Corneal transplantation
Corneal transplantation, also known as corneal grafting, is a surgical procedure where a damaged or diseased cornea is replaced by donated corneal tissue (the graft). When the entire cornea is replaced it is known as penetrating keratoplasty and when only part of the cornea is replaced it is known as lamellar keratoplasty. Keratoplasty simply means surgery to the cornea. The graft is taken from a recently deceased individual with no known diseases or other factors that may affect the chance of survival of the donated tissue or the health of the recipient.
The cornea is the transparent front part of the eye that covers the iris, pupil and anterior chamber. The surgical procedure is performed by ophthalmologists, physicians who specialize in eyes, and is often done on an outpatient basis. Donors can be of any age, as is shown in the case of Janis Babson, who donated her eyes after dying at the age of 10.[1][2] Corneal transplantation is performed when medicines, keratoconus conservative surgery and cross-linking can no longer heal the cornea.
This surgical procedure usually treats corneal blindness,[3][4] with success rates of at least 41% as of 2021.[5][6][7]
Indications include the following:
Risks[edit]
The risks are similar to other intraocular procedures, but additionally include graft rejection (lifelong), detachment or displacement of lamellar transplants and primary graft failure. Use of immunosuppressants including cyclosporine A, tacrolimus, mycophenolate mofetil, sirolimus, and leflunomide to prevent graft rejection is increasing but there is insufficient evidence to ascertain which immunosuppressant is better.[8] In a Cochrane review which included low to moderate quality evidence, adverse effects were found to be common with systemic mycophenolate mofetil, but less common with topical cyclosporine A or tacrolimus.
There is also a risk of infection. Since the cornea has no blood vessels (it takes its nutrients from the aqueous humor) it heals much more slowly than a cut on the skin. While the wound is healing, it is possible that it might become infected by various microorganisms. This risk is minimized by antibiotic prophylaxis (using antibiotic eyedrops, even when no infection exists).
There is a risk of cornea rejection, which occurs in about 10% of cases.[9] Graft failure can occur at any time after the cornea has been transplanted, even years or decades later. The causes can vary, though it is usually due to new injury or illness. Treatment can be either medical or surgical, depending on the individual case. An early, technical cause of failure may be an excessively tight stitch cheesewiring through the sclera.
Infectious disease transmission through corneal transplantation is exceedingly rare.[10] All corneal grafts are screened for the presence of viruses such as HIV or hepatitis through antibody or nucleic acid testing, and there has never been a reported case of HIV transmission through corneal transplant surgery.[11] Prior to the development of reliable HIV testing, many countries instituted bans on corneal donation by gay men. For example, on 20 May 1994, the United States banned corneal donation by any man who has had sex with another man in the preceding 5 years, even if all HIV testing is negative (a policy which continues to be enforced today).[12]
Alternatives[edit]
Contact lenses[edit]
Different types of contact lenses may be used to delay or eliminate the need for corneal transplantation in corneal disorders.
Epidemiology[edit]
Corneal transplant is one of the most common transplant procedures.[22] Although approximately 100,000 procedures are performed worldwide each year, some estimates report that 10,000,000 people are affected by various disorders that would benefit from corneal transplantation.[23]
In Australia, approximately 2,000 grafts are performed each year.[22] According to the NHS Blood and Transplant, over 2,300 corneal transplant procedures are performed each year in the United Kingdom.[24] In the one-year period ending 31 March 2006, 2,503 people received corneal transplants in the UK.[25]
Research[edit]
High speed lasers[edit]
Blades are being replaced by high speed lasers in order to make surgical incisions more precise. These improved incisions allow the cornea to heal more quickly and the sutures to be removed sooner. The cornea heals more strongly than with standard blade operations. Not only does this dramatically improve visual recovery and healing, it also allows the possibility for improvement in visual outcomes.
Since 2004, Amnitrans Eyebank in Rotterdam, The Netherlands, provides donor corneas pre-cut for advanced keratoplasty procedures, such as DSEK, DSAEK, FS-DSEK and DMEK. In 2007, Seattle-based SightLife, one of the leading corneal tissue banks in the world, introduced a process for the preparation of donated corneal tissue using a femtosecond laser. This process is known as custom corneal tissue.
Society and culture[edit]
Cost[edit]
A 2013 cost-benefit analysis by the Lewin Group for Eye Bank Association of America, estimated an average cost of $16,500 for each corneal transplant.[39]