Cornea is the anterior most, transparent part of the eye. It is the only part of the eye that can be transplanted. The unique part is that, of all the transplants in the body, like liver, kidney, heart etc., it has the highest success rate.
It is akin to a bulb, if the wiring is intact (nerve supply to the eye and retina) then replacing the diseased cornea will result in good vision.
Until recently the full thickness of the cornea used to be replaced (i.e. all the five layers).
So all the layers of the patient’s cornea are removed and replaced with cornea from the donor (donated eye). The cornea is kept in place with fine sutures, which is stitched manually. This surgery is now done only for those patients who have disease involving all the layers (i.e. full thickness) of the cornea. It is commonly done for the cornea that has recovered from infections.
With advancements in technology and techniques we are now able to replace the layer of the cornea that is diseased. So for diseases that involve the anterior part of the cornea, we remove those layers and replace them with the same layers from the donated cornea. This is called Deep Anterior Lamellar Keratoplasty or DALK.
This is usually done for certain genetic diseases and degenerative diseases.
For diseases that involve the posterior layers of the cornea we replace just the diseased posterior layers. This procedure is called DSEK/DSAEK or DMEK.
This is commonly done for eyes where the inner layer of the cornea is damaged during or after cataract surgery.
The advances in science and surgery have now made us capable of using the donated cornea for more than one patient. So earlier if a person's eyes were donated after death, two people would see but now eye donation can benefit four potentially corneally blind people.
So they can see the light, donate your sight
The Eye is the Lamp of the Body. So if your Eye is healthy, your whole body will be full of Light