Our objective was to compare the success of artificial corneal devices versus donor (human) corneas in people who had already had at least one donor cornea transplant that had not worked.
There are several types of corneal transplantations. The type of transplantation depends on how much of the cornea (front part of the eye) is removed and replaced. When the entire cornea is removed and replaced completely, it is called a full thickness penetrating keratoplasty (PK). If only part of the cornea is removed and replaced by the same part from a donor, the surgery is named based on the parts transplanted (e.g. endothelial keratoplasty (EK) refers to transplantation of the inner or endothelial layers of the cornea).
Corneal transplantation is one of the most successful tissue or organ transplantations. However, sometimes the transplantation fails and the donor tissue becomes opaque (cloudy). We looked only at people who had failed at least one PK and required another corneal surgery.
In some medical centers, artificial corneas are recommended after a person has had just one failure of a donor PK; in other centers, an artificial cornea is not recommended until after a person has had several donor PKs fail. At some centers an artificial cornea is never offered. Currently, no guidelines are available as to how many donor corneal transplants can be performed in an eye that has failed a corneal transplantation.
Corneal transplantation with either a donor cornea or an artificial cornea (known as a keratoprosthesis) involves removal of the cloudy cornea and replacement with a clear cornea or corneal device. Some examples of keratoprostheses (KPros) are the Boston KPro (Types I and II), AlphaCor, osteo-odonto-keratoprosthesis (OOKP), and Fyodorov-Zuev KPro. The Boston KPro is the most commonly implanted artificial corneal device.
Key results and conclusions
We found no controlled trials that have compared the success, including vision and side effects, of artificial corneas against donor corneas in people whose previous donor corneal transplants have failed. The best treatment for someone whose PK has failed is not known. There is no high-quality evidence to guide surgeons and patients as to the best treatment to use after a donor transplant fails. Therefore, a trial comparing the use of artificial versus human donor corneas after PK failure is needed. Comparative clinical trials are needed to provide the missing information and would offer significant benefit to an ever-increasing pool of people with visual disability due to a cloudy cornea, most of whom are still at working age or in school.
The optimal management for those individuals who have failed a conventional corneal transplantation is not known. Currently, in some centers, artificial corneal devices routinely are recommended after just one graft failure, and in others, not until after multiple graft failures, or not at all. To date, there have been no controlled trials comparing the visual outcomes and complications of artificial corneal devices (particularly the Boston type 1 keratoprosthesis which is the most commonly implanted artificial corneal device) with repeat donor corneal transplantation, in order to guide surgeons and their patients. It is apparent that such a trial is needed and would offer significant benefit to an ever-increasing pool of people with visual disability due to corneal opacification, most of whom are still in productive stages of their lives.
Individuals who have failed one or more full thickness penetrating keratoplasties (PKs) may be offered repeat corneal surgery using an artificial or donor cornea. An artificial or prosthetic cornea is known as a keratoprosthesis. Both donor and artificial corneal transplantations involve removal of the diseased and opaque recipient cornea (or the previously failed cornea) and replacement with another donor or prosthetic cornea.
To assess the effectiveness of artificial versus donor corneas in individuals who have had one or more failed donor corneal transplantations.
We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2013, Issue 10), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to November 2013), EMBASE (January 1980 to November 2013), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to November 2013), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 27 November 2013.
Two review authors independently assessed reports from the electronic searches to identify randomized controlled trials (RCTs) or controlled clinical trials (CCTs). We resolved discrepancies by discussion or consultation with a third review author.
For discussion purposes, we assessed findings from observational cohort studies and non-comparative case series. No data synthesis was performed.
We did not identify any RCTs or CCTs comparing artificial corneas with donor corneas for repeat corneal transplantations.