Corneal transplantation is the most frequently performed human transplant procedure in the world. There are more corneal transplants performed than any other tissue or organ transplant.
According to the WHO’s World Report on Vision (2019) blindness from corneal disease (and injury) is the fifth leading cause of blindness, and a corneal transplant is the last remaining treatment option to restore the sight for many.
Today, around the world, there are an estimated 12.7 million people waiting for a corneal transplant. (Gain et al, 2015) Most reside in low-middle income nations where they are without an eye bank or without routine access to tissue. For many, their only option is to import tissue from other parts of the world that are in a position to share. This can relieve access in the short term, for a few, but the practice of exporting and importing brings with it, its own challenges. Therefore, steps to develop local eye banks remain the gold standard for every nation.
Who needs a corneal transplant?
A corneal transplant may be needed to treat injury (e.g. chemical burn or penetrating eye injury), acquired conditions (e.g. trachoma) or hereditary condition (e.g. keratoconus). Some common conditions are:
Keratoconus (or conical cornea) is a disease that results in thinning of the central zone of the cornea, the front surface of the eye. As this progresses, normal eye pressure causes the round shape of the cornea to distort and an irregular cone-like bulge develops, resulting in significant visual impairment. For further information please visit Keratoconus Australia.
Bullous Keratopathy is a generic term for corneal swelling (oedema) in a bullous-like fashion. When this happens, the outer surface of the cornea – called the epithelium – becoming covered in raised-blisters. It involves a loss of clarity and the development of clouding over of the cornea – which in turn results in reduced or a loss of vision.
The loss of clarity, and the development of the clouding, is due to the gradual impairment of the precious surface-endothelial-cells which are responsible for keeping the cornea clear and healthy. Without these cells the cornea cannot remain clear.
It can occur for many reasons including hereditary (family/genetics) susceptibility, previous eye surgery, or just simply advancing years. In Australia, for example, it is the second most common condition requiring a transplant, accounting for 25% of all transplants performed. The success rate of a transplant for this condition, as measured by transplanted corneas surviving one year post-operatively, is 90.6%.
Fuchs’ dystrophy is a disease of the cornea. It is when cells in the corneal layer called the endothelium gradually die off. These cells normally pump fluid from the cornea to keep it clear. When they die, fluid builds up and the cornea gets swollen and puffy. For further information please visit AAO.
Type of corneal transplants
The cornea has 5 layers. Depending on the condition of the recipient, the surgeon may transplant all 5 layers or just 1 or a few layers. The aim is to retain as much of the recipient’s healthy tissue as possible, and only replace the diseased part. Eye banks carefully prepare (cut the layers) of the donated tissue to meet the recipient’s need. The tissue is then sent to the operating room ready for transfer to the recipient.
For further information about corneal transplantation please visit the AAO.
Reference: Gain P, Jullienne R, He Z, Aldossary M, Acquart S, Cognasse F, Thuret G. Global survey of corneal transplantation and eye banking. JAMA Ophthalmol. 2016;134:167-73.