Corneal grafting, also known as corneal transplantation, is a surgical procedure where a damaged or diseased cornea is replaced by donor corneal tissue from a recently deceased person. Eye banks collect healthy corneas from decedents - a careful history is taken to ensure that the donor had no known diseases which might affect the viability of the donor cornea - and these are then used by ophthalmologists (eye surgeons) in corneal graft surgery. Corneal transplants are fairly common operations there are about 1000 performed in Australia each year and the success rate is high (although this will vary depending on the indication for grafting). The probability of rejection is less than that of other transplants because the cornea has no blood supply.
The most common indication for corneal graft surgery in Australia is keratoconus, with 32% of grafts performed for this reason. Other indications include bullous keratopathy, failed previous corneal grafts, corneal dystrophies and herpetic eye disease. The success rate for all corneal transplants where 'success' is defined as graft survival after 5 years is 73%. Note that the success rate (as mentioned above) will depend on the indication for grafting and is very much related to the pre-operative condition of the host cornea. For example, corneal transplants for keratoconus are almost 100% successful due to the fact that this condition does not usually involve the peripheral cornea.
Penetrating keratoplasty (PK) is the most common form of corneal graft surgery. Over 90% of corneal transplants in Australia are PK. In this procedure the whole thickness of the cornea (including the corneal endothelium) is replaced by donor tissue. The corneal endothelium is the most posteriorly located structure of the cornea and is critical for the normal health and functioning of the cornea. Lamellar keratoplasty (LK) involves removal of only partial corneal thickness and can be considered when the recipient's corneal endothelium is relatively healthy (and not affected by the disease or condition that has necessitated the corneal graft). Unlike PK, in which endothelial cell viability of the donor cornea is critical to graft success, donor endothelium is not a consideration in LK and by retaining the host's own healthy endothelium, the risk of corneal graft rejection is greatly reduced. LK has become more popular over the last few years, with deep lamellar keratoplasty (DLK) being the most common form of lamellar corneal transplantation.
During the corneal graft surgery, the surgeon will fasten the donor cornea to the host cornea either by use of a running suture or multiple interrupted sutures. These sutures will generally stay in place for about 1 to 2 years. After they are removed, about 10% of corneal graft patients will require no refractive correction, about 60% will be required to wear spectacles and approximately 30% will need to be fitted with contact lenses (usually of the rigid type) due to the presence of post-graft irregular astigmatism in the donor cornea. Wearing contact lenses does slightly increase the risk of corneal graft rejection. However, due to the advances in contact lens technology over the last 10 years, most corneal graft patients who are required to wear contact lenses generally do so without any major problems.
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