In Vitro Evaluation of the Feasibility of Slit-Lamp Nd:YAG Laser Descemetorhexis

Influence of the Size and Charge of Carbon Quantum Dots on Their Corneal Penetration and Permeation Enhancing Properties

Reaching the corneal endothelium through the topical administration of therapeutic drugs remains a challenge in ophthalmology. Besides, endothelial cells are not able to regenerate, and diseases at this site can lead to corneal blindness. Targeting the corneal endothelium implies efficient penetration through the three corneal layers, which still remains difficult for small molecules. Carbon quantum dots (CQDs) have demonstrated great potential for ocular nanomedicine. This study focuses on the corneal penetration abilities of differently charged CQDs and their use as permeation enhancers for drugs. Excised whole bovine eyes were used as an ex vivo model to investigate corneal penetration of CQDs derived from glucosamine using β-alanine, ethylenediamine, or spermidine as a passivation agent. It was found that negatively charged CQDs have limited corneal penetration ability, while positively charged CQDs derived from glucosamine hydrochloride and spermidine (CQD-S) penetrate the entire corneal epithelium all the way down to the endothelium. CQD-S were shown to enhance the penetration of FITC-dextran 150 kDa, suggesting that they could be used as efficient penetration enhancers for therapeutic delivery to the corneal endothelium.

New developments in corneal endothelial cell replacement

Corneal transplantation is currently the most effective treatment to restore corneal clarity in patients with endothelial disorders. Endothelial transplantation, either by Descemet membrane endothelial keratoplasty (DMEK) or by Descemet stripping (automated) endothelial keratoplasty (DS(A)EK), is a surgical approach that replaces diseased Descemet membrane and endothelium with tissue from a healthy donor eye. Its application, however, is limited by the availability of healthy donor tissue. To increase the pool of endothelial grafts, research has focused on developing new treatment options as alternatives to conventional corneal transplantation. These treatment options can be considered as either 'surgery-based', that is tissue-efficient modifications of the current techniques (e.g. Descemet stripping only (DSO)/Descemetorhexis without endothelial keratoplasty (DWEK) and Quarter-DMEK), or 'cell-based' approaches, which rely on in vitro expansion of human corneal endothelial cells (hCEC) (i.e. cultured corneal endothelial cell sheet transplantation and cell injection). In this review, we will focus on the most recent developments in the field of the 'cell-based' approaches. Starting with the description of aspects involved in the isolation of hCEC from donor tissue, we then describe the different natural and bioengineered carriers currently used in endothelial cell sheet transplantation, and finally, we discuss the current 'state of the art' in novel therapeutic approaches such as endothelial cell injection.

Animal models of corneal endothelial dysfunction to facilitate development of novel therapies

Progressive corneal endothelial disease eventually leads to corneal edema and vision loss due to the limited regenerative capacity of the corneal endothelium in vivo and is a major indication for corneal transplantation. Despite the relatively high success rate of corneal transplantation, there remains a pressing global clinical need to identify improved therapeutic strategies to address this debilitating condition. To evaluate the safety and efficacy of novel therapeutics, there is a growing demand for pre-clinical animal models of corneal endothelial dysfunction. In this review, experimentally induced, spontaneously occurring and genetically modified animal models of corneal endothelial dysfunction are described to assist researchers in making informed decisions regarding the selection of the most appropriate animal models to meet their research goals.