Two main groups of patients have participated in the VISICORT project:
1. Patients who have already had a corneal transplant operation and are either experiencing a complication such as rejection or have had no complications.
2. Patients who are about to have a corneal transplant operation and agree to have their clinical information and biological samples collected at the time of the transplant and at several time-points over the first three years after transplantation. In this group, the clinical information collected over time will allow for immune response signals associated with rejection and other complications to be identified.