Abstract: Corneal blindness represents one of the world’s three major causes of blindness, and the fundamental problem of corneal transplantation is a severe shortage of donor tissues worldwide, resulting in approximately 1.5 million new cases of blindness annually. To address the growing need for corneal transplants two main approaches are being pursued: allogenic and bioengineering cornea. Bioengineering corneas are constructed by naturally generating an extracellular matrix (ECM) component as the scaffold structure with or without corneal cells. It is well established that the scaffold structure directs the fate of cells, therefore, the fabrication of the correct scaffold structure components could produce an ideal corneal substitute, able to mimic the native corneal function. Another key factor in the construction of tissue engineering cornea is seed cells. However, unlike the epithelium and stroma cells, human cornea endothelium cells (HCECs) are notorious for having a limited proliferative capacity in vivo because of the mitotic block at the G1 phase of the cell cycle due to “contact-inhibition”. This review will focus on the main concepts of recent progress towards the scaffold and seed cells, especially endothelial cells for bioengineering cornea, along with future perspectives.

Abstract: Since the 21st century, the development of corneal tissue engineering technology has been developing rapidly. With the progress of biomaterials, cell culture and tissue engineering technology, tissue engineering cornea has gained great development in both basic scientific research and clinical application. In particular, tissue engineered corneal scaffolds are the core components of tissue engineered corneas. It is the focus of current research on tissue engineering cornea to search for scaffolds with good biocompatibility, high safety and good biomechanical properties. In this paper, the recent research progress of tissue engineering corneal materials is reviewed.

Abstract: Cornea serves as the partial front barrier and major light reflection organ of the eye. The integrity of corneal surface is essential for ocular function. Injuries or congenital diseases could significantly destruct the homeostasis of the ocular surface, especially the microenvironment of limbal epithelial stem cells (LESCs), and will eventually cause dysfunction of corneal regeneration and diminish of LESCs. The loss of LESCs by different reasons are named limbal stem cell deficiency (LSCD), which is one of the leading cause of vision loss worldwide. To restore the corneal surface, LESC transplantation in the form of tissue or cell cultures is currently a viable and promising method to treat LSCD. In this review, we aim to introduce the characters and niche of LESCs, and discuss different aspects of its application in cornea surface reconstruction.

Abstract: In this review, recent studies regarding riboflavin-ultraviolet A (UVA) collagen cross-linking for the treatment of acanthamoeba keratitis (AK) were reviewed. English written studies about acanthamoeba, keratitis, riboflavin and collagen cross-linking were retrieved from PubMed search engine (www.ncbi.nlm.nih.gov/pubmed). Although there were significant numbers of cases reporting the effectiveness of riboflavin-UVA collagen cross-linking in AK, experimental studies (in vivo and in vitro) failed to verify amoebicidal or cysticidal effect of riboflavin-UVA collagen cross-linking. In conclusion, the efficacy of riboflavin-UVA collagen cross-linking for the treatment of AK is still debatable. It is necessary to conduct a prospective case-control study for clear guidance for clinicians.

Abstract: Age-related macular degeneration (ARMD), one of the most common causes of blindness, should be considered more due to its exponential increase in the coming 20 years as a result of increasing the age of the population. Whereas more recent studies offered newer scaling systems for ARMD, traditionally it is classified as the early and late stages. The main injury in this disease occurred in retinal pigment epithelium (RPE) and the retina. RPE cells have a crucial role in hemostasis and supporting photoreceptors. In the early stages, damages to RPE are minimal and mainly no treatment is needed because most patients are asymptomatic. However, in the late stages, RPE impairment may lead to the invasion of choroidal vessels into the retina. Although anti-angiogenic agents can inhibit this abnormal growth of blood vessels, they cannot stop it completely, and finally, total loss of retinal cells may occur (geographical atrophy). Since this prevalent disease has not had any cure yet, the concept of substituting the RPE cells should be considered. Repairing the injury to central nervous system cells is almost impossible because the regenerative capacity of these cells is limited. Recently, the use of regenerative substitutes has been suggested to replace damaged tissues. Amniotic membrane (AM) has been raised as a suitable substitute for damaged RPE cells due to all of its unique properties: pluripotency, anti-angiogenic effect, and anti-inflammatory effect. Based on the few studies that have been published so far, it seems that the use of this membrane in the treatment of ARMD can be helpful, but more studies are needed.

 Conjunctival flaps have previously proven to be effective in preserving the globe for individuals with severe ocular surface disease. Infectious keratitis, neurotrophic keratitis, nontraumatic corneal melts, descemetoceles, perforations, and corneal burns are all indications for this procedure. The flaps promote nutrition, metabolism, structure, and vascularity, as well as reduce pain, irritation, inflammation, and infection. Furthermore, patients avoid the emotional and psychological repercussions of enucleation or evisceration, while requiring fewer postoperative medications and office visits. Currently, fewer flaps are performed due to the emergence of additional therapeutic techniques, such as serum tears, bandage lenses, corneal grafting, Oxervate, amniotic membrane, and umbilical cord grafting. However, despite newer conservative medical methods, conjunctival flaps have been demonstrated to be useful and advantageous. Moreover, future technologies and approaches for globe preservation and sight restoration after prior conjunctival flaps are anticipated. Herein, we review the history, advantages, and disadvantages of various surgical techniques: Gundersen’s bipedicle flap, partial limbal advancement flap, selective pedunculated conjunctival flap with or without Tenon’s capsule, and Mekonnen’s modified inferior palpebral-bulbar conjunctival flap. The surgical pearls and recommendations offered by the innovators are also reviewed, including restrictions and potential complications. Procedures for visual rehabilitation in selective cases after conjunctival flap are reviewed as well.