Development of a defined ACF OC medium has been a long-standing goal. Three approaches have been considered. Stoiber et al.
25 tested for OC a serum-free medium derived from a medium for short-term corneal storage at +4°C (Eurosol; Bausch and Lomb, Irvine, CA).
25 Other teams selected, from several serum-free media, an ACF medium developed for the multiplication of ECs of umbilical veins (Endothelial Serum-Free Medium; Life Technologies/Invitrogen, Carlsbad, CA).
9 13 14 15 Last, other researchers kept the MEM base but replaced the 2% of FCS with β-FGF
16 or ovalbumin.
17 We took a different approach, combining our laboratory’s expertise in corneal banking and that of an ACF medium manufacturer with no experience in ophthalmology. Having tested nearly 25 prototypes (data not shown), we developed a defined medium specifically suited to corneal OC. The results obtained by the aforementioned teams with FCS elimination were difficult to compare among themselves and with our results because the methodology and assessment criteria differed. Only three studies directly compared human corneas that had undergone randomized storage either in a conventional medium (MEM+2% FCS) or an FCS-free medium.
9 17 25 In terms of ECD preservation, the Eurosol medium produced results similar to those of the conventional media
25 during 5 weeks of OC—the Endothelial Serum-Free Medium
9 and the MEM+ovalbumin
17 during the first 3 weeks only. Our series is the first to show, through a controlled study, an unequivocal benefit from preserving ECs with an ACF medium. Cell preservation at D30 of storage, which was 18% greater than with FCS/dextran, represents an unprecedented improvement in OC technique. It is important to note that our test had several interesting methodological features: a high number of corneas (
n = 28 pairs) allowing statistical comparisons; inclusion only of pairs of corneas with a starting ECD greater than 2000 cells/mm
2 and so theoretically fit for clinical use; immersion of corneas directly in the media under test, without prior placement in another medium containing animal compounds; strict reproduction of routine OC conditions (with medium renewal under laminar flow hood at D2 and D14, as routinely practiced in most French eye banks); triple measurement series, at the start and end of storage and after deswelling; measurement of ECD, an essential assessment criterion, by an image analysis system and on a large number of cells, thus ensuring objective and accurate results; immediate measurement of cell mortality; analysis of morphometry, which some eye banks are starting to consider important; and assessment of transparency and stromal folding, which ophthalmic surgeons deem paramount.