Journal of Clinical and Experimental Transplantation
Open Access

Corneal transplantation is that the most generally practiced sort of clinical allografting. First successfully administered almost a century ago, its place in clinical practice was well established before the vagaries of immunological privilege and allograft rejection were appreciated. Early on, the cornea and anterior segment of the attention were established as ‘privileged sites’ which led to a widely held view that corneal grafts were invariably successful. This is often far away from the reality.

Paradoxically, corneal transplantation is both the foremost successful and therefore the least successful sort of clinical transplantation. Grafts finished dystrophic conditions, particularly keratoconus, seldom reject, with a graft survival rate of fifty after 5 years. However, grafts finished acquired diseases fare badly. This is often an excellent pity since acquired corneal blindness is second to cataract as an explanation for visual loss on a world scale.

The mechanisms of those frequent failures are many. Various factors account for the divergences which are reflected within the wide variations in outcome seen between various centres. This variation is common in other branches of transplantation, is mentioned because the ‘Centre erect’, and defies specific elucidation.

In recent years, the importance of recipient factors has been established and is further confirmed by their study. Corneal inflammation and vascularization are known to be related to a high risk of rejection. Disease erodes corneal privilege. Patients with acquired diseases are far more likely to reject their corneal transplants.

The importance of allograft rejection is further confirmed by the tiny but significant benefit bestowed by class I HLA matching. That a degree of sophistication II matching was related to less rejection than zero HLA-DR matches is interesting in sight of an emerging understanding of the varied mechanisms contributing to corneal allograft rejection. It’s generally believed that indirect presentation of antigen is vital in allograft rejection and particularly so in corneal rejection where the graft carries fewer passenger cells.

The essential elements of this process involved the bone marrow derived cells of the host, principally macrophages and interstitial dendritic cells, presenting foreign histocompatibility antigens of the donor to the host immunocytes. This process is class II restricted. The concept of indirect presentation of antigen is vital in understanding the biology of corneal allograft rejection and in establishing the principles of management for patients undergoing this procedure. Corneal allografts are more likely to be rejected if placed during a recipient cornea replete with high numbers of inflammatory cells. Grafts complicated, for one reason or another, by postoperative inflammation are more likely to severe allograft rejection. Postoperative care is aimed toward reducing the influx of host inflammatory cells into the graft. the utilization of non-reactive monofilament nylon sutures, the utilization of topical corticosteroids, the prompt and energetic treatment of inflammatory events, like infections or ulceration, are directed at reducing the buildup of host inflammatory cells within the graft.

The importance of clinicians making appropriate decisions is emphasized by the higher results achieved by high volume surgeons. This divergence is probably going to be the results of making better management decisions supported greater experience than on better developed surgical skills. Immediate post-surgical failure is rare.

It is important that the authors have taken the evaluation of graft outcome beyond an assessment of endothelial failure. Not all grafts which are clear and functioning provide good vision, and not all grafts providing reasonable levels of acuity contribute to the patient’s visual ability within the general sense. Although the bulk of grafts are finished visual reasons the evaluation of their outcome is complicated. Best corrected acuity isn’t always satisfactory for patients. More relevant is that the level of acuity with a sort of correction which is suitable and usable by the patient. Furthermore, binocular acuity is vital. Visual ability is said to vision within the better eye, instead of the more severe eye. Unless patients achieve vision within the grafted eye better than or comparable the contralateral eye little or no is gained from the procedure.

The claim of Vail and his colleagues that, ‘Far more is understood concerning corneal transplantation within the UK than was known at the outset of the Corneal Transplantation Follow up Study’, is entirely justified. What’s disappointing is that the authors are forced to supply their conclusions at such an early stage. As a 1 year study the info won’t supply anywhere near their full potential of data. Transplantation may be a future intervention demanding future evaluation. Anything less is often misleading. For instance, the 1 year graft survival rate is 88% and, because the authors means, is comparable the 91% reported by the Australian keratoplasty Registry at 1 year. However, prolonged follow from the Australian patients demonstrates an alarming deterioration of grafts with time. By 5 years the graft survival rate has fallen to 74% and by 10 years to 62%. Furthermore, any assessment of acuity or visual function isn’t meaningful within a year. Final acuity with a stable refraction isn’t achievable within a year and sometimes not within 3 years. Studies like this could not be subject to the uncertainties of grant funding with a finite time-frame. They ought to be mandatory. Evaluation along the lines described by Vail and his colleagues is that the only satisfactory thanks to evaluate the method of transplantation and will be a neighborhood of the operation of all eye banks.