An in vitro assessment of the thermoreversible PLGA-PEG-PLGA copolymer: Implications for Descemet's membrane endothelial keratoplasty.

BACKGROUND: To explore the use of a thermoreversible copolymer gel coating to prevent donor tissue scrolling in Descemet's membrane endothelial keratoplasty (DMEK). METHODS: PLGA-PEG-PLGA triblock copolymer was synthesised via ring opening polymerisation. Two formulations were fabricated and gelation properties characterised using rheological analyses. Endothelial cytotoxicity of the copolymer was assessed using a Trypan Blue exclusion assay. Thickness of the copolymer gel coating on the endothelial surface was analysed using anterior segment optical coherence tomography (OCT) (RTVue-100, Optovue Inc.). Gold nanoparticles were added to the copolymer to aid visualisation using OCT. Prevention of Descemet membrane donor scrolling was represented via a novel, in vitro, immersion of copolymer coated donor graft material. RESULTS: Two different formulations of PLGA-PEG-PLGA copolymer were successfully fabricated and the desired peak gelling temperature of 24°C was achieved by polymer blending. Application of 20%, 30% and 40% (wt/vol) polymer concentrations resulted in a statistically significant increase in polymer thickness on the endothelium (p < 0.001). There was no detectable endothelial cytotoxicity. The polymer was easy to apply to the endothelium and prevented scrolling of the DMEK graft. CONCLUSION: This PLGA-PEG-PLGA thermoreversible copolymer gel could be exploited as a therapeutic aid for preventing DMEK graft scrolling.

Management of intraoperative iris prolapse: stepwise practical approach.

Iris prolapse is not an uncommon occurrence during cataract surgery. It usually occurs through the main incision during hydrodissection and is commonly associated with floppy-iris syndrome; however, it can manifest in cases with no known predisposition and can occur at any stage during surgery. The mechanism is explained by the Bernoulli principle and its effect on iris position during the movement of fluid within the eye. Predisposing factors are iris configuration, anterior chamber depth, and position and architecture of the corneal tunnel. Strategies for prevention and management include the use of pharmacological agents, ophthalmic viscosurgical devices, and iris retractors. These strategies can be augmented by alteration and adaptation of the surgeon's technique.