Author’s reply

Abstract

Lam et al mention that many controversies still exist regarding the optimal management of patients with end-stage ocular surface disease, including the timing of penetrating keratoplasty (PK) after allograft limbal transplantation (ALT). Following ALT, the entire corneal surface epithelium is regenerated from the transplanted limbal stem cells (SC). Current understanding of limbal SC regeneration kinetics indicates that they produce relatively long-lasting transient amplifying cells (TACs), which then give rise to the specialized cells of the corneal epithelium. It is generally believed that these TACs are located in the peripheral cornea.1Zieske J.D. Perpetuation of stem cells in the eye.Eye. 1994; 8: 163-169Crossref PubMed Scopus (102) Google Scholar Performing PK as a staged procedure after limbal transplantation removes a large volume of TACs, which could theoretically result in increased stress on the transplanted limbal SCs. Two patients who underwent successful PK in our series2Rao S.K. Rajagopal R. Sitalakshmi G. Padmanabhan P. Limbal allografting from related live donors for corneal surface reconstruction.Ophthalmology. 1999; 106: 822-828Abstract Full Text Full Text PDF PubMed Scopus (122) Google Scholar exhibited signs of limbal SC deficiency which were not present earlier. Repeated surgery in an eye with ALT, and the introduction of fresh antigens during staged PK, increase the chances of sensitizing the host defense mechanisms. Performing combined limbal and corneal transplantation using tissue from the same donor, obviates these disadvantages. However, we agree that this increases the technical complexity of the surgical procedure and that such decisions are best made on a case-by-case basis. Because clinical graft rejection episodes were documented in our patients who received HLA-matched limbal allografts, we agree with Lam et al that systemic immunosuppression is necessary, even with HLA-matched donor limbal tissue. We also strongly recommend against the use of related live donor tissue without HLA-matching. The use of amniotic membrane transplantation (AMT) is very effective in reconstructing the ocular surface in eyes with extensive symblepharon formation and we currently use this approach in patients with advanced conjunctival cicatrization. The role of AMT in promoting corneal surface epithelialization after limbal allograft transplantation is, however, less clear. Removal of the corneal portion of the amniotic membrane has been recommended in eyes undergoing limbal transplantation with AMT.3Shimazaki J. Yang H.Y. Tsubota K. Amniotic membrane transplantation for ocular surface reconstruction in patients with chemical and thermal burns.Ophthalmology. 1997; 104: 2068-2076Abstract Full Text PDF PubMed Scopus (403) Google Scholar The prognosis for patients with end-stage ocular surface disease has improved considerably in the past decade. New approaches are constantly being reported, including the use of newer immunosuppressive agents.4Dua H.S. Azuara-Blanco A. Allo-limbal transplantation in patients with limbal cell deficiency.Br J Ophthalmol. 1999; 83: 414-419Crossref PubMed Scopus (128) Google Scholar We look forward to the results of Lam et al, using HLA-matched related live donor limbal tissue with systemic immunosuppression.