Print me a cornea - Are we there yet?

Corneal diseases are the third most prevalent cause of blindness after cataract and glaucoma. It is estimated that about 5 million people in the world are affected by bilateral corneal blindness with an additional 23 million with unilateral blindness. Cornea transplantation is the standard practice for the management of various cornea related pathologies like fibrosis, ulcers, keratitis, etc. The high transplant cost, increased risk of graft failure/rejection, and long waiting list due to limited availability of good quality donor cornea imposes a huge clinical burden. Recently, biofabrication technologies are gaining a lot of attention because of their potential to direct hierarchical assembly of three-dimensional (3D) biological structures for tissue construction for various biomedical and clinical applications. In this regard, 3D bioprinting, which involves layer-by-layer deposition of acellular or cell-laden bioink in a specific pattern corresponding to the organotypic morphology of tissues/organs, has been extensively investigated for the fabrication of corneal substitutes. In addition to this methodology, novel biofabrication techniques have been explored for the fabrication of corneal tissues using bioinks with optical and mechanical performances comparable to native cornea tissue. In this review, we highlight the recent advances and offer future perspectives in the fabrication of corneal tissue equivalents that can be potentially employed for effective clinical repair, reconstruction, and regeneration of the cornea.