Newer Modes of Corneal Grafting / Corneal Surgery
A corneal transplant or grafting, also called keratoplasty, is a surgical procedure performed to replace all or part of the damaged cornea with corneal tissue received from a healthy donor. The cornea is a clear and protective dome-shaped covering over the iris (coloured part of the eye) and the pupil (small central black circle in the iris) of the eye made up of six delicate layers.
The cornea acts as a lens and helps in projecting light onto the retina (light-sensitive layer at the back of the eye). A damaged or diseased cornea may change the shape and reduce transparency of the cornea, which can disrupt the projection of light and result in impaired vision. A cornea transplant can treat severe infection or damage, relieve pain and improve vision.
Corneal transplant/graft procedures will be carried out depending on which part of the cornea needs to be replaced, and will be performed under general or local anaesthesia.
Full thickness corneal transplants or penetrating keratoplasty
Penetrating keratoplasty involves the removal of the damaged corneal area and replacing it with a donated cornea. Your surgeon will use a circular cutting instrument called a trephine to cut through the thickness of the damaged cornea. The new cornea will be placed and sutured with tiny stitches around its edges.
Partial thickness corneal transplants
Partial thickness transplant involves the transplantation of only parts of the cornea. The techniques depend on which layers of the cornea have to be transplanted – the front or back portion of the cornea.
- Front portion corneal transplant may include:
- Anterior lamellar keratoplasty: It involves the removal of only the outer layers of the cornea and replacement with a donor graft.
- Deep anterior lamellar keratoplasty: It involves the removal of only the outer and middle layers of the cornea and replacement with a donor graft.
In both of these procedures, the donor cornea is fixed in place with stitches.
- Back portion corneal transplant: The inner layers of your cornea will be removed without damaging the outer layers by making a small incision in the side of your eyeball. The donor graft will replace the removed corneal tissue. The techniques for removal of the inner corneal layers include:
- Descemet’s stripping endothelial keratoplasty: This involves replacement of the inner corneal lining along with a part of the corneal stroma (corneal supporting tissue).
- Descemet’s membrane endothelial keratoplasty: This involves replacement of only the inner layer cells of the cornea.
In both of these procedures, the replaced corneal tissues are held with the help of a temporary air bubble instead of stitches.
Phototherapeutic Keratectomy (PTK)
Superficial corneal disorders can be effectively treated with PTK. In this procedure, the surgeon will remove the top layer of your cornea (epithelium) and use the excimer laser to treat the cornea. This type of laser removes tiny, precise amounts of the scar tissue and smoothes the corneal surface to improve vision. It also helps in reshaping the cornea. Following the procedure, antibiotic eye drops may be instilled to prevent infections and a bandage lens placed on your eyes for protection. PTK has the benefit of providing permanent results.
Laser eye surgery is a procedure in which a computer-controlled excimer laser is used to reshape the corneal surface.