Ultrastructural analysis of explanted CyPass microstents and correlation with clinical findings

Complications after CyPass® Micro-Stent explantation: a case series

PURPOSE

To describe the in toto explantation of the CyPass® Micro-Stent and its conceivable complications.

METHODS

This is a case series of eighteen eyes from fourteen patients who underwent CyPass® Micro-Stent implantation due to mild to moderate glaucoma and who subsequently suffered from loss of endothelial cell density. Consequently, the CyPass® Micro-Stent was in toto explanted. The surgical procedure and its complications are described and compared with trimming of the CyPass® Micro-Stent.

RESULTS

A postoperative hyphema was developed in 8 of the 18 eyes. In four of them the hyphema was self-limiting, while in two patients an anterior chamber irrigation was necessary. One patient suffered from a severe intracameral bleeding and iridodialysis during explantation, so that the base of the iris had to be scleral fixated. The remaining explantations were without complications.

CONCLUSION

Dealing with implanted CyPass® Micro-Stents poses a challenge for ophthalmic surgeons. An in toto removal can be traumatic, since the CyPass stent often is fibrotic encapsulated and fused with the surrounding tissue. Alternatively, trimming of the CyPass is also a viable option to avoid further endothelial damage. Reported complications of CyPass trimming are consistent with those that can occur after explantation. Further data on the development of the endothelial cells after trimming or explantation are not yet available. Therefore, it remains open whether trimming of the CyPass, in contrast to complete removal, carries the risk of further endothelial cell loss.

[Minimally invasive glaucoma surgery-Comparison of angle based procedures]

Surgical procedures are playing an increasing role in the care of patients with glaucoma. Within the last decade, new surgical procedures have been established, which are summarized under the term minimally invasive glaucoma surgery (MIGS). A wide variety of different procedures are aimed at the structures in the angle of the anterior chamber, such as the trabecular meshwork and Schlemm's canal, to improve the physiological outflow or to improve the alternative uveoscleral outflow. The implementation of the treatment goal differs in the individual procedures, as does the maximum pressure reduction that can be achieved. Compared to trabeculectomy with the use of cytostatic agents, the achievable pressure reduction is usually significantly lower. In contrast, the significantly lower intraoperative and postoperative complication rates are emphasized as an advantage of these procedures. With increasing clinical experience and the growth of sufficient data on these new surgical procedures, a well-founded classification in the treatment algorithm of glaucoma surgery becomes easier; nevertheless, due to the small differences with respect to efficacy and safety profile, the final decision for an individual procedure often remains dependent on the surgeon's personal preferences.

Non-Viral Gene Therapy in Trabecular Meshwork Cells to Prevent Fibrosis in Minimally Invasive Glaucoma Surgery

The primary cause of failure for minimally invasive glaucoma surgery (MIGS) is fibrosis in the trabecular meshwork (TM) that regulates the outflow of aqueous humour, and no anti-fibrotic drug is available for intraocular use in MIGS. The myocardin-related transcription factor/serum response factor (MRTF/SRF) pathway is a promising anti-fibrotic target. This study aims to utilise a novel lipid nanoparticle (LNP) to deliver MRTF-B siRNA into human TM cells and to compare its effects with those observed in human conjunctival fibroblasts (FF). Two LNP formulations were prepared with and without the targeting peptide cΥ, and with an siRNA concentration of 50 nM. We examined the biophysical properties and encapsulation efficiencies of the LNPs, and evaluated the effects of MRTF-B silencing on cell viability, key fibrotic genes expression and cell contractility. Both LNP formulations efficiently silenced MRTF-B gene and were non-cytotoxic in TM and FF cells. The presence of cΥ made the LNPs smaller and more cationic, but had no significant effect on encapsulation efficiency. Both TM and FF cells also showed significantly reduced contractibility after transfection with MRTF-B siRNA LNPs. In TM cells, LNPs with cΥ achieved a greater decrease in contractility compared to LNPs without cΥ. In conclusion, we demonstrate that the novel CL4H6-LNPs are able to safely and effectively deliver MRTF-B siRNA into human TM cells. LNPs can serve as a promising non-viral gene therapy to prevent fibrosis in MIGS.