chorioretinal adhesion, as well as subsequent filling of the vitreous cavity with long-lasting substitutes (expansile gas or silocone oil) to prevent the connection between the subretinal space and the vitreous cavity via the breaks before the chorioretinal adhesion firm enough. However, the postoperative face-down position and the not very satisfactory first retinal reattachment rate place a heavy burden on patients. With the development of technology and materials engineering, researchers have developed biomaterials that can be used as a retinal patch to seal retinal breaks and prevent the connection of subretinal space and vitreous cavity via breaks, thus replacing the long-lasting vitreous substitutes and eliminating the postoperative face-down position. Preclinical studies have demonstrated that biomaterial sealants have enough biocompatibility and efficacy in the in vitro and in vivo experiments. Some sealants have been used in clinical trials on a small scale, and the results indicate promising application prospects of the biomaterial sealants as retinal patches in the repair of RRD. Herein, we review the recent advances in biomaterials as retinal patches for the repair of RRD, focusing on the biomaterial categories, methods, and procedures for sealing retinal breaks, as well as their biocompatibility and efficacy, current limitations, and development perspectives.

Biocompatibility and Efficacy of a Linearly Cross-Linked Sodium Hyaluronic Acid Hydrogel as a Retinal Patch in Rhegmatogenous Retinal Detachment Repairment

To prevent the migration of retinal pigment epithelium (RPE) cells into the vitreous cavity through retinal breaks after the pars plana vitrectomy for the repair of rhegmatogenous retinal detachment (RRD), sealing retinal breaks with an appropriate material appears to be a logical approach. According to a review of ocular experiments or clinical trials, the procedure for covering retinal breaks with adhesives is complex. A commercially available cross-linked sodium hyaluronic acid (HA) hydrogel (Healaflow®) with the injectable property was demonstrated to be a perfect retinal patch in RRD clinical trials by our team. Based on the properties of Healaflow®, a linearly cross-linked sodium HA hydrogel (HA-engineered hydrogel) (Qisheng Biological Preparation Co. Ltd. Shanghai, China) with the injectable property was designed, whose cross-linker and cross-linking method was improved. The purpose of this study is to report the characteristics of an HA-engineered hydrogel using Healaflow® as a reference, and the biocompatibility and efficacy of the HA-engineered hydrogel as a retinal patch in the rabbit RRD model. The HA-engineered hydrogel exhibited similar dynamic viscosity and cohesiveness and G′ compared with Healaflow®. The G′ of the HA-engineered hydrogel varied from 80 to 160 Pa at 2% strain under 25°C, and remained constantly higher than G″ over the range of frequency from 0.1 to 10 Hz. In the animal experiment, clinical examinations, electroretinograms, and histology suggested no adverse effects of the HA-engineered hydrogel on retinal function and morphology, confirming its favorable biocompatibility. Simultaneously, our results demonstrated the efficacy of the HA-engineered hydrogel as a retinal patch in the RRD model of rabbit eyes, which can aid in the complete reattachment of the retina without the need for expansile gas or silicone oil endotamponade. The HA-engineered hydrogel could play the role of an ophthalmologic sealant due to its high viscosity and cohesiveness. This pilot study of a small series of RRD models with a short-term follow-up provides preliminary evidence to support the favorable biocompatibility and efficacy of the HA-engineered hydrogel as a promising retinal patch for sealing retinal breaks in retinal detachment repair. More cases and longer follow-up studies are needed to assess its safety and long-term effects.

BioAdhere: tailor-made bioadhesives for epiretinal visual prostheses

Introduction: Visual prostheses, i.e. epiretinal stimulating arrays, are a promising therapy in treating retinal dystrophies and degenerations. In the wake of a new generation of devices, an innovative method for epiretinal fixation of stimulator arrays is required. We present the development of tailor-made bioadhesive peptides (peptesives) for fixating epiretinal stimulating arrays omitting the use of traumatic retinal tacks. Materials and methods: Binding motifs on the stimulating array (poly[chloro-p-xylylene] (Parylene C)) and in the extracellular matrix of the retinal surface (collagens I and IV, laminin, fibronectin) were identified. The anchor peptides cecropin A (CecA), KH1, KH2 (author's initials) and osteopontin (OPN) were genetically fused to reporter proteins to assess their binding behavior to coated microtiter plates via fluorescence-based assays. Domain Z (DZ) of staphylococcal protein A was used as a separator to generate a bioadhesive peptide. Following ISO 10993 "biological evaluation of medical materials", direct and non-direct cytotoxicity testing (L-929 and R28 retinal progenitor cells) was performed. Lastly, the fixating capabilities of the peptesives were tested in proof-of-principle experiments. Results: The generation of the bioadhesive peptide required evaluation of the N- and C-anchoring of investigated APs. The YmPh-CecA construct showed the highest activity on Parylene C in comparison with the wildtype phytase without the anchor peptide. eGFP-OPN was binding to all four investigated ECM proteins (collagen I, laminin > collagen IV, fibronectin). The strongest binding to collagen I was observed for eGFP-KH1, while the strongest binding to fibronectin was observed for eGFP-KH2. The selectivity of binding was checked by incubating eGFP-CecA and eGFP-OPN on ECM proteins and on Parylene C, respectively. Direct and non-direct cytotoxicity testing of the peptide cecropin-A-DZ-OPN using L-929 and R28 cells showed good biocompatibility properties. Proof-of-concept experiments in post-mortem rabbit eyes suggested an increased adhesion of CecA-DZ-OPN-coated stimulating arrays. Conclusion: This is the first study to prove the applicability and biocompatibility of peptesives for the fixation of macroscopic objects.

Application of Collagen I and IV in Bioengineering Transparent Ocular Tissues

Collagens represent a major group of structural proteins expressed in different tissues and display distinct and variable properties. Whilst collagens are non-transparent in the skin, they confer transparency in the cornea and crystalline lens of the eye. There are 28 types of collagen that all share a common triple helix structure yet differ in the composition of their α-chains leading to their different properties. The different organization of collagen fibers also contributes to the variable tissue morphology. The important ability of collagen to form different tissues has led to the exploration and application of collagen as a biomaterial. Collagen type I (Col-I) and collagen type IV (Col-IV) are the two primary collagens found in corneal and lens tissues. Both collagens provide structure and transparency, essential for a clear vision. This review explores the application of these two collagen types as novel biomaterials in bioengineering unique tissue that could be used to treat a variety of ocular diseases leading to blindness.

Reattachment of Rhegmatogenous Retinal Detachment via Fibrin Tissue Adhesive

Purpose

To manage reattachment of rhegmatogenous retinal detachment using tissue adhesive (fibrin glue) in five patients.

Methods

Five eyes of five patients with rhegmatogenous retinal detachment were treated with 23-gauge pars plana vitrectomy and the application of fibrin glue (Tisseel Lyo) into the break under air without laser photocoagulation or cryopexy.

Results

The median age of patients was 64 (range, 46–82) years, and the median duration of symptoms was 15 (range, 7–60) days. Three eyes had inferior and two had superior rhegmatogenous retinal detachments. Successful retinal reattachment was achieved in all cases and maintained during the followıng 10 to 24 months. The median best-corrected visual acuity improved from 2 / 100 preoperatively to a Snellen visual acuity of 20 / 50 by 6 months postoperatively. No postoperative complications were detected during the follow-up period.

Conclusions

Excellent adhesive effects of fibrin glue with respect to sealing retinal tears with no side effects were seen in our study. With further prospective studies, this technique could be an alternative method to conventional retinopexy.

Lyophilized amniotic membrane patch (LAMPatch) as a replacement of tamponades in the treatment of primary rhegmatogenous retinal detachment

BACKGROUND

The basis of retinal detachment repair is sealing the retinal breaks. In order to seal the retinal breaks, chorioretinal adhesion around these lesions has to be achieved. Laser retinopexy is not immediate thus necessitates the use of a temporal endotamponade to maintain both tissues in apposition. We propose the use of a patch of lyophilized human amniotic membrane (LAMPatch) in order to occlude the retinal tear effectively until the chorioretinal adhesion is settled, overcoming the risks and limitations of the current tamponades.

METHODS

23-gauge vitrectomy was performed on eyes with primary retinal detachment with single retinal breaks of less than one-hour extension. A LAMPatch was deployed over the retinal breaks after retina was repositioned with perfluorocarbon. Neither gas nor silicon oil were injected.

RESULTS

Six eyes of six patients with total or partial retinal detachment were included. Retinas remained reattached in all cases until the end on follow-up (3, 5 months). Best-corrected visual acuity at 1-week postop was between 20/30 and 20/100. Neither elevations of intraocular pressure, cataracts nor signs of inflammation were registered during follow-up. No second surgeries were needed.

CONCLUSION

This technique has proven to be safe and effective in this small case series. No intraocular pressure rise, inflammation or cataracts were registered until last follow-up visit.