Artificial Cornea: Past, Current, and Future Directions.

Gráinne Holland,Maria Gonzalez,Laura Sánchez-Abella,Neil Lagali,Thomas Ritter,Damien Dupin,Andrea Haiek,Aritz Bidaguren,Iraida Loinaz,Elizabeth B Moloney,Abhay Pandit,Eva Larra

doi:10.3389/fmed.2021.770780

Abstract

Corneal diseases are a leading cause of blindness with an estimated 10 million patients diagnosed with bilateral corneal blindness worldwide. Corneal transplantation is highly successful in low-risk patients with corneal blindness but often fails those with high-risk indications such as recurrent or chronic inflammatory disorders, history of glaucoma and herpetic infections, and those with neovascularisation of the host bed. Moreover, the need for donor corneas greatly exceeds the supply, especially in disadvantaged countries. Therefore, artificial and bio-mimetic corneas have been investigated for patients with indications that result in keratoplasty failure. Two long-lasting keratoprostheses with different indications, the Boston type-1 keratoprostheses and osteo-odonto-keratoprostheses have been adapted to minimise complications that have arisen over time. However, both utilise either autologous tissue or an allograft cornea to increase biointegration. To step away from the need for donor material, synthetic keratoprostheses with soft skirts have been introduced to increase biointegration between the device and native tissue. The AlphaCor™, a synthetic polymer (PHEMA) hydrogel, addressed certain complications of the previous versions of keratoprostheses but resulted in stromal melting and optic deposition. Efforts are being made towards creating synthetic keratoprostheses that emulate native corneas by the inclusion of biomolecules that support enhanced biointegration of the implant while reducing stromal melting and optic deposition. The field continues to shift towards more advanced bioengineering approaches to form replacement corneas. Certain biomolecules such as collagen are being investigated to create corneal substitutes, which can be used as the basis for bio-inks in 3D corneal bioprinting. Alternatively, decellularised corneas from mammalian sources have shown potential in replicating both the corneal composition and fibril architecture. This review will discuss the limitations of keratoplasty, milestones in the history of artificial corneal development, advancements in current artificial corneas, and future possibilities in this field.

Highlights

Located at the front of the eye, covering the pupil, iris, and anterior chamber, the cornea is the primary component of the ocular optical system [1]
This study suggested the poly(ethylene glycol) diacrylate (PEGDA)-agarose based interpenetrating network (IPN) can be used in the future to replace the OOKP lamina [89]
Artificial corneas range from KPros with biological interfaces for treating intractable cases where donor corneas fail, to cellfree medical devices intended to be a primary replacement for donor corneas

Summary

Introduction

Located at the front of the eye, covering the pupil, iris, and anterior chamber, the cornea is the primary component of the ocular optical system [1]. The cornea is made up of three cellular layers- epithelium, stroma, and endothelium; and two acellular layers- Bowman’s and Descemet’s membranes (Figure 1) [2]. The outermost layer, the epithelium, which makes up 10% of the total corneal thickness, consists of stratified cells with tight junctions, that form a protective barrier. Separating the posterior corneal stroma and endothelium is the Descemet’s membrane, which is a dense, thick, somewhat transparent, cellfree matrix [4]. For those with corneal melting disorders, the Descemet’s membrane is sometimes the only layer remaining to keep the eye’s integrity. The cornea is a highly complex tissue, innervated and avascular

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Conclusion