Corneal transplantation in BritainBMJ 1995; 310 doi: https://doi.org/10.1136/bmj.310.6991.1347 (Published 27 May 1995) Cite this as: BMJ 1995;310:1347
- A B Tullo,
- P A Dyer
- Consultant ophthalmic surgeon Royal Eye Hospital, Manchester M13 9WH
- Consultant clinical scientist Tissue Type Laboratory, St Mary's Hospital, Manchester M13 0JH
Organisation is good; clinical outcome should get better
Over 3000 corneal transplant operations are performed each year in Britain, making this the commonest type of allografting. In most procedures a full thickness corneal button, about 8 mm in diameter, is removed and replaced. The change from using fresh tissue (within 24 hours of death) to stored tissue during the 1980s converted keratoplasty from an out of hours procedure to a mainly planned, routine operation. Cold storage (for up to 8 days at 4°C) and organ culture (for up to 30 days at 34°C) both allow for planned surgery. Organ culture allows a reserve of tissue for genuine emergencies and affords ample time for the required routine screening of donors for hepatitis B and C viruses and HIV. Extra advantages may follow the more widespread matching for HLA types.
After initiatives in the United States, Denmark, and the Netherlands, Britain's Corneal Transplant Service, based on banks in Bristol and Manchester, began in 1986. It now offers to accept, store, and issue material throughout Britain and the Republic of Ireland. Other banks, including those at Moorfields Eye Hospital and the corneoplastic unit at East Grinstead, send surplus tissue to the service, where longer storage times avoid wastage of tissue. In 1994 the Corneal Transplant Service attracted central funding from the Department of Health; it is administered by the United Kingdom Transplant Support Service Authority.
The coordination of activity has allowed collation of data on over 3000 grafts transplanted between 1987 and 1991 and followed up for one year. This first analysis of activity in Britain not only emphasised the impact of irregular corneal curvature (astigmatism) on visual acuity1 but is a timely contribution to the international debate on tissue matching2 fuelled by the results of other large studies in North America,3 Australia,4 and continental Europe.
Although results are best in patients with keratoconus (about 90% of grafts survive five years), nearly half the grafts in heavily vascularised recipients will fail within five years.5 The comfortable notion of full “immunological privilege” for the cornea was dispelled some years ago; topical immunosuppression has significantly improved outcome in high risk recipients, but the influence of tissue matching remains controversial.2
In a recent North American study, matching for HLA type did not reduce rejection in recipients who followed a rigorous protocol of topical steroid treatment.6 Interestingly, this study found that ABO blood group compatibility improved survival of the graft. In Britain the most cited work on the benefit of HLA matching in corneal grafting comes from East Grinstead.7 More recent reports from mainland Europe suggest benefits for matching for both class I (HLA-A, B, C)8 and class II (HLA-DR, DQ, DP)9 antigens. Data from the British corneal transplantation follow up study show that, when the fact that high risk patients often receive grafts matched for HLA type is controlled for, the risk of rejection rises with increasing mismatches for HLA-A and HLA-B specificities.10 Surprisingly, the opposite was true for HLA-DR mismatches. A true biological basis for this dichotomy of an effect for HLA class I but not class II antigens may exist as a similar observation has been reported from another study in corneal grafting11 and in liver transplantation12. Alternatively, poor definition of HLA polymorphisms, particularly for class II, would prevent accurate assessment of the matching of donor and recipient HLA types in corneal grafting.
Although considerable progress has been made in elaborating the mechanisms of rejection of corneal grafts,13 the confusion of data that currently faces eye surgeons14 required to manage high risk patients needs resolution now. Notwithstanding increased cost and a delay in surgery for some patients, class I matching should be defined (as, for example, no more than two mismatches) and should be made available only to carefully defined at risk patients—for example, recipients with deep corneal vascularisation or previous immunologically mediated failure. Prospective studies are still required to address the relevance of class II antigens15 by using molecular biological techniques that identify allele polymorphisms, ABO group matching, and sensitisation in patients who have received a corneal graft previously.16 The design of the studies should take into account the several studies already published or under way so that results are amenable to meta-analysis.17 A consensus on topical immunosuppression after transplantation would also be welcome.18
The network of a limited number of eye banks now underpinned by central funding has an economy of scale that will keep unit costs per cornea low compared with those in other countries. In addition, it will help to protect the service from the bureaucracy and fragmentation of the internal market. The prospects for most patients currently awaiting corneal transplantation in Britain are good, and those for high risk patients should continue to improve.