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The cornea is the clear front window of the eye that focuses light into the eye so that you can see. It is made up of layers of cells that work together to protect your eye and provide clear vision. Your cornea must be clear, smooth and healthy for good vision. If it is scarred, swollen, or damaged, light is not focused properly into the eye and your vision becomes blurry or you see glare. If your cornea cannot be healed or repaired, your ophthalmologist may recommend a corneal transplant. This is when the diseased cornea is replaced with a clear, healthy cornea from a human donor. There are different types of corneal transplants. In some cases, only the front and middle layers of the cornea are replaced. In others, only the inner layer is removed. Sometimes, the entire cornea needs to be replaced.
Eye disease and injuries can damage the cornea. Here are some common eye problems that can lead to a damaged cornea:
Full thickness corneal transplant
Your entire cornea may need to be replaced if both the front and inner corneal layers are damaged. This is called penetrating keratoplasty (PK), or full thickness corneal transplant. Your diseased or damaged cornea is removed. Then the clear donor cornea is sewn into place.
PK has a longer recovery period than other types of corneal transplants. Getting complete vision back after PK may take up to 1 year or longer.
With a PK, there is a slightly higher risk than with other types of corneal transplants that the cornea will be rejected. This is when the body’s immune system attacks the new cornea tissue.
Partial thickness corneal transplant
Sometimes the front and middle layers of the cornea are damaged. In this case, only those layers are removed. The endothelial layer, or the thin back layer, is kept in place. This transplant is called deep anterior lamellar keratoplasty (DALK) or partial thickness corneal transplant. DALK is commonly used to treat keratoconus or bulging of the cornea.
Healing time after DALK is shorter than after a full corneal transplant. There is also less risk of having the new cornea rejected.
Endothelial keratoplasty
In some eye conditions, the innermost layer of the cornea called the “endothelium” is damaged. This causes the cornea to swell, affecting your vision. Endothelial keratoplasty is a surgery to replace this layer of the cornea with healthy donor tissue. It is known as a partial transplant since only this inner layer of tissue is replaced.
There are a few types of endothelial keratoplasty. They are known as:
Each type removes damaged cells from an inner layer of the cornea called Descemet’s membrane. The damaged corneal layer is removed through a small incision. Then the new tissue is put in place. Just a few stitches—if any—are needed to close the incision. Much of the cornea is left untouched. This lowers the risk of having the new cornea cells being rejected after surgery.
Some things to know:
