What is the Cornea?

The cornea is the clear tissue that covers the surface of the eye.  When light enters the eye, it passes through the cornea and then through the pupil (the dark spot in the middle of the coloured iris). Behind the pupil is the lens, which helps focus the light onto the retina (the light sensitive film) at the back of the eye. The retina sends this signal from the eye to the brain.  The eye functions can be compared to a camera, with a system of lenses (cornea and lens), aperture (pupil) and film (retina).

The cornea must remain clear for you to see properly. However, a number of problems can damage the cornea, affecting your vision.  These include corneal scarring from trauma or infection, keratoconus, or other inherited corneal conditions.  When the cornea causes reduced vision, a cornea transplant can improved the vision by replacing the cloudy cornea with a clear donor cornea.

Types of Cornea Transplants

The cornea contains five distinct layers including the epithelium, Bowman’s membrane, stroma, Descemet’s membrane, and the endothelium.  Cornea transplants can replace all or some of these layers.

Types of cornea transplants include:

Full thickness corneal transplant (Penetrating keratoplasty): 

This procedure involves transplanting all five layers of the cornea from the donor to the recipient. Please click on the above link for more information.

Partial thickness corneal transplant (Lamellar keratoplasty): 

In this procedure, only some of the layers of the cornea are transplanted from the donor to the recipient.

In a lamellar cornea transplant, only selected layers of the cornea are transplanted.  This may only include the deepest layer, the endothelium, which is called a posterior lamellar cornea transplant. Commonly performed versions of this procedure include Descemet’s Stripping Endothelial Keratoplasty (DSEK) or Descemet’s Membrane Endothelial Keratoplasty (DMEK).  If the lamellar transplant only includes layers closer to the surface, it is termed an anterior lamellar cornea transplant.  A commonly performed version of this procedure is the Deep Anterior Lamellar Keratoplasty (DALK).  Lamellar keratoplasty may be more appropriate than penetrating keratoplasty when the disease process is limited to only a few layers of the cornea.