It might appear disrespectful to compare ocular tissue storage with the food industry, but to do so allows the recognition of some features they have in common. While acknowledging the

scientific contribution to the improvement of techniques in both areas, the range of methods used for preservation and storage have largely developed empirically, evolving over time. This

can make it difficult to implement change as there is always likely to be an understandable reluctance to alter methods ‘that work’. Sclera for transplantation has a long shelf life in

alcohol. Limbal tissue is currently thought to be at its best when ‘fresh’ (ie, whole eyes stored for less than 48 h) or after _in vitro_ expansion. Cryopreservation is not yet sufficiently

comparable but while the former is technically simple, organ culture offers a considerably extended storage time. Both techniques are used in the UK and a symbiotic relationship has existed

for many years, whereby large numbers of corneas in hypothermic storage media have been sent from Moorfields Eye Hospital, Norwich, East Grinstead and, more recently, Liverpool and Newcastle

to the eye banks at Bristol and Manchester for extended storage by organ culture. Thus, in the UK, this network of donor centres, coordinated through UK Transplant, allows >90% of ocular

tissue requirements for a population of 60 million to be met by just two eye banks using organ culture (http://www.uktransplant.org.uk). Only recently have there been any consistent

attempts to rationalize these methods, in use since the 1970s. Hypothermic storage was advanced considerably with the introduction of Optisol in the 1990s, and improvements to the

composition of organ culture medium are now being actively sought.2 Since virtually all eyes coming to an eye bank will have bacteria and fungi contaminating the ocular surface,3 there has

been much debate of the relative merits of organ culture _vs_ hypothermia. Cleaning protocols prior to storage substantially reduce this microbial load, and the antibiotics in organ culture

medium will be in the temperature range where they are most effective. There is also a greater opportunity of detecting persistent microbes, reducing the risk that contaminated corneas will

be transplanted. Retrospective comparisons suggest that this translates into a lower risk of postoperative endophthalmitis, although confirmation of this through a definitive, prospective

study is awaited. An advantage of hypothermic storage, where the aim is to suppress the metabolic and energy requirements of the tissue, is that it uses defined media. On the other hand,

organ culture aims to support cellular metabolism and currently relies on medium supplemented by bovine serum. Attempts to replace the serum, which contains a range of active components, are

underway, but this is not a trivial problem; in the meantime, serum is sourced from countries where no BSE has been reported. Other improvements could come from preventing stromal oedema

and minimizing changes in composition of the medium such as falling pH and glucose levels, all of which are stressful to the cornea. Given the microbiological circumstances of organ culture,

it has also been suggested that endotoxins may have a deleterious effect on corneas. In this issue of _Eye_, Spelsberg _et al_4 in Dusseldorf examined this potential influence of

endotoxins. They are to be congratulated not only on submitting data that suggests the endotoxins are _not_ influential but arrived at this conclusion by studying clinical outcome. There has

been substantial improvement in Europe in the organizational aspects of procurement and storage of ocular tissue (http://www.eeba.net). Recently, the routine accrual of clinical outcome

data in the UK is being undertaken with impressive return rates, thanks to the joint efforts of UK Transplant, the Royal College of Ophthalmologists and participating surgeons. Such data are

crucial for the implementation and validation of improved methodology and techniques. We cannot yet bank on catering for all the needs of surgeons who wish to transplant ocular tissue

effectively, but there are continuing opportunities to do so. REFERENCES * Armitage WJ, Hall SC, Routledge C . Recovery of endothelial function after vitrification of cornea at −110°C.

_Invest Ophthalmol Vis Sci_ 2002; 43: 2160–2164. PubMed  Google Scholar  * Thuret G, Chiquet C, Bernal F, Acquart S, Romanet J-P, Mouillon M et al. Prospective, randomised clinical and

endothelial evaluation of 2 storage times for corneal donor tissue in organ culture at 31°C. _Arch Opthalmol_ 2003; 121: 442–450. Article  Google Scholar  * Albon J, Armstrong M, Tullo AB .

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Sundmacher R . Endotoxin is storage medium of human corneal grafts and clinical course after penetrating normal-risk keratoplasty. _Eye_ 2004; (in press). Download references AUTHOR

INFORMATION AUTHORS AND AFFILIATIONS * Manchester Royal eye Hospital, Oxford Road, M13 9WH, UK A B Tullo & W J Armitage Authors * A B Tullo View author publications You can also search

for this author inPubMed Google Scholar * W J Armitage View author publications You can also search for this author inPubMed Google Scholar CORRESPONDING AUTHOR Correspondence to A B Tullo.

RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Tullo, A., Armitage, W. Ocular tissue for transplantation—fresh, chilled, warmed, frozen or pickled?.

_Eye_ 18, 865–866 (2004). https://doi.org/10.1038/sj.eye.6701344 Download citation * Received: 18 September 2003 * Accepted: 18 September 2003 * Published: 06 September 2004 * Issue Date: 01

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