The traditional corneal transplant involved replacing the entire (“penetrating”) cornea with a “sutured in” donated cornea (a penetrating keratoplasty). Sutures would typically be removed 18 months following the procedure, the patient then needing to wear a contact lens to achieve the best vision. There a significant risk of the donated cornea being identified as foreign and the patient’s own immune system reacting against it. This is termed rejection and the commonest reason for a corneal transplant failing. The transplanted eye also has an increased risk of damage, even with relatively minor trauma.
By selectively replacing only part (lamellar) of the patient’s cornea, there is a significant reduction in the risk of rejection. The risk of relatively minor trauma damaging the eye is also lessened. For some types of lamellar transplantation there is also a significant reduction in likelihood of requiring a contact lens to achieve good vision.
For these reasons, where technically possible, is preferable to perform lamellar over penetrating corneal transplantation. There are some cases where this is not possible and a penetrating keratoplasty is performed.