Processing

Cornea composition

The cornea is the transparent, front part of the eye that lets in light so that people can see. It consists of three basic layers: epithelium (outer layer), stroma and endothelium (inner layer). The endothelial cells keep the cornea clear.

Removal

For cornea transplantation, the removal team take out the entire eyeball, which is then placed in a small, sterile container, refrigerated, and shipped in saline solution. This is to prevent damage to the endothelial cells, which are crucial for the cornea’s function. A cornea can only be used for transplantation if it contains sufficient numbers of living endothelial cells.

Preservation

A member of staff inspects the eyeball with a slit lamp, a type of microscope that can be used to examine the eye in detail. After that, the cornea is cut out in a flow cabinet.

A cornea needs to contain over 2300 living endothelial cells per square millimetre to be eligible for transplantation. The employee therefore counts the number of cells using a microscope. If the number is high enough, the cornea will be transferred in a bottle of preservation medium and stored in a heated unit at a temperature of 31 °C. The medium ensures that any micro-organisms originating from the donor are deactivated, while keeping the endothelial cells alive.

Everything in the process is aimed at keeping the number of living endothelial cells as high as possible, so that the cornea is still clear after transplantation and the recipient will be able to see properly again.

Technical developments: lamellae

The objective of cornea transplantation is to restore the integrity and clarity of the cornea, improve the patient’s eyesight, or relieve pain. Besides full cornea transplantations (penetrating keratoplasty), lamellar keratoplasties are being performed increasingly frequently.

In this case, only the damaged part is replaced with a lamellar transplant. In the past, the surgeon would cut the lamellae in the OR, but nowadays ETB-BISLIFE  cuts these lamellae in advance.

For clinical use, different types of lamellae are distinguished: posterior lamellae (pre-cut DSAEK and pre-stripped DMEK) and anterior lamellae (ALKP and DALK).