What is the cornea?
The cornea is the clear, transparent structure that covers the eye, through which light passes to focus on the retina. The cornea is made of 3 different layers: an outer superficial layer (epithelium), a middle layer (stroma) and an inner thin layer (endothelium). The endothelium’s job is to keep water out of the cornea so that it stays clear.
Corneal diseases can impact the three different layers of the cornea. If your cornea is scarred, or struggles to stay clear because of disease, then your vision can become blurry. Scars from infection, trauma or diseases can lead to scarring, swelling and irregularities in the cornea. These can impact vision and create distortion and scatter of the light.
When the corneal clarity is severely affected, then surgery with corneal transplantation may be required. In a cornea transplant, the damaged corneal tissue is replaced by donor tissue. (cornea transplant video).
There are three main types of cornea transplant: (cornea transplant image.pdf)
Penetrating Keratoplasty (PK, PKP) is a full thickness cornea transplant. It is usually performed when all the layers of the cornea are affected. A donor graft is transplanted in the cornea and sutured to the host. It takes at least 1 year or more to heal properly; also it can create some changes in the normal corneal curvature (astigmatism) and patients usually need glasses after surgery.
Deep anterior lamellar keratoplasty (DALK) is a procedure where the anterior part of the cornea is replaced, leaving the patient’s endothelium intact. It is more useful in keratoconus and superficial stromal scars with an adequate corneal thickness.
Endothelial procedures (DSAEK, DSEK, DMEK) are aimed to change the endothelial layer and are indicated for Fuch’s dystrophy, PPMD and bullous keratopathy. A small disc of donor tissue is inserted in the eye and held in place by an air bubble. The air bubble pushes the graft into position. The patient is usually asked to lie on his back facing the ceiling for the first 24 hours. Patients that have undergone a cornea transplant require steroid eye drops to prevent rejection. Some patients might need to stay on steroid drops indefinitely.